Lewis Acid Coupled Electron Transfer of Metal-Oxygen Intermediates
- 주제(키워드) electron transfer , Lewis acids , metal-oxo complexes , metal-peroxo complexes , superoxides
- 등재 SCIE, SCOPUS
- 발행기관 Wiley-VCH Verlag
- 발행년도 2015
- 총서유형 Journal
- URI http://www.dcollection.net/handler/ewha/000000120593
- 본문언어 영어
- Published As http://dx.doi.org/10.1002/chem.201502693
- 저작권 이화여자대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
Redox-inactive metal ions and Brønsted acids that function as Lewis acids play pivotal roles in modulating the redox reactivity of metal-oxygen intermediates, such as metal-oxo and metal-peroxo complexes. The mechanisms of the oxidative C-H bond cleavage of toluene derivatives, sulfoxidation of thioanisole derivatives, and epoxidation of styrene derivatives by mononuclear nonheme iron(IV)-oxo complexes in the presence of triflic acid (HOTf) and Sc(OTf)3 have been unified as rate-determining electron transfer coupled with binding of Lewis acids (HOTf and Sc(OTf)3) by iron(III)-oxo complexes. All logarithms of the observed second-order rate constants of Lewis acid-promoted oxidative C-H bond cleavage, sulfoxidation, and epoxidation reactions of iron(IV)-oxo complexes exhibit remarkably unified correlations with the driving forces of proton-coupled electron transfer (PCET) and metal ion-coupled electron transfer (MCET) in light of the Marcus theory of electron transfer when the differences in the formation constants of precursor complexes were taken into account. The binding of HOTf and Sc(OTf)3 to the metal-oxo moiety has been confirmed for MnIV-oxo complexes. The enhancement of the electron-transfer reactivity of metal-oxo complexes by binding of Lewis acids increases with increasing the Lewis acidity of redox-inactive metal ions. Metal ions can also bind to mononuclear nonheme iron(III)-peroxo complexes, resulting in acceleration of the electron-transfer reduction but deceleration of the electron-transfer oxidation. Such a control on the reactivity of metal-oxygen intermediates by binding of Lewis acids provides valuable insight into the role of Ca2+ in the oxidation of water to dioxygen by the oxygen-evolving complex in photosystem II. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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