Heterolytic O-O Bond Cleavage Upon Single Electron Transfer to a Nonheme Fe(III)-OOH Complex

The one-electron reduction of the nonheme iron(III)-hydroperoxo complex, [Fe-III(OOH)(L-5(2))](2+) (L-5(2)=N-methyl-N,N',N'-tris(2-pyridylmethyl)ethane-1,2-diamine), carried out at -70 degrees C results in the release of dioxygen and in the formation of [Fe-II(OH)(L-5(2))](+) following a bimolecular process. This reaction can be performed either with cobaltocene as chemical reductant, or electrochemically. These experimental observations are consistent with the disproportionation of the hydroperoxo group in the putative Fe-II(OOH) intermediate generated upon reduction of the Fe-III(OOH) starting complex. One plausible mechanistic scenario is that this disproportionation reaction follows an O-O heterolytic cleavage pathway via a Fe-IV-oxo species.