2013 Fiscal Year Annual Research Report
金属イオン共役電子移動による高原子価金属オキソ錯体の水の酸化触媒活性制御
| Project/Area Number |
12J02902
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| Research Institution | Osaka University |
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Principal Investigator |
朴 ジユン 大阪大学, 大学院工学研究科, 特別研究員(DC1)
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| Keywords | Electron Transfer / Lewis Acid / C-H Bond Cleavage / Sulfoxidation / Unification |
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| Research Abstract |
Nonheme high-valent metal-oxo intermediates have merited considerable attention ever since they were identified as active species in the catalytic oxidation of organic substrates by metalloenzymes. Reactivity of nonheme high-valent metal-oxo species and their structural, spectroscopic, and chemical properties have extensively been investigated in biomimetic oxidation reaction, such as electron transfer, hydride transfer, C-H bond activation, and oxygen atom transfer (OAT) reactions. Reactivity of high-valent metal-oxo species can be influenced by the conditions surrounding high-valent metal-oxo moiety, such as not only, temperature, pressure, and pH, but also solvents, the ligand structure as well as topology and Lewis acid including redox-inactive metal ions and proton. We have shown that C-H bond cleavage of toluene derivatives and sulfoxidation of thioanisole derivatives by non-hemeiron (IV)-oxo, [(N4Py) Fe^<IV>(O)]^<2+> (N4Py = N, N-bis (2-pyridylmethyl)-N-bis (2-pyridyl) methyl- a
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mine), are remarkably enhanced by Lewis acid, such as Sc^<3+> ion and HOTf. Huge enhancement of the oxidizing reactivity of [(N4Py) Fe^<IV>(O)]^<2+> by Lewis acids result from strong binding of Sc^<3+> ion to the electron acceptors or protonation of electron acceptors, which causes large positive shifts in the one-electron reduction potentials, as observed in Sc^<3+> ion- and proton-coupled electron-transfer reduction of various electron acceptors. In the presence of Sc^<3+> ion and HOTf, oxidation reaction of toluene and thioanisole derivatives by [(N4Py) Fe^<IV>(O)^<2+> occur via proton-coupled electron transfer (PCET) and metal ion-coupled electron transfer (MCET) following formation of precursor complexes between substrates and [(N4Py) Fe^<IV>(O)]^<2+> as indicated by a unified correlation of log k_<ET> (k_<ET> is the first-order rate constant of electron transfer in the precursor complexes) vs the driving force of electron transfer (-ΔG_<et>) in light of the Marcus theory of outer-sphere electron transfer. Less
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
Lewis and Bronsted acid, such as metal ion and HOTf, effect on oxidation reaction by non-heme iron (IV)-oxo well studied in our system. And it can be used on other oxidation reaction which is never has been done by nonheme high-valent metal-oxo complex.
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| Strategy for Future Research Activity |
Lewis acids, such as redox inactive metal ion and proton, can promote oxidation reaction of organic substrate by nonheme iron (IV)-oxo complex via electron transfer. Huge enhancement came from precursor complex formation of metal ion-bounded or protomated nonheme iron (IV)_oxo and substrate. By using this super reactive species, the other oxidation reaction can be done which never has been studied by nonheme high-valent metal-oxo complex.
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Research Products
(4 results)
