Synthesis of tris(silyl)methanes by modified direct process

Abstract

Direct reaction of elemental silicon with a mixture of (dichloromethyl)silanes 1 [CL3 .nMenSiCHCl2: n = 0 (a), rt = 1 (b), n = 2 (c), n = 3 (d)] and hydrogen chloride has been studied in the presence of copper catalyst using a stirred bed reactor equipped with a spiral band agitator at various temperatures from 240 degreesC to 310 degreesC. Tris(silyl)methanes with Si-H bonds, 3a-d [Cl3 .nMenSiCH(SiHCl2)(2)], and 4a-d [Cl3 .nMenSiCH(SiCl3)(2)], were obtained as the major products and tris(silyl)methanes having no Si-H bond 5a-d [Cl3(3 .n)Me(n)SiCH(SiC3)(2)], as the minor product along with byproducts of bis(chIorosilyl)methanes, derived from the reaction of silicon with chloromethylsilane formed by the decomposition of I. In addition to those products, trichforosilane and tetrachlorosilane were produced by the reaction of elemental silicon with hydrogen chloride. The decomposition of I was suppressed and the production of polymeric carbosilanes reduced by adding hydrogen chloride to 1. Cadmium was a good promoter for the reaction, and the optimum temperature for this direct synthesis was 280 degreesC.