Dioxygen activation by copper sites: Relative stability and reactivity of (μ-η²:η²-peroxo)- and bis(μ-oxo)dicopper cores

Investigations of complexes comprising the title cores are summarized with a view toward understanding their interconversion and possible implications in metallobiochemistry. Detailed studies on the solvent and concentration dependence of the equilibrium between (μ-η²:η²-peroxo)dicopper(II) (A) and bis(μ-oxo)dicopper(III) (B) cores using mono- and binucleating ligands have elucidated the effects of ligand geometry, solubility, solvent donor ability and temperature on O-O bond cleavage and formation. These effects suggest that similar environmental influences may be significant in metalloenzymes and in particular, raise the possibility of either core being responsible for arene hydroxylation by tyrosinase. Recent studies on a synthetic system composed of a [Cu₂(μ-O)₂]²⁺ unit ligated to a mixed imine/amine ligand with an appended arene substituent substantiate the notion that core A or B may be competent in performing arene hydroxylation chemistry. (C) 1999 Elsevier Science S.A.