Co-reporter:Yuwen Wang, Arseni Kostenko, Shenglai Yao, and Matthias Driess
Journal of the American Chemical Society September 27, 2017 Volume 139(Issue 38) pp:13499-13499
Publication Date(Web):August 31, 2017
DOI:10.1021/jacs.7b07167
The first chelating bis(N-heterocyclic silylene)xanthene ligand [SiII(Xant)SiII] as well as its Ni complexes [SiII(Xant)SiII]Ni(η2-1,3-cod) and [SiII(Xant)SiII]Ni(PMe3)2 were synthesized and fully characterized. Exposing [SiII(Xant)SiII]Ni(η2-1,3-cod) to 1 bar H2 at room temperature quantitatively generated an unexpected dinuclear hydrido Ni complex with a four-membered planar Ni2Si2 core. Exchange of the 1,3-COD ligand by PMe3 led to [SiII(Xant)SiII]Ni(PMe3)2, which could activate H2 reversibly to afford the first SiII-stabilized mononuclear dihydrido Ni complex characterized by multinuclear NMR and single-crystal X-ray diffraction analysis. [SiII(Xant)SiII]Ni(η2-1,3-cod) is a strikingly efficient precatalyst for homogeneous hydrogenation of olefins with a wide substrate scope under 1 bar H2 pressure at room temperature. DFT calculations reveal a novel mode of H2 activation, in which the SiII atoms of the [SiII(Xant)SiII] ligand are involved in the key step of H2 cleavage and hydrogen transfer to the olefin.
Co-reporter:Prashanth W. Menezes, Arindam Indra, Chittaranjan Das, Carsten Walter, Caren Göbel, Vitaly Gutkin, Dieter Schmeiβer, and Matthias Driess
ACS Catalysis January 6, 2017 Volume 7(Issue 1) pp:103-103
Publication Date(Web):November 17, 2016
DOI:10.1021/acscatal.6b02666
A systematic structural elucidation of the near-surface active species of the two remarkably active nickel phosphides Ni12P5 and Ni2P on the basis of extensive analytical, microscopic, and spectroscopic investigations is reported. The latter can serve as complementary efficient electrocatalysts in the hydrogen (HER) versus oxygen evolution reaction (OER) in alkaline media. In the OER Ni12P5 shows enhanced performance over Ni2P due to the higher concentration of nickel in this phase, which enables the formation of an amorphous NiOOH/Ni(OH)2 shell on a modified multiphase with a disordered phosphide/phosphite core. The situation is completely reversed in the HER, where Ni2P displayed a significant improvement in electrocatalytic activity over Ni12P5 owing to a larger concentration of phosphide/phosphate species in the shell. Moreover, the efficiently combined use of the two nickel phosphide phases deposited on nickel foam in overall electrocatalytic water splitting is demonstrated by a strikingly low cell voltage and high stability with pronounced current density, and these catalysts could be an apt choice for applications in commercial alkaline water electrolysis.Keywords: electrocatalysis; nickel phosphide; overall water splitting; structural rearrangement; surface structure;
Co-reporter:Arindam Indra;Prashanth W. Menezes;Chittaranjan Das;Caren Göbel;Massimo Tallarida;Dieter Schmeiβer
Journal of Materials Chemistry A 2017 vol. 5(Issue 10) pp:5171-5177
Publication Date(Web):2017/03/07
DOI:10.1039/C6TA10650A
Ultra-small rock salt cobalt monoxide (CoO) nanoparticles were synthesized and subjected to partial oxidation (‘corrosion’) with ceric ammonium nitrate (CAN) to form mixed-valence CoOx (1 < x < 2) water oxidation catalysts. Spectroscopic, microscopic and analytical methods evidenced a structural reformation of cubic CoO to active CoOx with a spinel structure. The superior water oxidation activity of CoOx has been established in electrochemical water oxidation under alkaline conditions. Electrochemical water oxidation with CoOx was recorded at a considerably low overpotential of merely 325 mV at a current density of 10 mA cm−2 in comparison to 370 mV for CoO. Transformation of both octahedral CoII and CoIII sites into amorphous Co(OH)2–CoOOH is the key to high electrochemical activity while the presence of a higher amount of octahedral CoIII sites in CoOx is imperative for an efficient oxygen evolution process.
Co-reporter:Marcel-Philip Luecke;Digvijay Porwal;Arseni Kostenko;Yu-Peng Zhou;Shenglai Yao;Matthias Keck;Christian Limberg;Martin Oestreich
Dalton Transactions 2017 vol. 46(Issue 47) pp:16412-16418
Publication Date(Web):2017/12/06
DOI:10.1039/C7DT03301J
Reaction of FeX2(thf)n (X = Cl n = 1.5, Br n = 2) with the chelating 1,1′-bis(silylenyl)-substituted ferrocene ligand SiFcSiA (Fc = ferrocendiyl, Si = PhC(NtBu)2Si:) furnishes the corresponding dihalido Fe(II) complexes [(SiFcSi)FeX2] (X = Cl, 1 and X = Br, 2) in high yields. Reduction of the latter with an excess of KC8 in the presence of benzene and toluene leads to the unprecedented bis(silylene) stabilized Fe0 complexes [(SiFcSi)Fe-η6(C6H6)] 3 and [(SiFcSi)Fe-η6(C7H8)] 4, respectively. The 57Fe Mössbauer spectrum of 3 at 13 K exhibits parameters (σ = 0.3676 mm s−1; ΔEQ = 1.334 mm s−1) which are consistent with the presence of a pentacoordinated Fe0 atom in a pseudo trigonal–bipyramidal coordination environment, with two dative Si→Fe bonds and three coordination sites occupied by the η6-coordinated arene ligand. Results from DFT calculations, 57Fe Mössbauer parameters and the diamagnetic NMR spectra confirm the redox-innocent nature of these ligands and the zero oxidation state of the iron center. The catalytic ability of 3 was investigated with respect to ketone hydrogenation. In all cases, good to excellent yields to the corresponding alcohols were obtained at 50 °C and 50 bar H2 pressure. Electron-donating as well as -withdrawing substituents were tolerated with excellent to good yields. Conversions of bulkier ketones and unactivated aliphatic ketones lead merely to moderate yields. This represents the first example of a silylene-iron metal complex which has been utilized as a highly active precatalyst in the hydrogenation of ketones. The results underline the powerful ability of chelating bis(N-heterocyclic silylene) ligands acting as strong σ-donor ligands in stabilizing a new generation of low-valent, electron-rich transition metal complexes for catalytic transformations.
Co-reporter:Arindam Indra;Prashanth W. Menezes;Chittaranjan Das;Dieter Schmeißer
Chemical Communications 2017 vol. 53(Issue 62) pp:8641-8644
Publication Date(Web):2017/08/01
DOI:10.1039/C7CC03566G
Multi-shelled hollow spheres of cobalt manganese oxides (CMOs) deposited on Ni foam exhibited superior alkaline electrochemical water oxidation activity and surpassed those of bulk CMO and commercial noble metal-based catalysts. A higher amount of cobalt in the spinel structure resulted in the transformation of the tetragonal to the cubic phase with a decrease in the overpotential of oxygen evolution.
Co-reporter:Marcel Schmidt;Burgert Blom;Tibor Szilvási;Reinhard Schomäcker
European Journal of Inorganic Chemistry 2017 Volume 2017(Issue 9) pp:1284-1291
Publication Date(Web):2017/03/03
DOI:10.1002/ejic.201700148
For the first time, a significant boost in catalytic activity in the rhodium-catalysed hydroformylation of an alkene by using a bidentate bis(N-heterocyclic silylene) ligand is reported. This is shown by the hydroformylation of styrene at 30 bar CO/H2 pressure in the presence of [HRh(CO)(PPh3)3] with an excess of the ferrocenediyl-based bis-NHSi ligand 4, [({η5-C5H4{PhC(NtBu)2}Si})2Fe], which results in superior catalytic activity, compared with the bidentate diphosphines DPPF (3a) and xantphos (3b). In contrast, the hydroformylation of styrene in the presence of [HRh(CO)(PPh3)3] with excesses of the monodentate NHSi ligands [{PhC(NtBu)2}SiNMe2] (1) and [{C2H2(NtBu)2}Si:] (2) at 30 bar CO/H2 pressure revealed considerably slower conversion to the aldehyde products than [HRh(CO)(PPh3)3], with or without an excess of PPh3, showing catalyst deactivation. Surprisingly, the germanium analogue of 4 is shown to be virtually catalytically inactive. The superior activity of 4, compared with the xantphos-containing benchmark system, is rationalized on the basis of solution NMR spectroscopic studies, and the comparative catalyst cycles are elucidated using density functional theory (DFT) methods. The latter quantum-chemical studies explain very well the favourable energy pathway for the hydroformylation of styrene using 4 versus xantphos.
Co-reporter:Saeed Raoufmoghaddam, Yu-Peng Zhou, Yuwen Wang, Matthias Driess
Journal of Organometallic Chemistry 2017 Volume 829(Volume 829) pp:
Publication Date(Web):1 February 2017
DOI:10.1016/j.jorganchem.2016.07.014
•Synthesis and catalytic performance of monodentate, bidentate, and tridentate NHSi-transition metal complexes.•Stronger σ donor strength of NHSi ligands in comparison to NHCs and phosphines.•Catalytic performances of transition metal NHSi complexes.The present review highlights the role of N-heterocyclic silylene (NHSi) ligands, the silicon analogues of N-heterocyclic carbenes (NHCs), utilized in various catalytic organic transformations. The application of such novel ligands coordinated by different metal sites offers massive opportunities in organic synthesis. Despite significant advances in the synthesis of NHSi-based metal complexes, the use of these compounds in organic methodologies is still in its initial stages. Since NHSi ligands promote the σ donor-ability of phosphines and even that of NHCs, they can facilitate catalytic events by lowering the energy barrier of the rate limiting steps such as oxidative additions. This encourages scientists to utilize NHSi-metal complexes in exploiting catalyzed reactions and to revisit and improve various existing organic methodologies. This is demonstrated in several showcases of organic transformations including the Heck coupling, Suzuki coupling, alkyne and ketone hydrosilylation, amide reduction, cyclotrimerization of alkynes (in the absence and the presence of an organo cyanide), and Sonogashira cross-coupling reactions. The latter represents a novel and unexpected steering function of NHSi-based systems in homogeneous catalysis.Download high-res image (162KB)Download full-size image
Co-reporter:Dr. Terrance J. Hadlington;Dr. Tibor Szilvási; Dr. Matthias Driess
Angewandte Chemie International Edition 2017 Volume 56(Issue 45) pp:14282-14286
Publication Date(Web):2017/11/06
DOI:10.1002/anie.201708923
AbstractFacile oxygenation of the acyclic amido-chlorosilylene bis(N-heterocyclic carbene) Ni0 complex [{N(Dipp)(SiMe3)ClSi:Ni(NHC)2] (1; Dipp=2,6-iPr2C6H4; N-heterocyclic carbene=C[(iPr)NC(Me)]2) with N2O furnishes the first Si-metalated iminosilane, [DippN=Si(OSiMe3)Ni(Cl)(NHC)2] (3), in a rearrangement cascade. Markedly, the formation of 3 proceeds via the silanone (Si=O)–Ni π-complex 2 as the initial product, which was predicted by DFT calculations and observed spectroscopically. The Si=O and Si=N moieties in 2 and 3, respectively, show remarkable hydroboration reactivity towards H−B bonds of boranes, in the former case corroborating the proposed formation of a (Si=O)–Ni π-complex at low temperature.
Co-reporter:Dr. Chakadola Pa;Dr. Prashanth W. Menezes;Carsten Walter;Dr. Shenglai Yao;Matthias E. Miehlich;Dr. Vitaly Gutkin; Dr. Karsten Meyer; Dr. Matthias Driess
Angewandte Chemie International Edition 2017 Volume 56(Issue 35) pp:10506-10510
Publication Date(Web):2017/08/21
DOI:10.1002/anie.201706196
AbstractA highly active FeSe2 electrocatalyst for durable overall water splitting was prepared from a molecular 2Fe-2Se precursor. The as-synthesized FeSe2 was electrophoretically deposited on nickel foam and applied to the oxygen and hydrogen evolution reactions (OER and HER, respectively) in alkaline media. When used as an oxygen-evolution electrode, a low 245 mV overpotential was achieved at a current density of 10 mA cm−2, representing outstanding catalytic activity and stability because of Fe(OH)2/FeOOH active sites formed at the surface of FeSe2. Remarkably, the system is also favorable for the HER. Moreover, an overall water-splitting setup was fabricated using a two-electrode cell, which displayed a low cell voltage and high stability. In summary, the first iron selenide material is reported that can be used as a bifunctional electrocatalyst for the OER and HER, as well as overall water splitting.
Co-reporter:Dr. Terrance J. Hadlington;Dr. Tibor Szilvási; Dr. Matthias Driess
Angewandte Chemie International Edition 2017 Volume 56(Issue 26) pp:7680-7680
Publication Date(Web):2017/06/19
DOI:10.1002/anie.201704556
A conquest of bonds: Silicon(II) and nickel(0) atoms combined in a complex are capable of breaking the extremely strong B−O bonds of the catechol borane, HB(cat), thereby generating the first isolable hydroborylene nickel complex, whose blue color fills the sky in the picture. In their Communication on page 7470 ff., M. Driess et al. describe the synthesis and unprecedented reactivity of an acyclic silylene nickel(0) complex which yields the hydroborylene complex and even activates dihydrogen at 20 °C and 1 atm.
Co-reporter:Dr. Shenglai Yao;Yves Grossheim;Dr. Arseni Kostenko;M. Sc. Ernesto Ballestero-Martínez;Stefan Schutte;Mark Bispinghoff; Dr. Hansjörg Grützmacher; Dr. Matthias Driess
Angewandte Chemie International Edition 2017 Volume 56(Issue 26) pp:7465-7469
Publication Date(Web):2017/06/19
DOI:10.1002/anie.201703731
AbstractA facile, one-pot synthesis of [Na(OC≡As)(dioxane)x] (x=2.3–3.3) in 78 % yield is reported through the reaction of arsine gas with dimethylcarbonate in the presence of NaOtBu and 1,4-dioxane. It has been employed for the synthesis of the first arsaketenyl-functionalized germylene [LGeAsCO] (2, L=CH[CMeN(Dipp)]2; Dipp=2,6-iPr2C6H3) from the reaction with LGeCl (1). Upon exposure to ambient light, 2 undergoes CO elimination to form the 1,3-digerma-2,4-diarsacyclobutadiene [L2Ge2As2] (3), which contains a symmetric Ge2As2 ring with ylide-like Ge=As bonds. Remarkably, the CO ligand located at the arsenic center of 2 can be exchanged with PPh3 or an N-heterocyclic carbene iPrNHC donor (iPrNHC=1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) to afford the novel germylidenylarsinidene complexes [LGe-AsPPh3] (4) and [LGe-As(iPrNHC)] (5), respectively, demonstrating transition-metal-like ligand substitution at the arsinidene-like As atom. The formation of 2–5 and their electronic structures have been studied by DFT calculations.
Co-reporter:Dr. Terrance J. Hadlington;Dr. Tibor Szilvási; Dr. Matthias Driess
Angewandte Chemie International Edition 2017 Volume 56(Issue 26) pp:7470-7474
Publication Date(Web):2017/06/19
DOI:10.1002/anie.201702772
AbstractThe first 16 valence electron [bis(NHC)](silylene)Ni0 complex 1, [(TMSL)ClSi:Ni(NHC)2], bearing the acyclic amido-chlorosilylene (TMSL)ClSi: (TMSL=N(SiMe3)Dipp; Dipp=2,6-Pri2C6H4) and two NHC ligands (N-heterocyclic carbene=:C[(Pri)NC(Me)]2) was synthesized in high yield and structurally characterized. Compound 1 is capable of facile dihydrogen activation under ambient conditions to give the corresponding HSi-NiH complex 2. Most notably, 1 reacts with catechol borane to afford the unprecedented hydroborylene-coordinated (chloro)(silyl)nickel(II) complex 3, {[cat(TMSL)Si](Cl)Ni:BH(NHC)2}, via the cleavage of two B−O bonds and simultaneous formation of two Si−O bonds. The mechanism for the formation of 3 was rationalized by means of DFT calculations, which highlight the powerful synergistic effects of the Si:Ni moiety in the breaking of incredibly strong B−O bonds.
Co-reporter:Dr. Gengwen Tan;Jing Li;Dr. Li Zhang;Chao Chen;Dr. Yue Zhao; Dr. Xinping Wang; Dr. You Song; Dr. Yi-Quan Zhang; Dr. Matthias Driess
Angewandte Chemie International Edition 2017 Volume 56(Issue 41) pp:12741-12745
Publication Date(Web):2017/10/02
DOI:10.1002/anie.201707501
AbstractThe CoII and FeII complexes 1Co and 1Fe with a coordinated phosphorus radical were easily obtained through a charge-transfer approach from the MI precursors LMI(tol) (M=Co, Fe; L=CH(MeC=NDipp)2, Dipp=2,6-iPr2C6H3) to the diazafluorenylidene-substituted phosphaalkene 1. Structural, magnetic, and computational studies on 1Co and 1Fe indicate a weak antiferromagnetic interaction between the high-spin MII ion and the phosphorus radical, resulting in a triplet and quartet ground state, respectively. Complexes 1Co and 1Fe are the first examples of phosphorus-radical-coordinated transition-metal complexes synthesized by charge transfer, providing a new approach to access radicals of heavier main-group elements.
Co-reporter:Dr. Chakadola Pa;Dr. Prashanth W. Menezes;Carsten Walter;Dr. Shenglai Yao;Matthias E. Miehlich;Dr. Vitaly Gutkin; Dr. Karsten Meyer; Dr. Matthias Driess
Angewandte Chemie 2017 Volume 129(Issue 35) pp:10642-10646
Publication Date(Web):2017/08/21
DOI:10.1002/ange.201706196
AbstractA highly active FeSe2 electrocatalyst for durable overall water splitting was prepared from a molecular 2Fe-2Se precursor. The as-synthesized FeSe2 was electrophoretically deposited on nickel foam and applied to the oxygen and hydrogen evolution reactions (OER and HER, respectively) in alkaline media. When used as an oxygen-evolution electrode, a low 245 mV overpotential was achieved at a current density of 10 mA cm−2, representing outstanding catalytic activity and stability because of Fe(OH)2/FeOOH active sites formed at the surface of FeSe2. Remarkably, the system is also favorable for the HER. Moreover, an overall water-splitting setup was fabricated using a two-electrode cell, which displayed a low cell voltage and high stability. In summary, the first iron selenide material is reported that can be used as a bifunctional electrocatalyst for the OER and HER, as well as overall water splitting.
Co-reporter:Alexer Burchert;Dr. Robert Müller;Dr. Shenglai Yao;Caspar Schattenberg;Dr. Yun Xiong; Dr. Martin Kaupp; Dr. Matthias Driess
Angewandte Chemie 2017 Volume 129(Issue 22) pp:6395-6398
Publication Date(Web):2017/05/22
DOI:10.1002/ange.201700530
AbstractThe synthesis of the unprecedented monomeric SiII selenide complex (bis-NHC)Si=SeGaCl3 2 (bis-NHC=bis-N heterocyclic carbene, H2C[{NC(H)=C(H)N(Dipp)}C:]2, Dipp=2,6-iPr2C6H3), bearing the elusive SiSe ligand as a heavy CO homologue by the reaction of the silylone–GaCl3 adduct (bis-NHC)SiGaCl3 1 with elemental selenium in acetonitrile, is reported. The similar conversion of 1 with excess selenium conducted in THF afforded the SiSe2 complex (bis-NHC)Si(=Se)SeGaCl3 3. Remarkably, the reaction of 1 with Te=P(nBu)3 as a gentle Te transfer reagent led to the isolation of the monomeric SiTe2 complex (bis-NHC)SiTe2 4, the first structurally characterized Lewis acid free heavy CO2 homologue complex. The isolated compounds 2, 3, and 4 have been fully characterized, including single-crystal X-ray diffraction analyses. Their electronic structures and spectroscopic data have also been studied by quantum-chemical calculations.
Co-reporter:Yun Xiong, Shenglai Yao, Miriam Karni, Arseni Kostenko, Alexander Burchert, Yitzhak Apeloig and Matthias Driess
Chemical Science 2016 vol. 7(Issue 8) pp:5462-5469
Publication Date(Web):10 May 2016
DOI:10.1039/C6SC01839D
In contrast to molecular CO and CO2, their heavier mono- and dichalcogenide homologues, EX and EX2 (E = Si, Ge, Sn, Pb; X = O, S, Se, Te), are important support materials (e.g., SiO2) and/or semiconductors (e.g., SiS2) and exist typically as insoluble crystalline or amorphous polymers under normal conditions. Herein, we report the first successful synthesis and characterisation of an extraordinary series of isolable monomeric GeX and GeX2 complexes (X = S, Se, Te), representing novel classes of compounds and heavier congeners of CO and CO2. This could be achieved by solvent-dependent oxidation reactions of the new zero-valent germanium (‘germylone’)–GaCl3 precursor adduct (bis-NHC)Ge0→GaCl31 (bis-NHC = H2C[{NC(H)C(H)N(Dipp)}C:]2, Dipp = 2,6-iPr2C6H3) with elemental chalcogens, affording the donor–acceptor stabilised monomeric germanium(IV) dichalcogenide (bis-NHC)GeIV(X)X→GaCl3 (X = S, 2; X = Se, 3) and germanium(II) monochalcogenide complexes (bis-NHC)GeIIX→GaCl3 (X = Se, 4; X = Te, 5), respectively. Moreover, the reactivity of 4 and 5 towards elemental sulphur, selenium, and tellurium has been investigated. In THF, the germanium(II) monoselenide complex 4 reacts with activated elemental selenium to afford the desired germanium(IV) diselenide complex 3. Unexpectedly, both reactions of 4 and 5 with elemental sulphur, however, lead to the formation of germanium(IV) disulfide complex 2 under liberation of elemental Se and Te as a result of further oxidation of the germanium centre and replacement of the Se and Te atoms by sulphur atoms. All novel compounds 1–5 have been fully characterised, including single-crystal X-ray diffraction analyses, and studied by DFT calculations.
Co-reporter:Prashanth W. Menezes, Arindam Indra, Arno Bergmann, Petko Chernev, Carsten Walter, Holger Dau, Peter Strasser and Matthias Driess
Journal of Materials Chemistry A 2016 vol. 4(Issue 25) pp:10014-10022
Publication Date(Web):06 Jun 2016
DOI:10.1039/C6TA03644A
The fabrication and design of earth-abundant and high-performance catalysts for the oxygen evolution reaction (OER) are very crucial for the development and commercialization of sustainable energy conversion technologies. Although spinel catalysts have been widely explored for the electrochemical oxygen evolution reaction (OER), the role of two geometrical sites that influence their activities has not been well established so far. Here, we present more effective cobalt–zinc oxide catalysts for the OER than ‘classical’ Co3O4. Interestingly, the significantly higher catalytic activity of ZnCo2O4 than that of Co3O4 is somewhat surprising since both crystallize in the spinel-type structure. The reasons for the latter remarkable difference of ZnCo2O4 and Co3O4 could be deduced from structure–activity relationships of the bulk and near-surface of the catalysts using comprehensive electrochemical, microscopic and spectroscopic techniques with a special emphasis on the different roles of the coordination environment of metal ions (octahedral vs. tetrahedral sites) in the spinel lattice. The vital factors influencing the catalytic activity of ZnCo2O4 over Co3O4 could be directly attributed to the higher amount of accessible octahedral Co3+ sites induced by the preferential loss of zinc ions from the surface of the ZnCo2O4 catalyst. The enhanced catalytic activity is accompanied by a larger density of metal vacancies, defective sites and hydroxylation. The results obtained here clearly demonstrate how a surface structural modification and generation of defects of catalysts can enhance their OER performance.
Co-reporter:Arindam Indra, Prashanth W. Menezes, Kamalakannan Kailasam, Dirk Hollmann, Marc Schröder, Arne Thomas, Angelika Brückner and Matthias Driess
Chemical Communications 2016 vol. 52(Issue 1) pp:104-107
Publication Date(Web):15 Oct 2015
DOI:10.1039/C5CC07936E
The nature of a nickel-based co-catalyst deposited on a sol–gel prepared porous graphitic-carbon nitride (sg-CN), for photocatalytic H2 production from water, has been investigated. The formation of the active catalytic species, charge separation and recombination of the photogenerated electrons and holes during photochemical H2 evolution has been determined for the first time using in situ EPR spectroscopy.
Co-reporter:Dr. Shenglai Yao;Dr. Yun Xiong;Dr. Tibor Szilvási;Dr. Hansjörg Grützmacher;Dr. Matthias Driess
Angewandte Chemie 2016 Volume 128( Issue 15) pp:4859-4863
Publication Date(Web):
DOI:10.1002/ange.201600701
Abstract
The first 4π-electron resonance-stabilized 1,3-digerma-2,4-diphosphacyclobutadiene [LH2Ge2P2] 4 (LH=CH[CHNDipp]2 Dipp=2,6-iPr2C6H3) with four-coordinate germanium supported by a β-diketiminate ligand and two-coordinate phosphorus atoms has been synthesized from the unprecedented phosphaketenyl-functionalized N-heterocyclic germylene [LHGe-P=C=O] 2 a prepared by salt-metathesis reaction of sodium phosphaethynolate (P≡C−ONa) with the corresponding chlorogermylene [LHGeCl] 1 a. Under UV/Vis light irradiation at ambient temperature, release of CO from the P=C=O group of 2 a leads to the elusive germanium–phosphorus triply bonded species [LHGe≡P] 3 a, which dimerizes spontaneously to yield black crystals of 4 as isolable product in 67 % yield. Notably, release of CO from the bulkier substituted [LtBuGe-P=C=O] 2 b (LtBu=CH[C(tBu)N-Dipp]2) furnishes, under concomitant extrusion of the diimine [Dipp-NC(tBu)]2, the bis-N,P-heterocyclic germylene [DippNC(tBu)C(H)PGe]2 5.
Co-reporter:Dr. Shenglai Yao;Dr. Yun Xiong;Dr. Tibor Szilvási;Dr. Hansjörg Grützmacher;Dr. Matthias Driess
Angewandte Chemie International Edition 2016 Volume 55( Issue 15) pp:4781-4785
Publication Date(Web):
DOI:10.1002/anie.201600701
Abstract
The first 4π-electron resonance-stabilized 1,3-digerma-2,4-diphosphacyclobutadiene [LH2Ge2P2] 4 (LH=CH[CHNDipp]2 Dipp=2,6-iPr2C6H3) with four-coordinate germanium supported by a β-diketiminate ligand and two-coordinate phosphorus atoms has been synthesized from the unprecedented phosphaketenyl-functionalized N-heterocyclic germylene [LHGe-P=C=O] 2 a prepared by salt-metathesis reaction of sodium phosphaethynolate (P≡C−ONa) with the corresponding chlorogermylene [LHGeCl] 1 a. Under UV/Vis light irradiation at ambient temperature, release of CO from the P=C=O group of 2 a leads to the elusive germanium–phosphorus triply bonded species [LHGe≡P] 3 a, which dimerizes spontaneously to yield black crystals of 4 as isolable product in 67 % yield. Notably, release of CO from the bulkier substituted [LtBuGe-P=C=O] 2 b (LtBu=CH[C(tBu)N-Dipp]2) furnishes, under concomitant extrusion of the diimine [Dipp-NC(tBu)]2, the bis-N,P-heterocyclic germylene [DippNC(tBu)C(H)PGe]2 5.
Co-reporter:Toni T. Metsänen, Daniel Gallego, Tibor Szilvási, Matthias Driess and Martin Oestreich
Chemical Science 2015 vol. 6(Issue 12) pp:7143-7149
Publication Date(Web):14 Sep 2015
DOI:10.1039/C5SC02855H
Combined experimental and theoretical analysis of the carbonyl hydrosilylation catalysed by an iron(0) pincer complex reveals an unprecedented mechanism of action. The iron(0) complex is in fact a precatalyst that is converted into an iron(II) catalyst through oxidative addition of a hydrosilane. Neither the hydrogen atom nor the silicon atom bound to the iron(II) centre are subsequently transferred onto the carbonyl acceptor, instead remaining at the sterically inaccessible iron(II) atom throughout the catalytic cycle. A series of labelling, crossover and competition experiments as well as the use of a silicon-stereogenic hydrosilane as a stereochemical probe suggest that the iron(II) site is not directly involved in the hydrosilylation. Strikingly, it is the silyl ligand attached to the iron(II) atom that acts as a Lewis acid for carbonyl activation in this catalysis. The whole catalytic process occurs on the periphery of the transition metal. Computation of the new peripheral as well as plausible alternative inner and outer sphere mechanisms support the experimental findings.
