Showing papers by "Armando Gennaro published in 1993"

The electrochemical reduction mechanism of [N,N′-1,2-phenylenebis(salicylideneiminato)]cobalt(II)

Abstract: The electrochemical reduction mechanism of [CoL][L =N,N′-1,2-phenylenebis(salicylideneiminate)] has been investigated in dimethylformamide by means of cyclic voltammetry and controlled-potential electrolysis. The cobalt(II) complex shows three successive one-electron reduction processes. The first electron uptake is metal-centred yielding [CoIL]–, whereas the second and third electron transfers are both ligand based, corresponding to the reduction of one imine double bond. This leads to the formation of a new cobalt complex [CoI(HL–)]2– which has the CoII–CoI redox couple located at a potential ca. 600 mV negative of the potential of the same redox couple of the original [CoL] complex. Decay reactions of some reduction intermediates have been kinetically characterised and the corresponding rate constants have been determined.

Electrochemical Reduction of CO2 Catalysed by Transition Metal Complexes

Abstract: Cobalt and nickel complexes of N,N’—1,2—phenylenebis(salicylideneiminato) (salophen = L) have been investigated by cyclic voltammetry and controlled potential electrolysis as potential catalysts for the electrochemical activation of CO 2. In the case of [Ni(II)L], no catalysis was observed. The first electron uptake is ligand—based, yielding the radical anion [Ni(II)L].— which rapidly dimerizes. On the contrary, the electron transfer to [Co(II)L] is metal—centered giving the [Co(I)L]- complex which in AN containing LiClO4 as background electrolyte appears to catalyze the CO2 reduction to CO and C03 2-, in a potential region where direct CO2 reduction does not occur. Mechanistic investigations point to the interaction of CO2 with [Co(I)(L)Li] to give a precursor complex containing a head—to—tail CO2 dimer. Further reduction of the latter yields a Co—carbonyl complex which releases quite slowly the final CO2 reduction product CO.