Palladium-catalyzed selective dechlorination of polychloromethylsilanes with trichlorosilane

Abstract

Selective dechlorination of the chloromethyl-containing silanes (Cl3-nCHn)SiCl3-mMem (n = 0-2 (1-3), m = 0-3 (a-d)) with trichlorosilane was studied in the presence of group 10 transition-metal compounds at reaction temperatures between 100 and 150 degrees C in sealed bombs. The reactions give the corresponding less chlorinated compounds in good yields without reducing Si-Cl bonds, only when Pd(OAc)(2) and PdCl2 were used as catalysts. The dechlorination rate of chlorinated methylchlorosilanes depends on the substituents on silicon and the number of chlorine atoms on the chlorinated carbon: the rate increases as the number of chlorine atoms on carbon and of methyl groups on silicon increase. The reactivity difference between (trichloromethyl)-, (dichloromethyl)-, and (monochloromethyl)chlorosilanes allows selective stepwise reduction from SiCC1(3) to SiCHCl2 to SiCH2Cl and, finally, to SiCH3 by controlling the amount of trichlorosilane reductant and the reaction conditions. The catalytic reactivity of transition-metal compounds decreases in the following order: Pd(OAc)(2) > PdCl2 much greater than Pt-C, H2PtCl6, Ni(OAc)(2), NiCl2 > Pd(PPh3)(2)Cl-2, K2PtCl4.