Oxidant types in copper–dioxygen chemistry: the ligand coordination defines the Cun-O2 structure and subsequent reactivity

The considerable recent advances in copper–dioxygen coordination chemistry demonstrate the existence of a variety of dioxygen-derived Cun-O2 complexes, forming a basis for discussion of alternate oxidant types in copper chemistry and biochemistry. Peroxo complexes may react as nucleophilic reagents, and several types of electrophilic mono- or dicopper (hydro)peroxides exist. Side-on peroxo-dicopper(II) species effect aromatic hydroxylations, including phenolic substrates, in model systems and in the enzyme tyrosinase. Bis-(mu)-oxo-dicopper(III) entities are capable of hydrogen-atom abstraction reactions, or atom transfer to phosphines and sulfides. The scope and mechanisms of mononuclear Cu(II) superoxides or peroxides are yet to be established, but may be relevant to monooxygenases like peptidylglycine (alpha)hydroxylating monooxygenase.