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The industry-scale production of methylchloromonosilanes in the Müller–Rochow Direct Process is accompanied by the formation of a residue, the direct process residue (DPR), comprised of disilanes MenSi2Cl6-n (n=1–6). Great research efforts have been devoted to the recycling of these disilanes into monosilanes to allow reintroduction into the siloxane production chain. In this work, disilane cleavage by using alkali and alkaline earth metal salts is reported. The reaction with metal hydrides, in particular lithium hydride (LiH), leads to efficient reduction of chlorine containing disilanes but also induces disproportionation into mono- and oligosilanes. Alkali and alkaline earth chlorides, formed in the course of the reduction, specifically induce disproportionation of highly chlorinated disilanes, whereas highly methylated disilanes (n>3) remain unreacted. Nearly quantitative DPR conversion into monosilanes was achieved by using concentrated HCl/ether solutions in the presence of lithium chloride.

Organotinchlorides of the general formula R3SnCl and R2SnCl2 (R = Me, n-Bu, Ph) can easily be converted into the corresponding hydrides R3SiH and R2SiH2 employing NaH in diethylene glycol dialkyl ethers.Using trialkyltinhydrides like Bu3SnH in combination with a catalyst (tertiary amines, N-heterocycles, phosphonium or ammonium salts), Si-Cl bonds in mono- and disilanes are hydrogenated.In the case of disilanes, Si-Si bond cleavage and concurrent hydrogenation can be afforded with strongly nucleophilic catalysts.Partial hydrogenation is also possible.The whole process can be run cyclically. - Keywords: Alkylstannylhydride; Hydrogenation; Organochlorsilane.

The 193 nm laser flash photolysis of gas-phase 1,2-dimethyldisilane has been found to give a broad-band absorption in the wavelength range 454-515 nm, which is plausibly shown to be due to the transient species methylsilylene, MeSiH.By carrying out the title studies, the first direct kinetic studies of MeSiH, second-order rate constants hve been obtained for reactions of MeSiH with SiH4, MeSiH3, Me2SiH2 and Me3SiH, in the temperature range 360-580 K.The reactions are fast but show negative activation energies, increasing from -7.5 kJ mol-1 for SiH4 to -18.4 kJ mol-1 for Me3SiH.The data are interpreted as proceeding via an intermediate complex, whose rearrangement becomes rate-determining at higher temperatures.Comparisons of reactivity of MeSiH with those of other silylenes reveal the general pattern of methyl substituent effects of these complexes.In conjunction with ab initio theory (for the reaction of SiH2 with SiH4) these show that the electrophilic interaction probably precedes the nucleophilic interaction, although the latter is important in the rate-determining (second) step for the insertion reactions of both MeSiH and SiMe2.Combination of MeSiH insertion rate constants with the reverse unimolecular decomposition rate constants of the product disilanes enable the calculation of an improved value of 202 +/- 6 kJ mol-1 for Δf HΘ (MeSiH).