Generation of a μ -1,2-hydroperoxo Fe III Fe III and a μ -1,2-peroxo Fe IV Fe III Complex

μ -1,2-Peroxo-diferric intermediates ( P ) of non-heme diiron enzymes are proposed to convert upon protonation either to high-valent active species or to activated P′ intermediates via hydroperoxo-diferric intermediates. Protonation of synthetic μ -1,2-peroxo model complexes occurred at the μ -oxo and not at the μ -1,2-peroxo bridge. Here we report a stable μ -1,2-peroxo complex {Fe III ( μ -O)( μ -1,2-O 2 )Fe III } using a dinucleating ligand and study its reactivity. The reversible oxidation and protonation of the μ -1,2-peroxo-diferric complex provide μ -1,2-peroxo Fe IV Fe III and μ -1,2-hydroperoxo-diferric species, respectively. Neither the oxidation nor the protonation induces a strong electrophilic reactivity. Hence, the observed intramolecular C-H hydroxylation of preorganized methyl groups of the parent μ -1,2-peroxo-diferric complex should occur via conversion to a more electrophilic high-valent species. The thorough characterization of these species provides structure-spectroscopy correlations allowing insights into the formation and reactivities of hydroperoxo intermediates in diiron enzymes and their conversion to activated P′ or high-valent intermediates.