Co-reporter:Prashanth W. Menezes, Arindam Indra, Diego González-Flores, Nastaran Ranjbar Sahraie, Ivelina Zaharieva, Michael Schwarze, Peter Strasser, Holger Dau, and Matthias Driess
ACS Catalysis 2015 Volume 5(Issue 4) pp:2017
Publication Date(Web):February 16, 2015
DOI:10.1021/cs501724v
Future advances in renewable and sustainable energy require advanced materials based on earth-abundant elements with multifunctional properties. The design and the development of cost-effective, robust, and high-performance catalysts that can convert oxygen to water, and vice versa, is a major challenge in energy conversion and storage technology. Here we report cobalt oxide nanochains as multifunctional catalysts for the electrochemical oxygen evolution reaction (OER) at both alkaline and neutral pH, oxidant-driven, photochemical water oxidation in various pH, and the electrochemical oxygen reduction reaction (ORR) in alkaline medium. The cobalt oxide nanochains are easily accessible on a multigram scale by low-temperature degradation of a cobalt oxalate precursor. What sets this study apart from earlier ones is its synoptical perspective of reversible oxygen redox catalysis in different chemical and electrochemical environments.Keywords: cobalt oxide; morphology; multifunctional catalyst; oxygen evolution; oxygen reduction; water oxidation
Co-reporter:Shenglai Yao, Tibor Szilvási, Nils Lindenmaier, Yun Xiong, Shigeyoshi Inoue, Mario Adelhardt, Jörg Sutter, Karsten Meyer and Matthias Driess
Chemical Communications 2015 vol. 51(Issue 28) pp:6153-6156
Publication Date(Web):27 Feb 2015
DOI:10.1039/C5CC00147A
The selective transformation of white phosphorus with a β-diketiminato iron(I) toluene complex under mild reaction conditions is reported which furnishes a new dinuclear iron(III) Fe2(P2)2 complex with two bridging P22− ligands. Its reduction with potassium results in the formation of the first delocalised mixed-valent bis-diphosphido iron(II,III) complex which is isostructural with the neutral Fe2P4 precursor.
Co-reporter:Prashanth W. Menezes, Arindam Indra, Ophir Levy, Kamalakannan Kailasam, Vitaly Gutkin, Johannes Pfrommer and Matthias Driess
Chemical Communications 2015 vol. 51(Issue 24) pp:5005-5008
Publication Date(Web):13 Feb 2015
DOI:10.1039/C4CC09671A
Nickel–manganese oxides with variable Ni:Mn ratios, synthesised from heterobimetallic single-source precursors, turned out to be efficient water oxidation catalysts. They were subjected to oxidant-driven, photo- and electro-catalytic water oxidation showing superior activity and remarkable stability. In addition, a structure–activity relation could be established.
Co-reporter:Burgert Blom; Amro Said; Tibor Szilvási; Prashanth W. Menezes; Gengwen Tan; Judith Baumgartner
Inorganic Chemistry 2015 Volume 54(Issue 17) pp:8840-8848
Publication Date(Web):August 25, 2015
DOI:10.1021/acs.inorgchem.5b01643
The synthesis and striking reactivity of the unprecedented N-heterocyclic silylene and germylene (“metallylene”) alkaline-earth metal (Ae) complexes of the type [(η5-C5Me5)2Ae←:E(NtBuCH)2] (3, 4, and 7–9; Ae = Ca, E = Ge 3; Ae = Sr, E = Ge 4; Ae = Sr, E = Si 7; Ae = Ba, E = Si 8; Ae = Ba, E = Ge 9) are reported. All complexes have been characterized by spectroscopic means, and their bonding situations investigated by density functional theory (DFT) methods. Single-crystal X-ray diffraction analyses of examples revealed relatively long Si–Ae and Ge–Ae distances, respectively, indicative of weak E:→Ae (E = Si, Ge) dative bonds, further supported by the calculated Wiberg bond indices , which are rather low in all cases (∼0.5). Unexpectedly, the complexes undergo facile transformation to 1,4-diazabuta-1,3-diene Ae metal complexes of the type [(η5-C5Me5)2Ae(κ2-{NtBu═CHCH═NtBu})] (Ae = Sr 10, Ae = Ba 11) or in the case of calcium to the dinuclear complex [(η5-C5Me5)2Ca←:N(tBu)═CHCH═(tBu)N:→Ca(η5-C5Me5)2] (12) under concomitant liberation of elemental silicon and germanium. The formation of elemental silicon and germanium is proven by inductively coupled plasma atomic emission spectroscopy, transmission electron microscopy, selected area electron diffraction, and energy dispersive X-ray spectroscopy. Notably, the decomposition of the Si(II)→Ba complex 8 produces allo-silicon, a rare allotropic form of elemental silicon. Similarly, the analogous Ge(II)→Ba complex 9, upon decomposition, forms tetragonal germanium, a dense and rare allotrope of elemental germanium. The energetics of this unprecedented alkaline-earth-metal-induced liberation of elemental silicon and germanium was additionally studied by DFT methods, revealing that the transformations are pronouncedly exergonic and considerably larger for the N-heterocyclic germylene complexes than those of the corresponding silicon analogues.
Co-reporter:Burgert Blom, Günter Klatt, Daniel Gallego, Gengwen Tan and Matthias Driess
Dalton Transactions 2015 vol. 44(Issue 2) pp:639-644
Publication Date(Web):04 Nov 2014
DOI:10.1039/C4DT03148B
The first N-heterocyclic silylene (NHSi) complexes of any s-block element to date are reported for calcium: [(η5-C5Me5)2Ca←:Si(O-C6H4-2-tBu){(NtBu)2CPh}] (6) and [(η5-C5Me5)2Ca←:Si(NtBuCH)2] (7). Complexes 6 and 7 are isolable in a facile way upon reaction of the corresponding free N-heterocyclic silylenes (NHSis) with [(η5-C5Me5)2Ca] (2). Complexes 6 and 7 were fully characterised by spectroscopic means and the single crystal X-ray diffraction analysis of 6 is also reported. Analysis of the bonding situation by DFT methods including a Bader Atoms in molecules (AIM) analysis is also reported. The bonding interaction between the Si and Ca centres in complexes 6 and 7 can best be viewed as σ-donor–acceptor interactions, with a considerable ionic contribution in the bond. The reactivity towards the oxygen containing substrates THF and benzophenone is also discussed.
Co-reporter:Yun Xiong;Shenglai Yao;Tibor Szilvási
European Journal of Inorganic Chemistry 2015 Volume 2015( Issue 14) pp:2377-2380
Publication Date(Web):
DOI:10.1002/ejic.201500154
Abstract
The unexpected isomerization of the potassium bis(N-heterocyclic carbene)borate [BPh2(tBuNHC)2]K (2′) (tBuNHC = 3-tert-butylimidazole-2-ylidene) in toluene, affording the unique potassium imidazolyl–NHC–borate [BPh2(tBuIm)(tBuNHC)]K (2) (tBuIm = 3-tert-butyl-2-imidazolyl), is reported. The latter crystallizes as the centrosymmetric dimer 22. According to the results of DFT calculations, the rearrangement of 2′ is basically triggered by the solvation of the K+ ion: while 2′ is most stable in THF solutions, the formation of 2 is feasible in least coordinating toluene and drastically favored through dimerization to give 22. The latter reacts with GeCl2·dioxane to form solely the unprecedented chlorogermyliumylideneborate [BPh2(tBuIm)(tBuNHC)]GeCl (3). Treatment of 3 with KHB(sBu)3 furnishes the corresponding hydridogermyliumylideneborate complex [BPh2(tBuIm)(tBuNHC)]GeH (4) in 66 % yield.
Co-reporter:Yun Xiong;Shenglai Yao;Tibor Szilvási
European Journal of Inorganic Chemistry 2015 Volume 2015( Issue 14) pp:
Publication Date(Web):
DOI:10.1002/ejic.201500434
Abstract
Invited for the cover of this issue is the group of Matthias Driess at the Technische Universität Berlin, Germany. The cover image shows the unexpected rearrangement of the bis(N-heterocyclic carbene)borate chelating ligand induced by the “Kalium” (German for potassium) ion in toluene. This rearrangement affords a unique imidazolyl–NHC–borate potassium salt, which represents a new chelating bis(donor) ligand, allowing access to a novel hydridogermyliumylideneborate complex.
Co-reporter:Yun Xiong;Shenglai Yao;Tibor Szilvási
European Journal of Inorganic Chemistry 2015 Volume 2015( Issue 14) pp:
Publication Date(Web):
DOI:10.1002/ejic.201590053
Co-reporter:Dr. Arindam Indra;Dr. Prashanth W. Menezes ;Dr. Matthias Driess
ChemSusChem 2015 Volume 8( Issue 5) pp:776-785
Publication Date(Web):
DOI:10.1002/cssc.201402812
Abstract
Artificial photosynthesis by harvesting solar light into chemical energy could solve the problems of energy conversion and storage in a sustainable way. In nature, CO2 and H2O are transformed into carbohydrates by photosynthesis to store the solar energy in chemical bonds and water is oxidized to O2 in the oxygen-evolving center (OEC) of photosystem II (PS II). The OEC contains CaMn4O5 cluster in which the metals are interconnected through oxido bridges. Inspired by biological systems, manganese-oxide-based catalysts have been synthesized and explored for water oxidation. Structural, functional modeling, and design of the materials have prevailed over the years to achieve an effective and stable catalyst system for water oxidation. Structural flexibility with eg1 configuration of MnIII, mixed valency in manganese, and higher surface area are the main requirements to attain higher efficiency. This Minireview discusses the most recent progress in heterogeneous manganese-oxide-based catalysts for efficient chemical, photochemical, and electrochemical water oxidation as well as the structural requirements for the catalyst to perform actively.
Co-reporter:Dr. Shenglai Yao;M.Sc. Nils Lindenmaier;Dr. Yun Xiong;Dr. Shigeyoshi Inoue;Dr. Tibor Szilvási;Dipl.-Chem. Mario Adelhardt;Dr. Jörg Sutter;Dr. Karsten Meyer;Dr. Matthias Driess
Angewandte Chemie 2015 Volume 127( Issue 4) pp:1266-1270
Publication Date(Web):
DOI:10.1002/ange.201409469
Abstract
The unusual reactivity of the newly synthesized β-diketiminato cobalt(I) complexes, [(LDepCo)2] (2 a, LDep=CH[C(Me)N(2,6-Et2C6H3)]2) and [LDippCo⋅toluene] (2 b, LDipp=CH[CHN(2,6-iPr2C6H3)]2), toward white phosphorus was investigated, affording the first cobalt(I) complexes [(LDepCo)2(μ2:η4,η4-P4)] (3 a) and [(LDippCo)2(μ2:η4,η4-P4)] (3 b) bearing the neutral cyclo-P4 ligand with a rectangular-planar structure. The redox chemistry of 3 a and 3 b was studied by cyclic voltammetry and their chemical reduction with one molar equivalent of potassium graphite led to the isolation of [(LDepCo)2(μ2:η4,η4-P4)][K(dme)4] (4 a) and [(LDippCo)2(μ2:η4,η4-P4)][K(dme)4] (4 b). Unexpectedly, the monoanionic Co2P4 core in 4 a and 4 b, respectively, contains the two-electron-reduced cyclo-P42− ligand with a square-planar structure and mixed-valent cobalt(I,II) sites. The electronic structures of 3 a, 3 b, 4 a, and 4 b were elucidated by NMR and EPR spectroscopy as well as magnetic measurements and are in agreement with results of broken-symmetry DFT calculations.
Co-reporter:Gengwen Tan;Dr. Stephan Enthaler;Dr. Shigeyoshi Inoue;Dr. Burgert Blom ;Dr. Matthias Driess
Angewandte Chemie 2015 Volume 127( Issue 7) pp:2242-2246
Publication Date(Web):
DOI:10.1002/ange.201409739
Abstract
The NiII-mediated tautomerization of the N-heterocyclic hydrosilylcarbene L2Si(H)(CH2)NHC 1, where L2=CH(CCH2)(CMe)(NAr)2, Ar=2,6-iPr2C6H3; NHC=3,4,5-trimethylimidazol-2-yliden-6-yl, leads to the first N-heterocyclic silylene (NHSi)–carbene (NHC) chelate ligand in the dibromo nickel(II) complex [L1Si:(CH2)(NHC)NiBr2] 2 (L1=CH(MeCNAr)2). Reduction of 2 with KC8 in the presence of PMe3 as an auxiliary ligand afforded, depending on the reaction time, the N-heterocyclic silyl–NHC bromo NiII complex [L2Si(CH2)NHCNiBr(PMe3)] 3 and the unique Ni0 complex [η2(Si-H){L2Si(H)(CH2)NHC}Ni(PMe3)2] 4 featuring an agostic SiHNi bonding interaction. When 1,2-bis(dimethylphosphino)ethane (DMPE) was employed as an exogenous ligand, the first NHSi–NHC chelate-ligand-stabilized Ni0 complex [L1Si:(CH2)NHCNi(dmpe)] 5 could be isolated. Moreover, the dicarbonyl Ni0 complex 6, [L1Si:(CH2)NHCNi(CO)2], is easily accessible by the reduction of 2 with K(BHEt3) under a CO atmosphere. The complexes were spectroscopically and structurally characterized. Furthermore, complex 2 can serve as an efficient precatalyst for Kumada–Corriu-type cross-coupling reactions.
Co-reporter:Dr. Shenglai Yao;Dipl.-Chem. Florian Meier;M.Sc. Nils Lindenmaier;Dipl.-Chem. Robert Rudolph;Dr. Burgert Blom;Dipl.-Chem. Mario Adelhardt;Dr. Jörg Sutter;Dr. Stefan Mebs;Priv.-Doz.Dr. Michael Haumann;Dr. Karsten Meyer;Dr. Martin Kaupp;Dr. Matthias Driess
Angewandte Chemie 2015 Volume 127( Issue 42) pp:12686-12690
Publication Date(Web):
DOI:10.1002/ange.201506788
Abstract
Eine vollständige Serie von biomimetischen [2Fe-2S]-Clustern [(LDepFe)2(μ-S)2] (3, LDep=CH[CMeN(2,6-Et2C6H3)]2), [(LDepFe)2(μ-S)2K] (4), [(LDepFe)2(μ-S)2][Bu4N] (5, Bu=n-butyl) und [(LDepFe)2(μ-S)2K2] (6) wurde hergestellt und charakterisiert. Das homovalente [2Fe(3+/3+)-2S]-Cluster 3 ist durch die Reaktion von [(LDepFe)2(μ-H)2] 2 mit elementarem Schwefel zugänglich. Die chemische Reduktion von 3 mit einem Moläquivalent elementaren Kalium ergibt das Kontaktionenpaar K+[2Fe-2S]− (4) in Form eines eindimensionalen Koordinationspolymers, das sich wiederum mit [Bu4N]Cl zum separierten Ionenpaar [Bu4N]+[2Fe-2S]− (5) umsetzen lässt. Weitere Reduktion von 4 mit Kalium erlaubt den Zugang zum superreduzierten homovalenten [2Fe(2+/2+)-2S]-Cluster 6. Bemerkenswert hierbei ist, dass es sich bei den Komplexen 4 und 5 um [2Fe-2S]-Cluster mit einem jeweils stark delokalisierten Fe2+Fe3+-Paar handelt, was durch 57Fe-Mößbauer-, Röntgenabsorptions- und Röntgenemissionsspektroskopie (XAS, XES) in Übereinstimmung mit DFT-Rechnungen gesichert ist.
Co-reporter:Dipl.-Chem. Kerstin Hansen;Dr. Tibor Szilvási;Dr. Burgert Blom;Dr. Matthias Driess
Angewandte Chemie 2015 Volume 127( Issue 50) pp:15274-15277
Publication Date(Web):
DOI:10.1002/ange.201508149
Abstract
Die Reaktion des Arylchlorosilylen-NHC-Addukts ArSi(NHC)Cl (1; Ar=2,6-Trip2-C6H3, NHC=(MeC)2(NMe)2C) mit einem Moläquivalent LiPH2.dme (dme=1,2-Dimethoxyethan) liefert das erste 1,2-Dihydrophosphasilen-Addukt ArSi(NHC)(H)PH (2). Dieses Produkt ist in Lösung instabil und kann eine Kopf-Schwanz-Dimerisierung unter Bildung von [ArSi(H)-PH]2 (3) und “freiem” NHC eingehen. Weitere Stabilisierung von 2 mittels Komplexierung mit {W(CO)5} liefert den isolierbaren 1,2-Dihydrophosphasilen-Wolfram-Komplex [ArSi(NHC)(H)P(H)W(CO)5] (4). Zusätzlich konnte das 1-Silyl-2-hydrophosphasilen ArSi(NHC)(H)PSiMe3 (5) synthetisiert und strukturell charakterisiert werden. Dichtefunktionalrechnungen bestätigen, dass die SiP-Bindung in 2 und 4 hauptsächlich zwitterionisch ist, mit drastisch reduziertem Doppelbindungscharakter.
Co-reporter:Dr. Shenglai Yao;M.Sc. Nils Lindenmaier;Dr. Yun Xiong;Dr. Shigeyoshi Inoue;Dr. Tibor Szilvási;Dipl.-Chem. Mario Adelhardt;Dr. Jörg Sutter;Dr. Karsten Meyer;Dr. Matthias Driess
Angewandte Chemie International Edition 2015 Volume 54( Issue 4) pp:1250-1254
Publication Date(Web):
DOI:10.1002/anie.201409469
Abstract
The unusual reactivity of the newly synthesized β-diketiminato cobalt(I) complexes, [(LDepCo)2] (2 a, LDep=CH[C(Me)N(2,6-Et2C6H3)]2) and [LDippCo⋅toluene] (2 b, LDipp=CH[CHN(2,6-iPr2C6H3)]2), toward white phosphorus was investigated, affording the first cobalt(I) complexes [(LDepCo)2(μ2:η4,η4-P4)] (3 a) and [(LDippCo)2(μ2:η4,η4-P4)] (3 b) bearing the neutral cyclo-P4 ligand with a rectangular-planar structure. The redox chemistry of 3 a and 3 b was studied by cyclic voltammetry and their chemical reduction with one molar equivalent of potassium graphite led to the isolation of [(LDepCo)2(μ2:η4,η4-P4)][K(dme)4] (4 a) and [(LDippCo)2(μ2:η4,η4-P4)][K(dme)4] (4 b). Unexpectedly, the monoanionic Co2P4 core in 4 a and 4 b, respectively, contains the two-electron-reduced cyclo-P42− ligand with a square-planar structure and mixed-valent cobalt(I,II) sites. The electronic structures of 3 a, 3 b, 4 a, and 4 b were elucidated by NMR and EPR spectroscopy as well as magnetic measurements and are in agreement with results of broken-symmetry DFT calculations.
Co-reporter:Gengwen Tan;Dr. Stephan Enthaler;Dr. Shigeyoshi Inoue;Dr. Burgert Blom ;Dr. Matthias Driess
Angewandte Chemie International Edition 2015 Volume 54( Issue 7) pp:2214-2218
Publication Date(Web):
DOI:10.1002/anie.201409739
Abstract
The NiII-mediated tautomerization of the N-heterocyclic hydrosilylcarbene L2Si(H)(CH2)NHC 1, where L2=CH(CCH2)(CMe)(NAr)2, Ar=2,6-iPr2C6H3; NHC=3,4,5-trimethylimidazol-2-yliden-6-yl, leads to the first N-heterocyclic silylene (NHSi)–carbene (NHC) chelate ligand in the dibromo nickel(II) complex [L1Si:(CH2)(NHC)NiBr2] 2 (L1=CH(MeCNAr)2). Reduction of 2 with KC8 in the presence of PMe3 as an auxiliary ligand afforded, depending on the reaction time, the N-heterocyclic silyl–NHC bromo NiII complex [L2Si(CH2)NHCNiBr(PMe3)] 3 and the unique Ni0 complex [η2(Si-H){L2Si(H)(CH2)NHC}Ni(PMe3)2] 4 featuring an agostic SiHNi bonding interaction. When 1,2-bis(dimethylphosphino)ethane (DMPE) was employed as an exogenous ligand, the first NHSi–NHC chelate-ligand-stabilized Ni0 complex [L1Si:(CH2)NHCNi(dmpe)] 5 could be isolated. Moreover, the dicarbonyl Ni0 complex 6, [L1Si:(CH2)NHCNi(CO)2], is easily accessible by the reduction of 2 with K(BHEt3) under a CO atmosphere. The complexes were spectroscopically and structurally characterized. Furthermore, complex 2 can serve as an efficient precatalyst for Kumada–Corriu-type cross-coupling reactions.
Co-reporter:Dr. Shenglai Yao;Dipl.-Chem. Florian Meier;M.Sc. Nils Lindenmaier;Dipl.-Chem. Robert Rudolph;Dr. Burgert Blom;Dipl.-Chem. Mario Adelhardt;Dr. Jörg Sutter;Dr. Stefan Mebs;Priv.-Doz.Dr. Michael Haumann;Dr. Karsten Meyer;Dr. Martin Kaupp;Dr. Matthias Driess
Angewandte Chemie International Edition 2015 Volume 54( Issue 42) pp:12506-12510
Publication Date(Web):
DOI:10.1002/anie.201506788
Abstract
A complete series of biomimetic [2Fe-2S] clusters, [(LDepFe)2(μ-S)2] (3, LDep=CH[CMeN(2,6-Et2C6H3)]2), [(LDepFe)2(μ-S)2K] (4), [(LDepFe)2(μ-S)2][Bu4N] (5, Bu=n-butyl), and [(LDepFe)2(μ-S)2K2] (6), could be synthesized and characterized. The all-ferric [2Fe-2S] cluster 3 is readily accessible through the reaction of [(LDepFe)2(μ-H)2] (2) with elemental sulfur. The chemical reduction of 3 with one molar equivalent of elemental potassium affords the contact ion pair K+[2Fe-2S]− (4) as a one-dimensional coordination polymer, which in turn reacts with [Bu4N]Cl to afford the separate ion pair [Bu4N]+[2Fe-2S]− (5). Further reduction of 4 with potassium furnishes the super-reduced all-ferrous [2Fe-2S] cluster 6. Remarkably, complexes 4 and 5 are [2Fe-2S] clusters with extensively delocalized Fe2+Fe3+ pairs as evidenced by 57Fe Mössbauer, X-ray absorption and emission spectroscopy (XAS, XES) and in accordance with DFT calculations.
Co-reporter:Dipl.-Chem. Kerstin Hansen;Dr. Tibor Szilvási;Dr. Burgert Blom;Dr. Matthias Driess
Angewandte Chemie International Edition 2015 Volume 54( Issue 50) pp:15060-15063
Publication Date(Web):
DOI:10.1002/anie.201508149
Abstract
The reaction of the arylchlorosilylene–NHC adduct ArSi(NHC)Cl [Ar=2,6-Trip2-C6H3; NHC=(MeC)2(NMe)2C] 1 with one molar equiv of LiPH2.dme (dme=1,2-dimethoxyethane) affords the first 1,2-dihydrophosphasilene adduct 2 (ArSi(NHC)(H)PH). The latter is labile in solution and can undergo head-to-tail dimerization to give [ArSi(H)PH]2 3 and “free” NHC. Further stabilization of 2 by complexation with {W(CO)5} affords the isolable 1,2-dihydrophosphasilene–tungsten complex 4 [ArSi(NHC)(H)P(H)W(CO)5]. Additionally, the new 1-silyl-2-hydrophosphasilene ArSi(NHC)(H)PSiMe3 5 could be synthesized and structurally characterized. DFT studies confirmed that the SiP bond in 2 and 4 is mostly zwitterionic with drastically decreased double-bond character.
Co-reporter:Kerstin Hansen, Tibor Szilvási, Burgert Blom, and Matthias Driess
Organometallics 2015 Volume 34(Issue 24) pp:5703-5708
Publication Date(Web):December 10, 2015
DOI:10.1021/acs.organomet.5b00772
The first [M(CO)5] complexes (M = Cr, Mo, W) bearing a donor-stabilized “half-parent” phosphasilene, in which the lone pair of the phosphorus atom coordinates to a metal center, have been synthesized and fully characterized. The latter complexes 2a (M = Cr), 2b (M = Mo), and 2c (M = W) result from conversion of the “half-parent” phosphasilene-DMAP adduct 1, LSi(dmap)═PH (DMAP = 4-N,N-dimethylaminopyridine; L = CH[(C═CH2)CMe(NAr)2]; Ar = 2,6-iPr2C6H3), with [M(CO)5thf] in 65–72% yields. The somewhat unexpected reactivity of LSi(dmap)═(H)P:→W(CO)5 2c toward the strong Lewis acid tris(pentafluorophenyl)borane was investigated. Strikingly, the borane does not abstract the DMAP donor. Most notable, the NMR spectroscopic and structural features of 2a–c, in accord with results by density functional theory calculations, clearly indicate that the already low Si═P π-bond character in 1 is almost quenched through coordination of the [M(CO)5] group, suggesting that 2a–c rather represent push–pull donor→silylene→phosphinidene→metal [DMAP→Si(L):→P(H):→M(CO)5] than Si═P→M complexes.
Co-reporter:Kerstin Hansen;Dr. Tibor Szilvási;Dr. Burgert Blom;Dr. Elisabeth Irran;Dr. Matthias Driess
Chemistry - A European Journal 2015 Volume 21( Issue 52) pp:18930-18933
Publication Date(Web):
DOI:10.1002/chem.201504113
Abstract
Reaction of the arylchlorosilylene-NHC adduct ArSi(NHC)Cl [Ar=2,6-Trip2C6H3; NHC=(MeC)2(NMe)2C:] 1 with one molar equiv of lithium diphenylphosphanide affords the first stable NHC-stabilized acyclic phosphinosilylene adduct 2 (ArSi(NHC)PPh2), which could be structurally characterized. Compound 2, when reacted with one molar equiv selenium and sulfur, affords the silanechalcogenones 4 a and 4 b (ArSi(NHC)(E)PPh2, 4 a: E=Se, 4 b: E=S), respectively. Conversion of 2 with an excess of Se and S, through additional insertion of one chalcogen atom into the SiP bond, leads to 3 a and 3 b (ArSi(NHC)(E)-E-P(E)Ph2, 3 a: E=Se, 3 b: E=S), respectively. Additionally, the exposure of 2 to N2O or CO2 yielded the isolable NHC-stabilized silanone 4 c, Ar(NHC)(Ph2P)SiO.
Co-reporter:Dr. Prashanth W. Menezes;Dr. Arindam Indra;Dr. Nastaran Ranjbar Sahraie;Arno Bergmann;Dr. Peter Strasser;Dr. Matthias Driess
ChemSusChem 2015 Volume 8( Issue 1) pp:164-171
Publication Date(Web):
DOI:10.1002/cssc.201402699
Abstract
Recently, there has been much interest in the design and development of affordable and highly efficient oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) catalysts that can resolve the pivotal issues that concern solar fuels, fuel cells, and rechargeable metal-air batteries. Here we present the synthesis and application of porous CoMn2O4 and MnCo2O4 spinel microspheres as highly efficient multifunctional catalysts that unify the electrochemical OER with oxidant-driven and photocatalytic water oxidation as well as the ORR. The porous materials were prepared by the thermal degradation of the respective carbonate precursors at 400 °C. The as-prepared spinels display excellent performances in electrochemical OER for the cubic MnCo2O4 phase in comparison to the tetragonal CoMn2O4 material in an alkaline medium. Moreover, the oxidant-driven and photocatalytic water oxidations were performed and they exhibited a similar trend in activity to that of the electrochemical OER. Remarkably, the situation is reversed in ORR catalysis, that is, the oxygen reduction activity and stability of the tetragonal CoMn2O4 catalyst outperformed that of cubic MnCo2O4 and rivals that of benchmark Pt catalysts. The superior catalytic performance and the remarkable stability of the unifying materials are attributed to their unique porous and robust microspherical morphology and the intrinsic structural features of the spinels. Moreover, the facile access to these high-performance materials enables a reliable and cost-effective production on a large scale for industrial applications.
