Cyclic Voltammetric Study of Electroreduction of Dichlorosilanes

Abstract

The electroreduction of organo-substituted dichlorosilanes, , , , , , , and in THF, is reported. A two-step reduction scheme (: and : ) is suggested in which the redox potentials and are separated by . A simulation of the irreversible voltammograms indicates multiple pathways in producing silyl anion, among them the decomposition of dianion and/or the disproportionation of silyl anion radicals, which is further corroborated by low-temperature cyclic voltammetric measurements. Subsequently, silyl anion undergoes nucleophilic attack on another chlorosilane molecule to form Si–Si bonds. Taft substituent constants have been applied and proved effective in correlating the substituent effect on the reduction of dichlorosilanes. For dialkyl-substituted chlorosilanes, the Taft analysis of the polar contribution of substituents to the cathodic peak shift gives a positive , which indicates an nucleophilic reaction in the formation of silyl dianion intermediate. The steric effect of substituents, however, is largely responsible for the stability of the transition state.