A mononuclear nonheme cobalt(ii) complex, [(TMG3tren)CoII(OTf)](OTf) (1), activates dioxygen in the presence of hydrogen atom donor substrates, such as tetrahydrofuran and cyclohexene, resulting in the generation of a cobalt(ii)-alkylperoxide intermediate (2), which then converts to the previously reported cobalt(iv)-oxo complex, [(TMG3tren)CoIV(O)]2+-(Sc(OTf)3)n(3), in >90% yield upon addition of a redox-inactive metal ion, Sc(OTf)3. Intermediates2and3represent the cobalt analogues of the proposed iron(ii)-alkylperoxide precursor that converts to an iron(iv)-oxo intermediateviaO-O bond heterolysis in pterin-dependent nonheme iron oxygenases. In reactivity studies,2shows an amphoteric reactivity in electrophilic and nucleophilic reactions, whereas3is an electrophilic oxidant. To the best of our knowledge, the present study reports the first example showing the generation of cobalt-oxygen intermediates by activating dioxygen at a cobalt(ii) center and the reactivities of the cobalt-oxygen intermediates in oxidation reaction.
Bibliographical noteFunding Information:
This work was supported by the NRF of Korea through CRI (NRF-2021R1A3B1076539 to W. N.) and Basic Science Research Program (NRF-2020R1I1A1A01074630 to Y.-M. L. and NRF-2019R1I1A1A01055822 to M. S. S.) and the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy – EXC 2008 – 390540038 – UniSysCat to K. R. and H. D. and the Heisenberg-Professorship to K. R. XAS measurements at SSRL BL 2-2 were made possible by support from U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515 and DE-SC0012704, as well as the National Institutes of Health (P30-EB-009998).
© The Royal Society of Chemistry 2021.