Co-reporter:Leora Shapiro; Matthias Driess; David Avnir
ChemCatChem 2015 Volume 7( Issue 14) pp:2033-2037
Publication Date(Web):
DOI:10.1002/cctc.201500240
Abstract
The extraction of the two competing reactions from the same catalyst—a composite catalytic-complex@catalytic-metal—is reported. A Wilkinson rhodium based catalyst entrapped within metallic palladium catalyst is shown to perform both hydroformylation and hydrogenation with a ratio that depends on H2 and CO pressures. Here we demonstrate this special reactivity in a one-pot, four step sequence, which include hydroformylations of phenyl acetylenes, reduction of nitrobenzene to aniline, carbonyl-amine condensations forming imines; and imine reductions.
Co-reporter:Dr. Yun Xiong;Dr. Shenglai Yao;Dr. Robert Müller;Dr. Martin Kaupp;Dr. Matthias Driess
Angewandte Chemie International Edition 2015 Volume 54( Issue 35) pp:10254-10257
Publication Date(Web):
DOI:10.1002/anie.201504489
Abstract
The synthesis and characterization of the first bis-N-heterocyclic carbene stabilized monomeric silicon disulfide (bis-NHC)SiS2 2 (bis-NHC=H2C[{NC(H)C(H)N(Dipp)}C:]2, Dipp=2,6-iPr2C6H3) is reported. Compound 2 is prepared in 89 % yield from the reaction of the zero-valent silicon complex (′silylone′) 1 [(bis-NHC)Si] with elemental sulfur. Compound 2 can react with GaCl3 in acetonitrile to give the corresponding (bis-NHC)Si(S)SGaCl3 Lewis acid–base adduct 3 in 91 % yield. Compound 3 is also accessible through the reaction of the unprecedented silylone-GaCl3 adduct [(bis-NHC)SiGaCl3] 4 with elemental sulfur. Compounds 2, 3, and 4 could be isolated and characterized by elemental analyses, HR-MS, IR, 13C- and 29Si-NMR spectroscopy. The structures of 3 and 4 could be determined by single-crystal X-ray diffraction analyses. DFT-derived bonding analyses of 2 and 3 exhibited highly polar SiS bonds with moderate pπ–pπ bonding character.
Co-reporter:Dr. Yun Xiong;Dr. Shenglai Yao;Dr. Robert Müller;Dr. Martin Kaupp;Dr. Matthias Driess
Angewandte Chemie 2015 Volume 127( Issue 35) pp:10392-10395
Publication Date(Web):
DOI:10.1002/ange.201504489
Abstract
The synthesis and characterization of the first bis-N-heterocyclic carbene stabilized monomeric silicon disulfide (bis-NHC)SiS2 2 (bis-NHC=H2C[{NC(H)C(H)N(Dipp)}C:]2, Dipp=2,6-iPr2C6H3) is reported. Compound 2 is prepared in 89 % yield from the reaction of the zero-valent silicon complex (′silylone′) 1 [(bis-NHC)Si] with elemental sulfur. Compound 2 can react with GaCl3 in acetonitrile to give the corresponding (bis-NHC)Si(S)SGaCl3 Lewis acid–base adduct 3 in 91 % yield. Compound 3 is also accessible through the reaction of the unprecedented silylone-GaCl3 adduct [(bis-NHC)SiGaCl3] 4 with elemental sulfur. Compounds 2, 3, and 4 could be isolated and characterized by elemental analyses, HR-MS, IR, 13C- and 29Si-NMR spectroscopy. The structures of 3 and 4 could be determined by single-crystal X-ray diffraction analyses. DFT-derived bonding analyses of 2 and 3 exhibited highly polar SiS bonds with moderate pπ–pπ bonding character.
Co-reporter:Arindam Indra, Prashanth W. Menezes, Felix Schuster, Matthias Driess
Journal of Photochemistry and Photobiology B: Biology 2015 Volume 152(Part A) pp:156-161
Publication Date(Web):November 2015
DOI:10.1016/j.jphotobiol.2014.11.012
•Chemical and photochemical water oxidation with manganese oxide.•Stepwise oxidation of low valent manganese monooxide to active catalyst.•Efficient water oxidation with higher amount of MnIII species.•Degeneracy in eg orbital facilitates structural flexibility in manganese oxide.Development of efficient bio-inspired water oxidation system with transition metal oxide catalyst has been considered as the one of the most challenging task in the recent years. As the oxygen evolving center of photosystem II consists of Mn4CaO5 cluster, most of the water oxidation study was converged to build up manganese oxide based catalysts. Here we report the synthesis of efficient artificial water oxidation catalysts by transferring the inactive manganese monooxide (MnO) under highly oxidizing conditions with ceric ammonium nitrate (CAN) and ozone (O3). MnO was partially oxidized to form mixed-valent manganese oxide (MnOx) with CAN whereas completely oxidized to mineral phase of ε-MnO2 (Akhtenskite) upon treatment of O3 in acidic solution, which we explore first time as a water oxidation catalyst. Chemical water oxidation, as well as the photochemical water oxidation in the presence of sacrificial electron acceptor and photosensitizer with the presented catalysts were carried out that followed the trends: MnOx > MnO2 > MnO. Structural and activity correlation reveals that the presence of larger extent of Mn(III) in MnOx is the responsible factor for higher activity compared to MnO2. Mn(III) species in octahedral system with eg1 configuration furnishes and facilitates the Mn–O and Mn–Mn bond enlargement with required structural flexibility and disorder in the manganese oxide structure which indeed facilitates water oxidation.
Co-reporter:Gengwen Tan ; Tibor Szilvási ; Shigeyoshi Inoue ; Burgert Blom
Journal of the American Chemical Society 2014 Volume 136(Issue 27) pp:9732-9742
Publication Date(Web):June 18, 2014
DOI:10.1021/ja504448v
The reaction of AlBr3 with 1 molar equiv of the chelating bis(N-heterocyclic carbene) ligand bis(N-Dipp-imidazole-2-ylidene)methylene (bisNHC, 1) affords [(bisNHC)AlBr2]+Br– (2) as an ion pair in high yield, representing the first example of a bisNHC–Al(III) complex. Debromination of the latter with 1 molar equiv of K2Fe(CO)4 in tetrahydrofuran (THF) furnishes smoothly, in a redox reaction, the (bisNHC)(Br)Al[Fe(CO)4] complex 3, in which the Al(I) center is stabilized by the Fe(CO)4 moiety through Al(I):→Fe(0) coordination. Strikingly, the Br/H ligand exchange reactions of 3 using potassium hydride as a hydride source in THF or tetrahydropyran (THP) do not yield the anticipated hydridoaluminum(I) complex (bisNHC)Al(H)[Fe(CO)4] (4a) but instead lead to (bisNHC)Al(2-cyclo-OC4H7)[Fe(CO)4] (4) and (bisNHC)Al(2-cyclo-OC5H9)[Fe(CO)4] (5), respectively. The latter are generated via C–H bond activation at the α-carbon positions of THF and THP, respectively, in good yields with concomitant elimination of dihydrogen. This is the first example whereby a low-valent main-group hydrido complex facilitates metalation of sp3 C–H bonds. Interestingly, when K[BHR3] (R = Et, sBu) is employed as a hydride source to react with 3 in THF, the reaction affords (bisNHC)Al(OnBu)[Fe(CO)4] (6) as the sole product through C–O bond activation and ring opening of THF. The mechanisms for these novel C–H and C–O bond activations mediated by the elusive hydridoaluminum(I) complex 4a were elucidated by density functional theory (DFT) calculations. In contrast, the analogous hydridogallium(I) complex (bisNHC)Ga(H)[Fe(CO)4] (9) can be obtained directly in high yield by the reaction of the (bisNHC)Ga(Cl)[Fe(CO)4] precursor 8 with 1 molar equiv of K[BHR3] (R = Et, sBu) in THF at room temperature. The isolation of 9 and its inertness toward cyclic ethers might be attributed to the higher electronegativity of gallium versus aluminum. The stronger Ga(I)–H bond, in turn, hampers α-C–H metalation or C–O bond cleavage in cyclic ethers, the latter of which is supported by DFT calculations.
Co-reporter:Yun Xiong ; Tibor Szilvási ; Shenglai Yao ; Gengwen Tan
Journal of the American Chemical Society 2014 Volume 136(Issue 32) pp:11300-11303
Publication Date(Web):July 29, 2014
DOI:10.1021/ja506824s
Employing the potassium salt of the monoanionic bis(NHC)borate 1 (NHC = N-Heterocyclic Carbene) enables the synthesis and isolation of the bis(NHC)borate-stabilized chlorogermyliumylidene precursor 2 in 61% yield. A Cl/H exchange reaction of 2 using potassium trisec.-butylborhydride as a hydride source leads to the isolation of the first germyliumylidene hydride [HGe:+] complex 3 in 91% yield. The Ge(II)–H bond in the latter compound has an unexpected reactivity as shown by the reaction with the potential hydride scavenger [Ph3C]+[B(C6F5)4]−, furnishing the corresponding HGe: → CPh3 cation in the ion pair 4 as initial product. Compound 4 liberates HCPh3 in the presence of 3 to give the unusual dinuclear HGe: → Ge: cation in 5. The latter represents the first three-coordinate dicationic Ge(II) species stabilized by an anionic bis(NHC) chelate ligand and a Ge(II) donor. All novel compounds were fully characterized, including X-ray diffraction analyses.
Co-reporter:Kerstin Hansen ; Tibor Szilvási ; Burgert Blom
Journal of the American Chemical Society 2014 Volume 136(Issue 40) pp:14207-14214
Publication Date(Web):September 16, 2014
DOI:10.1021/ja507785z
The reaction of LSiBr(NH2) (4) (L = CH[(C═CH2)CMe(NAr)2]; Ar = 2,6-iPr2C6H3) with lithium bis(trimethylsilyl)amide in the presence of pyridine or 4-dimethylaminopyridine (DMAP) resulted in the activation of the α C–H bond of pyridine or DMAP, affording the products LSi(dmap)NH2 (6) and LSi(pyridine)NH2 (7a), respectively. Remarkably, this metal-free aromatic C–H activation occurs at room temperature. The emerging aminosilanes were isolated and fully characterized. Isotope labeling experiments and detailed DFT calculations, elucidating the reaction mechanism, were performed and provide compelling evidence of the formation of the “half-parent” iminosilane 1, LSi═NH, which facilitates this transformation due to its amplified ylidic character by the chelate ligand L. Furthermore, the elusive iminosilane 1 could be trapped by benzophenone and trimethylsilylazide affording the corresponding products, 8 and 9, respectively, thereby confirming its formation as a key intermediate.
Co-reporter:Arindam Indra ; Prashanth W. Menezes ; Nastaran Ranjbar Sahraie ; Arno Bergmann ; Chittaranjan Das ; Massimo Tallarida ; Dieter Schmeißer ; Peter Strasser
Journal of the American Chemical Society 2014 Volume 136(Issue 50) pp:17530-17536
Publication Date(Web):November 21, 2014
DOI:10.1021/ja509348t
Catalytic water splitting to hydrogen and oxygen is considered as one of the convenient routes for the sustainable energy conversion. Bifunctional catalysts for the electrocatalytic oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are pivotal for the energy conversion and storage, and alternatively, the photochemical water oxidation in biomimetic fashion is also considered as the most useful way to convert solar energy into chemical energy. Here we present a facile solvothermal route to control the synthesis of amorphous and crystalline cobalt iron oxides by controlling the crystallinity of the materials with changing solvent and reaction time and further utilize these materials as multifunctional catalysts for the unification of photochemical and electrochemical water oxidation as well as for the oxygen reduction reaction. Notably, the amorphous cobalt iron oxide produces superior catalytic activity over the crystalline one under photochemical and electrochemical water oxidation and oxygen reduction conditions.
Co-reporter:Yun Xiong, Shenglai Yao and Matthias Driess
Chemical Communications 2014 vol. 50(Issue 4) pp:418-420
Publication Date(Web):01 Nov 2013
DOI:10.1039/C3CC48166B
Starting from the chlorogermyliumylidene chloride salt [L(Cl)Ge:]Cl (1) (L = 1,1′-methylene-3,3′-di-2,6-diisopropyl-phenylimidazole-2,2′-diylidene), the chloride ion can be easily substituted by BPh4 to yield [L(Cl)Ge:]BPh4 (3). Reaction of the latter with NaN3 furnishes [L(N3)Ge:]BPh4 (4). In contrast, the direct reaction of 1 with NaN3 affords exclusively the first azidogermyliumylidene azide salt [L(N3)Ge:]N3 (2). The latter represents the first isolable diazido Ge(II) complex with a covalently bonded azido ligand and a weakly coordinating azide anion as the counterion. All new compounds 2, 3, and 4 were fully characterized, including using X-ray diffraction analysis.
Co-reporter:Gengwen Tan, Wenyuan Wang, Burgert Blom and Matthias Driess
Dalton Transactions 2014 vol. 43(Issue 16) pp:6006-6011
Publication Date(Web):06 Jan 2014
DOI:10.1039/C3DT53321B
The labile germylene hydride LCyGeH is capable of activating CO2 affording the corresponding formate LCyGeOCH(O) (2) (LCy = cyclo-C6H8-1-NAr-2-C(Ph)NAr, Ar = 2,6-iPr2C6H3). Compound 2 and the previously reported LGeOCH(O) (L = CH(MeCNAr)2, Ar = 2,6-iPr2C6H3) (2′) could be further converted to methanol with the AlH3·NMe3 alane-amine adduct as a hydrogen source upon workup with water. A plausible mechanism for the conversion of the formate complexes to methanol is proposed based on additional results from the conversion of 2′ with the milder hydride delivery agent LAlH2.
Co-reporter:Dr. Arindam Indra;Dr. Mark Greiner;Dr. Axel Knop Gericke;Dr. Robert Schlögl;Dr. David Avnir;Dr. Matthias Driess
ChemCatChem 2014 Volume 6( Issue 7) pp:1935-1939
Publication Date(Web):
DOI:10.1002/cctc.201402042
Abstract
The immobilization of a water-soluble rhenium complex in metallic silver matrices has resulted in a highly efficient catalyst for epoxidation, which has better epoxidation catalytic activity than the individual components. This unprecedented synergism could be obtained only by using the novel immobilization methodology, and not by using the standard adsorption process. The composite catalyst has been fully characterized (by using XRD, TEM, SEM, energy-dispersive X-ray spectroscopy, and atomic X-ray mapping), and the synergism has originated as a result of the proximity of the two components. Photoemission spectroscopic studies confirm the presence of +6 and +7 oxidation states of rhenium in metallic silver in the active catalyst.
Co-reporter:Kerstin Hansen;Tibor Szilvási;Dr. Burgert Blom;Dr. Elisabeth Irran;Dr. Matthias Driess
Chemistry - A European Journal 2014 Volume 20( Issue 7) pp:1947-1956
Publication Date(Web):
DOI:10.1002/chem.201303906
Abstract
The stabilization of the labile, zwitterionic “half-parent” phosphasilene 4 L′SiPH (L′=CH[(CCH2)CMe(NAr)2]; Ar=2,6-iPr2C6H3) could now be accomplished by coordination with two different donor ligands (4-dimethylaminopyridine (DMAP) and 1,3,4,5-tetramethylimidazol-2-ylidene), affording the adducts 8 and 9, respectively. The DMAP-stabilized zwitterionic “half-parent” phosphasilene 8 is capable of transferring the elusive parent phosphinidene moiety (:PH) to an unsaturated organic substrate, in analogy to the “free” phosphasilene 4. Furthermore, compounds 4 and 8 show an unusual reactivity of the SiP moiety towards small molecules. They are capable of adding dimethylzinc and of activating the SH bonds in H2S and the NH bonds in ammonia and several organoamines. Interestingly, the DMAP donor ligand of 8 has the propensity to act as a leaving group at the phosphasilene during the reaction. Accordingly, treatment of 8 with H2S affords, under liberation of DMAP, the unprecedented thiosilanoic phosphane LSiS(PH2) 16 (L=HC(CMe[2,6-iPr2C6H3N])2). Compounds 4 and 8 react with ammonia both affording L′Si(NH2)PH2 17, respectively. In addition, the reaction of 8 with isoproylamine, p-toluidine, and pentafluorophenylhydrazine lead to the corresponding phosphanylsilanes L′Si(PH2)NHR (R=iPr 18 a; R=C6H5CH3 18 b, R=NH(C6F5) 18 c), respectively.
Co-reporter:Dr. Prashanth W. Menezes;Dr. Arindam Indra;Patrick Littlewood;Dr. Michael Schwarze;Dr. Caren Göbel;Dr. Reinhard Schomäcker ;Dr. Matthias Driess
ChemSusChem 2014 Volume 7( Issue 8) pp:2202-2211
Publication Date(Web):
DOI:10.1002/cssc.201402169
Abstract
We present a facile synthesis of bioinspired manganese oxides for chemical and photocatalytic water oxidation, starting from a reliable and versatile manganese(II) oxalate single-source precursor (SSP) accessible through an inverse micellar molecular approach. Strikingly, thermal decomposition of the latter precursor in various environments (air, nitrogen, and vacuum) led to the three different mineral phases of bixbyite (Mn2O3), hausmannite (Mn3O4), and manganosite (MnO). Initial chemical water oxidation experiments using ceric ammonium nitrate (CAN) gave the maximum catalytic activity for Mn2O3 and MnO whereas Mn3O4 had a limited activity. The substantial increase in the catalytic activity of MnO in chemical water oxidation was demonstrated by the fact that a phase transformation occurs at the surface from nanocrystalline MnO into an amorphous MnOx (1<x<2) upon treatment with CAN, which acted as an oxidizing agent. Photocatalytic water oxidation in the presence of [Ru(bpy)3]2+ (bpy=2,2′-bipyridine) as a sensitizer and peroxodisulfate as an electron acceptor was carried out for all three manganese oxides including the newly formed amorphous MnOx. Both Mn2O3 and the amorphous MnOx exhibit tremendous enhancement in oxygen evolution during photocatalysis and are much higher in comparison to so far known bioinspired manganese oxides and calcium–manganese oxides. Also, for the first time, a new approach for the representation of activities of water oxidation catalysts has been proposed by determining the amount of accessible manganese centers.
Co-reporter:Gengwen Tan, Burgert Blom, Daniel Gallego, and Matthias Driess
Organometallics 2014 Volume 33(Issue 1) pp:363-369
Publication Date(Web):December 5, 2013
DOI:10.1021/om4011033
Reaction of the heteroleptic N-heterocyclic chlorosilylene L(Cl)Si: (1; L = PhC(NtBu)2) with [Cu(tmeda)(CH3CN)][OTf] (2; tmeda = N,N,N′,N′-tetramethylethylenediamine, OTf = OSO2CF3 (triflate)) affords the Cu(I) complex [L(Cl)Si:→Cu(tmeda)][OTf] (3) in high yield as the first example of a heteroleptic N-heterocyclic silylene copper complex. Similarly, the reaction of L(OtBu)Si: (4; L = PhC(NtBu)2) with 2 affords [L(OtBu)Si: → Cu(tmeda)][OTf] (5) and that of L(NMe2)Si: (6) with 2 leads to [L(NMe2)Si:→Cu(tmeda)][OTf] (7). Complex 3 shows a rather strong interaction in the solid state between the O atom of the triflate anion and the three-coordinate Cu(I) center with a Cu···O distance of 2.312 Å. In contrast, complex 7 features only a weak interaction (ca. 3.28 Å), while in complex 5 the cation and anion are fully separated. Strikingly, the reaction of the chelating oxo-bridged silylene :Si(L)(μ2-O)(L)Si: (8) with the copper source [Cu(CH3CN)4][OTf] (9) affords the dinuclear complex salt [Cu2{η1:η1-LSi(μ2-O)SiL}2][OTf]2 (10), featuring a novel metallacyclooctane dication, selectively in a good yield. Complex 10 also exhibits a very strong interaction between the copper centers in the dication and the oxygen atoms of triflate anions in the solid state, evidenced by a Cu···O separation of only 2.141 Å. All complexes were fully characterized.
Co-reporter:Burgert Blom, Markus Pohl, Gengwen Tan, Daniel Gallego, and Matthias Driess
Organometallics 2014 Volume 33(Issue 19) pp:5272-5282
Publication Date(Web):September 19, 2014
DOI:10.1021/om5005918
Starting from the unsymmetric N,N′-substituted thiourea compounds (R)N(H)C(═S)N(H)(tBu) (1, R = Dipp: 2,6-iPr2-C6H3; 2, R = 1-adamantyl), the corresponding asymmetric carbodiimines (R)N═C═N(tBu) (3, R = Dipp; 4, R = 1-adamantyl) are readily accessible in high yields upon reduction with LiHMDS (Li[N(SiMe3)2]). The reaction of compound 3 with PhLi followed by SiCl4 afforded, in a one-pot reaction, the asymmetric benzamidinato-stabilized trichlorosilane [PhC{(NtBu)(NDipp)}]SiCl3 (5). Similarly, silanes [PhC{(NtBu)(NDipp)}]SiHCl2 (6), [(NMe2)C{(NtBu)(NDipp)}]SiHCl2 (7), and [PhC{(NtBu)(NAd)}]SiHCl2 (8) could also be isolated. All novel trichloro- or dichlorohydridosilanes were fully spectroscopically characterized and studied by single-crystal X-ray diffraction analyses, the latter revealing in all cases a distorted-trigonal bipyramidal five-coordinate silicon center. The reactions of silanes 5–8 with K2[Fe(CO)4] were also explored: In the case of the reaction of silane 5 with K2[Fe(CO)4], no reaction was observed even after prolonged heating. However, in the case of the silanes 6–8, the selective formation of the corresponding hydrido SiII:→Fe0 complexes [[R1C{(NtBu)(NR2)}](H)Si:→Fe(CO)4] (9, R1 = Ph, R2 = Dipp; 10, R1 = NMe2, R2 = Dipp; 11, R1 = Ph, R2 = 1-adamantyl) could be achieved. Complexes 9–11 represent unprecedented hydrido-N-heterocyclic silylene complexes, bearing asymmetric ligand backbones. Complexes 9–11 were fully spectroscopically characterized, and in addition the single-crystal X-ray structure analysis of compound 10 is reported.
Co-reporter:Robert Rudolph, Burgert Blom, Shenglai Yao, Florian Meier, Eckhard Bill, Maurice van Gastel, Nils Lindenmaier, Martin Kaupp, and Matthias Driess
Organometallics 2014 Volume 33(Issue 12) pp:3154-3162
Publication Date(Web):June 11, 2014
DOI:10.1021/om500381t
The first synthesis of a monoradical Ni(μ-S2)Fe core in the [(Nacnac)Ni(μ-S2)Fe(dmpe)2] complex 3 could be accomplished in good yields by PMe3 elimination from the zerovalent iron complex [(dmpe)2(PMe3)Fe] (2; dmpe =1,2-bis(dimethylphosphine)ethane) upon reaction with the supersulfido nickel(II) complex [(Nacnac)Ni(S2)] (1; Nacnac = CH{(CMe)(2,6-iPr2C6H3N)}2). Complex 3 bears Ni(II) and Fe(II) centers, both of which are in a low-spin state. A single electron is located in the HOMO and is somewhat delocalized over the Ni(μ-S2)Fe core, so that the bridging disulfur subunit exhibits some “subsulfide” S23– character. Compound 3 represents a bioinspired example of a monoradical with a Ni(μ-S2)Fe structural motif, reminiscent of the Ni(μ-S2)Fe core structure of the active site in [NiFe] hydrogenases. Its oxidation with [Fe(η5-C5H5)2][B(C6H3(CF3)2)4] affords the product [(Nacnac)Ni(μ-S)2Fe(dmpe)2][B(C6H3(CF3)2)4] (4), and complex 3 can alternatively be prepared via a reductive route upon reaction of [Co(η5-C5Me5)2][(Nacnac)NiS2] (6) with the Fe(0) precursor 2. All synthesized complexes were fully characterized, including in some cases single-crystal X-ray diffraction analysis, magnetometry, EPR, NMR, and 57Fe Mössbauer spectroscopy. DFT calculations were used to compute the spectroscopic parameters and to establish the electronic structure of 3 and its oxidized and reduced forms and related complexes.
Co-reporter:Daniel Gallego, Shigeyoshi Inoue, Burgert Blom, and Matthias Driess
Organometallics 2014 Volume 33(Issue 23) pp:6885-6897
Publication Date(Web):November 23, 2014
DOI:10.1021/om500966t
The first neutral bis(metallylene)pyridine pincer-type [ENE] ligands (E = SiII, GeII) were synthesized, and their coordination chemistry and reactivity toward iron was studied. First, the unprecedented four-coordinate complexes κ2E,E′-[ENE]FeCl2 were isolated. Unexpectedly and in contrast to other related pyridine-based pincer-type Fe(II) complexes, the N atom of pyridine is reluctant to coordinate to the Fe(II) site due to the enhanced σ-donor strength of the E atoms, which disfavors this coordination mode. Subsequent reduction of κ2Si,Si′-[SiNSi]FeCl2 with KC8 in the presence of PMe3 or direct reaction of the [ENE] ligands using Fe(PMe3)4 produced the highly electron-rich iron(0) complexes [ENE]Fe(PMe3)2. The reduction of the iron center substantially changes its coordination features, as shown by the results of a single-crystal X-ray diffraction analysis of [SiNSi]Fe(PMe3)2. The iron center, in the latter, exhibits a pseudosquare pyramidal (PSQP) coordination environment, with a coordinative (pyridine)N→Fe bond, and a trimethylphosphine ligand occupying the apical position. This geometry is very unusual for Fe(0) low-spin complexes, and variable-temperature 1H and 31P NMR spectra of the [ENE]Fe(PMe3)2 complexes revealed that they represent the first examples of configurationally stable PSQP-coordinated Fe(0) complexes: even after heating at 70 °C for >7 days, no changes are observed. The substitution reaction of [ENE]Fe(PMe3)2 with CO resulted in the isolation of [ENE]Fe(CO)2 and the hitherto unknown κ2E,E′-[ENE]Fe(CO)2L (L = CO, PMe3) complexes. All complexes were fully characterized (NMR, MS, XRD, IR, and 57Fe Mössbauer spectroscopy), showing the highest electron density on the iron center for pincer-type complexes reported to date. DFT calculations and 57Fe Mössbauer spectroscopy confirmed the innocent behavior of these ligands. Moreover, preliminary results showed that these complexes can serve as active precatalysts for the hydrosilylation of ketones.
Co-reporter:Johannes Pfrommer;Dr. Michael Lublow;Anahita Azarpira;Dr. Caren Göbel;Marcel Lücke;Dr. Alexer Steigert;Martin Pogrzeba;Dr. Prashanth W. Menezes;Dr. Anna Fischer;Dr. Thomas Schedel-Niedrig;Dr. Matthias Driess
Angewandte Chemie International Edition 2014 Volume 53( Issue 20) pp:5183-5187
Publication Date(Web):
DOI:10.1002/anie.201400243
Abstract
In regard to earth-abundant cobalt water oxidation catalysts, very recent findings show the reorganization of the materials to amorphous active phases under catalytic conditions. To further understand this concept, a unique cobalt-substituted crystalline zinc oxide (Co:ZnO) precatalyst has been synthesized by low-temperature solvolysis of molecular heterobimetallic Co4−xZnxO4 (x=1–3) precursors in benzylamine. Its electrophoretic deposition onto fluorinated tin oxide electrodes leads after oxidative conditioning to an amorphous self-supported water-oxidation electrocatalyst, which was observed by HR-TEM on FIB lamellas of the EPD layers. The Co-rich hydroxide-oxidic electrocatalyst performs at very low overpotentials (512 mV at pH 7; 330 mV at pH 12), while chronoamperometry shows a stable catalytic current over several hours.
