Electrochemical studies of iron(III) Schiff base complexes—II. Dimeric μ-OXO[FeIII(N2O2)]2O complexes

The electrochemical reduction of mu-oxo bridged Fe-III dimers (L)Fe-O-Fe(L), where L is a Schiff base, has been investigated in aprotic solvents by cyclic voltammetry and coulometry with UV-vis spectroscopy. Three complexes deriving from Schiff base ligands with N2O2 environments are described. The reduction of (L)Fe-III-O-Fe-III(L) occurs at a potential around -1 V/SCE and releases the monomeric Fe-II(L) complex. A mechanism is proposed using high speed cyclic voltammetry. The reduction pattern is affected by dioxygen through the high reactivity of Fe-II(L). These mu-oxo bridged Fe-III dimers (L)Fe-O-Fe(L) can also be cleaved by Cl- addition and yield the monomeric Fe-III(L) complexes. Finally, the Fe-O bond is not so strong because it cleaves either by electrochemical reduction or by chemical addition of Cl-.