ELECTROCHEMICAL INVESTIGATIONS OF THE COMPLEXES RESULTING FROM THE ACID-PROMOTED DEOXYGENATION AND DIMERIZATION OF (N,N'-ETHYLENEBIS(SALICYLIDENEAMINATO))OXOVANADIUM(IV)

Electrochemical confirmation that (N,N'-ethylenebis(salicylidenoaminato))oxovanadium(IV), VO(salen), reacts with trifluoromethanesulfonic acid (CF3SO3H) or triphenylmethyl tetrafluoroborate (Ph3C(BF4)) to form a deoxygenated complex, V(IV)(salen)2+, and a mu-oxodinuclear complex, [(salen)VOV(salen)]X2, (X = CF3SO3- or BF4-) is presented. Cyclic voltammograms of VO(salen) in the presence of CF3SO3H or Ph3C(BF4) exhibit reversible waves with formal potentials near 0.5 and 0.8 V (vs Ag/AgCl). The cathodic wave at 0.5 V is argued to arise from the combined reduction of V(salen)2+ and the mu-oxo dimeric complex and the wave at 0.8 V from the oxidation of the V(salen)2+ complex. The diffusion coefficients of these three complexes in acetonitrile were determined. The dimerization of VO(salen) is initiated by deoxygenation of the V=O center by H+ or Ph3C+ to produce V(salen)2+ which enters into an equilibrium with a second VO(salen) complex to produce the mu-oxo dimer. The kinetics of the second order dimerization reaction were monitored, and the equilibrium contant for the formation of the mu-oxo dimer in acetonitrile was evaluated as 0.7 mM-1.