Co-reporter:Gengwen Tan;Dr. Burgert Blom;Daniel Gallego;Dr. Elisabeth Irran ;Dr. Matthias Driess
Chemistry - A European Journal 2014 Volume 20( Issue 30) pp:9400-9408
Publication Date(Web):
DOI:10.1002/chem.201402017
Abstract
The reduction of CO2 to CO with silyl-copper(I) complexes bearing various silyl groups has been investigated. The silyl-copper(I) complexes [LSi(X)Cu(IPr)] 2–5 (X=OtBu (2), OH (3), H (4), OC6F5 (5); L=CH{CCH2}(CMe)(NAr)2, IPr=(CHNAr)2C:, Ar=2,6-iPr2C6H3) bearing OtBu, OH, H, and OC6F5 as functional groups are readily accessible by the activation of the CuO and CuH bonds in (IPr)CuX with silylene LSi: (1). These complexes are not readily accessible by the commonly used transmetallation reaction, rendering this methodology rather unique and facile in synthesizing silicon-functionalized silyl-metal complexes. The functional groups at the silicon atoms in compounds 2–5 enable the silyl groups to feature different nucleophilicity, which affords different activities toward CO2 reduction to CO. The silyl moieties of complexes 2 and 3, containing electron-donating groups (i.e., OtBu and OH) at the silicon centers, are more nucleophilic than that of compound 4 and 5, bearing a hydride and the electron-withdrawing group OC6F5 at the silicon centers, respectively. Consistent with this observation, compounds 2 and 3 show higher activity in CO2 reduction to CO compared to compounds 4 and 5, and the latter cases are zero-order reactions with respect to 4 and 5 (4: k=7.8×10−6 mol L−1 s−1; 5: 2.7×10−8 mol L−1 s−1). This suggests that the more nucleophilic the silyl moiety in a silyl-copper(I) complex is, the higher is the efficiency in CO2 reduction to CO. In addition, the siloxyl-copper(I) complexes [LSi(X)OCu(IPr)] 6–9 [X=OtBu (6), OH (7), H (8), OC6F5 (9)] were isolated as the products from the corresponding reduction reactions. Complexes 2–4 and 6–8 were characterized by spectroscopic and structural means.
Co-reporter:Burgert Blom ; Gengwen Tan ; Stephan Enthaler ; Shigeyoshi Inoue ; Jan Dirk Epping
Journal of the American Chemical Society 2013 Volume 135(Issue 48) pp:18108-18120
Publication Date(Web):November 7, 2013
DOI:10.1021/ja410234x
Reaction of FeCl2 with the chelating bis-N-heterocyclic carbene (NHC) bis-(N-Dipp-imidazole-2-ylidene)methylene (abbreviated {(DippC:)2CH2}) (Dipp = 2,6-di-isopropylphenyl) affords the complex [FeCl2{(DippC:)2CH2}] (1) in high yield. Reduction of complex 1 with excess KC8 with a 10-fold molar excess of PMe3 affords the Fe(II) complex [FeH{(DippC:)2CH2}(PMe3)(η2-PMe2CH2)] (2) as a mixture of three stereoisomers. Complex 2, the first example of any iron(II) complex bearing mutually an NHC and PMe3 ligand, is likely obtained from the in situ, reductively generated 16 VE Fe(0) complex, [Fe{(DippC:)2CH2}(PMe3)2] (2′), following intramolecular C–H activation of one of the phosphorus-bound CH3 groups. Complex 2 is unstable in aromatic solvents and forms, via a novel synthetic transformation involving intramolecular reductive elimination and concomitant PMe3 elimination, the Fe (0) arene complex [Fe{(DippC:)2CH2}(η6-C6D6)] (4-d6) in C6D6. Complex 4-d6 represents the first example of an NHC stabilized iron (0) arene complex. The transformation from 2 to 4-d6 can be accelerated at higher temperature and at 60 °C forms immediately. Alternatively, the reduction of 1 in the presence of toluene or benzene affords the complexes [Fe{(DippC:)2CH2}(η6-C7H8)] (3) and [Fe{(DippC:)2CH2}(η6-C6H6)] (4), selectively and in good yields. DFT calculations characterizing the bonding situation in 3 and 4 reveal similar energies of the HOMO and LUMO orbitals, with the LUMO orbital of both complexes located on the Dipp rings of the bis-NHC. The HOMO orbital reflects a π-back-bonding interaction between the Fe(0) center and the chelating NHC ligand, while the HOMO-1 is associated with the arene interaction with the Fe(0) site. The calculations do not suggest any noninnocence of the coordinated arene in either complex. Moreover, the 57Fe Mössbauer spectrum of 4 at 80K exhibits parameters (δ = 0.43 mm·s–1; ΔEQ = 1.37 mm·s–1) which are consistent with a five-coordinate Fe(0) system, rendering 3 and 4 the first examples of well-defined authentic Fe(0)-η6-arene complexes of the type [Fe(η6-arene)L2] (L = η1 or 2 neutral ligand, mono or bidentate). Some reactivitiy studies of 3 are also reported: The reaction of 3 with excess CO selectively yields the five-coordinate piano-stool complex [Fe{(DippC:)2CH2}(CO)3] (6) in near quantitative yields, while the reaction of complex 3 with C6D6 under heating affords by toluene elimination 4-d6. The catalytic ability of 4 was also investigated with respect to amide reduction to amines, for a variety of substrates using Ph2SiH2 as a hydride source. In all cases good to excellent yields to the corresponding amines were obtained. The use of 4 as a precatalyst represents the first example of a well-defined Fe(0) complex to effect this catalytic process.
Co-reporter:Yun Xiong ; Shenglai Yao ; Gengwen Tan ; Shigeyoshi Inoue
Journal of the American Chemical Society 2013 Volume 135(Issue 13) pp:5004-5007
Publication Date(Web):March 21, 2013
DOI:10.1021/ja402477w
By employing the chelate dicarbene 1, the new chlorogermyliumylidene complex 2 could be synthesized and isolated in 95% yield. Dechlorination of 2 with sodium naphthalenide furnishes the unique cyclic germadicarbene 3 which could be isolated in 45% yield. Compound 3 is the first isolable Ge(0) complex with a single germanium atom stabilized by a dicarbene. Its molecular structure is in accordance with DFT calculations which underline the peculiar electronic structure of 3 with two lone pairs of electrons at the Ge atom.
Co-reporter:Burgert Blom ; Stephan Enthaler ; Shigeyoshi Inoue ; Elisabeth Irran
Journal of the American Chemical Society 2013 Volume 135(Issue 17) pp:6703-6713
Publication Date(Web):April 9, 2013
DOI:10.1021/ja402480v
The first electron-rich N-heterocyclic silylene (NHSi)–iron(0) complexes are reported. The synthesis of the starting complex is accomplished by reaction of the electron-rich Fe0 precursor [(dmpe)2Fe(PMe3)] 1 (dmpe =1,2-bis(dimethylphosphino)ethane) with the N-heterocyclic chlorosilylene LSiCl (L = PhC(NtBu)2) 2 to give, via Me3P elimination, the corresponding iron complex [(dmpe)2Fe(←:Si(Cl)L)] 3. Reaction of in situ generated 3 with MeLi afforded [(dmpe)2Fe(←:Si(Me)L)] 4 under salt metathesis reaction, while its reaction with Li[BHEt3] yielded [(dmpe)2Fe(←:Si(H)L)] 5, a rare example of an isolable SiII hydride complex and the first such example for iron. All complexes were fully characterized by spectroscopic means and by single-crystal X-ray diffraction analyses. DFT calculations further characterizing the bonding situation between the SiII and Fe0 centers were also carried out, whereby multiple bonding character is detected in all cases (Wiberg Bond Index >1). For the first time, the catalytic activity of a SiII hydride complex was investigated. Complex 5 was used as a precatalyst for the hydrosilylation of a variety of ketones in the presence of (EtO)3SiH as a hydridosilane source. In most cases excellent conversions to the corresponding alcohols were obtained after workup. The reaction pathway presumably involves a ketone-assisted 1,2-hydride transfer from the SiII to Fe0 center, as a key elementary step, resulting in a betaine-like silyliumylidene intermediate. The appearance of the latter intermediate is supported by DFT calculations, and a mechanistic proposal for the catalytic process is presented.
Co-reporter:Kerstin Hansen ; Tibor Szilvási ; Burgert Blom ; Shigeyoshi Inoue ; Jan Epping
Journal of the American Chemical Society 2013 Volume 135(Issue 32) pp:11795-11798
Publication Date(Web):July 29, 2013
DOI:10.1021/ja4072699
The simplest parent phosphinidene, :PH (1), has been observed only in the gas phase or low temperature matrices and has escaped rigorous characterization because of its high reactivity. Its liberation and transfer to an unsaturated organic molecule in solution has now been accomplished by taking advantage of the facile homolytic bond cleavage of the fragile Si═P bond of the first zwitterionic phosphasilene LSi=PH (8) (L = CH[(C═CH2)CMe(NAr)2]; Ar = 2,6-iPr2C6H3). The latter bears two highly localized lone pairs on the phosphorus atom due to the LSi═PH ↔ LSi+–PH– resonance structures. Strikingly, the dissociation of 8 in hydrocarbon solutions occurs even at room temperature, affording the N-heterocyclic silylene LSi: (9) and 1, which leads to oligomeric [PH]n clusters in the absence of a trapping agent. However, in the presence of an N-heterocyclic carbene as an unsaturated organic substrate, the fragile phosphasilene 8 acts as a :PH transfer reagent, resulting in the formation of silylene 9 and phosphaalkene 11 bearing a terminal PH moiety.
Co-reporter:Daniel Gallego ; Andreas Brück ; Elisabeth Irran ; Florian Meier ; Martin Kaupp ; Matthias Driess ;John F. Hartwig
Journal of the American Chemical Society 2013 Volume 135(Issue 41) pp:15617-15626
Publication Date(Web):September 20, 2013
DOI:10.1021/ja408137t
The first [ECE]Ni(II) pincer complexes with E = SiII and E = GeII metallylene donor arms were synthesized via C–X (X = H, Br) oxidative addition, starting from the corresponding [EC(X)E] ligands. These novel complexes were fully characterized (NMR, MS, and XRD) and used as catalyst for Ni-catalyzed Sonogashira reactions. These catalysts allowed detailed information on the elementary steps of this catalytic reaction (transmetalation → oxidative addition → reductive elimination), resulting in the isolation and characterization of an unexpected intermediate in the transmetalation step. This complex, {[ECE]Ni acetylide → CuBr} contains both nickel and copper, with the copper bound to the alkyne π-system. Consistent with these unusual structural features, DFT calculations of the {[ECE]Ni acetylide → CuBr} intermediates revealed an unusual E–Cu–Ni three-center–two-electron bonding scheme. The results reveal a general reaction mechanism for the Ni-based Sonogashira coupling and broaden the application of metallylenes as strong σ-donor ligands for catalytic transformations.
Co-reporter:Gengwen Tan, Yun Xiong, Shigeyoshi Inoue, Stephan Enthaler, Burgert Blom, Jan D. Epping and Matthias Driess
Chemical Communications 2013 vol. 49(Issue 49) pp:5595-5597
Publication Date(Web):01 May 2013
DOI:10.1039/C3CC41965G
The facile synthesis of the first stable selenosilanoic acid–base adduct LSi(Se)OH(dmap) 3 (L = CH[C(Me)NAr]2, Ar = 2,6-iPr2C6H3, dmap = 4-dimethylaminopyridine), the heavier analogue of the thiosilanoic acid adduct LSi(S)OH(dmap) 1, is reported. Both adducts 1 and 3 react readily with MesCu (Mes = 2,4,6-trimethylphenyl) to form the novel dimeric Cu(I) complexes [LSi(E)OCu]2 (4: E = S; 5: E = Se) with unprecedented intermolecular SiE → Cu–O–Si coordination modes. The latter are efficient pre-catalysts for the Cu(I)-mediated aziridination of styrene with PhIN(Ts) (Ts = tosyl).
Co-reporter:Dr. Burgert Blom;Miriam Stoelzel ; Matthias Driess
Chemistry - A European Journal 2013 Volume 19( Issue 1) pp:40-62
Publication Date(Web):
DOI:10.1002/chem.201203072
Abstract
This account is a review on the synthesis and transition-metal coordination chemistry of N-heterocyclic silylenes (NHSi’s) over the last 20 years till the present time (2012). Recently, fascinating and novel synthetic methods have been developed to access transition-metal–NHSi complexes as an emerging class of compounds with a wealth of intriguing reactivity patterns. The striking influence of coordinating NHSi’s to transition-metal complex fragments affording different reactivities to the “free” NHSi is a connecting theme (“leitmotif”) throughout the review, and highlights the potential of these compounds which lie at the interface of contemporary main-group and classical organometallic chemistry towards new molecular catalysts for small-molecule activation.
Co-reporter:Dr. Arindam Indra;Dr. Prashanth W. Menezes;Dr. Ivelina Zaharieva;Elham Baktash;Johannes Pfrommer;Dr. Michael Schwarze;Dr. Holger Dau;Dr. Matthias Driess
Angewandte Chemie International Edition 2013 Volume 52( Issue 50) pp:13206-13210
Publication Date(Web):
DOI:10.1002/anie.201307543
Co-reporter:Marianna Tsaroucha;Dr. Yilmaz Aksu;Dr. Jan Dirk Epping;Dr. Matthias Driess
ChemPlusChem 2013 Volume 78( Issue 1) pp:62-69
Publication Date(Web):
DOI:10.1002/cplu.201200259
Abstract
Stannyl-substituted [(RZn)4(OR′)4] cubanes with different tin-containing alkoxy groups [Ph3SnOZnMe] (1), [Ph3SnOZnEt] (2), [Me3SnOZntBu] (3), and [Ph3SnOZntBu] (4) are easily accessible by Brønsted acid–base reaction of the corresponding triorganotin hydroxides with ZnMe2, ZnEt2, and Zn(tBu)2, respectively. All new compounds 1–4 were characterized by various spectroscopic methods and the structures of 1 and 3 were confirmed by single-crystal X-ray diffraction analysis. The thermal degradation of the precursors 1–4 under dry synthetic air (20 % O2, 80 %N2) was studied and the final oxide materials were characterized by employing powder X-ray diffraction (PXRD) analysis, inductively coupled plasma-optical emission spectrometry (ICP-OES), transmission and scanning electron microscopy (SEM and TEM), energy dispersive X-ray spectroscopy (EDX), and atomic force microscopy (AFM). Remarkably, compounds 1 and 2 proved to be suitable as single-source precursors (SSPs) for the efficient preparation of tin-doped ZnO nanoparticles with tunable tin concentrations as a promising system for steering and improving the optoelectronic properties of tin-doped ZnO. Using 3 as SSP furnishes tin-containing ZnO materials with good electron mobilities at relatively low processing temperatures (350 °C) for thin-film transistor (TFT) applications. All the thin films of tin-doped ZnO prepared by spin-coating on silicon wafers are of great homogeneity and amorphous structure, which is promising for future applications in the field of transparent conducting oxides (TCOs).
Co-reporter:Dr. Burgert Blom;Miriam Stoelzel ; Matthias Driess
Chemistry - A European Journal 2013 Volume 19( Issue 1) pp:
Publication Date(Web):
DOI:10.1002/chem.201290224
Co-reporter:Dr. Yun Xiong;Dr. Shenglai Yao ;Dr. Matthias Driess
Angewandte Chemie 2013 Volume 125( Issue 16) pp:4398-4407
Publication Date(Web):
DOI:10.1002/ange.201209766
Abstract
Die Reaktivität der Ketone (R2CO) ist deutlich besser untersucht als die ihrer schweren Homologen R2EO (E=Si, Ge, Sn, Pb). Die Gründe dafür sind die hohe Polarität der EO-Bindung und die daraus folgende Neigung zur Oligomerisation. Erst kürzlich konnten große Erfolge bei der Synthese von isolierbaren Verbindungen mit EO-Bindungen erzielt werden, darunter Donor-stabilisierte isolierbare Silanone und das erste echte Germanon. Diese Verbindungen zeigen in ihrer Reaktivität drastische Unterschiede zu Ketonen und bilden darüber hinaus vielseitige Synthesebausteine in der Silicium-Sauerstoff- und Germanium-Sauerstoff-Chemie. Diese und andere erstaunliche Erfolge werden im vorliegenden Kurzaufsatz beschrieben.
Co-reporter:Subrata Kundu;Florian Felix Pfaff;Enrico Miceli;Dr. Ivelina Zaharieva;Dr. Christian Herwig;Dr. Shenglai Yao;Dr. Erik R. Farquhar;Dr. Uwe Kuhlmann;Dr. Eckhard Bill;Dr. Peter Hildebrt;Dr. Holger Dau;Dr. Matthias Driess;Dr. Christian Limberg;Dr. Kallol Ray
Angewandte Chemie 2013 Volume 125( Issue 21) pp:5732-5736
Publication Date(Web):
DOI:10.1002/ange.201300861
Co-reporter:Dr. Yun Xiong;Dr. Shenglai Yao;Dr. Shigeyoshi Inoue;Dr. Jan Dirk Epping ;Dr. Matthias Driess
Angewandte Chemie 2013 Volume 125( Issue 28) pp:7287-7291
Publication Date(Web):
DOI:10.1002/ange.201302537
Co-reporter:Dr. Shenglai Yao;Dr. Peter Hrobárik;Dipl.-Chem. Florian Meier;Dipl.-Chem. Robert Rudolph;Dr. Eckhard Bill;Dr. Elisabeth Irran;Dr. Martin Kaupp;Dr. Matthias Driess
Chemistry - A European Journal 2013 Volume 19( Issue 4) pp:
Publication Date(Web):
DOI:10.1002/chem.201203642
Abstract
A unique heterobimetallic disulfur monoradical, complex 2, with a diamond-shaped {NiS2Pt} core has been synthesized by two-electron reduction of a supersulfido-(nacnac)nickel(II) complex (nacnac=β-diketiminato) with [Pt(Ph3P)2(η2-C2H4)] as a platinum(0) source and isolated in 82 % yield. Strikingly, the results of DFT calculations in accordance with spectroscopic (EPR, paramagnetic NMR) and structural features of the complex revealed that the bonding situation of the S2 ligand is between the elusive “half-bonded” S2 radical trianion () and two separated S2− ligands. Accordingly, the NiII center is partially oxidized, whereas the PtII site is redox innocent. The complex can be reversibly oxidized to the corresponding Ni,Pt-disulfido monocation, compound 3, with a SS single bond, and reacts readily with O2 to form the corresponding superoxonickel(II) and disulfidoplatinum(II) (4) complexes. These compounds have been isolated in crystalline form and fully characterized, including IR and multi-nuclear NMR spectroscopy as well as ESI mass spectrometry. The molecular structures of compounds 2–4 have been confirmed by single-crystal X-ray crystallography.
Co-reporter:Dr. Yun Xiong;Dr. Shenglai Yao;Dr. Shigeyoshi Inoue;Dr. Jan Dirk Epping ;Dr. Matthias Driess
Angewandte Chemie 2013 Volume 125( Issue 28) pp:
Publication Date(Web):
DOI:10.1002/ange.201304199
Co-reporter:Subrata Kundu;Florian Felix Pfaff;Enrico Miceli;Dr. Ivelina Zaharieva;Dr. Christian Herwig;Dr. Shenglai Yao;Dr. Erik R. Farquhar;Dr. Uwe Kuhlmann;Dr. Eckhard Bill;Dr. Peter Hildebrt;Dr. Holger Dau;Dr. Matthias Driess;Dr. Christian Limberg;Dr. Kallol Ray
Angewandte Chemie 2013 Volume 125( Issue 21) pp:
Publication Date(Web):
DOI:10.1002/ange.201303268
Co-reporter:Dr. Yun Xiong;Dr. Shenglai Yao ;Dr. Matthias Driess
Angewandte Chemie International Edition 2013 Volume 52( Issue 16) pp:4302-4311
Publication Date(Web):
DOI:10.1002/anie.201209766
Abstract
In contrast to the well-established chemistry of ketones (R2CO), the reactivity of the elusive heavier congeners R2EO (E=Si, Ge, Sn, Pb) is far less explored because of the high polarity of the EO bonds and hence their tendency to oligomerize with no activation barrier. Very recently, great advances have been achieved in the synthesis of isolable compounds with EO bonds, including the investigation of donor-stabilized isolable silanones and the first stable “genuine” germanone. These compounds show drastically different reactivities compared to ketones and represent versatile building blocks in silicon–oxygen and germanium–oxygen chemistry. This and other exciting achievements are described in this Minireview.
Co-reporter:Subrata Kundu;Florian Felix Pfaff;Enrico Miceli;Dr. Ivelina Zaharieva;Dr. Christian Herwig;Dr. Shenglai Yao;Dr. Erik R. Farquhar;Dr. Uwe Kuhlmann;Dr. Eckhard Bill;Dr. Peter Hildebrt;Dr. Holger Dau;Dr. Matthias Driess;Dr. Christian Limberg;Dr. Kallol Ray
Angewandte Chemie International Edition 2013 Volume 52( Issue 21) pp:5622-5626
Publication Date(Web):
DOI:10.1002/anie.201300861
Co-reporter:Subrata Kundu;Florian Felix Pfaff;Enrico Miceli;Dr. Ivelina Zaharieva;Dr. Christian Herwig;Dr. Shenglai Yao;Dr. Erik R. Farquhar;Dr. Uwe Kuhlmann;Dr. Eckhard Bill;Dr. Peter Hildebrt;Dr. Holger Dau;Dr. Matthias Driess;Dr. Christian Limberg;Dr. Kallol Ray
Angewandte Chemie International Edition 2013 Volume 52( Issue 21) pp:
Publication Date(Web):
DOI:10.1002/anie.201303268
Co-reporter:Dr. Yun Xiong;Dr. Shenglai Yao;Dr. Shigeyoshi Inoue;Dr. Jan Dirk Epping ;Dr. Matthias Driess
Angewandte Chemie International Edition 2013 Volume 52( Issue 28) pp:7147-7150
Publication Date(Web):
DOI:10.1002/anie.201302537
Co-reporter:Dr. Yun Xiong;Dr. Shenglai Yao;Dr. Shigeyoshi Inoue;Dr. Jan Dirk Epping ;Dr. Matthias Driess
Angewandte Chemie International Edition 2013 Volume 52( Issue 28) pp:
Publication Date(Web):
DOI:10.1002/anie.201304199
Co-reporter:Shenglai Yao and Matthias Driess
Accounts of Chemical Research 2012 Volume 45(Issue 2) pp:276
Publication Date(Web):August 29, 2011
DOI:10.1021/ar200156r
Small-molecule activation by transition metals is essential to numerous organic transformations, both biological and industrial. Creating useful metal-mediated activation systems often depends on stabilizing the metal with uncommon low oxidation states and low coordination numbers. This provides a redox-active metal center with vacant coordination sites well suited for interacting with small molecules.Monovalent nickel species, with their d9 electronic configuration, are moderately strong one-electron reducing agents that are synthetically attractive if they can be isolated. They represent suitable reagents for closing the knowledge gap in nickel-mediated activation of small molecules. Recently, the first strikingly stable dinuclear β-diketiminate nickel(I) precursor complexes were synthesized, proving to be suitable promoters for small-molecule binding and activation. They have led to many unprecedented nickel complexes bearing activated small molecules in different reduction stages.In this Account, we describe selected achievements in the activation of nitrous oxide (N2O), O2, the heavier chalcogens (S, Se, and Te), and white phosphorus (P4) through this β-diketiminatonickel(I) precursor species. We emphasize the reductive activation of O2, owing to its promise in oxidation processes. The one-electron-reduced O2 activation product, that is, the corresponding β-diketiminato-supported Ni–O2 complex, is a genuine superoxonickel(II) complex, representing an important intermediate in the early stages of O2 activation. It selectively acts as an oxygen-atom transfer agent, hydrogen-atom scavenger, or both towards exogenous organic substrates to yield oxidation products.The one-electron reduction of the superoxonickel(II) moiety was examined by using elemental potassium, β-diketiminatozinc(II) chloride, and β-diketiminatoiron(I) complexes, affording the first heterobimetallic complexes featuring a [NiO2M] subunit (M is K, Zn, or Fe). Through density functional theory (DFT) calculations, the geometric and electronic structures of these complexes were established and their distinctive reactivity, including the unprecedented monooxygenase-like activity of a bis(μ-oxo)nickel–iron complex, was studied. The studies have further led to other heterobimetallic complexes containing a [NiO2M] core, which are useful for understanding the influence of the heterometal on structure–reactivity relationships. The activation of N2O led directly to the hydrogen-atom abstraction product bis(μ-hydroxo)nickel(II) species and prevented isolation of any intermediate. In contrast, the activation of elemental S, Se, and Te with the same nickel(I) reagent furnished activation products with superchalcogenido E2– (E is S, Se, or Te) and dichalcogenido E22– ligand in different activation stages. The isolable supersulfidonickel(II) subunit may serve as a versatile building block for the synthesis of heterobimetallic disulfidonickel(II) complexes with a [NiS2M] core.In the case of white phosphorus, the P4 molecule has been coordinated to the nickel(I) center of dinuclear β-diketiminatonickel(I) precursor complexes; however, the whole P4 subunit is a weaker electron acceptor than the dichalcogen ligands E2, thus remaining unreduced. This P4 binding mode is rare and could open new doors for subsequent functionalization of P4.Our advances in understanding how these small molecules are bound to a nickel(I) center and are activated for further transformation offer promise for designing new catalysts. These nickel-containing complexes offer exceptional potential for nickel-mediated transformations of organic molecules and as model compounds for mimicking active sites of nickel-containing metalloenzymes.
Co-reporter:Yun Xiong, Shenglai Yao, Shigeyoshi Inoue, Andreas Berkefeld and Matthias Driess
Chemical Communications 2012 vol. 48(Issue 100) pp:12198-12200
Publication Date(Web):02 Nov 2012
DOI:10.1039/C2CC36926E
The novel chlorogermyliumylidene complex L[ClGe:]+ (L = 1,8-bis(tri-n-butylphosphanzenyl)naphthalene) with a ‘naked’ Cl− as a counter anion was synthesized through reaction of L with Cl2Ge: and fully characterized. Its reaction with elemental sulfur afforded the first germathionium [ClGeS]+ cation containing species. The latter has also been fully characterized, including single-crystal X-ray diffraction analysis.
Co-reporter:Miriam Stoelzel;Dr. Carsten Präsang;Dr. Shigeyoshi Inoue;Dr. Stephan Enthaler ;Dr. Matthias Driess
Angewandte Chemie International Edition 2012 Volume 51( Issue 2) pp:399-403
Publication Date(Web):
DOI:10.1002/anie.201105722
Co-reporter:Dipl.-Chem. Wenyuan Wang;Dr. Shigeyoshi Inoue;Dr. Elisabeth Irran ;Dr. Matthias Driess
Angewandte Chemie International Edition 2012 Volume 51( Issue 15) pp:3691-3694
Publication Date(Web):
DOI:10.1002/anie.201200632
Co-reporter:Dipl.-Chem. Wenyuan Wang;Dr. Shigeyoshi Inoue;Dr. Stephan Enthaler;Dr. Matthias Driess
Angewandte Chemie International Edition 2012 Volume 51( Issue 25) pp:6167-6171
Publication Date(Web):
DOI:10.1002/anie.201202175
Co-reporter:Dr. Yun Xiong;Dr. Shenglai Yao;Dr. Shigeyoshi Inoue;Dr. Elisabeth Irran ;Dr. Matthias Driess
Angewandte Chemie International Edition 2012 Volume 51( Issue 40) pp:10074-10077
Publication Date(Web):
DOI:10.1002/anie.201205840
Co-reporter:Dr. Andreas Brück;M.Sc. Daniel Gallego;Dipl.-Chem. Wenyuan Wang;Elisabeth Irran;Dr. Matthias Driess;Dr. John F. Hartwig
Angewandte Chemie International Edition 2012 Volume 51( Issue 46) pp:11478-11482
Publication Date(Web):
DOI:10.1002/anie.201205570
Co-reporter:Dr. Yun Xiong;Dr. Shenglai Yao;Dr. Shigeyoshi Inoue;Dr. Elisabeth Irran ;Dr. Matthias Driess
Angewandte Chemie 2012 Volume 124( Issue 40) pp:10221-10224
Publication Date(Web):
DOI:10.1002/ange.201205840
Co-reporter:Dr. Andreas Brück;M.Sc. Daniel Gallego;Dipl.-Chem. Wenyuan Wang;Elisabeth Irran;Dr. Matthias Driess;Dr. John F. Hartwig
Angewandte Chemie 2012 Volume 124( Issue 46) pp:11645-11649
Publication Date(Web):
DOI:10.1002/ange.201205570
Co-reporter:Miriam Stoelzel;Dr. Carsten Präsang;Dr. Shigeyoshi Inoue;Dr. Stephan Enthaler ;Dr. Matthias Driess
Angewandte Chemie 2012 Volume 124( Issue 2) pp:411-415
Publication Date(Web):
DOI:10.1002/ange.201105722
Co-reporter:Dr. Burgert Blom;Dr. Matthias Driess;Daniel Gallego ;Dr. Shigeyoshi Inoue
Chemistry - A European Journal 2012 Volume 18( Issue 42) pp:13355-13360
Publication Date(Web):
DOI:10.1002/chem.201202399
Abstract
A series of unprecedented bis-silylene titanium(II) complexes of the type [(η5-C5H5)2Ti(LSiX)2] (L=PhC(NtBu)2; X=Cl, CH3, H) has been prepared using a phosphane elimination strategy. Treatment of the [(η5-C5H5)2Ti(PMe3)2] precursor (1) with two molar equivalents of the N-heterocyclic chlorosilylene LSiCl (2), results in [(η5-C5H5)2Ti(LSiCl)2] (3) with concomitant PMe3 elimination. The presence of a SiCl bond in 3 enabled further functionalization at the silicon(II) center. Accordingly, a salt metathesis reaction of 3 with two equivalents of MeLi results in [(η5-C5H5)2Ti(LSiMe)2] (4). Similarly, the reaction of 3 with two equivalents of LiBHEt3 results in [(η5-C5H5)2Ti(LSiH)2] (5), which represents the first example of a bis-(hydridosilylene) metal complex. All complexes were fully characterized and the structures of 3 and 4 elucidated by single-crystal X-ray diffraction analysis. DFT calculations of complexes 3–5 were also carried out to assess the nature of the titanium–silicon bonds. Two σ and one π-type molecular orbital, delocalized over the Si-Ti-Si framework, are observed.
