Electrocarboxylation of chloroacetonitrile mediated by electrogenerated cobalt(I) phenanthroline

The electrocarboxylation of chloroacetonitrile mediated by Co(II)(phen)₃]²⁺ has been investigated. Cyclic voltammetry studies of Co(II)(phen)₃]²⁺ have shown that Co(I)(phen)₃]⁺, an 18 electron complex, activates chloroacetonitrile by an oxidative addition through the loss of a phenanthroline ligand to give RCo(III)(phen)₂Cl]⁺. The unstable one-electron-reduced complex underwent Co–C bond cleavage. In carbon dioxide saturated solution, CO₂ insertion proceeds after reduction of the alkylcobalt complex. A catalytic current is observed which corresponds to the electrocarboxylation of chloroacetonitrile into cyanoacetic acid. Electrolyses confirmed the process and gave faradic yield of 62% in cyanoacetic acid at potentials that are about 0.3 V less cathodic than the one required for Ni(salen).