Synthesis and reactivity of a mononuclear non-haem cobalt(IV)-oxo complex.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 28337985.
- Also identified by DOI 10.1038/ncomms14839 and PMC identifier 5376677.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Terminal cobalt(IV)-oxo (Co<sup>IV</sup>-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)Co<sup>IV</sup>(O)]<sup>2+</sup> (2) by irradiating [Co<sup>II</sup>(13-TMC)(CF<sub>3</sub>SO<sub>3</sub>)]<sup>+</sup> (1) in the presence of [Ru<sup>II</sup>(bpy)<sub>3</sub>]<sup>2+</sup>, Na<sub>2</sub>S<sub>2</sub>O<sub>8</sub>, 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<sup>-1</sup>, 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 Co<sup>IV</sup>-O species in cobalt-catalysed oxidation of organic substrates as well as in the catalytic oxidation of water that evolves molecular oxygen.