Co-reporter:Dr. Yun Xiong;Dr. Shenglai Yao ;Dr. Matthias Driess
Chemistry - A European Journal 2012 Volume 18( Issue 11) pp:3316-3320
Publication Date(Web):
DOI:10.1002/chem.201103656
Abstract
The facile one-pot reaction of the stable N-heterocyclic silylene LSi: 1 (L(ArN)C(CH2) CHC(Me)(NAr), Ar=2,6-iPr2C6H3) with Me2Zn, Me3Al, H3Al-NMe3, and MeLi has been investigated. The silicon(II) atom in 1 is capable of insertion into the corresponding MC and AlH bonds under very mild reaction conditions. Thus, Me2Zn furnishes the bis(silyl) zinc complex LSi(Me)ZnSi(Me)L 2 as the sole product, irrespective of the molar ratio of the starting materials applied. Moreover, the reactions of 1 with Me3Al, H3Al-NMe3, and MeLi lead directly to the 1,1-addition products LSi(Me)(Al(thf)Me2) 3, LSi(H)(AlH2(NMe3)) 4, and LSi(Me)Li(thf)3 5, respectively. All new compounds 2–5 were fully characterized by multinuclear NMR spectroscopy, mass spectrometry, elemental analyses, and single-crystal X-ray diffraction analyses.
Co-reporter:Dr. Kerim Samedov;Dr. Yilmaz Aksu ;Dr. Matthias Driess
Chemistry - A European Journal 2012 Volume 18( Issue 25) pp:7766-7779
Publication Date(Web):
DOI:10.1002/chem.201103594
Abstract
The syntheses and structural elucidation of dimeric [Sn(OCyHex)2] (1), its corresponding (cyclohexoxy)alkalistannates(II) [{M(OCyHex)3Sn}2] (M=Li (2), Na (3), K (4)), and of the first heteroleptic heterotermetallic Li/In/Sn–haloalkoxide clusters [X2In{LiSn2(OCyHex)6}] (X=Br (5), Cl (6)) with a double seco-norcubane core are reported. They represent suitable precursors for new amorphous indium tin oxide (ITO) materials as transparent conducting oxides with drastically reduced concentrations of expensive indium, while maintaining their high electrical performance. In fact, compounds 5 and 6 were successfully degraded under dry synthetic air at relatively low temperature, resulting in new semiconducting tin-rich ITOs homogeneously dispersed in a tin oxide/lithium oxide matrix. The obtained particles were investigated and characterised by different analytical techniques, such as powder XRD, IR spectroscopy, SEM, TEM and energy-dispersive X-ray spectroscopy (EDX). The analytical data confirm that the final materials consist of tin-containing indium oxide embedded in an amorphous tin oxide matrix. The typical broadening and shift of the observed indium oxide reflections to higher 2θ values in the powder XRD pattern clearly indicated that tin centres were successfully incorporated into the In2O3 lattice and partially occupied In3+ sites. Investigations by EDX mapping proved that Sn was homogeneously distributed in the final materials. Thin-film field-effect transistors (FETs) were fabricated by spin-coating of silicon wafers with solutions of 5 in toluene and subsequent calcination under dry air (25–700 °C). The FETs prepared with precursor 5 exhibited excellent performances, as shown by a charge-carrier mobility of 6.36×10−1 cm2 V−1 s (calcination at 250 °C) and an on/off current ratio of 106.
Co-reporter:Dr. Shenglai Yao;Dr. Yun Xiong ;Dr. Matthias Driess
Chemistry - A European Journal 2012 Volume 18( Issue 36) pp:11356-11361
Publication Date(Web):
DOI:10.1002/chem.201201335
Abstract
Synthesis and characterization of the first manganese(II)-containing heavier thiocarboxylate analogues, [LDipSi(S)OMnLDep] (4; LDip=CH[C(Me)N(2,6-iPr2C6H3)]2, LDep=CH[C(Me)N(2,6-Et2C6H3)]2) and [LDipGe(S)OMnLDep] (5) are described. They are accessible through reaction of the silicon and germanium analogues of the respective thiocarboxylic acids [LDipE(S)OH] (E=Si, Ge) with the β-diketiminato (nacnac) manganese(II) hydride precursor [(LDepMn)2(μ-H)2] (3) in high yield. The first Mn nacnac hydride 3 has been prepared by the reaction of manganese bromide [(LDepMn)2(μ-Br)2] (2) with KBEt3H. Compounds 4 and 5 represent the first transition-metal heavier thiocarboxylates with the SiS and GeS functionalities. All new compounds are paramagnetic and were characterized by elemental analysis, IR spectroscopy, MS (EI), and single-crystal X-ray diffraction analyses. Due to the NE (E=Si, Ge) and E=SMn donor–acceptor interaction as well as the carboxylate-like π-electron delocalization within the E(S)O moieties, the ES double bonds in these compounds are resonance stabilized.
Co-reporter:Yun Xiong;Shenglai Yao
Chemistry – An Asian Journal 2012 Volume 7( Issue 9) pp:2145-2150
Publication Date(Web):
DOI:10.1002/asia.201200379
Abstract
Modifying the β-diketimine ligand LH 1 (LH=[ArNC(Me)CHC(Me)NHAr], Ar=2,6-iPr2C6H3) through replacement of the proton in 3-position by a benzyl group (Bz) leads to the new BzLH ligand 2, which could be isolated in 77 % yield. According to 1H NMR spectroscopy, 2 is a mixture of the bis(imino) form [(ArNC(Me)]2CH(Bz) 2a and its tautomer [ArNC(Me)C(Bz)C(Me)NHAr] 2b. Nevertheless, lithiation of the mixture of 2a and 2b affords solely the N-lithiated β-diketiminate [ArNC(Me)C(Bz)C(Me)NLiAr], BzLLi 3. The latter reacts readily with GeCl2⋅dioxane to form the chlorogermylene BzLGeCl 4, which serves as a precursor for a new zwitterionic germylene by dehydrochlorination with LiN(SiMe3)2. This reaction leads to the zwitterionic germylene BzL′Ge: 5 (BzL′=ArNC(CH2)C(Bz)C(Me)NAr) which could be isolated in 83 % yield. The benzyl group has a distinct influence on the reactivity of zwitterionic 5 in comparison to its benzyl-free analogue, as shown by the reaction of 5 with phenylacetylene, which yields solely the 1,4-addition product 6, that is, the alkynyl germylene BzLGeCCPh. Compounds 2–8 have been fully characterized by multinuclear NMR spectroscopy, mass spectrometry, elemental analyses, and single-crystal X-ray diffraction analyses.
Co-reporter:Dr. Kerim Samedov;Dr. Yilmaz Aksu;Dr. Matthias Driess
ChemPlusChem 2012 Volume 77( Issue 8) pp:663-674
Publication Date(Web):
DOI:10.1002/cplu.201200086
Abstract
The syntheses, structural characterization, and thermal degradation of a series of the new indium and gallium siloxide dimers [{Me2In(OSiEt3)}2] (1), [{Me2Ga(OSiEt3)}2] (2), [{Me2In(OSi(OtBu)3)}2] (3), [{Me2Ga(OSi(OtBu)3)}2] (4), and In[OSi(OtBu)3)] (5) is reported. Compounds 1–4 are readily accessible by facile Brönsted reaction of InMe3 or GaMe3 with the corresponding silanols Et3SiOH and (tBuO)3SiOH, respectively. Compound 5 could be obtained by analogous protolysis of [In{N(SiMe3)2}3] with an excess amount of (tBuO)3SiOH. The suitability of 1–5 to serve as molecular precursors for low-temperature synthesis of amorphous indium and gallium oxide for electronic applications was probed. Thus their thermal degradation was studied by Thermogravimetric/differential thermogravimetry analysis (TGA/DTG). Compounds 1–4 were decomposed under dry synthetic air (20 % O2, 80 % N2) at low temperature to yield amorphous indium oxide and gallium oxide particles, respectively. In contrast, thermal degradation of 5 affords amorphous indium silicate. All of these products were analyzed by multiple techniques including powder X-ray diffraction analysis (PXRD), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX). Thin-film field-effect transistors (FETs) could be fabricated through spin-coating of silicon-wafers with solutions of 1 in toluene and subsequent calcination under dry synthetic air at 350 °C. These films exhibit very good FET performance with a field-effect mobility of 3.0×10−1 cm2 V−1 s and an on/off current ratio of 108.
Co-reporter:Matthew Asay, Cameron Jones, and Matthias Driess
Chemical Reviews 2011 Volume 111(Issue 2) pp:354
Publication Date(Web):December 6, 2010
DOI:10.1021/cr100216y
Co-reporter:Shigeyoshi Inoue ; Jan D. Epping ; Elisabeth Irran
Journal of the American Chemical Society 2011 Volume 133(Issue 22) pp:8514-8517
Publication Date(Web):May 9, 2011
DOI:10.1021/ja2033475
The first donor-stabilized tetrasilacyclobutadiene dication species has been synthesized and fully characterized. Its unexpected formation occurs by the Lewis acid assisted reaction of the N-heterocyclic chloro silylene [L(Si:)Cl] (L = PhC(NtBu)2; amidinate) with Cp*ZrCl3 (Cp* = pentamethylcyclopentadienyl) in the molar ratio of 3:2. Remarkably, the four-membered Si4 core consists of two N-donor stabilized silylium subunits and two silylene-like moieties. The dicationic charge is somewhat delocalized on the Si4 core, which is supported by DFT calculations.
Co-reporter:Shigeyoshi Inoue ; Wenyuan; Wang ; Carsten Präsang ; Matthew Asay ; Elisabeth Irran
Journal of the American Chemical Society 2011 Volume 133(Issue 9) pp:2868-2871
Publication Date(Web):February 15, 2011
DOI:10.1021/ja200462y
The first N-donor-stabilized phosphasilene LSi(SiMe3)═PSiMe3 (L = PhC(NtBu)2) has been synthesized in 87% yield through 1,2-silyl migration of the (Me3Si)2P-substituted, N-heterocyclic silylene [LSi−P(SiMe3)2]. Remarkably, the latter reacts with dichlorotriphenylphosphorane Ph3PCl2 to give the unprecedented 4π-electron Si2P2-cycloheterobutadiene [(LSi)2P2] with two-coordinate phosphorus atoms. The striking molecular structures as well as the 29Si and 31P NMR spectroscopic features of both products indicate the presence of zwitterionic Si═P bonds which is also in accordance with results by DFT calculations.
Co-reporter:William D. Woodul ; Emma Carter ; Robert Müller ; Anne F. Richards ; Andreas Stasch ; Martin Kaupp ; Damien M. Murphy ; Matthias Driess ;Cameron Jones
Journal of the American Chemical Society 2011 Volume 133(Issue 26) pp:10074-10077
Publication Date(Web):June 11, 2011
DOI:10.1021/ja204344e
Stoichiometric reduction of the bulky β-diketiminato germanium(II) chloride complex [(ButNacnac)GeCl] (ButNacnac = [{N(Dip)C(But)}2CH]−, Dip = C6H3Pri2-2,6) with either sodium naphthalenide or the magnesium(I) dimer [{(MesNacnac)Mg}2] (MesNacnac = [(MesNCMe)2CH]−, Mes = mesityl) afforded the radical complex [(ButNacnac)Ge:]• in moderate yields. X-ray crystallographic, EPR/ENDOR spectroscopic, computational, and reactivity studies revealed this to be the first authenticated monomeric, neutral germanium(I) radical.
Co-reporter:Yilmaz Aksu, Stefano Frasca, Ulla Wollenberger, Matthias Driess, and Arne Thomas
Chemistry of Materials 2011 Volume 23(Issue 7) pp:1798
Publication Date(Web):March 4, 2011
DOI:10.1021/cm103087p
The preparation of porous, i.e., high surface area electrodes from transparent conducting oxides, is a valuable goal in materials chemistry as such electrodes can enable further development of optoelectronic, electrocatalytic, or bioelectronic devices. In this work the first tin-rich mesoporous indium tin oxide is prepared using the molecular heterobimetallic single-source precursor, indium tin tris-tert-butoxide, together with an appropriate structure-directing template, yielding materials with high surface areas and tailorable pore size. The resulting mesoporous tin-rich ITO films show a high and durable electrical conductivity and transparency, making them interesting materials for hosting electroactive biomolecules such as proteins. In fact, its unique performance in bioelectronic applications has been demonstrated by immobilization of high amounts of cytochrome c into the mesoporous film which undergo redox processes directly with the conductive electrode material.Keywords: bioelectrochemistry; cytochrome c; device; electrode; indium tin oxide ITO;
Co-reporter:Chika I. Someya, Shigeyoshi Inoue, Carsten Präsang, Elisabeth Irran and Matthias Driess
Chemical Communications 2011 vol. 47(Issue 23) pp:6599-6601
Publication Date(Web):26 Apr 2011
DOI:10.1039/C1CC11789K
Cationic and zwitterionic boryl bromide species and a borenium–boryl bromide cation have been synthesised which represent new N-donor stabilised cationic boron compounds with β-diketiminate ligands. The unexpected borenium–boryl bromide results from a head-to-tail dimerisation of the corresponding zwitterionic boryl bromide accompanied by proton migration. The electronic nature of these new species was studied by DFT calculations.
Co-reporter:Sebastian Krackl;Jian-Gong Ma;Yilmaz Aksu
European Journal of Inorganic Chemistry 2011 Volume 2011( Issue 11) pp:1725-1732
Publication Date(Web):
DOI:10.1002/ejic.201001236
Abstract
A series of monodentate, triply bonded Mo2(OR)6 complexes [R = MBE (1) (MBE = 2-methylbut-3-ene-2-yl), MMP (2) (MMP = 1-methoxy-2-methylpropane-2-yl), Terp (3) [Terp = 2-(4-methylcyclohex-3-enyl)propane-2-yl], which exhibit C–C double bonds or an ether function in the ligand sphere, were synthesized and characterized by multinuclear (1H, 13C and 95Mo) NMR studies. The partial alcoholysis of the latter complexes with neopentyl alcohol (neopentOH) led to the heteroleptic alkoxides Mo2(OR)n(Oneopent)6–n (4–7) {n = 2 [for R = tBu (4), MBE (5), MMP (6)], 4 [for R = Terp (7)]}. This concept was further applied to the synthesis of Mo2(O2DMH)2(OtBu)2 (8) (DMH = 2,5 dimethylhexyl) by starting from the Mo2(OtBu)6 precursor. The 1H NMR spectra for the heteroleptic complexes 4–8 show signals that are significantly shifted to a higher field for the RO ligand protons compared to those of their homoleptic analogues. This is the result of a change in the spatial position of the alkoxide ligands (RO) in the homoleptic compared to the heteroleptic complexes that leads to a different magnetic environment for the alkoxide ligands due to the magnetic anisotropy of the Mo–Mo triple bond. 95Mo NMR studies of the complexes 1–8 show that the resonance strongly depends on the substitution pattern of the alkoxide and that a shift to higher field is observed when going from the tertiary to the primary alkoxides. The molecular structures for 4–8 were determined by single-crystal X-ray diffraction, and all of the complexes show a staggered conformation as well as an asymmetric ligand distribution, which results in unequal Mo–O bond lengths. For the heteroleptic complexes 4–7, the RO ligands (R = tBu, MBE, MMP and Terp, respectively) exhibit the longest bond lengths, which suggests that the position of the ligand strongly depends on the steric congestion of the α-carbon atom of the alkoxide ligand. In 6, the methoxy function enables an intramolecular OMo coordination as is indicated by a Mo–O distance of 2.2464(7) Å. This fact is supported by a lengthening of the Mo–Mo triple bond.
Co-reporter:Dr. Yun Xiong;Dr. Shenglai Yao;Dr. Elisabeth Irran ;Dr. Matthias Driess
Chemistry - A European Journal 2011 Volume 17( Issue 40) pp:11274-11279
Publication Date(Web):
DOI:10.1002/chem.201101610
Abstract
The first donor-stabilized silylated silicoxonium species [LSiOSiMe3]+ (L=(RN)C(CH2)CHCMe(NR), R=2,6-iPr2C6H3) have been synthesized from the reaction of the dmap-supported (dmap=p-dimethylaminopyridine) silanone complex [LSi(dmap)O] (1) with trimethylsilyl halides. Although the reaction with Me3SiCl leads directly to the SiO addition product [LSi(Cl)OSiMe3] (2), the ionic silicoxonium bromide [L(dmap)SiOSiMe3]+Br− (3) can be obtained as a primary product of the reaction with Me3SiBr, which affords [LSi(Br)OSiMe3] (4) with release of the dmap ligand at room temperature in THF. In the case of Me3SiI, the reaction furnishes the silicoxonium iodide [L(dmap)SiOSiMe3]+I− (5) as the most stable species. Compounds 2–5 were isolated and fully characterized through multinuclear NMR spectroscopy, mass spectrometry, elemental analyses, and single-crystal X-ray diffraction analyses.
Co-reporter:Dr. Shenglai Yao;Dr. Yun Xiong;Wenyuan Wang ;Dr. Matthias Driess
Chemistry - A European Journal 2011 Volume 17( Issue 17) pp:4890-4895
Publication Date(Web):
DOI:10.1002/chem.201003409
Abstract
The first isolable pyridine-stabilized germanone has been prepared and its reactivity toward trimethylaluminum has been investigated. The germanone adduct results from a stepwise conversion that starts from 4-dimethylaminopyridine (DMAP) and the ylide-like N-heterocyclic germylene LGe: (L=CH{(CCH2)(CMe)[N(aryl)]2}, aryl=2,6-iPr2C6H3) (1) at room temperature, and gives the corresponding germylene–pyridine adduct L(DMAP)Ge: (2) in 91 % yield. The latter reacts with N2O at room temperature to form the desired germanone complex L(DMAP)GeO (3) in 73 % yield. The GeO distance of 1.646(2) Å in 3 is the shortest hitherto reported for a GeO species. The reaction of 3 with trimethylaluminum leads solely to the addition product LGe(Me)O[Al(DMAP)Me2] (4). The latter results from insertion of the GeO subunit into an AlMe bond of AlMe3 and concomitant migration of the DMAP ligand from germanium to the aluminum atom. Compounds 2–4 have been fully characterized by analytical and spectroscopic methods. Their molecular structures have been established by single-crystal X-ray crystallographic analysis.
Co-reporter:Sebastian Krackl;Dr. Anna Company;Dr. Yilmaz Aksu;Dr. David Avnir;Dr. Matthias Driess
ChemCatChem 2011 Volume 3( Issue 1) pp:227-232
Publication Date(Web):
DOI:10.1002/cctc.201000239
Abstract
The general method of doping metals with organic, bio-organic, and polymeric dopants is extended to inorganic dopants. Specifically, the heteropolyacids H3[P(M3O10)4] (PMA; M=Mo, W) were successfully entrapped within a metallic silver matrix. The obtained PMA@Ag composites were fully characterized by PXRD, surface area, SEM, TEM and EDX measurements, showing a homogenous distribution of the catalyst in the support. The new composite materials are successfully applied in the catalytic alkylation of arenes, as demonstrated by the successful adamantylation of toluene or anisole with 1-bromoadamantane. Furthermore, this reaction is applied with the less reactive 1-chloroadamantane in both the supported and unsupported case. PMoA, which easily decomposes under the applied reaction conditions, is protected by entrapment and shows increased activity when supported in the silver matrix. In the same reaction, the entrapped PWA shows a drastically increased reaction rate compared to the free acid, which further confirms the positive synergistic effects of the entrapment process. Both heterogenized catalysts are successfully recycled and reused, but the reaction time steadily increases in successive cycles due to agglomeration of the catalyst, which results in a lower accessibility of the dopant. Moreover, the alkylation can be extended to other alkyl chloride substrates, as demonstrated for tert-butyl chloride.
Co-reporter:Sebastian Krackl;Dr. Anna Company;Dr. Stephan Enthaler;Dr. Matthias Driess
ChemCatChem 2011 Volume 3( Issue 7) pp:1186-1192
Publication Date(Web):
DOI:10.1002/cctc.201100007
Abstract
A variety of homoleptic and heteroleptic, triply bonded dimolybdenum hexaalkoxides, [(Mo2(OR)6] and [Mo2(OR)4(OR′)2], were successfully applied as dual pre-catalysts in both, the epoxidation of olefins with tert-butyl hydroperoxide and the deoxygenation of diorganosulfoxides with silanes, to form the corresponding sulfides. In the epoxidation of cyclooctene, the pre-catalysts demonstrated an intriguingly high activity, with turnover frequencies (TOFs) of above 60 000 h−1 at elevated temperatures (≈50 °C) and even very high activity at room temperature. Furthermore, using [Mo2(OtBu)6] as a pre-catalyst, we studied the effect of the solvent and we extended the epoxidation reaction to more demanding olefins, which revealed a particularly high activity even towards primary alkenes. In addition, the same pre-catalysts, in comparison to previously reported Mo-based systems, exhibited excellent activities for the deoxygenation of phenyl methyl sulfoxide to thioanisole in the presence of silanes (TOFs>160 h−1). A number of other diorganosulfoxides were used in the catalytic deoxygenation to investigate the scope and limitations of the system, displaying an excellent performance for differently substituted substrates.
Co-reporter:Shenglai Yao, Yun Xiong, and Matthias Driess
Organometallics 2011 Volume 30(Issue 7) pp:1748-1767
Publication Date(Web):March 4, 2011
DOI:10.1021/om200017h
This account describes recent progress (>2006) in the synthesis and structural characterization of isolable N-heterocyclic silylenes (NHSi's) and their fascinating reactivities with respect to an emergent topic in main-group chemistry: metal-free small-molecule activation. Since the seminal discovery of stable N-heterocyclic silicon analogues of nucleophilic Wanzlick−Arduengo-type carbenes in 1994, new types of NHSi's have emerged with unique electronic features and strikingly different reactivities. Among them, the first zwitterionic (ylide-like) silylene LSi: (L = CH[(C═CH2)CMe][NAr]2; Ar = 2,6-Pri2C6H3) and unprecedented N-heterocyclic bis(silylenes) with amidinate ligands and Si(I)−Si(I) bonds were synthesized. Their striking electronic structures open new doorways to metal-free activation of C−H, C−X, Si−X, E−H (E = group 15, group 16 elements), P−P, E−O (E = C, N), and E−E bonds (E = O, S, Se, Te).
Co-reporter:Wenyuan Wang, Shigeyoshi Inoue, Shenglai Yao, and Matthias Driess
Organometallics 2011 Volume 30(Issue 23) pp:6490-6494
Publication Date(Web):November 14, 2011
DOI:10.1021/om200970s
The new N-heterocyclic chlorogermylene 1 has been synthesized in a four-step procedure starting from N-cyclohexylidene-2,6-diisopropyl-benzenamine. Dehydrochlorination of 1 with an N-heterocyclic carbene furnished the corresponding germylene 2 in good yield. The Ge(II) centers in 1 and 2 are stabilized by nitrogen π-donors and two bulky aryl groups. The reactivity of germylene 2 toward ammonia and water was investigated. Thus, ammonolysis and hydrolysis of 2 at ambient temperature led to the germylene amide 3 and the first monomeric germylene hydroxide 4, respectively. The new compounds 1–4 were fully characterized, including X-ray diffraction analyses.
Co-reporter:Dr. Matthew Asay;Dr. Shigeyoshi Inoue ;Dr. Matthias Driess
Angewandte Chemie 2011 Volume 123( Issue 41) pp:9763-9766
Publication Date(Web):
DOI:10.1002/ange.201104805
Co-reporter:Stephan Heitz;Dr. Yilmaz Aksu;Dr. Christoph Merschjann;Dr. Matthias Driess
Chemistry - A European Journal 2011 Volume 17( Issue 14) pp:3904-3910
Publication Date(Web):
DOI:10.1002/chem.201002743
Abstract
The synthesis and characterization of the first heterobimetallic methylzinc–magnesium alkoxide clusters [Me6MgZn6(OR)8] [R=Et (1 a), n-Pr (1 b), nBu (1 c)] with a bis-cubane-shaped MgZn6O8 core is described. The thermal degradation of 1 a–c and mixtures of 1 a and the homometallic MeZn–alkoxide cubane [{MeZnOtBu}4] (2) in dry synthetic air led to wide-band-gap semiconducting MgxZn1−xO nanoparticles at temperatures below 500 °C. The final materials were characterized by different analytical techniques such as PXRD, REM, TEM, EDX, and IR spectroscopy. The morphology of the as-prepared magnesium-containing ZnO samples is influenced by the different organo groups (alkoxo) in the precursors. EDX mapping showed that magnesium is uniformly distributed in the ZnO matrix. The incorporation of magnesium led to a distortion of the ZnO lattice with increased a axis and decreased c axis parameters. Room-temperature photoluminescence (PL) spectra reveal that the near-band-edge (NBE) emission of Mg2+-doped ZnO is shifted to higher energies relative to that of pure ZnO.
