Synthesis and reactivity of a mononuclear non-haem cobalt(IV)-oxo complex.

Terminal cobalt(IV)-oxo (CoIV -O) species have been implicated as key intermediates in various cobalt-mediated oxidation reactions. Herein we report the photocatalytic generation of a mononuclear non-haem [(13-TMC)CoIV (O)]2+ (2) by irradiating [CoII (13-TMC)(CF3 SO3 )]+ (1) in the presence of [RuII (bpy)3 ]2+ , Na2 S2 O8 , and water as an oxygen source. The intermediate 2 was also obtained by reacting 1 with an artificial oxidant (that is, iodosylbenzene) and characterized by various spectroscopic techniques. In particular, the resonance Raman spectrum of 2 reveals a diatomic Co-O vibration band at 770 cm-1 , which provides the conclusive evidence for the presence of a terminal Co-O bond. In reactivity studies, 2 was shown to be a competent oxidant in an intermetal oxygen atom transfer, C-H bond activation and olefin epoxidation reactions. The present results lend strong credence to the intermediacy of CoIV -O species in cobalt-catalysed oxidation of organic substrates as well as in the catalytic oxidation of water that evolves molecular oxygen.