1066-35-9Relevant articles and documents
Dual Role of Doubly Reduced Arylboranes as Dihydrogen- and Hydride-Transfer Catalysts
Von Grotthuss, Esther,Prey, Sven E.,Bolte, Michael,Lerner, Hans-Wolfram,Wagner, Matthias
, (2019)
Doubly reduced 9,10-dihydro-9,10-diboraanthracenes (DBAs) are introduced as catalysts for hydrogenation as well as hydride-transfer reactions. The required alkali metal salts M2[DBA] are readily accessible from the respective neutral DBAs and Li metal, Na metal, or KC8. In the first step, the ambiphilic M2[DBA] activate H2 in a concerted, metal-like fashion. The rates of H2 activation strongly depend on the B-bonded substituents and the counter cations. Smaller substituents (e.g., H, Me) are superior to bulkier groups (e.g., Et, pTol), and a Mes substituent is even prohibitively large. Li+ ions, which form persistent contact ion pairs with [DBA]2-, slow the H2-addition rate to a higher extent than more weakly coordinating Na+/K+ ions. For the hydrogenation of unsaturated compounds, we identified Li2[4] (Me substituents at boron) as the best performing catalyst; its substrate scope encompasses Ph(H)CNtBu, Ph2CCH2, and anthracene. The conversion of E-Cl to E-H bonds (E = C, Si, Ge, P) was best achieved by using Na2[4]. The latter protocol provides facile access also to Me2Si(H)Cl, a most important silicone building block. Whereas the H2-transfer reaction regenerates the dianion [4]2- and is thus immediately catalytic, the H--transfer process releases the neutral 4, which has to be recharged by Na metal before it can enter the cycle again. To avoid Wurtz-type coupling of the substrate, the reduction of 4 must be performed in the absence of the element halide, which demands an alternating process management (similar to the industrial anthraquinone process).
Controllably oxidized copper flakes as multicomponent copper-based catalysts for the Rochow reaction
Liu, Shaomian,Wang, Yingli,Zhu, Yongxia,Wang, Guangna,Zhang, Zailei,Che, Hongwei,Jia, Lihua,Su, Fabing
, p. 7826 - 7833 (2014)
The metallic Cu flakes prepared by milling metallic Cu powder were controllably oxidized in air at different temperatures to obtain the Cu-based catalysts containing multicomponents of Cu, Cu2O, and CuO. These catalysts are explored in the Rochow reaction using silicon powder and methyl chloride (MeCl) as reactants to produce dimethyldichlorosilane (M2), which is the most important organosilane monomer in the industry. The samples were characterized by X-ray diffraction, temperature-programmed reduction, thermogravimetric analysis, oxidimetry analysis, particle size analysis, transmission electron microscopy, and scanning electron microscopy. Compared to the metallic Cu powder and Cu flakes, the controllably oxidized Cu flakes containing Cu, Cu2O, and CuO species show much higher M2 selectivity and silicon conversion in the Rochow reaction. The enhanced catalytic performance may stem from the larger interfacial contact among the gas MeCl, solid Si particles, and solid Cu-based catalyst flakes, as well as the synergistic effect among the different Cu species. The work would be helpful to the development of novel Cu-based catalysts for organosilane synthesis.
Kinetics of Insertion Reactions of Dimethylsilylene
Davidson, Iain M. T.,Lawrence, F. Timothy,Ostah, Naaman A.
, p. 859 - 860 (1980)
Dimethylsilylene, generated by photolysis of dodecamethylcyclohexasilane, inserts into the silicon-hydrogen bond in trimethylsilane and pentamethyldisilane with approximately zero activation energy, while insertion into hydrogen chloride requires an activation energy of 28 kJ mol-1; the results for silicon-hydrogen insertion shed some light on the mechanism of the thermolysis of pentamethyldisilane.
Unlocking the Catalytic Hydrogenolysis of Chlorosilanes into Hydrosilanes with Superbases
Durin, Gabriel,Berthet, Jean-Claude,Nicolas, Emmanuel,Cantat, Thibault
, p. 10855 - 10861 (2021)
The efficient synthesis of hydrosilanes by catalytic hydrogenolysis of chlorosilanes is described using an iridium (III) pincer catalyst. A careful selection of a nitrogen base (including sterically hindered guanidines and phosphazenes) can unlock the preparation of Me3SiH, Et3SiH, and Me2SiHCl in high yield (up to 98%) directly from their corresponding chlorosilanes.
Hydrosilane synthesis via catalytic hydrogenolysis of halosilanes using a metal-ligand bifunctional iridium catalyst
Beppu, Teruo,Sakamoto, Kei,Nakajima, Yumiko,Matsumoto, Kazuhiro,Sato, Kazuhiko,Shimada, Shigeru
, p. 75 - 80 (2018)
Hydrogenolysis of various halosilanes was catalysed by iridium amido complexes to produce hydrosilanes. Selective monohydrogenolysis of di- and trichlorosilanes similarly proceeded, resulting in the formation of chlorohydrosilanes (R2SiHCl or RSiHCl2) as synthetically important building blocks for various organosilicon compounds. A mechanistic study supported the in-situ formation of an iridium hydride species as a key intermediate, which could transfer the hydride to the silicon atom through a metal–ligand bifunctional mechanism. One-pot hydrotrimethylsilylation of olefins was achieved via successive hydrogenolysis and hydrosilylation reactions starting from Me3SiCl.