Co-reporter:Dr. Shigeyoshi Inoue;Dr. Matthias Driess
Angewandte Chemie International Edition 2011 Volume 50( Issue 25) pp:5614-5615
Publication Date(Web):
DOI:10.1002/anie.201101812
Co-reporter:Dr. Matthew Asay;Dr. Shigeyoshi Inoue ;Dr. Matthias Driess
Angewandte Chemie International Edition 2011 Volume 50( Issue 41) pp:9589-9592
Publication Date(Web):
DOI:10.1002/anie.201104805
Co-reporter:Antje Meltzer ; Shigeyoshi Inoue ; Carsten Präsang
Journal of the American Chemical Society 2010 Volume 132(Issue 9) pp:3038-3046
Publication Date(Web):February 11, 2010
DOI:10.1021/ja910305p
The strikingly different behavior of the ylide-like, N-heterocyclic silylene LSi: (5: L = CH[(C═CH2)CMe(NAr)2]; Ar = 2,6-iPrC6H3) versus its LSi→Ni(CO)3 complex 13 to activate E−H bonds (E = S, N) of small molecules is reported. Remarkably, conversion of 5 with hydrogen sulfide leads exclusively to the first isolable silathioformamide, L′Si(═S)H (16: L′ = CH[C(Me)NAr]2; Ar = 2,6-iPrC6H3) with a donor-supported Si═S double bond and four-coordinate silicon. The latter result demonstrates the unusual ambivalent reactivity of 5 by combining two modes of reactivity involving S−H bond activation and subsequent 1,4- and 1,1-addition, respectively. In addition, 5 can serve as a ligand with well-balanced σ-donor and π-acceptor capabilities toward transition metals. This has been demonstrated by the isolable [Ni0(arene)] complexes 12a−e (arene = MenC6H6−n, n = 0−3), which are ideal precursors for the formation of the corresponding Ni(CO)3 complex 13. The latter activates a S−H bond in hydrogen sulfide, too, but the presence of the Ni(CO)3 moiety governs the formation of the complex 17, bearing an unprecedented β-diketiminate silicon(II) thiol ligand: L′Si(SH): (L′ = CH[C(Me)NAr]2; Ar = 2,6-iPrC6H3). Likewise, the Si(II)→Ni(CO)3 coordination in 13 steers exclusively 1,4-addition of ammonia, isopropylamine, and phenylhydrazine onto the silylene ligand 5, leading to the corresponding β-diketiminate silicon(II) amide or hydrazide complexes L′Si(NHR)→Ni(CO)3 (23a−c: R = H, iPr, N(H)Ph). IR measurements reveal that the carbonyl stretching frequencies of the Ni(CO)3 moiety in 23a−c are shifted to even lower wavenumbers in comparison to those of NHCs or phosphines. In other words, the β-diketiminate silicon(II) amide ligands in 23a−c represent the strongest donors in the series of N-heterocyclic silylenes reported as yet.
Co-reporter:Jan. D. Epping ; Shenglai Yao ; Miriam Karni ; Yitzhak Apeloig
Journal of the American Chemical Society 2010 Volume 132(Issue 15) pp:5443-5455
Publication Date(Web):March 29, 2010
DOI:10.1021/ja1004812
The electronic structures and nature of silicon−chalcogen double bonds Si═X (X = O, S) with four-coordinate silicon in the unique silanoic silylester 2 and silanoic thioester 3 have been investigated for the first time, by 29Si solid state NMR measurements and detailed DFT and ab initio calculations. 29Si solid state NMR spectroscopy of the precursor silylene 1 was also carried out. The experimental and computational study of 2 and 3, which was also supported by a detailed computational study of smaller model systems with Si═O and Si═S bonds, provides a deeper understanding of the isotropic and tensor components of their NMR chemical shifts. The general agreement between the experimental NMR spectra and the calculations strongly support our previous NMR assignment deduced from experiment. The calculations revealed that in 2 δ(29Si(═O))iso is shifted upfield relative to H2Si═O by as much as 175 ppm; the substituents are responsible for ca. 100 ppm of this shift, while the remaining upfield shift is caused by change in the coordination number from three to four at the Si═O moiety. The change in coordination number leads to a nearly cylindrical symmetry in the plane which is perpendicular to the Si═O molecular axis (δ11 ≈ δ22), in contrast to the significant anisotropy found in this plane in typical doubly bonded compounds. The change in r(Si═O) or in the degree of pyramidality at the Si═O center which accompanies the change in coordination number has practically no effect on the chemical shift. δ(29Si(═S))iso in 3 is shifted downfield significantly relative to that in 2, and a similar trend is found in smaller models with Si═S vs those with Si═O subunits. This downfield shift can be explained by the smaller σ−π* energy difference in the Si═S bond, relative to that of the Si═O bond. The NMR measurements of 2 and 3 having a four-coordinate silicon−chalcogen moiety, and the calculations of their tensor components, their bond polarities, and their Wiberg bond indices revealed that the Si═X moieties in both 2 and 3 have a significant π(Si═X) character; yet, in both molecules there is a substantial contribution from a zwitterionic Si+—X− resonance structure, which is more pronounced in 2.
Co-reporter:Yun Xiong ; Shenglai Yao ; Robert Müller ; Martin Kaupp
Journal of the American Chemical Society 2010 Volume 132(Issue 20) pp:6912-6913
Publication Date(Web):May 4, 2010
DOI:10.1021/ja1031024
The new silanone complex 3 is accessible in 82% yield and is capable of undergoing addition of ammonia under mild conditions, yielding the sila-hemiaminal 4 and, at the same time, its unique tautomer 5, the first silanoic amide. The unexpected formation of 3 is due to the presence of the basic exocyclic methylene group in the C3N2 ligand backbone. Strikingly, the tautomers 4 and 5 are in equilibrium in solution and can be cocrystallized in benzene or THF solutions having a SiOH···O═Si hydrogen bond as confirmed by single-crystal X-ray diffraction analysis.
Co-reporter:Wenyuan Wang ; Shigeyoshi Inoue ; Shenglai Yao
Journal of the American Chemical Society 2010 Volume 132(Issue 45) pp:15890-15892
Publication Date(Web):September 8, 2010
DOI:10.1021/ja106458p
The first isolable oxygen-bridged bis-silylene 1 has been synthesized by facile dehydrochloration of the corresponding disiloxane [LSiH(Cl)−O−SiH(Cl)L] precursor [L = PhC(NtBu)2] with LiN(SiMe3)2. Compound 1 contains three-coordinate, pyramidal Si(II) atoms in a bent disiloxane-like moiety and reacts readily with [Ni(COD)2] to afford the unique bis-silylene oxide nickel complex 3.
Co-reporter:Stephan Heitz, Yilmaz Aksu, Christoph Merschjann, and Matthias Driess
Chemistry of Materials 2010 Volume 22(Issue 4) pp:1376
Publication Date(Web):February 1, 2010
DOI:10.1021/cm9021535
Nanocrystalline MgO powders with variable surface defect concentrations are simply accessible by solid-state thermolysis at relatively low temperatures utilizing the molecular single-source precursors (SSPs) [MeMgOR]4 (R = iPr, tBu, CyHex) and the first bis-cubanes Me6Mg7(OR)8 (Et, Pr, Bu). The decomposition conditions including heating rates, tempering times, and atmospheres have been varied, and the structure and purity of the obtained samples were analyzed by means of different analytical techniques (TGA, PXRD, TEM, EDX, elemental analysis and BET measurements). The crystal sizes vary from approximately 8 to 15 nm depending on the heating rates, tempering times and nature of the applied SSP. Photoluminescence spectroscopy (PLS) of the samples suggests the presence of defects, which could be attributed to different surface oxide sites of the MgO particles depending on the thermolysis conditions, in particular the heating rate and tempering time.
Co-reporter:Stephan Heitz, Jan-Dirk Epping, Yilmaz Aksu, and Matthias Driess
Chemistry of Materials 2010 Volume 22(Issue 16) pp:4563
Publication Date(Web):July 20, 2010
DOI:10.1021/cm100415m
Facile synthesis and characterization of the first heterobimetallic lithium-methylmagnesium-alkoxide clusters [Li(thf)(MeMg)3(μ3-OR)4] (R = iPr (1a), tBu (1b), CyHex (1c)) having a cubane-shaped LiMg3O4 core is reported. They have been employed as molecular single-source precursors for “bottom up” synthesis of Li-containing MgO nanoparticles with varying Li-concentrations. This can be achieved by solid state decomposition of homogeneous mixtures of the latter compounds (1a−c) with the corresponding homometallic alkylmagnesium alkoxide cubanes [MeMg(μ3-OR)]4 (R = iPr (2a), tBu (2b), CyHex (2c)). Characterization of the final obtained materials was accomplished by a combination of different analytical techniques such as TGA, PXRD, TEM, Raman spectroscopy, 7Li MAS NMR spectroscopy, elemental analysis, and nitrogen adsorption. The different parameters that affect the composition and morphology of the Li-containing MgO nanoparticles have been examined. It has been found that Li concentrations up to 1 wt % lead to well-defined crystalline materials, where the Li ions are likely incorporated in the magnesium oxide lattice, whereas higher Li concentrations afford less-ordered materials, which consist of additional crystalline and amorphous phases.
Co-reporter:Jian-Gong Ma, Yilmaz Aksu, Laurence J. Gregoriades, Joachim Sauer and Matthias Driess
Dalton Transactions 2010 vol. 39(Issue 1) pp:103-106
Publication Date(Web):05 Nov 2009
DOI:10.1039/B917585G
Heterobimetallic drive and cooperativity lead to a striking scenario for C–H bond activation and heteroaggregation involving MoIII dimers. Reaction of (RO)3MoMo(OR)3 with molar excess of ZnMe2 at–78 °C affords the novel mixed Zn, Mo oxo clusters [Mo2(MeZn)6(μ2-Me)(μ3-CH2)2(OR)7] 1 (R = neopentyl) and 2 (R = cyclohexyl) preserving the MoMo triple bond, while the same reaction performed at ambient temperature gives rise to the related cluster [Mo2(MeZn)6(μ2-CH2)(μ3-CH2)2(OR)6] 3. These complexes represent the first examples of heterobimetallic MoMo complexes with bridging methyl and methylene groups and agostic C–H→Mo interactions, as well as penta-coordinate carbon. The complexes 1–3 were characterized by elemental analyses, multinuclear NMR and single-crystal X-ray diffraction analysis.
Co-reporter:Yun Xiong, Shenglai Yao and Matthias Driess
Dalton Transactions 2010 vol. 39(Issue 39) pp:9282-9287
Publication Date(Web):09 Jul 2010
DOI:10.1039/C0DT00148A
The striking reactivity of donor-stabilised silanone LSi(DMAP)O (1) [L = N(Ar)C(CH2)CHC(Me)N(Ar), Ar = 2,6-iPr2C6H3, DMAP = p-dimethylaminopyridine] toward Lewis acidic metal substrates Zn(OAc)2, ZnMe2, and AlMe3 is reported. Two unprecedented addition products onto the SiO double bond, [LSi(OAc)(μ-O)Zn(OAc)(DMAP)2] (2) and [LSi(OAc)(μ-O)]2Zn(DMAP) (3), and two terminal complexes LSi(DMAP)O→ZnMe2 (4) and LSi(DMAP)O→AlMe3 (5) were obtained. Compounds 4 and 5 are unique, representing the first isolable and structurally characterised terminal SiO→Zn and SiO→Al complexes. All new compounds were fully characterised by 1H, 13C, and 29Si NMR spectroscopy, EI-MS, elemental analysis and single-crystal X-ray diffraction analyses.
Co-reporter:Ann-Katrin Jungton, Antje Meltzer, Carsten Präsang, Thomas Braun, Matthias Driess and Anna Penner
Dalton Transactions 2010 vol. 39(Issue 23) pp:5436-5438
Publication Date(Web):05 May 2010
DOI:10.1039/C0DT00236D
The first zwitterionic silyl-iridium(V) complex 3 is generated by insertion of silylene 1 into an iridium–hydrogen bond of the iridium(V) hydride 2, [(η5-C5Me5)IrH4]. Complex 3 undergoes proton migration from an IrH moiety to the terminal CH2 group of the silyl ligand to furnish the N-donor stabilised Ir(III)-silylene complex 5.
Co-reporter:Yun Xiong Dr.;Shenglai Yao Dr. Dr.
Angewandte Chemie International Edition 2010 Volume 49( Issue 37) pp:6642-6645
Publication Date(Web):
DOI:10.1002/anie.201002970
Co-reporter:Dr. Shenglai Yao;Dr. Christian Herwig;Dr. Yun Xiong;Dr. Anna Company;Dr. Eckhard Bill;Dr. Christian Limberg;Dr. Matthias Driess
Angewandte Chemie International Edition 2010 Volume 49( Issue 39) pp:7054-7058
Publication Date(Web):
DOI:10.1002/anie.201001914
Co-reporter:Dr. Carsten Präsang;Miriam Stoelzel;Dr. Shigeyoshi Inoue;Dr. Antje Meltzer ;Dr. Matthias Driess
Angewandte Chemie International Edition 2010 Volume 49( Issue 51) pp:10002-10005
Publication Date(Web):
DOI:10.1002/anie.201005903
Co-reporter:Dr. Carsten Präsang;Miriam Stoelzel;Dr. Shigeyoshi Inoue;Dr. Antje Meltzer ;Dr. Matthias Driess
Angewandte Chemie 2010 Volume 122( Issue 51) pp:10199-10202
Publication Date(Web):
DOI:10.1002/ange.201005903
Co-reporter:Yun Xiong Dr.;Shenglai Yao Dr. Dr.
Angewandte Chemie 2010 Volume 122( Issue 37) pp:6792-6795
Publication Date(Web):
DOI:10.1002/ange.201002970
Co-reporter:Yun Xiong, Shenglai Yao and Matthias Driess
Organometallics 2010 Volume 29(Issue 4) pp:987-990
Publication Date(Web):January 19, 2010
DOI:10.1021/om901034w
Cycloaddition reactions of the thermally stable N-heterocyclic silylene LSi: 1 {L = CH[(C═CH2)CMe][N(Ar)]2], Ar = 2,6-iPr2C6H3} with acetone azine (1,1,4,4-tetramethyl-2,3-diazabuta-1,3-diene) and buta-1,3-diene derivatives have been probed. Unexpectedly, acetone azine undergoes a unique [3+1] cycloaddition to give the 1-sila-2,3-diazacyclobutane 2 and its 1-sila-2,3-diazacyclobutane isomer 3. The latter rearranges further to decrease ring strain, affording the corresponding 1-sila-4,5-diazacyclohex-3-ene 4. In contrast, reaction of 1 with isoelectronic 2,3-dimethylbuta-1,3-diene furnishes the expected [4+1] cycloaddition product silacyclopentane 5. The new compounds 2−5 were spectroscopically characterized, including single-crystal X-ray analyses of 2, 4, and 5.
Co-reporter:William D. Woodul, Anne F. Richards, Andreas Stasch, Matthias Driess and Cameron Jones
Organometallics 2010 Volume 29(Issue 16) pp:3655-3660
Publication Date(Web):July 19, 2010
DOI:10.1021/om100595a
The reaction of a sterically bulky β-diketiminato lithium complex [Li(ButNacnac)] (ButNacnac = [{N(Dip)C(But)}2CH]−, Dip = C6H3Pri2-2,6) with GeCl2·dioxane has given the germanium(II) chloride complex [(ButNacnac)GeCl] (3). Both it and its known tin analogue, [(ButNacnac)SnCl] (4), were crystallographically characterized and found to be monomeric in the solid state. The reduction of both complexes with elemental lithium in THF led to lithium complexes of N-heterocyclic germylidenide and stannylidenide anions, viz., [(THF)Li{η5-EC(But)C(H)C(But)N(Dip)}] (E = Ge, 5; Sn, 6). The reduction of the germanium(II) precursor, 3, also afforded the germanium(II) amide complex [(ButNacnac)Ge{N(H)(Dip)}] (7). The mechanisms of formation of the complexes are thought to involve a number of steps, including reductive ring contraction reactions. The crystallographic and spectroscopic data for [(THF)Li{η5-EC(But)C(H)C(But)N(Dip)}] indicate a significant degree of aromatic π-delocalization within their heterocycles.
Co-reporter:Shenglai Yao, Xinhao Zhang, Yun Xiong, Helmut Schwarz, and Matthias Driess
Organometallics 2010 Volume 29(Issue 21) pp:5353-5357
Publication Date(Web):June 22, 2010
DOI:10.1021/om100383y
N-Heterocyclic germylene LGe [L = CH{(C═CH2)(CMe)(N(aryl))2}, aryl = 2,6-iPr2C6H3] 1 reacts with HN(C6F5)2 solely to give the 1,4-addition product L′GeN(C6F5)2 2 (L′ = CH(CMe)2[N(aryl)]2), which contains a Ge(II)-N(C6F5)2 moiety. In contrast, HN(SiMe3)2 does not add to 1 but induces isomerization of 1 to generate the first N(aryl)H-substituted, heteroaromatic azagermabenzen-1-ylidene intermediate. The latter readily undergoes 1,4-addition to a second equivalent of 1 to form the unprecedented bis(germylene) 3, which contains two- and three-coordinate Ge(II) centers. The isomerization process and the nature of the six π-electron aromatic character of the C4NGe heterocycle in 2 are explored and supported by DFT calculations.
Co-reporter:NicolasA. Marinos;Stephan Enthaler Dr. Dr.
ChemCatChem 2010 Volume 2( Issue 7) pp:846-853
Publication Date(Web):
DOI:10.1002/cctc.201000036
Abstract
The diprotic, tridentate O,S,O-ligands LH2 {[RC(=O)CH2]2S; R=tBu (3 a) or Ph (3 b)}, comprising hard (O) and soft (S) donor atoms, have been employed for the first time in zinc-mediated hydrosilylation of various ketones, giving, after protolytic workup, the corresponding alcohols. The respective precatalysts used are novel thiobis(enolato) zinc complexes, [LZn(tmeda)] [L=3 a−2H+ (4 a) or 3 b−2H+ (4 b); tmeda= N,N,N′,N′-tetramethylethylenediamine], [LZn(bipy)] [L=3 a−2H+ (5 a); bipy=2,2′-bipyridine], [LZn(phen)] [L=3 a−2H+ (6 a); phen=1,10-phenanthroline], and [LZn(dabco)] [L=[3 a−2H+] (7 a); dabco=1,4-diazabicyclo[2.2.2]octane]. These complexes are accessible by simple Brønsted acid–base reaction of 3 a or 3 b with dimethylzinc in a 1:1 molar ratio in the presence of tmeda, bipy, phen, or dabco as auxiliary ligands. The first four complexes are isolated as yellow or colorless crystals in 76 % (4 a), 53 % (4 b), 58 % (5 a), and 61 % (6 a) yields, whereas 7 a (74 % yield) is isolated as colorless powder. The zinc center in 4 a, 4 b, 5 a, and 6 a has trigonal bipyramidal coordination, as proven by single-crystal X-ray diffraction analysis. Remarkably, 4 a shows the highest catalytic activity hitherto reported for zinc-catalyzed hydrosilylation over a wide range of substrates with a turnover frequency of 970 h−1. Furthermore, a catalytic mechanism is proposed.
Co-reporter:Shenglai Yao Dr.;Yun Xiong Dr. Dr.
Chemistry - A European Journal 2010 Volume 16( Issue 4) pp:1281-1288
Publication Date(Web):
DOI:10.1002/chem.200902467
Abstract
A series of N-heterocyclic carbene-stabilized silanechalcogenones 2 a,b (SiO), 3 a,b (SiS), 4 a,b (SiSe), and 5 a,b (SiTe) are described. The silanone complexes 2 a,b were prepared by facile oxygenation of the carbene–silylene adducts 1 a,b with N2O, whereas their heavier congeners were synthesized by gentle chalcogenation of 1 a,b with equimolar amounts of elemental sulfur, selenium, and tellurium, respectively. These novel compounds have been isolated in a crystalline form in high yields and have been fully characterized by a variety of techniques including IR spectroscopy, ESIMS, and multinuclear NMR spectroscopy. The structures of 2 b, 3 a, 4 a, 4 b, and 5 b have been confirmed by single-crystal X-ray crystallography. Due to the NHCSi donor–acceptor electronic interaction, the SiE (E=O, S, Se, Te) moieties within these compounds are well stabilized and thus the compounds possess several ylide-like resonance structures. Nevertheless, these species also exhibit considerable SiE double-bond character, presumably through a nonclassical SiE π-bonding interaction between the chalcogen lone-pair electrons and two antibonding SiN σ* orbitals, as evidenced by their high stretching vibration modes and the shortening of the Si–E distances (between 5.4 and 6.3 %) compared with the corresponding SiE single-bond lengths.
Co-reporter:Shenglai Yao Dr.;Yun Xiong Dr.;Carsten Milsmann Dr.;Eckhard Bill Dr.;Stefan Pfirrmann Dipl.-Chem.;Christian Limberg Dr. Dr.
Chemistry - A European Journal 2010 Volume 16( Issue 2) pp:436-439
Publication Date(Web):
DOI:10.1002/chem.200902820
Co-reporter:Yun Xiong Dr.;Shenglai Yao Dr. Dr.
Chemistry – An Asian Journal 2010 Volume 5( Issue 2) pp:322-327
Publication Date(Web):
DOI:10.1002/asia.200900434
Abstract
The syntheses and reactivity of the two N-heterocyclic carbene (NHC) silylene complexes 2 and 4 have been investigated. The latter are easily accessible by reaction of the zwitterionic, N-heterocyclic silylene LSi: 1 [L=Ar-N-C(=CH2)CHC(Me)-N-Ar, Ar=2,6-iPr2C6H3] with 1,3,4,5-tetramethylimidazol-2-ylidene and 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene, respectively. While compound 2 undergoes facile rearrangement above −20 °C to give the unsymmetrical N-heterocyclic silylcarbene 3, the derivative 4 remains unchanged even after boiling in benzene. The remarkable reactivity of 3 and 4 towards cyclohexylisocyanide has been examined which leads in a unique series of CH, SiH, and CN bond activations to the new triaminosilanes 5 and 6, respectively. The novel compounds 3, 4, 5, and 6 were fully characterized by 1H, 13C, and 29Si NMR spectroscopy, EI-MS, elemental analysis, and single-crystal X-ray diffraction.
Co-reporter:Anna Company Dr.;Shenglai Yao Dr.;Kallol Ray Dr. Dr.
Chemistry - A European Journal 2010 Volume 16( Issue 31) pp:9669-9675
Publication Date(Web):
DOI:10.1002/chem.201001138
Abstract
Although O2 activation by metals such as iron and copper has been a matter of intensive research in the last decades, this type of chemistry for nickel systems is still in its infancy. Moreover, studies regarding the oxidizing ability of the resulting “Nin–O2” species towards exogenous substrates are scarce. In this work, we report on the reactivity of an isolable and thermally stable mononuclear superoxo–nickel compound [NiII(β-diketiminato)(O2)] (1) towards different types of organic substrates. In addition, we have been able to prove that the β-diketiminato ligand can undergo partial intramolecular oxidation due to close proximity between the isopropyl groups of the β-diketiminato-aryl and the superoxo subunits. Compound 1 performs hydrogen-atom abstraction from O-H and N-H groups and most importantly it shows an unprecedented dioxygenase-like reactivity in the oxidation of 2,4,6-tri-tert-butylphenol. The latter reaction most likely occurs through the mediation of a putative [NiIII-oxo] intermediate, affording an unprecedented oxidation product of the phenol that incorporates two oxygen atoms from a single O2 subunit. Results presented herein provide evidence of the striking oxidizing ability of dioxygen–nickel species and further support the viability to use such systems as oxidation catalysts analogous to its heavy metal congener, palladium.
Co-reporter:Antje Meltzer ; Carsten Präsang
Journal of the American Chemical Society 2009 Volume 131(Issue 21) pp:7232-7233
Publication Date(Web):May 8, 2009
DOI:10.1021/ja9026727
The first silicon(II) hydroxide and related electronically tunable NHSi ligands have been synthesized in the coordination sphere of a [Ni(CO)3] moiety through facile addition of water and other electrophiles to the corresponding NHSi-tricarbonylnickel complex. The latter modified silicon (II) ligands are unique and exhibit striking donor/acceptor capabilities depending on their substitution pattern. While strong Lewis acids [H+ or B(C6F5)3] lead to modified silicon(II) ligands in the coordination sphere of nickel with an increased π-acceptor and decreased σ-donor character (PF3-like), by contrast, addition of water or trifluoromethanesulfonic acid furnishes the corresponding donor-stabilized silicon(II)−nickel complexes with a inverse donor/acceptor strength similar to those of triorganophosphines and NHCs.
Co-reporter:Yun Xiong ; Shenglai Yao
Journal of the American Chemical Society 2009 Volume 131(Issue 22) pp:7562-7563
Publication Date(Web):May 12, 2009
DOI:10.1021/ja9031049
The unique isolable silanone complex 3 has been synthesized and isolated in 94% yield by the remarkably facile oxygenation of the NHC−silylene precursor 2 featuring a Si(II) atom with unusually high nucleophilicity. The latter precursor is easily accessible by reaction of the stable silylene 1 with the corresponding N-heterocyclic carbene (NHC) at −60 °C. The remarkably short Si═O distance of 1.541(2) Å in 3 suggests the presence of a betaine-like Si═O π system with balanced electrostatics.
Co-reporter:Shenglai Yao, Yun Xiong and Matthias Driess
Chemical Communications 2009 (Issue 42) pp:6466-6468
Publication Date(Web):08 Sep 2009
DOI:10.1039/B914060C
The unique isolable N-heterocyclic carbene (NHC)→germanone complexes 3a and 3b were synthesised and structurally characterised, starting from the corresponding NHC–germylene precursors 2a and 2b through straightforward oxygenation with N2O.
Co-reporter:Wenyuan Wang, Shigeyoshi Inoue, Shenglai Yao and Matthias Driess
Chemical Communications 2009 (Issue 19) pp:2661-2663
Publication Date(Web):23 Mar 2009
DOI:10.1039/B900592G
Convenient salt metathesis reaction of the N-heterocyclic germanium(II) nucleophile LGeK(Et2O)2 [L = C(Me)CHC(Me)N(2,6-iPr2C6H3)] with the β-diketiminato Ge(II) chloride L′GeCl [L′ = CH{CMe(NR)}2, R = 2,6-iPr2C6H3] and the tin analogue L′SnCl furnishes the corresponding novel digermylene having a Ge(I)–Ge(I) bond and the first germylene–stannylene with a Ge(I)–Sn(I) bond, respectively; spectroscopic, structural and theoretical analysis of the latter compounds revealed that they bear Ge–M (M = Ge and Sn) σ bonds with ionic character.
Co-reporter:Yun Xiong ; Shenglai Yao ; Eckhard Bill
Inorganic Chemistry 2009 Volume 48(Issue 16) pp:7522-7524
Publication Date(Web):July 10, 2009
DOI:10.1021/ic901088c
The synthesis and characterization of the first heterobinuclear tetraphosphorus complexes 3a and 3b with a [Si(μ,η2:2-P4)Ni] core are reported. The latter result from conversion of the silylene-activated P4 ligand LSiP4 (1; L = CH[(C═CH2)CMe][N(2,6-iPr2C6H3)]2) with the β-diketiminatonickel(I) complexes [(L′Ni)2·toluene] (L′ = CH[CMeN(2,6-iPr2C6H3)]2) and [(L′′Ni)2·toluene] (L′′ = CH[CMeN(2,6-Et2C6H3)]2), respectively. Unexpectedly, the complexes 3a and 3b feature a [Si(μ,η2:2-P4)Ni] core with nickel(I) centers as shown by X-ray diffraction analysis, electron paramagnetic resonance, and magnetic measurements. The latter prove that the products are paramagnetic both in the solid state and in solution because of the presence of tetrahedral nickel(I) sites.
Co-reporter:Surajit Jana, Yilmaz Aksu and Matthias Driess
Dalton Transactions 2009 (Issue 9) pp:1516-1521
Publication Date(Web):08 Jan 2009
DOI:10.1039/B816623D
A convenient and efficient synthesis of the stable monolithium alkylzinc alkoxo cubanes {Li(thf)(RZn)3(OR′)4} [R = Me, R′ = iPr (1), tBu (2); R = Et, R′ = iPr (3), tBu (4)] is reported. They are well soluble in organic solvents and suitable molecular precursors for the formation of Li-containing ZnO nanoparticles. The compounds are accessible by a convenient one-pot reaction of the respective dialkylzinc with lithium alkoxides in the presence of water and can be isolated as white solids in 35–50% yield. Higher yields (80–85%) for 1 and 3 can be achieved by applying excess iPrOH instead of H2O as protolysis source. The compounds 1–4 were characterized by elemental analyses, multinuclear NMR and FT-IR spectroscopy, and single-crystal X-ray diffraction analysis (1 and 2). Interestingly, thermal treatment of solutions of 1 and 2, respectively, in anhydrous benzyl alkohol at 190 °C yields pure and highly crystalline Li-containing ZnO nanoparticles as evidenced by powder X-ray diffraction analysis (PXRD), Transition Electron Microscopy (TEM), FT-IR and 7Li MAS NMR spectroscopy.
Co-reporter:Yun Xiong, Shenglai Yao and Matthias Driess
Dalton Transactions 2009 (Issue 3) pp:421-423
Publication Date(Web):08 Dec 2008
DOI:10.1039/B820285K
Unexpected formation of the novel dianionic N,C-chelate ligand LD2−{HC[C(Me)-NR][C(NHR)=CH]}2− occurs by a twice silicon-assisted C–H bond activation of a terminal methyl group on a β-diketiminato ligand backbone, starting from the corresponding lithium β-diketiminide and silicon tetrabromide to give the new N-heterocyclic dibromosilanes 2 and 3.
