Mechanism of the electrochemical reduction of benzyl chlorides catalysed by Co(salen)

The electrochemical reduction of benzyl and 4-(trifluoromethyl)benzyl chlorides catalysed by Co(salen) (H(2)salen, N,N'-bis(salicylidene)-ethane-1 ,2-diamine) was studied in acetonitrile. Electrogenerated (Co-I(salen))(-) reacts with the halide to give an organocobalt(III) complex. Further one-electron reduction of the latter yields an unstable intermediate that undergoes rapid decomposition by cleavage of the Co-C bond. The mechanism of bond breaking in the one-electron-reduced organocobalt(II) complex was investigated. The results of preparative-scale electrolysis on solutions containing Co(salen) and benzyl chloride, performed under different experimental conditions, in particular in the presence of radical or carbanion scavengers, indicate homolytic cleavage of the Co-C bond. (C) 1998 Elsevier Science S.A. All rights reserved.