GAS-PHASE PHOTOCHEMICAL REACTIONS OF DODECAMETHYLCYCLOHEXASILANE WITH SILICON COMPOUNDS. KINETICS OF SOME INSERTION REACTIONS OF DIMETHYLSILYLENE
Davidson, Iain M.T.,Ostah, Naaman A.
, p. 149 - 158 (1981)
Attempts to measure the kinetics of gas-phase insertion reactions of dimethylsilylene, generated by photolysis of dodecamethylcyclohexasilane, are described.Insertion of dimethylsilylene into silicon-hydrogen bonds was the main reaction with trimethylsilane, pentamethyldisilane, and sym-tetramethyldisilane; in all cases the activation energy for insertion was zero, and the rate constants were in the ratio of 1:3.1:4.3.Dimethylsilylene also inserted cleanly into hydrogen chloride with an activation energy of 28 kJ mol-1.Photochemical reactions with methylchlorosilanes were much more complex, involving little or no silylene chemistry; such reactions as did occur appeared to proceed almost entirely by radical mechanisms.
Chlorine Abstraction from Silicon-Chlorine Bonds by Trimethylsilyl Radicals
Davidson, Iain M. T.,Matthews, J. Ioan
, p. 2277 - 2280 (1981)
Attempts to measure the kinetics of the unusual abstraction reaction, Me3Si. + Me2SiCl2 -> Me3SiCl + Me2Si.Cl using thermal radical sources were unsuccessful.Kinetic data were obtained by using a photochemical radical source, yielding unconvetional Arrhenius parameters, the significance of which is discussed.
Synthesis of Functional Monosilanes by Disilane Cleavage with Phosphonium Chlorides
Santowski, Tobias,Sturm, Alexander G.,Lewis, Kenrick M.,Felder, Thorsten,Holthausen, Max C.,Auner, Norbert
, p. 3809 - 3815 (2019)
The Müller–Rochow direct process (DP) for the large-scale production of methylchlorosilanes MenSiCl4?n (n=1–3) generates a disilane residue (MenSi2Cl6?n, n=1–6, DPR) in thousands of tons annually. This report is on methylchlorodisilane cleavage reactions with use of phosphonium chlorides as the cleavage catalysts and reaction partners to preferably obtain bifunctional monosilanes MexSiHyClz (x=2, y=z=1; x,y=1, z=2; x=z=1, y=2). Product formation is controlled by the reaction temperature, the amount of phosphonium chloride employed, the choice of substituents at the phosphorus atom, and optionally by the presence of hydrogen chloride, dissolved in ethers, in the reaction mixture. Replacement of chloro by hydrido substituents at the disilane backbone strongly increases the overall efficiency of disilane cleavage, which allows nearly quantitative silane monomer formation under comparably moderate conditions. This efficient workup of the DPR thus not only increases the economic value of the DP, but also minimizes environmental pollution.
Direct Formation of (CH3)2HSiCl from Silicon and CH3Cl
Magrini, Kimberly A.,Falconer, John L.,Koel, Bruce E.
, p. 5563 - 5568 (1989)
A Cu-catalyzed reaction procedure was found for the selective formation of dimethylchlorosilane from the direct reaction of CH3Cl with solid Si.The new procedure is a two-step process.A Cu/Si sample is prepared by evaporating Cu onto clean polycrystalline Si under ultrahigh vacuum, and the Cu/Si surface is first activated by exposure to 10percent HSiCl3/CH3Cl at 598 K.After the HSiCl3/CH3Cl mixture is evacuated from the reactor, the activated Cu/Si surface is reacted in fresh CH3Cl.For low surface concentrations of Cu, the partially hydrogenated silane, (CH3)2HSiCl, is selectively produced.Trichlorosilane was also found to activate polycrystalline Si (in the absence of Cu) for production of highly chlorinated methylchlorosilanes at a much higher rate than on the Cu/Si surface but with poor selectivity to (CH3)2HSiCl.All reactions are carried out at atmospheric pressure in a reactor that is attached to an ultrahigh-vacuum chamber.This allows surface analysis by Auger electron spectroscopy, which detected SiClx on reacted surfaces.These SiClx sites, which appear necessary for methylchlorosilane formation, are apparently formed during activation by HSiCl3.
PROCESS FOR THE STEPWISE SYNTHESIS OF SILAHYDROCARBONS
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Page/Page column 54; 58, (2021/12/08)
The invention relates to a process for the stepwise synthesis of silahydrocarbons bearing up to four different organyl substituents at the silicon atom, wherein the process includes at least one step a) of producing a bifunctional hydridochlorosilane by a redistribution reaction, selective chlorination of hydridosilanes with an ether/HCI reagent, or by selective chlorination of hydridosilanes with SiCI4, at least one step b) of submitting a bifunctional hydridochloromonosilane to a hydrosilylation reaction, at least one step c) of hydrogenation of a chloromonosilane, and a step d) in which a silahydrocarbon compound is obtained in a hydrosilylation reaction.