Co-reporter:Arne Thomas Dr. Dr.
Angewandte Chemie International Edition 2009 Volume 48( Issue 11) pp:1890-1892
Publication Date(Web):
DOI:10.1002/anie.200805136
Co-reporter:Antje Meltzer;Carsten Präsang Dr.;Carsten Milsmann Dr.
Angewandte Chemie International Edition 2009 Volume 48( Issue 17) pp:3170-3173
Publication Date(Web):
DOI:10.1002/anie.200900290
Co-reporter:Shenglai Yao Dr.;Yun Xiong Dr.;Xinhao Zhang Dr.;Maria Schlangen Dr.;Helmut Schwarz Dr.;Carsten Milsmann Dipl.-Chem. Dr.
Angewandte Chemie International Edition 2009 Volume 48( Issue 25) pp:4551-4554
Publication Date(Web):
DOI:10.1002/anie.200901132
Co-reporter:Shenglai Yao Dr.;Yun Xiong Dr.;Matthias Vogt Dipl.-Chem.;Hansjörg Grützmacher Dr.;Christian Herwig Dr.;Christian Limberg Dr. Dr.
Angewandte Chemie International Edition 2009 Volume 48( Issue 43) pp:8107-8110
Publication Date(Web):
DOI:10.1002/anie.200903772
Co-reporter:Yilmaz Aksu Dr. Dr.
Angewandte Chemie International Edition 2009 Volume 48( Issue 42) pp:7778-7782
Publication Date(Web):
DOI:10.1002/anie.200901204
Co-reporter:Yun Xiong Dr.;Shenglai Yao Dr. Dr.
Chemistry - A European Journal 2009 Volume 15( Issue 22) pp:5545-5551
Publication Date(Web):
DOI:10.1002/chem.200900318
Co-reporter:Yun Xiong;Shenglai Yao
Chemistry – An Asian Journal 2009 Volume 4( Issue 8) pp:1323-1328
Publication Date(Web):
DOI:10.1002/asia.200900127
Abstract
A way to synthesize the transient zwitterionic silylene L′Si: 8 {L’=CH[(C=CH2)CMe(N(tBu))2]} and achieve its facile dimerization to the remarkable N-heterobicyclic disilane 82 is described. At first, employing the β-diketiminate ligand L [L=CH(CMeN(tBu))2], both starting materials LH (2) and its N-lithium salt LLi (3) can react with SiBr4 to yield the silylene precursor L′SiBr2 (4) by silicon-induced CH activation at an exocyclic methyl group on the backbone of the ligand. Compound 4 reacts with SiBr4 above room temperature to afford the unexpected terminal CH(SiBr3)-substituted dibromosilane 6 along with the unique tricyclic trisilane 7. Reduction of 4 with KC8 at 0 °C furnishes the novel N-heterobicyclic disilane 82, which is a formal dimer of the desired zwitterionic silylene L′Si: (8). It has been reasoned that compound 82 may results from [4+1] cycloaddition of two molecules of 8 to give the transient dimer 82′, which subsequently undergoes hydrogen transfer from a terminal methyl group on the backbone of the C3N2Si ligand to the low-coordinate Si atom. The latter dimerization can be rationalized by the intrinsic zwitterionic character of 8 and insufficient steric protection through the tBu groups at the nitrogen atoms. The novel compounds 3, 4, 6, 7, and 82 have been characterized by 1H, 13C, and 29Si NMR spectroscopy, mass spectrometry, and elemental analysis. Additionally, the structures of 3, 6, 7, and 82 were also established by single-crystal X-ray diffraction analyses.
Co-reporter:Yun Xiong Dr.;Shenglai Yao Dr. Dr.
Chemistry - A European Journal 2009 Volume 15( Issue 34) pp:8542-8547
Publication Date(Web):
DOI:10.1002/chem.200901337
Abstract
The reactivity of the zwitterionic N-heterocyclic silylene (NHS) LSi: 1 (L=ArNC(Me)CHC(CH2)NAr, Ar=2,6-iPr2C6H3), towards diphenyldiazomethane (Ph2CN2), trimethylsilyl azide (Me3SiN3), and cyclohexyl isocyanide (C6H11NC) is reported. The addition of Ph2CN2 to 1 leads to the diiminylsilane LSi(NCPh2)22 (80 % yield), whereas the treatment of 1 with Me3SiN3 gives the spirobicyclic silatetrazoline LSi(NNSiMe3)23 (67 % yield), and addition of C6H11NC gives the silyl cyanide LSi(R)CN (R=cyclohexyl) 4 (32 % yield) along with the unexpected azasilacyclobutane 5 (41 % yield). The novel compounds were fully characterized by 1H, 13C, and 29Si NMR spectroscopy, ESIMS, elemental analysis, and single-crystal X-ray diffraction.
Co-reporter:Yun Xiong, Shenglai Yao and Matthias Driess
Organometallics 2009 Volume 28(Issue 6) pp:1927-1933
Publication Date(Web):February 27, 2009
DOI:10.1021/om801157u
The insertion of the thermally stable ylide-like silylene LSi: (1) {L = CH[(C═CH2)CMe][N(Ar)]2], Ar = 2,6-iPr2C6H3} into C−X and Si−X bonds of various small haloalkanes and halosilanes (MeI, PhCH2Br, CH2Cl2, CH2ClI, CH2Br2, CHCl3, MeCCl3, HSiCl3, and MeSiCl3) has been investigated. Surprisingly, the outcome of the reactions is in marked contrast to previous results employing related isolable silylenes. Exclusive formation of 1,1-insertion products LSi(R)X is observed, in a few cases along with a small amount of dihalosilane LSiX2 or monohalosilane LSi(H)X. It is proposed that the reaction occurs via polar 1,4-addition and subsequent rearrangement of the latter kinetic (initial) product to give the 1,1-insertion product. The new compounds have been characterized by 1H, 13C, and 29Si NMR spectroscopy and by single-crystal X-ray diffraction analyses.
Co-reporter:Shenglai Yao, Yun Xiong, Christoph van Wüllen and Matthias Driess
Organometallics 2009 Volume 28(Issue 6) pp:1610-1612
Publication Date(Web):February 23, 2009
DOI:10.1021/om801178g
Addition of equimolar amounts of B(C6F5)3 to the N-heterocyclic silacyclopropenes [LSi(C2H2)] (2; L = CH{(C═CH2)(CMe)(2,6-iPr2C6H3N)2}) affords the first isolable, zwitterionic silacyclopropenylium−boranide compounds 3. Protonation of 2 with the convenient Brønsted acid H(OEt2)2+B(C6F5)4− leads to quantitative formation of the corresponding silacyclopropenylium salt [4-B(C6F5)4].
Co-reporter:Antje Meltzer;Carsten Präsang Dr.;Carsten Milsmann Dr.
Angewandte Chemie 2009 Volume 121( Issue 17) pp:3216-3219
Publication Date(Web):
DOI:10.1002/ange.200900290
Co-reporter:Shenglai Yao Dr.;Yun Xiong Dr.;Xinhao Zhang Dr.;Maria Schlangen Dr.;Helmut Schwarz Dr.;Carsten Milsmann Dipl.-Chem. Dr.
Angewandte Chemie 2009 Volume 121( Issue 25) pp:4621-4624
Publication Date(Web):
DOI:10.1002/ange.200901132
Co-reporter:Yilmaz Aksu Dr. Dr.
Angewandte Chemie 2009 Volume 121( Issue 42) pp:7918-7922
Publication Date(Web):
DOI:10.1002/ange.200901204
Co-reporter:Shigeyoshi Inoue and Matthias Driess
Organometallics 2009 Volume 28(Issue 17) pp:5032-5035
Publication Date(Web):August 18, 2009
DOI:10.1021/om9005802
Conversion of the β-diketiminato Ge(II) chloride LGeCl [L = CH{CMe(NAr)}2, Ar = 2,6-iPr2C6H3] (1) and its tin homologue LSnCl (2) with the anionic iron complex K[Fe(η5-C5H5)(CO)2] leads to the iron-germylene LGeFe(η5-C5H5)(CO)2 (3) and iron-stannylene LSnFe(η5-C5H5)(CO)2 (4), respectively. The compounds 3 amd 4 were characterized by NMR, IR, and UV−vis spectroscopy as well as theoretical studies. The structure of 3 was also determined by X-ray crystallography. The experimental and computed structures show clealy that the Fe−E (E = Ge, Sn) bond is a single bond in compounds 3 and 4. They represent the isolable iron-germylene and -stannylene σ-complexes. Notably, compound 3 is the first example of iron-germylene σ-complexes ever characterized by X-ray analysis.
Co-reporter:Shenglai Yao, Christoph van Wüllen and Matthias Driess
Chemical Communications 2008 (Issue 42) pp:5393-5395
Publication Date(Web):18 Sep 2008
DOI:10.1039/B811952J
The isolable ylide-like N-heterocyclic germylene LGe: (2) {L = CH[(CCH2)CMe][N(aryl)]2, aryl = 2,6-iPr2C6H3} shows an unprecedented dual reactivity toward terminal alkynes: its reaction with acetylene leads via[4+2] cycloaddition to the novel intramolecular donor stabilised germylene 3, while conversion of phenylacetylene furnishes the analogous cycloadduct 4 along with a C–H bond activation product, the novel N-donor stabilised alkynyl germylene 5.
Co-reporter:Klaus Merz, Mariluna Moreno, Elke Löffler, Lamy Khodeir, Andre Rittermeier, Karin Fink, Konstantinos Kotsis, Martin Muhler and Matthias Driess
Chemical Communications 2008 (Issue 1) pp:73-75
Publication Date(Web):12 Nov 2007
DOI:10.1039/B714806B
The remarkably distinct reactivity of hydridozinc heterobimetallic cubanes [(HZnOtBu)4−n(thf·LiOtBu)n] 1a–1d towards CO2 is reported—the hydride transfer from Zn–H to CO2 is drastically accelerated in the presence of Li ions in 1b–1d which led to the respective metal formate hydrates; the systems are inspiring models for the selective conversion of water gas into formates on lithium-promoted ZnO supports.
Co-reporter:Shenglai Yao Dr.;Christoph vanWüllen Dr.;Xiao-Ying Sun Dr. Dr.
Angewandte Chemie 2008 Volume 120( Issue 17) pp:3294-3297
Publication Date(Web):
DOI:10.1002/ange.200704939
Co-reporter:Shenglai Yao Dr.;Christoph vanWüllen Dr.;Xiao-Ying Sun Dr. Dr.
Angewandte Chemie International Edition 2008 Volume 47( Issue 17) pp:3250-3253
Publication Date(Web):
DOI:10.1002/anie.200704939
Co-reporter:Shenglai Yao Dr.;Yun Xiong Dr.;Markus Brym Dr. Dr.
Chemistry – An Asian Journal 2008 Volume 3( Issue 1) pp:113-118
Publication Date(Web):
DOI:10.1002/asia.200700285
Abstract
The first silicon analogues of carbonic (carboxylic) esters, the silanoic thio-, seleno-, and tellurosilylesters 3 (SiS), 4 (SiSe), and 5 (SiTe), were prepared and isolated in crystalline form in high yield. These thermally robust compounds are easily accessible by direct reaction of the stable siloxysilylene L(Si:)OSi(H)L′ 2 (L=HC(CMe)2[N(aryl)2], L′=CH[(CCH2)-CMe][N(aryl)]2; aryl=2,6-iPr2C6H3) with the respective elemental chalcogen. The novel compounds were fully characterized by methods including multinuclear NMR spectroscopy and single-crystal X-ray diffraction analysis. Owing to intramolecular NSi donor–acceptor support of the SiX moieties (X=S, Se, Te), these compounds have a classical valence-bond N+–Si–X− resonance betaine structure. At the same time, they also display a relatively strong nonclassical SiX π-bonding interaction between the chalcogen lone-pair electrons (nπ donor orbitals) and two antibonding SiN orbitals (σ*π acceptor orbitals mainly located at silicon), which was shown by IR and UV/Vis spectroscopy. Accordingly, the SiX bonds in the chalcogenoesters are 7.4 (3), 6.7 (4), and 6.9 % (5) shorter than the corresponding SiX single bonds and, thus, only a little longer than those in electronically less disturbed SiX systems (“heavier” ketones).
Die ersten siliciumanalogen Carbonsäureester (Carboxylester) wurden hergestellt und in hoher Ausbeute in kristalliner Form isoliert: Der Thiosilonsäuresilylester 3 (SiS) und seine Se- bzw. Te-Analoga 4 (SiSe) bzw. 5 (SiTe). Die Verbindungen 3–5 sind durch direkte Reaktion des stabilen Siloxysilylens L(Si:)OSi(H)L′ 2 (L=HC(CMe)2[N(aryl)2], L′=CH[(CCH2)CMe][N(aryl)]2; aryl=2,6-iPr2C6H3) mit dem entsprechenden Chalkogen leicht zugänglich. Die neuen Verbindungen wurden vollständig charakterisiert, einschließlich Multikern-NMR Spektroskopie und Einkristallstrukturanalyse. Aufgrund intramolekularer NSi Donor–Acceptorunterstützung der SiX Gruppen (X=S, Se, Te) besitzen diese eine klassische Valence-Bond N+–Si–X− Betain-Resonanzstruktur. Gleichzeitig zeigen diese auch das Vorliegen einer relativ starken nichtklassischen SiX π-Bindungswechselwirkung zwischen den freien Elektronenpaaren am Chalkogen (nπ Donororbitale) und den beiden antibindenden SiN Bindungen (σ* Acceptororbitale mit überwiegender Lokalisierung an Silicium), was durch IR und UV/Vis Spektroskopie gesichert ist. In Einklang damit sind die SiX Abstände in den Chalkogenoestern mit 7.4 (3), 6.7 (4), and 6.9 % (5) kürzer als die entsprechenden Abstände von SiX Einfachbindungen und damit auch nur wenig länger als die Abstände in elektronisch weniger gestörten SiX Systemen (“schwere” Ketone).
Co-reporter:Shenglai Yao, Markus Brym, Klaus Merz and Matthias Driess
Organometallics 2008 Volume 27(Issue 14) pp:3601-3607
Publication Date(Web):June 25, 2008
DOI:10.1021/om800269f
The first stable β-diketiminate germanium(II) complexes LGeY [L = CH{(CMe)(2,6-iPr2C6H3N)}2] with terminal phosphanyl groups Y (Y = PH2, PHR, and PR2) are described. Thus, LGePH2 (2) is synthesized by salt metathesis reaction of LGeCl (1) with lithium phosphanide and can be isolated in the form of orange crystals in 83% yield. Its silylation with 1 molar equiv of Me3SiOTf (OTf = OSO2CF3) in the presence of triethylamine as auxiliary base leads solely to LGeP(H)SiMe3 (3). In contrast, reaction of 2 with 2 molar equiv of Me3SiOTf does not lead to the desired product LGeP(SiMe3)2 (4), but LGeOTf (6) and HP(SiMe3)2 are formed. However, compound 4 is conveniently accessible from 1 and the corresponding lithium phosphanide LiP(SiMe3)2. While attempts to metalate the PH2 group in 2 applying BuLi and Me2Zn, respectively, lead merely to Ge−P fission and undesired side products, its conversion with tBu2Hg occurs without Ge−P fission but P−P bond formation to give the novel P,P′-bis(phosphanylgermylene) LGeP(H)-P(H)GeL (5), elemental mercury, and isobutane. Compounds 2−6 have been fully characterized, including elemental analyses, NMR spectroscopy, and single-crystal X-ray diffraction analysis.
Co-reporter:Shenglai Yao Dr.;Eckhard Bill Dr.;Carsten Milsmann Dipl.-Chem.;Karl Wieghardt Dr. Dr.
Angewandte Chemie International Edition 2008 Volume 47( Issue 37) pp:7110-7113
Publication Date(Web):
DOI:10.1002/anie.200802234
Co-reporter:Shenglai Yao, Stefan Block, Markus Brym and Matthias Driess
Chemical Communications 2007 (Issue 37) pp:3844-3846
Publication Date(Web):23 Aug 2007
DOI:10.1039/B710888E
The synthesis and structures of the first heteroleptic β-diketiminato complexes of lead(II) with terminal phenolato, bis(trimethylsilyl)amido, bis(trimethylsilyl)phosphanido and silylidenephosphanido ligands are reported; 207Pb NMR spectroscopic data indicate that lead(II) can serve as a σ-donor or acceptor centre, depending on the electronegativity of the terminal ligand.
Co-reporter:Yun Xiong Dr.;Shenglai Yao Dr.;Markus Brym Dr. Dr.
Angewandte Chemie International Edition 2007 Volume 46(Issue 24) pp:
Publication Date(Web):4 MAY 2007
DOI:10.1002/anie.200701203
Silylene bites twice in the first insertion of a silylene into a PP bond of the P4 tetrahedron. Reaction of the silylene 1 (see scheme; R=2,6-diisopropylphenyl) with white phosphorus at ambient temperature gives 2 with a tricyclic SiP4 core. The electronic situation in 2 favors the insertion of a second equivalent of 1 into a PP bond of the SiP4 skeleton, affording the novel strained tricyclic silaphosphane 3 with a Si2P4 core.
Co-reporter:Shenglai Yao Dr.;Markus Brym Dr.;Christoph van Wüllen Dr. Dr.
Angewandte Chemie International Edition 2007 Volume 46(Issue 22) pp:
Publication Date(Web):13 APR 2007
DOI:10.1002/anie.200700398
Kipping's dream has (almost) become reality with the first isolable silanone-like complex 2, prepared by borane-assisted addition of water to the stable silylene 1. The short Si–O bond in 2 points to considerable SiO character. In contrast, treatment of 1 with water in the absence of a borane leads to the crystalline siloxy silylene 3, an unprecedented mixed-valent disiloxane with di- and tetravalent silicon atoms (R=2,6-iPr2C6H3).
Co-reporter:Yun Xiong Dr.;Shenglai Yao Dr.;Markus Brym Dr. Dr.
Angewandte Chemie 2007 Volume 119(Issue 24) pp:
Publication Date(Web):4 MAY 2007
DOI:10.1002/ange.200701203
Silylen beißt gleich zweimal zu bei der ersten Insertion eines Silylens in eine P-P-Bindung des P4-Tetraeders. Die Reaktion des Silylens 1 (R=2,6-Diisopropylphenyl) mit weißem Phosphor bei Raumtemperatur ergibt zunächst 2 mit einem tricyclischen SiP4-Gerüst, doch die elektronische Situation in 2 begünstigt die Insertion eines zweiten Äquivalents 1 in eine P-P-Bindung unter Bildung des gespannten tricyclischen Silaphosphans 3 mit Si2P4-Kern.
Co-reporter:Shenglai Yao Dr.;Markus Brym Dr.;Christoph van Wüllen Dr. Dr.
Angewandte Chemie 2007 Volume 119(Issue 22) pp:
Publication Date(Web):13 APR 2007
DOI:10.1002/ange.200700398
Kippings Traum ist mit dem ersten isolierbaren Silanon-artigen Komplex 2 (fast) wahr geworden. Verbindung 2 entstand bei der boranunterstützten Addition von Wasser an das stabile Silylen 1. Die kurze Si-O-Bindung in 2 spricht für einen erheblichen SiO-Charakter. Wird 1 dagegen nur mit Wasser behandelt, erhält man das kristalline Siloxysilylen 3, ein neuartiges gemischtvalentes Disiloxan mit zwei- und vierwertigen Siliciumatomen (R=2,6-iPr2C6H3).
Co-reporter:Miriam Gonschorowsky;Klaus Merz
European Journal of Inorganic Chemistry 2006 Volume 2006(Issue 2) pp:
Publication Date(Web):1 DEC 2005
DOI:10.1002/ejic.200500823
The cyclohexyl-substituted (hydroxymethyl)phosphane CyP(CH2OH)2 (1) has been prepared by reaction of the corresponding primary phosphane CyPH2 with aqueous formaldehyde. Compound 1 has been used as building block for the synthesis of new functionalized water-soluble phosphorus compounds. Thus, Mannich-type condensation of 1 with excess glycine affords the air-stable amino acid phosphane conjugate CyP[CH2N(H)CH2COOH]2 (2). Simple oxidation of 1 with hydrogen peroxide and elemental sulfur leads to the crystalline chalcogenide derivatives CyP(O)(CH2OH)2 (3) and CyP(S)(CH2OH)2 (4). X-ray diffraction analyses of the latter revealed distinct intermolecular hydrogen bonding motifs and possess different types of hydrogen bond networks to each other due to the different proton acceptor ability of the chalcogen atom X of the P=X group (X = O, S): while the oxygen atom of the P=O moiety in 3 serves as proton acceptor, affording a P=O–HO bifurcated network, the sulfur atom of the P=S group denies hydrogen bonding interactions. In addition, the ligand ability of 1 has been studied towards Pt(+2) and Cu(+1) ions: Reaction of 1 with Pt(COD)Cl2 (COD = cycloocta-1,5-diene) furnishes the air-stable complex cis-[PtCl2{CyP(CH2OH)2}2] (5), while the crystalline dimeric Cu(+1) complex [CuI{CyP(CH2OH)2}2]2 (6) results from the reaction of CuI with two molar equivalents of 1. The complex 6 shows a intermolecular hydrogen bonding pattern different from that of 1, 3 and 4, respectively. The new coordination compounds 5 and 6 represent metal-phosphane labelled alcohols which are promising building blocks for the synthesis of metal-based drugs. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Co-reporter:Matthias Driess Dr.;Shenglai Yao Dr.;Markus Brym Dr.;Christoph van Wüllen Dr.
Angewandte Chemie International Edition 2006 Volume 45(Issue 26) pp:
Publication Date(Web):7 JUN 2006
DOI:10.1002/anie.200600237
An electronic chameleon: The planar cyclogermylene 1 can be described by the resonance structures 1 A and 1 B. It is accessible in 79 % yield by dehydrohalogenation of the corresponding (β-diketiminato)chlorogermylene by LiN(SiMe3)2. Although the contribution of the dipolar resonance structure 1 A is relatively small, its influence is seen in the transformations of 1 with Me3SiOTf or 1,2-dibromoethane. R=2,6-diisopropylphenyl.
Co-reporter:Matthias Driess, Stefan Block, Markus Brym,Michael T. Gamer
Angewandte Chemie International Edition 2006 45(14) pp:2293-2296
Publication Date(Web):
DOI:10.1002/anie.200504145
Co-reporter:Matthias Driess Dr.;Shenglai Yao Dr.;Markus Brym Dr.;Christoph van Wüllen Dr.
Angewandte Chemie 2006 Volume 118(Issue 26) pp:
Publication Date(Web):7 JUN 2006
DOI:10.1002/ange.200600237
Ein elektronisches Chamäleon ist das planare Cyclogermylen 1, das mit den Resonanzstrukturen 1 A und 1 B beschrieben werden kann. Es ist in 79 % Ausbeute durch Dehydrochlorierung des entsprechenden (β-Diketiminato)chlorogermylens mit LiN(SiMe3)2 zugänglich. Obwohl der Anteil der dipolaren Resonanzstruktur 1 A relativ gering ist, zeigt das Germylen in Umsetzungen mit Me3SiOTf oder 1,2-Dibromethan eine betainartige Reaktivität. R=2,6-Diisopropylphenyl.
Co-reporter:Matthias Driess Dr.;Stefan Block Dipl.-Chem.;Markus Brym Dr.;Michael T. Gamer Dr.
Angewandte Chemie 2006 Volume 118(Issue 14) pp:
Publication Date(Web):3 MAR 2006
DOI:10.1002/ange.200504145
Außergewöhnlich stabil – auch mit einem Wasserstoffatom am niedrigkoordinierten Phosphorzentrum: Eine einfache Synthese führt zu den thermisch stabilen Phosphasilenen (E)/(Z)-1 mit terminaler PH-Gruppe. Diese werden durch Dimethylzink in Gegenwart von tmeda (Tetramethylethylendiamin) selektiv zum P-Zinkio-substituierten Phosphasilen 2 metalliert, das in der E-Konfiguration vorliegt. R=2,4,6-Triisopropylphenyl.
Co-reporter:Matthias Driess Dr.;Shenglai Yao Dr.;Markus Brym Dr.;Christoph van Wüllen Dr.
Angewandte Chemie International Edition 2006 Volume 45(Issue 40) pp:
Publication Date(Web):20 SEP 2006
DOI:10.1002/anie.200602327
Desperately seeking silyenylium: Electrophilic attack of silylene 1 (R=2,6-diisopropylphenyl) by B(C6F5)3 and H+ afforded the silylene-like zwitterion 2 and the “free” silyliumylidene cation 3 (in the presence of the noncoordinating [B(C6F5)4]− anion), respectively. Cations 2 and 3 represent a novel class of low-coordinate silicon cations with promising potential for the synthesis of heteroleptic silylenes.
Co-reporter:V. Ischenko;S. Polarz;D. Grote;V. Stavarache;K. Fink;M. Driess
Advanced Functional Materials 2005 Volume 15(Issue 12) pp:
Publication Date(Web):12 OCT 2005
DOI:10.1002/adfm.200500087
Zinc oxide in the form of nanoscale materials can be regarded as one of the most important semiconductor oxides at present. However, the question of how chemical defects influence the properties of nanoscale zinc oxide materials has seldom been addressed. In this paper, we report on the introduction of defects into nanoscale ZnO, their comprehensive analysis using a combination of techniques (powder X-ray diffraction (PXRD), X-ray absorption spectroscopy/extended X-ray absorption fine structure (XAS/EXAFS), electron paramagnetic resonance (EPR), magic-angle spinning nuclear magnetic resonance (MAS-NMR), Fourier-transform infrared (FTIR), UV-vis, and photoluminescence (PL) spectroscopies coupled with ab-initio calculations), and the investigation of correlations between the different types of defects. It is seen that defect-rich zinc oxide can be obtained under kinetically controlled conditions of ZnO formation. This is realized by the thermolysis of molecular, organometallic precursors in which ZnO is pre-organized on a molecular scale. It is seen that these precursors form ZnO at low temperatures far from thermodynamic equilibrium. The resulting nanocrystalline ZnO is rich in defects. Depending on conditions, ZnO of high microstructural strain, high content of oxygen vacancies, and particular content of heteroatom impurities can be obtained. It is shown how the mentioned defects influence the electronic properties of the semiconductor nanoparticles.
Co-reporter:Matthias Driess;Joachim Aust;Klaus Merz
European Journal of Inorganic Chemistry 2005 Volume 2005(Issue 5) pp:
Publication Date(Web):15 MAR 2005
DOI:10.1002/ejic.200400820
The syntheses and structures of the new zirconium(+3) silylphosphanido complexes {[Cp2ZrP(H)R]2} 1a {Cp = η5-C5H5; R = SiMe2C(iPr)Me2}, 1b (R = SiiPr3), and 1c (R = SiF(tBu)(2,4,6-iPr3C6H2) are reported. The latter are easily accessible by the reaction of the lithium salts of the corresponding primary silylphosphanes with the Schwartz reagent [Cp2Zr(H)Cl] in THF at –70 °C. They can be isolated in the form of diamagnetic red-black crystals in 68–85 % yield. The central structural motif of the complexes consists of planar (1a, 1b) and slightly puckered Zr2P2 rings (1c), and contains two d1-Zr(+3) centers, which are antiferromagnetically coupled (super exchange, through-bond interaction) although the transannular Zr–Zr separation is around 360 pm. Thus, the compounds have a biradicaloid electronic structure. Heating of solutions of 1a–c in toluene in the presence of Pd/C or [(Ph3P)2Pt(C2H4)] results in catalytic dehydrogenation of the P–H bonds, affording the first neutral zirconocene–phosphinidene dimers [Cp2ZrPR]23a–c in the form of deep red crystals in 72–88 % yield. The composition of the products is proven by multinuclear NMR spectroscopy, mass spectrometry and correct C,H-combustion analyses. The molecular structures of 3a and 3c were additionally confirmed by X-ray crystal structure analyses, showing that they consist of Zr2P2 rings with significantly shorter Zr–P distances than those observed in 1a and 1c. Interestingly, the dehydrogenation of the mostly sterically crowded derivative 1c occurs also in boiling toluene solutions without using a catalyst, but the process is prevented in a H2 atmosphere. This suggests that the Zr(+3) centers in 1c can serve as active sites for the P–H bonding activation, which, however, are deactivated in the presence of H2. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Co-reporter:Matthias Driess, Nicoleta Muresan,Klaus Merz
Angewandte Chemie International Edition 2005 44(41) pp:6738-6741
Publication Date(Web):
DOI:10.1002/anie.200501997
Co-reporter:Matthias Driess Dr.;Nicoleta Muresan Dr.;Klaus Merz Dr.;Michael Päch Dr.
