Ligand effects on dioxygen activation by copper and nickel complexes: Reactivity and intermediates

Copper and nickel complexes having various active-oxygen species MnO2 ( n = 1 or 2), such as trans-(-1,2-peroxo)Cu (II)(2), bis(-oxo)M (III)(2), bis(-superoxo)Ni (II)(2), and ligand-based alkylperoxo-M (II)(n), can be produced by a series of tetradentate tripodal ligands (TMPA analogues) containing sterically demanding 6-methyl substituent(s) on the pyridyl group(s), where TMPA = tris(2-pyridylmethyl)amine. Roles of the methyl substituent(s) for the formation of the active-oxygen species and their oxidation reactivities are reported.