Characterization of a nonheme mononuclear peroxoiron(III) intermediate by UV Vis and EPR spectroscopy and mass spectrometry

Some nonheme hydroperoxoiron(III) species have been recently characterized by several groups. The reported examples were obtained by adding H2O2 in excess to an Fe-II complex with a neutral polypyridine ligand. We show here that on deprotonation, the purple low-spin hydroperoxoiron(III) complex [(LFeOOH)-Fe-5-O-III](2+) [L-5 = N-methyl-N,N',N'-tris(2-pyridylmethyl)ethane-1,2-diamine] gives a blue high spin species which we characterized as the eta(2)-peroxoiron(III) species [(LFeO2)-Fe-5-O-III](+). It seems that with such an auxiliary ligand, the hydroperoxo group is acidic in contrast with its basicity when it is coordinated to a heme group.