ELECTROCHEMICAL REDUCTION OF CARBON-DIOXIDE CATALYZED BY [COI(SALOPHEN)LI]

The electrochemical reduction of CO2 to CO and CO3(2-), in acetonitrile containing LiClO4 as background electrolyte, is catalyzed by [Co(I)(salophen)Li]. Although relatively slow, the reduction takes place at moderate overvoltages and the stability of the catalytic system, tested through long-term electrolysis, is fairly good. Mechanistic investigations point to the interaction of CO2 with [Co(I)(salophen)Li], to give a precursor complex containing a head-to-tail CO2 dimer which is C-bonded to cobalt and further stabilized by Li+. Electron addition to the latter, followed by elimination of CO3(2-) yields a cobalt-carbonyl complex, which slowly releases the final reduction product CO. Electrochemical studies of Co(salophen) under CO atmosphere have shown the intermediate cobalt-carbonyl complex to be [Co(I)(salophen)(CO)]-