A Manganese(V)-Oxo Complex: Synthesis by Dioxygen Activation and Enhancement of Its Oxidizing Power by Binding Scandium Ion
- 등재 SCIE, SCOPUS
- 발행기관 American Chemical Society
- 발행년도 2016
- 총서유형 Journal
- URI http://www.dcollection.net/handler/ewha/000000136208
- 본문언어 영어
- Published As http://dx.doi.org/10.1021/jacs.6b03874
- 저작권 이화여자대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
A mononuclear non-heme manganese(V)-oxo complex, [MnV(O)(TAML)]- (1), was synthesized by activating dioxygen in the presence of olefins with weak allylic C-H bonds and characterized structurally and spectroscopically. In mechanistic studies, the formation rate of 1 was found to depend on the allylic C-H bond dissociation energies (BDEs) of olefins, and a kinetic isotope effect (KIE) value of 16 was obtained in the reactions of cyclohexene and cyclohexene-d10. These results suggest that a hydrogen atom abstraction from the allylic C-H bonds of olefins by a putative MnIV-superoxo species, which is formed by binding O2 by a high-spin (S = 2) [MnIII(TAML)]- complex, is the rate-determining step. A Mn(V)-oxo complex binding Sc3+ ion, [MnV(O)(TAML)]--(Sc3+) (2), was also synthesized in the reaction of 1 with Sc3+ ion and then characterized using various spectroscopic techniques. The binding site of the Sc3+ ion was proposed to be the TAML ligand, not the Mn-O moiety, probably due to the low basicity of the oxo group compared to the basicity of the amide carbonyl group in the TAML ligand. Reactivity studies of the Mn(V)-oxo intermediates, 1 and 2, in oxygen atom transfer and electron-transfer reactions revealed that the binding of Sc3+ ion at the TAML ligand of Mn(V)-oxo enhanced its oxidizing power with a positively shifted one-electron reduction potential (ΔEred = 0.70 V). This study reports the first example of tuning the second coordination sphere of high-valent metal-oxo species by binding a redox-inactive metal ion at the supporting ligand site, thereby modulating their electron-transfer properties as well as their reactivities in oxidation reactions. © 2016 American Chemical Society.
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