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) (H2salen, N,N′-bis(salicylidene)-ethane-1,2-diamine) was studied in acetonitrile. Electrogenerated (Co1(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 CoC 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 CoC bond.