Angewandte Chemie 2005 Volume 117(Issue 41) pp:
Publication Date(Web):21 SEP 2005
DOI:10.1002/ange.200501990
Dominocyclisierung zweier Phosphinidenmoleküle: Die Methylierung des nucleophilen Phosphinidens 1 mit Methyltriflat liefert den ungewöhnlichen Phosphoniumkäfig 2, was für das Phospheniumion 3 als reaktive Zwischenstufe spricht.
Co-reporter:Matthias Driess Dr.;Nicoleta Muresan Dr.;Klaus Merz Dr.
Angewandte Chemie 2005 Volume 117(Issue 41) pp:
Publication Date(Web):27 SEP 2005
DOI:10.1002/ange.200501997
Sogar das elektropositive Element Silicium löst Elektronentransferprozesse in Amidobis(enolat)-Komplexen aus: Dies belegen die Umsetzungen von Halogeniden RSiX3 mit HN[CH2C(O)tBu]2 in Gegenwart einer Base. Bei kleinen Substituenten R erhält man die pentakoordinierten Komplexe 1 (R=H, Cl, Br, Ph), mit der sperrigeren tBu3Si-Gruppe den tetrakoordinierten Komplex 2.
Co-reporter:Matthias Driess, Nicoleta Muresan, Klaus Merz,Michael P
ch
Angewandte Chemie International Edition 2005 44(41) pp:6734-6737
Publication Date(Web):
DOI:10.1002/anie.200501990
Co-reporter:Maria-Chrysanthi Kafentzi, Maylis Orio, Marius Réglier, Shenglai Yao, Uwe Kuhlmann, Peter Hildebrandt, Matthias Driess, A. Jalila Simaan and Kallol Ray
Dalton Transactions 2016 - vol. 45(Issue 40) pp:NaN16000-16000
Publication Date(Web):2016/07/28
DOI:10.1039/C6DT02391F
Two new heterobimetallic [LNiO2Cu(RPY2)]+ (RPY2 = N-substituted bis 2-pyridyl(ethylamine) ligands with R = indane, 3a or R = Me, 3b) complexes have been spectroscopically trapped at low temperatures. They were prepared by reacting the mononuclear side-on LNiII superoxo precursor bearing a β-diketiminate ligand (L = [HC-(CMeNC6H3(iPr)2)2]) with the Cu(I) complexes. In contrast to the oxo groups in known high-valent [M2(μ-O)2]n+ (M = Fe, Co, Ni, Cu) cores that display electrophilic reactivities, 3a and 3b display rather nucleophilic oxo cores active in aldehyde deformylation reactions. However, the spectroscopic and reactivity properties of 3a/3b are found to be distinct relative to that of the previously reported [LNiO2Cu(MeAN)]+ complex containing a more basic (nucleophilic) N,N,N′,N′,N′-pentamethyl-dipropylenetriamine (MeAN) ligand at the copper centre. The geometry and electronic properties of the copper ligands affect the electron density of the oxygen atoms of the heterodinuclear {Ni(μ-O)2} core and 3a/3b undergo slower nucleophilic and faster electrophilic reactions than the previously reported [LNiO2Cu(MeAN)]+ intermediate. The present study therefore demonstrates the tuning of the electrophilicity/nucleophilicity of the oxygen atoms of the heterobimetallic [Ni(μ-O)2Cu]2+ cores by controlling the electron donation from the ancillary ligands, and underlines the significance of subtle electronic changes in the physical and chemical properties of the biologically relevant heterobimetallic metal–dioxygen intermediates.
Co-reporter:Arindam Indra, Prashanth W. Menezes, Kamalakannan Kailasam, Dirk Hollmann, Marc Schröder, Arne Thomas, Angelika Brückner and Matthias Driess
Chemical Communications 2016 - vol. 52(Issue 1) pp:NaN107-107
Publication Date(Web):2015/10/15
DOI:10.1039/C5CC07936E
The nature of a nickel-based co-catalyst deposited on a sol–gel prepared porous graphitic-carbon nitride (sg-CN), for photocatalytic H2 production from water, has been investigated. The formation of the active catalytic species, charge separation and recombination of the photogenerated electrons and holes during photochemical H2 evolution has been determined for the first time using in situ EPR spectroscopy.
Co-reporter:Prashanth W. Menezes, Arindam Indra, Ophir Levy, Kamalakannan Kailasam, Vitaly Gutkin, Johannes Pfrommer and Matthias Driess
Chemical Communications 2015 - vol. 51(Issue 24) pp:NaN5008-5008
Publication Date(Web):2015/02/13
DOI:10.1039/C4CC09671A
Nickel–manganese oxides with variable Ni:Mn ratios, synthesised from heterobimetallic single-source precursors, turned out to be efficient water oxidation catalysts. They were subjected to oxidant-driven, photo- and electro-catalytic water oxidation showing superior activity and remarkable stability. In addition, a structure–activity relation could be established.
Co-reporter:Yun Xiong, Shenglai Yao and Matthias Driess
Chemical Communications 2014 - vol. 50(Issue 4) pp:NaN420-420
Publication Date(Web):2013/11/01
DOI:10.1039/C3CC48166B
Starting from the chlorogermyliumylidene chloride salt [L(Cl)Ge:]Cl (1) (L = 1,1′-methylene-3,3′-di-2,6-diisopropyl-phenylimidazole-2,2′-diylidene), the chloride ion can be easily substituted by BPh4 to yield [L(Cl)Ge:]BPh4 (3). Reaction of the latter with NaN3 furnishes [L(N3)Ge:]BPh4 (4). In contrast, the direct reaction of 1 with NaN3 affords exclusively the first azidogermyliumylidene azide salt [L(N3)Ge:]N3 (2). The latter represents the first isolable diazido Ge(II) complex with a covalently bonded azido ligand and a weakly coordinating azide anion as the counterion. All new compounds 2, 3, and 4 were fully characterized, including using X-ray diffraction analysis.
Co-reporter:Yun Xiong, Shenglai Yao, Shigeyoshi Inoue, Andreas Berkefeld and Matthias Driess
Chemical Communications 2012 - vol. 48(Issue 100) pp:NaN12200-12200
Publication Date(Web):2012/11/02
DOI:10.1039/C2CC36926E
The novel chlorogermyliumylidene complex L[ClGe:]+ (L = 1,8-bis(tri-n-butylphosphanzenyl)naphthalene) with a ‘naked’ Cl− as a counter anion was synthesized through reaction of L with Cl2Ge: and fully characterized. Its reaction with elemental sulfur afforded the first germathionium [ClGeS]+ cation containing species. The latter has also been fully characterized, including single-crystal X-ray diffraction analysis.
Co-reporter:Gengwen Tan, Yun Xiong, Shigeyoshi Inoue, Stephan Enthaler, Burgert Blom, Jan D. Epping and Matthias Driess
Chemical Communications 2013 - vol. 49(Issue 49) pp:NaN5597-5597
Publication Date(Web):2013/05/01
DOI:10.1039/C3CC41965G
The facile synthesis of the first stable selenosilanoic acid–base adduct LSi(Se)OH(dmap) 3 (L = CH[C(Me)NAr]2, Ar = 2,6-iPr2C6H3, dmap = 4-dimethylaminopyridine), the heavier analogue of the thiosilanoic acid adduct LSi(S)OH(dmap) 1, is reported. Both adducts 1 and 3 react readily with MesCu (Mes = 2,4,6-trimethylphenyl) to form the novel dimeric Cu(I) complexes [LSi(E)OCu]2 (4: E = S; 5: E = Se) with unprecedented intermolecular SiE → Cu–O–Si coordination modes. The latter are efficient pre-catalysts for the Cu(I)-mediated aziridination of styrene with PhIN(Ts) (Ts = tosyl).
Co-reporter:Wenyuan Wang;Shigeyoshi Inoue;Shenglai Yao
Chemical Communications 2009(Issue 19) pp:
Publication Date(Web):2009/05/07
DOI:10.1039/B900592G
Convenient salt metathesis reaction of the N-heterocyclic germanium(II) nucleophile LGeK(Et2O)2 [L = C(Me)CHC(Me)N(2,6-iPr2C6H3)] with the β-diketiminato Ge(II) chloride L′GeCl [L′ = CH{CMe(NR)}2, R = 2,6-iPr2C6H3] and the tin analogue L′SnCl furnishes the corresponding novel digermylene having a Ge(I)–Ge(I) bond and the first germylene–stannylene with a Ge(I)–Sn(I) bond, respectively; spectroscopic, structural and theoretical analysis of the latter compounds revealed that they bear Ge–M (M = Ge and Sn) σ bonds with ionic character.
Co-reporter:Chika I. Someya, Shigeyoshi Inoue, Carsten Präsang, Elisabeth Irran and Matthias Driess
Chemical Communications 2011 - vol. 47(Issue 23) pp:NaN6601-6601
Publication Date(Web):2011/04/26
DOI:10.1039/C1CC11789K
Cationic and zwitterionic boryl bromide species and a borenium–boryl bromide cation have been synthesised which represent new N-donor stabilised cationic boron compounds with β-diketiminate ligands. The unexpected borenium–boryl bromide results from a head-to-tail dimerisation of the corresponding zwitterionic boryl bromide accompanied by proton migration. The electronic nature of these new species was studied by DFT calculations.
Co-reporter:Shenglai Yao, Yun Xiong and Matthias Driess
Chemical Communications 2009(Issue 42) pp:NaN6468-6468
Publication Date(Web):2009/09/08
DOI:10.1039/B914060C
The unique isolable N-heterocyclic carbene (NHC)→germanone complexes 3a and 3b were synthesised and structurally characterised, starting from the corresponding NHC–germylene precursors 2a and 2b through straightforward oxygenation with N2O.
Co-reporter:Shenglai Yao, Christoph van Wüllen and Matthias Driess
Chemical Communications 2008(Issue 42) pp:NaN5395-5395
Publication Date(Web):2008/09/18
DOI:10.1039/B811952J
The isolable ylide-like N-heterocyclic germylene LGe: (2) {L = CH[(CCH2)CMe][N(aryl)]2, aryl = 2,6-iPr2C6H3} shows an unprecedented dual reactivity toward terminal alkynes: its reaction with acetylene leads via[4+2] cycloaddition to the novel intramolecular donor stabilised germylene 3, while conversion of phenylacetylene furnishes the analogous cycloadduct 4 along with a C–H bond activation product, the novel N-donor stabilised alkynyl germylene 5.
Co-reporter:Shenglai Yao, Stefan Block, Markus Brym and Matthias Driess
Chemical Communications 2007(Issue 37) pp:NaN3846-3846
Publication Date(Web):2007/08/23
DOI:10.1039/B710888E
The synthesis and structures of the first heteroleptic β-diketiminato complexes of lead(II) with terminal phenolato, bis(trimethylsilyl)amido, bis(trimethylsilyl)phosphanido and silylidenephosphanido ligands are reported; 207Pb NMR spectroscopic data indicate that lead(II) can serve as a σ-donor or acceptor centre, depending on the electronegativity of the terminal ligand.
Co-reporter:Yun Xiong, Shenglai Yao, Miriam Karni, Arseni Kostenko, Alexander Burchert, Yitzhak Apeloig and Matthias Driess
Chemical Science (2010-Present) 2016 - vol. 7(Issue 8) pp:NaN5469-5469
Publication Date(Web):2016/05/10
DOI:10.1039/C6SC01839D
In contrast to molecular CO and CO2, their heavier mono- and dichalcogenide homologues, EX and EX2 (E = Si, Ge, Sn, Pb; X = O, S, Se, Te), are important support materials (e.g., SiO2) and/or semiconductors (e.g., SiS2) and exist typically as insoluble crystalline or amorphous polymers under normal conditions. Herein, we report the first successful synthesis and characterisation of an extraordinary series of isolable monomeric GeX and GeX2 complexes (X = S, Se, Te), representing novel classes of compounds and heavier congeners of CO and CO2. This could be achieved by solvent-dependent oxidation reactions of the new zero-valent germanium (‘germylone’)–GaCl3 precursor adduct (bis-NHC)Ge0→GaCl31 (bis-NHC = H2C[{NC(H)C(H)N(Dipp)}C:]2, Dipp = 2,6-iPr2C6H3) with elemental chalcogens, affording the donor–acceptor stabilised monomeric germanium(IV) dichalcogenide (bis-NHC)GeIV(X)X→GaCl3 (X = S, 2; X = Se, 3) and germanium(II) monochalcogenide complexes (bis-NHC)GeIIX→GaCl3 (X = Se, 4; X = Te, 5), respectively. Moreover, the reactivity of 4 and 5 towards elemental sulphur, selenium, and tellurium has been investigated. In THF, the germanium(II) monoselenide complex 4 reacts with activated elemental selenium to afford the desired germanium(IV) diselenide complex 3. Unexpectedly, both reactions of 4 and 5 with elemental sulphur, however, lead to the formation of germanium(IV) disulfide complex 2 under liberation of elemental Se and Te as a result of further oxidation of the germanium centre and replacement of the Se and Te atoms by sulphur atoms. All novel compounds 1–5 have been fully characterised, including single-crystal X-ray diffraction analyses, and studied by DFT calculations.
Co-reporter:Burgert Blom, Daniel Gallego and Matthias Driess
Inorganic Chemistry Frontiers 2014 - vol. 1(Issue 2) pp:NaN148-148
Publication Date(Web):2014/01/13
DOI:10.1039/C3QI00079F
The present account is a review of all N-heterocyclic silylene (NHSi) transition metal complexes that have been employed in catalytic transformations, reported up to the present time (2013). NHSi transition metal complexes now enjoy indefatigable attention since their facile isolation was realised by the report of the first isolable NHSis by West and Denk in 1994. Despite considerable research activity since then, in comparison to ubiquitous N-heterocyclic carbene (NHC) complexes, NHSi complexes are still comparatively rare. Accordingly, in comparison to the plethora of reports associated with NHC complexes, implicated in catalytic processes, only scant examples exist for NHSi complexes. Some of these reports include Heck or Suzuki type coupling, alkyne cyclotrimerisation, ketone hydrosilylation, amide reduction or Sonogashira cross-coupling reactions, and are discussed in detail here. These endeavours pave the way for new families of catalysts based on NHSis and highlight the potential future applications of these emerging and rather unexplored complexes in novel catalytic processes.
Co-reporter:Arindam Indra, Prashanth W. Menezes, Chittaranjan Das, Dieter Schmeißer and Matthias Driess
Chemical Communications 2017 - vol. 53(Issue 62) pp:NaN8644-8644
Publication Date(Web):2017/06/27
DOI:10.1039/C7CC03566G
Multi-shelled hollow spheres of cobalt manganese oxides (CMOs) deposited on Ni foam exhibited superior alkaline electrochemical water oxidation activity and surpassed those of bulk CMO and commercial noble metal-based catalysts. A higher amount of cobalt in the spinel structure resulted in the transformation of the tetragonal to the cubic phase with a decrease in the overpotential of oxygen evolution.
Co-reporter:Arindam Indra, Prashanth W. Menezes, Chittaranjan Das, Caren Göbel, Massimo Tallarida, Dieter Schmeiβer and Matthias Driess
Journal of Materials Chemistry A 2017 - vol. 5(Issue 10) pp:NaN5177-5177
Publication Date(Web):2017/02/09
DOI:10.1039/C6TA10650A
Ultra-small rock salt cobalt monoxide (CoO) nanoparticles were synthesized and subjected to partial oxidation (‘corrosion’) with ceric ammonium nitrate (CAN) to form mixed-valence CoOx (1 < x < 2) water oxidation catalysts. Spectroscopic, microscopic and analytical methods evidenced a structural reformation of cubic CoO to active CoOx with a spinel structure. The superior water oxidation activity of CoOx has been established in electrochemical water oxidation under alkaline conditions. Electrochemical water oxidation with CoOx was recorded at a considerably low overpotential of merely 325 mV at a current density of 10 mA cm−2 in comparison to 370 mV for CoO. Transformation of both octahedral CoII and CoIII sites into amorphous Co(OH)2–CoOOH is the key to high electrochemical activity while the presence of a higher amount of octahedral CoIII sites in CoOx is imperative for an efficient oxygen evolution process.
Co-reporter:Prashanth W. Menezes, Arindam Indra, Arno Bergmann, Petko Chernev, Carsten Walter, Holger Dau, Peter Strasser and Matthias Driess
Journal of Materials Chemistry A 2016 - vol. 4(Issue 25) pp:NaN10022-10022
Publication Date(Web):2016/06/06
DOI:10.1039/C6TA03644A
The fabrication and design of earth-abundant and high-performance catalysts for the oxygen evolution reaction (OER) are very crucial for the development and commercialization of sustainable energy conversion technologies. Although spinel catalysts have been widely explored for the electrochemical oxygen evolution reaction (OER), the role of two geometrical sites that influence their activities has not been well established so far. Here, we present more effective cobalt–zinc oxide catalysts for the OER than ‘classical’ Co3O4. Interestingly, the significantly higher catalytic activity of ZnCo2O4 than that of Co3O4 is somewhat surprising since both crystallize in the spinel-type structure. The reasons for the latter remarkable difference of ZnCo2O4 and Co3O4 could be deduced from structure–activity relationships of the bulk and near-surface of the catalysts using comprehensive electrochemical, microscopic and spectroscopic techniques with a special emphasis on the different roles of the coordination environment of metal ions (octahedral vs. tetrahedral sites) in the spinel lattice. The vital factors influencing the catalytic activity of ZnCo2O4 over Co3O4 could be directly attributed to the higher amount of accessible octahedral Co3+ sites induced by the preferential loss of zinc ions from the surface of the ZnCo2O4 catalyst. The enhanced catalytic activity is accompanied by a larger density of metal vacancies, defective sites and hydroxylation. The results obtained here clearly demonstrate how a surface structural modification and generation of defects of catalysts can enhance their OER performance.
Co-reporter:Surajit Jana, Yilmaz Aksu and Matthias Driess
Dalton Transactions 2009(Issue 9) pp:NaN1521-1521
Publication Date(Web):2009/01/08
DOI:10.1039/B816623D
A convenient and efficient synthesis of the stable monolithium alkylzinc alkoxo cubanes {Li(thf)(RZn)3(OR′)4} [R = Me, R′ = iPr (1), tBu (2); R = Et, R′ = iPr (3), tBu (4)] is reported. They are well soluble in organic solvents and suitable molecular precursors for the formation of Li-containing ZnO nanoparticles. The compounds are accessible by a convenient one-pot reaction of the respective dialkylzinc with lithium alkoxides in the presence of water and can be isolated as white solids in 35–50% yield. Higher yields (80–85%) for 1 and 3 can be achieved by applying excess iPrOH instead of H2O as protolysis source. The compounds 1–4 were characterized by elemental analyses, multinuclear NMR and FT-IR spectroscopy, and single-crystal X-ray diffraction analysis (1 and 2). Interestingly, thermal treatment of solutions of 1 and 2, respectively, in anhydrous benzyl alkohol at 190 °C yields pure and highly crystalline Li-containing ZnO nanoparticles as evidenced by powder X-ray diffraction analysis (PXRD), Transition Electron Microscopy (TEM), FT-IR and 7Li MAS NMR spectroscopy.
Co-reporter:Yun Xiong, Shenglai Yao and Matthias Driess
Dalton Transactions 2010 - vol. 39(Issue 39) pp:NaN9287-9287
Publication Date(Web):2010/07/09
DOI:10.1039/C0DT00148A
The striking reactivity of donor-stabilised silanone LSi(DMAP)O (1) [L = N(Ar)C(CH2)CHC(Me)N(Ar), Ar = 2,6-iPr2C6H3, DMAP = p-dimethylaminopyridine] toward Lewis acidic metal substrates Zn(OAc)2, ZnMe2, and AlMe3 is reported. Two unprecedented addition products onto the SiO double bond, [LSi(OAc)(μ-O)Zn(OAc)(DMAP)2] (2) and [LSi(OAc)(μ-O)]2Zn(DMAP) (3), and two terminal complexes LSi(DMAP)O→ZnMe2 (4) and LSi(DMAP)O→AlMe3 (5) were obtained. Compounds 4 and 5 are unique, representing the first isolable and structurally characterised terminal SiO→Zn and SiO→Al complexes. All new compounds were fully characterised by 1H, 13C, and 29Si NMR spectroscopy, EI-MS, elemental analysis and single-crystal X-ray diffraction analyses.
Co-reporter:Ann-Katrin Jungton, Antje Meltzer, Carsten Präsang, Thomas Braun, Matthias Driess and Anna Penner
Dalton Transactions 2010 - vol. 39(Issue 23) pp:NaN5438-5438
Publication Date(Web):2010/05/05
DOI:10.1039/C0DT00236D
The first zwitterionic silyl-iridium(V) complex 3 is generated by insertion of silylene 1 into an iridium–hydrogen bond of the iridium(V) hydride 2, [(η5-C5Me5)IrH4]. Complex 3 undergoes proton migration from an IrH moiety to the terminal CH2 group of the silyl ligand to furnish the N-donor stabilised Ir(III)-silylene complex 5.
Co-reporter:Yun Xiong, Shenglai Yao and Matthias Driess
Dalton Transactions 2009(Issue 3) pp:NaN423-423
Publication Date(Web):2008/12/08
DOI:10.1039/B820285K
Unexpected formation of the novel dianionic N,C-chelate ligand LD2−{HC[C(Me)-NR][C(NHR)=CH]}2− occurs by a twice silicon-assisted C–H bond activation of a terminal methyl group on a β-diketiminato ligand backbone, starting from the corresponding lithium β-diketiminide and silicon tetrabromide to give the new N-heterocyclic dibromosilanes 2 and 3.
Co-reporter:Jian-Gong Ma, Yilmaz Aksu, Laurence J. Gregoriades, Joachim Sauer and Matthias Driess
Dalton Transactions 2010 - vol. 39(Issue 1) pp:NaN106-106
Publication Date(Web):2009/11/05
DOI:10.1039/B917585G
Heterobimetallic drive and cooperativity lead to a striking scenario for C–H bond activation and heteroaggregation involving MoIII dimers. Reaction of (RO)3MoMo(OR)3 with molar excess of ZnMe2 at–78 °C affords the novel mixed Zn, Mo oxo clusters [Mo2(MeZn)6(μ2-Me)(μ3-CH2)2(OR)7] 1 (R = neopentyl) and 2 (R = cyclohexyl) preserving the MoMo triple bond, while the same reaction performed at ambient temperature gives rise to the related cluster [Mo2(MeZn)6(μ2-CH2)(μ3-CH2)2(OR)6] 3. These complexes represent the first examples of heterobimetallic MoMo complexes with bridging methyl and methylene groups and agostic C–H→Mo interactions, as well as penta-coordinate carbon. The complexes 1–3 were characterized by elemental analyses, multinuclear NMR and single-crystal X-ray diffraction analysis.
Co-reporter:Gengwen Tan, Wenyuan Wang, Burgert Blom and Matthias Driess
Dalton Transactions 2014 - vol. 43(Issue 16) pp:NaN6011-6011
Publication Date(Web):2014/01/06
DOI:10.1039/C3DT53321B
The labile germylene hydride LCyGeH is capable of activating CO2 affording the corresponding formate LCyGeOCH(O) (2) (LCy = cyclo-C6H8-1-NAr-2-C(Ph)NAr, Ar = 2,6-iPr2C6H3). Compound 2 and the previously reported LGeOCH(O) (L = CH(MeCNAr)2, Ar = 2,6-iPr2C6H3) (2′) could be further converted to methanol with the AlH3·NMe3 alane-amine adduct as a hydrogen source upon workup with water. A plausible mechanism for the conversion of the formate complexes to methanol is proposed based on additional results from the conversion of 2′ with the milder hydride delivery agent LAlH2.
Co-reporter:Burgert Blom, Günter Klatt, Daniel Gallego, Gengwen Tan and Matthias Driess
Dalton Transactions 2015 - vol. 44(Issue 2) pp:NaN644-644
Publication Date(Web):2014/11/04
DOI:10.1039/C4DT03148B
The first N-heterocyclic silylene (NHSi) complexes of any s-block element to date are reported for calcium: [(η5-C5Me5)2Ca←:Si(O-C6H4-2-tBu){(NtBu)2CPh}] (6) and [(η5-C5Me5)2Ca←:Si(NtBuCH)2] (7). Complexes 6 and 7 are isolable in a facile way upon reaction of the corresponding free N-heterocyclic silylenes (NHSis) with [(η5-C5Me5)2Ca] (2). Complexes 6 and 7 were fully characterised by spectroscopic means and the single crystal X-ray diffraction analysis of 6 is also reported. Analysis of the bonding situation by DFT methods including a Bader Atoms in molecules (AIM) analysis is also reported. The bonding interaction between the Si and Ca centres in complexes 6 and 7 can best be viewed as σ-donor–acceptor interactions, with a considerable ionic contribution in the bond. The reactivity towards the oxygen containing substrates THF and benzophenone is also discussed.
Co-reporter:Toni T. Metsänen, Daniel Gallego, Tibor Szilvási, Matthias Driess and Martin Oestreich
Chemical Science (2010-Present) 2015 - vol. 6(Issue 12) pp:NaN7149-7149
Publication Date(Web):2015/09/14
DOI:10.1039/C5SC02855H
Combined experimental and theoretical analysis of the carbonyl hydrosilylation catalysed by an iron(0) pincer complex reveals an unprecedented mechanism of action. The iron(0) complex is in fact a precatalyst that is converted into an iron(II) catalyst through oxidative addition of a hydrosilane. Neither the hydrogen atom nor the silicon atom bound to the iron(II) centre are subsequently transferred onto the carbonyl acceptor, instead remaining at the sterically inaccessible iron(II) atom throughout the catalytic cycle. A series of labelling, crossover and competition experiments as well as the use of a silicon-stereogenic hydrosilane as a stereochemical probe suggest that the iron(II) site is not directly involved in the hydrosilylation. Strikingly, it is the silyl ligand attached to the iron(II) atom that acts as a Lewis acid for carbonyl activation in this catalysis. The whole catalytic process occurs on the periphery of the transition metal. Computation of the new peripheral as well as plausible alternative inner and outer sphere mechanisms support the experimental findings.
Co-reporter:Klaus Merz, Mariluna Moreno, Elke Löffler, Lamy Khodeir, Andre Rittermeier, Karin Fink, Konstantinos Kotsis, Martin Muhler and Matthias Driess
Chemical Communications 2008(Issue 1) pp:NaN75-75
Publication Date(Web):2007/11/12
DOI:10.1039/B714806B
The remarkably distinct reactivity of hydridozinc heterobimetallic cubanes [(HZnOtBu)4−n(thf·LiOtBu)n] 1a–1d towards CO2 is reported—the hydride transfer from Zn–H to CO2 is drastically accelerated in the presence of Li ions in 1b–1d which led to the respective metal formate hydrates; the systems are inspiring models for the selective conversion of water gas into formates on lithium-promoted ZnO supports.
Co-reporter:Shenglai Yao, Tibor Szilvási, Nils Lindenmaier, Yun Xiong, Shigeyoshi Inoue, Mario Adelhardt, Jörg Sutter, Karsten Meyer and Matthias Driess
Chemical Communications 2015 - vol. 51(Issue 28) pp:NaN6156-6156
Publication Date(Web):2015/02/27
DOI:10.1039/C5CC00147A
The selective transformation of white phosphorus with a β-diketiminato iron(I) toluene complex under mild reaction conditions is reported which furnishes a new dinuclear iron(III) Fe2(P2)2 complex with two bridging P22− ligands. Its reduction with potassium results in the formation of the first delocalised mixed-valent bis-diphosphido iron(II,III) complex which is isostructural with the neutral Fe2P4 precursor.
