Mechanism of thermal decomposition of allyltrichlorosilane with formation of three labile intermediates: dichlorosilylene, allyl radical, and atomic chlorine

Abstract

It is experimentally found that allyltrichlorosilane dissociates under vacuum pyrolysis (~10^–2 Torr) at temperatures above 1100 K to form three labile intermediates: allyl radical, dichlorosilylene, and monoatomic chlorine. On the basis of experimental and theoretical data obtained, it is shown that the decomposition reaction proceeds in two steps. The first step is a typical reaction of homolytic decomposition to two radicals (C₃H₅ and SiCl₃) at the weakest Si—C bond. Due to weakness of the Si—Cl bond in the SiCl₃ radical, the energy of which is even somewhat lower than the dissociation energy of the Si—C bond in starting AllSiCl₃, this radical undergoes further dissociation to SiCl₂ and Cl, thus resulting in three intermediates of different classes of highly reactive species formed from AllSiCl₃.