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).
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.
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Suryanarayanan,B. et al.
, p. 65 - 71 (1973)
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Simon, Gerard,Lefort, Marcel,Birot, Marc,Dunogues, Jacques,Duffaut, Norbert,Calas, Raymond
, p. 279 - 286 (1981)
Partial reduction of MeSiCl3 and Me2SiCl2 using CaH2 or (TiH2)n at high temperature (300°C) leads to MeSiHCl2 and Me2SiHCl, respectively, in good yields but in low proportion. In the presence of AlCl3 as catalyst the reaction affords Me2SiCl2 and Me3SiCl, in yields higher than those previously observed in the absence of a reducing agent. These redistribution reactions involve MeSiHCl2 and Me2SiHCl as intermediates. Consequently Me2SiHCl with or without Me2SiCl2 and Alcl3 deposited on carbon black as catalyst can undergo disproportionation to give Me3SiCl.
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Kriegsmann,Engelhardt
, p. 100,108 (1961)
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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.
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Moedritzer,van Wazer
, p. 69,70, 74 (1968)
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PROCESS FOR THE PRODUCTION OF ORGANOHYDRIDOCHLOROSILANES
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Page/Page column 28; 29; 32; 33; 34; 41, (2019/04/16)
The invention relates to a process for the manufacture of organomonosilanes, in particular, bearing both hydrogen and chlorine substituents at the silicon atom by subjecting a silane substrate comprising one or more organomonosilanes, with the proviso that at least one of these silanes has at least one chlorine substituent at the silicon atom, to the reaction with one or more metal hydrides selected from the group of an alkali metal hydride and an alkaline earth metal hydride in the presence of one or more compounds (C) acting as a redistribution catalyst.
INTEGRATED PROCESS FOR THE MANUFACTURE OF METHYLCHLOROHYDRIDOMONOSILANES
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Page/Page column 35; 36; 37; 38; 39, (2019/04/16)
The present invention relates to an integrated process for the manufacture of methylchlorohydridomonosilanes in particular, from products of the Müller-Rochow Direct Process.
