Step wise and dissociative mechanisms of the electron transfer in electrochemical reactions involving organosilicon compounds: Molecular-thermodynamic approach1

Electrochemical reduction of organochlorosilanes and oxidation of hexaorganodisilanes may occur via dissociative and stepwise mechanisms, the choice between which is determined by the balance between fundamental structural parameters of elementoorganic molecules. The formation of radical anions of silyl-substituted chloromethane in the conditions of an electrochemical experiment is shown. The formation is due to α-silicon stabilization of the intermediate during the electron transfer. The role of conjugation and hyperconjugation in the organosilicon compounds’ reactivity is analyzed. When employing terms “ stepwise ” and “ dissociative ” mechanisms of the electron transfer, we follow tradition introduced and developed by J.-M. Saveant’s group 1] and recommended by the IUPAC Commission on Electrochemical Nomenclature 2]. The terms refer to an electrochemically reversible transfer of electron whose kinetics does not limit the process rate as a whole and to an electrochemically irreversible transfer which involves a bond cleavage in an elementary act of electron transfer. The term “ activation ” mechanism, which is sometimes applied to electrochemically irreversible processes, is more universal; however, it is somewhat not unique as compared with the term “ dissociative.” Coupled with “ associative,” the latter may be used for indicating processes that involve the formation of a bond in an elementary act of electron transfer.