A 1:1 copper-dioxygen adduct is an end-on bound superoxo copper(II) complex which undergoes oxygenation reactions with phenols

Employing a strongly electron-donating tripodal tetradentate ligand along with a reaction strategy designed to suppress binuclear peroxo complex formation, an end-on bound superoxo-copper(II) complex [Cu-II(NMe2-TMPA)(O-2(-))](+) (1) has been generated in solution [UV-vis (THF, -85 degrees C): lambda(max) = 418 nm (epsilon, 4300 M-1 cm-1), 615 nm (epsilon, 1100), 767 nm (epsilon, 840)]. Resonance Raman spectroscopy employing isotopically substituted dioxygen (including mixed isotope O-16/18(2)) proves the end-on superoxo Cu-II(O-2(-)) structural formulation, nu(O-O) = 1121 cm(-1); nu(Cu-O) = 472 cm(-1). The first demonstration of Cu-II(O-2(-)) oxidative reactivity with exogenous substrates, likely involving H-atom abstraction chemistry, comes with the finding that 1 effects the oxygenation and hydroperoxylation of substituted phenols.