Generation of a mu-1,2-hydroperoxo (FeFeIII)-Fe-III and a mu-1,2-peroxo (FeFeIII)-Fe-IV Complex

mu-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 mu-1,2-peroxo model complexes occurred at the mu-oxo and not at the mu-1,2-peroxo bridge. Here we report a stable mu-1,2-peroxo complex {Fe-III(mu-O)(mu-1,2-O-2)Fe-III} using a dinucleating ligand and study its reactivity. The reversible oxidation and protonation of the mu-1,2-peroxo-diferric complex provide mu-1,2-peroxo (FeFeIII)-Fe-IV and mu-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 mu-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. Iron coordination complexes can be used to gain insight on biologically relevant iron-oxygen compounds generated in iron metalloenzymes. Here, the authors characterise a mu-1,2-hydroperoxo (FeFeIII)-Fe-III and a mu-1,2-peroxo (FeFeIII)-Fe-IV, and study their reactivity in C-H activation.