Synthesis and Reactivity of a Non-Heme μ-Oxodicobalt(IV) Complex

Abstract

A mononuclear Co^III complex (1) of a bisamide-bisalkoxide donor ligand was synthesized and thoroughly characterized. The reaction of 1 with 0.5 equiv. of m-chloroperbenzoic acid (m-CPBA) in acetonitrile at −40 °C resulted in the formation of a μ-oxodicobalt(IV) complex (2), which was characterized by an array of spectroscopic techniques, including X-ray absorption spectroscopy which revealed a short Co−O_oxo distance of 1.67 Å. Reactivity studies of 2 towards oxidation/oxygenation of hydrocarbon C−H bond and triphenylphosphine or thioanisole derivatives have been examined. UV-vis spectroscopy studies showed the appearance of clear isosbestic points during the oxidation of substrates together with a neat transformation of 2 to 1. Detailed kinetic investigations established that 2 follows a Concerted Proton-Electron Transfer (CPET) mechanism for hydrocarbon oxidation and has a weak electrophilic character. Catalytic behavior of 1 was noted towards the oxygen atom transfer reactions. This study showcases the spectroscopic investigation and reactivity studies of a Co^IV(μ-O)Co^IV moiety. Although the Fe^IV analog of such a core has been described before, the study describes the first example with a Co^IV center.