Die Angestellten vor dem Nationalsozialismus

Speier, Hans

doi:10.13109/9783666359798

Cited by 31 publications

(3 citation statements)

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“…From catalyst 1a , HSiEt 3 is initially coordinated to the Pd(0) catalyst to give η 2 -silane complex 2a , and the step is exogonic by 1.3 kcal/mol (Figure ). The transition-metal η 2 -silane complexes have gained immense research interest as important intermediates in metal-catalyzed hydrosilylation reactions . The Si–H bond distance in complex 2a is calculated to be 1.620 Å (Figure ), longer than a normal single bond according to the covalent radius predictions (Si–H =1.48 Å) .…”

Section: Resultsmentioning

confidence: 98%

Mechanisms and Origins of Switchable Regioselectivity of Palladium- and Nickel-Catalyzed Allene Hydrosilylation with N-Heterocyclic Carbene Ligands: A Theoretical Study

et al. 2014

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The mechanisms and origins for the Pd- and Ni-catalyzed regioselective hydrosilylation of allene have been investigated by means of density functional theory (DFT) calculations. The free-energy profiles of Pd- and Ni-catalyzed reactions with small and bulky N-heterocyclic carbene (NHC) ligands are calculated to determine the mechanism for regioselectivities. The calculation results show that different metals (Ni vs Pd) lead to regiochemical reversals for the hydrosilylation of allene. The allylsilane is the major product via palladium catalysis with small NHC ligand, while the vinylsilane is the major product via nickel catalysis with bulky NHC ligand. Both electronic and steric factors play a key role in the regioselectivities for the hydrosilylation of allene via Pd and Ni catalysts. The calculation results are in good agreement with observed regioselectivities and could provide insights into the design of new catalysts for the regioselectivity of hydrosilylation reactions.

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Section: Resultsmentioning

confidence: 98%

Mechanisms and Origins of Switchable Regioselectivity of Palladium- and Nickel-Catalyzed Allene Hydrosilylation with N-Heterocyclic Carbene Ligands: A Theoretical Study

et al. 2014

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“…60 While radical initiators 61 and Lewis acids 62 are known to promote hydrosilation, transition metal catalysis 63 has emerged as the preferred method due its high activity, selectivity, and in some cases stereospecificity. 64 Traditional hydrosilation catalysts contain precious metals such as platinum 65 or rhodium, 66 although several highly active group 3 transition metal 67 and lanthanide-based 68 catalysts have also been reported. In contrast, the development of well-defined homogeneous iron catalysts for hydrosilation has been quite limited.…”

Section: Synthesis Of the Well-defined Catalyst Precursor 1-(n 2 )mentioning

confidence: 99%

Preparation and Molecular and Electronic Structures of Iron(0) Dinitrogen and Silane Complexes and Their Application to Catalytic Hydrogenation and Hydrosilation

2004

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Reduction of the five-coordinate iron(II) dihalide complexes (iPrPDI)FeX2 (iPrPDI = ((2,6-CHMe2)2C6H3N=CMe)2C5H3N; X = Cl, Br) with sodium amalgam under 1 atm of dinitrogen afforded the square pyramidal, high spin iron(0) bis(dinitrogen) complex (iPrPDI)Fe(N2)2. In solution, (iPrPDI)Fe(N2)2 loses 1 equiv of N2 to afford the mono(dinitrogen) adduct (iPrPDI)Fe(N2). Both dinitrogen compounds serve as effective precatalysts for the hydrogenation and hydrosilation of olefins and alkynes. Effecient catalytic reactions are observed with low catalyst loadings (< or = 0.3 mol %) at ambient temperature in nonpolar media. The catalytic hydrosilations are selective in forming the anti-Markovnikov product. Structural characterization of a high spin iron(0) alkyne and a bis(silane) sigma-complex has also been accomplished and in combination with isotopic labeling studies provides insight into the mechanism of both catalytic C-H and catalytic C-Si bond formation.

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“…The catalytic activity of 4a , b in hydrogenations prompted us to study also hydrosilylations, which are considered to be related to hydrogenations . Traditional hydrosilylation catalysts are Pt- or Rh-based, although several highly active early transition metals , and lanthanide-based catalysts have also been reported. In contrast, efforts to develop homogeneous rhenium-based catalysts for hydrosilylations with rhenium in low oxidation states have been limited.…”

Section: Catalytic Explorationsmentioning

confidence: 99%

Rhenium Nitrosyl Complexes for Hydrogenations and Hydrosilylations

et al. 2008

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The tris(acetonitrile)dibromonitrosylrhenium(I) compound (1a) was obtained by reduction of the paramagnetic [NMe4]2[Re(NO)Br5] salt with Zn in MeCN. Subsequent reaction of 1a with THF produced the THF derivative [Re(NO)(THF)(MeCN)2Br2] (1b). Reaction of 1b with PiPr3, Pcy3, or P(p-tolyl)3 yielded bis(acetonitrile)-cis-dibromo(nitrosyl)-trans-bis(phosphine)rhenium complexes (R = iPr 2a, cy 2b, p-tolyl 2c). Treatment of 2a,b with excess NaBH4 produced the known borohydride complexes [Re(H)(η 2 -BH4)(NO)(PR3)2] (R = iPr 3a, cy 3b). Replacement of the BH3 moiety of 3a,b in THF by ethylene (1 bar) produced the dihydride complexes [Re(H)2(η2 -C2H4)(NO)(PR3)2] (4) (R = iPr a, cy b). Protonation of 4a,b with HBF4·OEt2 afforded H2 and the monohydrido tetrafluoroborato species [Re(H)(NO)(PR3)2(η 2 -C2H4)(BF4)] (R = iPr 5a, cy 5b). X-ray diffraction studies were carried out on 1a, 2b,c, and 5b. Complexes 4a,b are catalytically active in olefin, imine, and ketone hydrogenations and in olefin and ketone hydrosilylations, as well as in the scrambling of H2/D2 to give HD under mild conditions.

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Die Angestellten vor dem Nationalsozialismus

Cited by 31 publications

References 0 publications

Mechanisms and Origins of Switchable Regioselectivity of Palladium- and Nickel-Catalyzed Allene Hydrosilylation with N-Heterocyclic Carbene Ligands: A Theoretical Study

Mechanisms and Origins of Switchable Regioselectivity of Palladium- and Nickel-Catalyzed Allene Hydrosilylation with N-Heterocyclic Carbene Ligands: A Theoretical Study

Preparation and Molecular and Electronic Structures of Iron(0) Dinitrogen and Silane Complexes and Their Application to Catalytic Hydrogenation and Hydrosilation

Rhenium Nitrosyl Complexes for Hydrogenations and Hydrosilylations

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