抄録
Two possible mechanisms for dioxygen cleavage on non-heme diiron enzyme models are studied with an approximate molecular orbital method, the extended Huckel method. Diiron peroxo model complexes with different μ-η1:η1-O2 and μ-η2:η2-O2 binding modes are distorted to corresponding dioxo complexes along an assumed O-O bond cleavage reaction coordinate. Fragment molecular orbital (FMO) and Walsh diagram analyses clarify the bonding and orbital interactions. While the π(g)* orbitals of O2 are initially occupied by two electrons, in the first dioxygen binding step two other electrons are effectively transferred from the 't(2g)' block to O2 to form O22-. To cleave the dioxygen O-O bond, it is necessary further to fill the σ(u)* orbital (high lying and unoccupied in the peroxide). The computations suggest that the μ-ν1:ν1-O2 mode is more effective for electron transfer from the d-block orbitals to the σ(u)*. Our calculations indicate that a C(3v)- or D(2d)-distorted methane can be activated if a coordinatively unsaturated iron, which has been proposed to exist in the diamond Fe2(μ- O)2 core of intermediate Q of methane monooxygenase, is generated. The complex is suggested to include a five-coordinate carbon species with an Fe- CH4 bond. We propose possible concerted reaction pathways for the conversion of methane to methanol on the supposed diiron active site of methane monooxygenase. Inversion at a five-coordinate carbon species is suggested to reasonably occur in an initially formed complex of methane and a model of intermediate Q, leading to inversion of stereochemistry at a labeled carbon center.
| 元の言語 | 英語 |
|---|---|
| ページ（範囲） | 12311-12321 |
| ページ数 | 11 |
| ジャーナル | Journal of the American Chemical Society |
| 巻 | 119 |
| 発行部数 | 50 |
| DOI | |
| 出版物ステータス | 出版済み - 12 17 1997 |
| 外部発表 | Yes |
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All Science Journal Classification (ASJC) codes
- Catalysis
- Chemistry(all)
- Biochemistry
- Colloid and Surface Chemistry
これを引用
Dioxygen cleavage and methane activation on diiron enzyme models : A theoretical study. / Yoshizawa, Kazunari; Ohta, Takehiro; Yamabe, Tokio; Hoffmann, Roald.
：: Journal of the American Chemical Society, 巻 119, 番号 50, 17.12.1997, p. 12311-12321.研究成果: ジャーナルへの寄稿 › 記事
}
TY - JOUR
T1 - Dioxygen cleavage and methane activation on diiron enzyme models
T2 - A theoretical study
AU - Yoshizawa, Kazunari
AU - Ohta, Takehiro
AU - Yamabe, Tokio
AU - Hoffmann, Roald
PY - 1997/12/17
Y1 - 1997/12/17
N2 - Two possible mechanisms for dioxygen cleavage on non-heme diiron enzyme models are studied with an approximate molecular orbital method, the extended Huckel method. Diiron peroxo model complexes with different μ-η1:η1-O2 and μ-η2:η2-O2 binding modes are distorted to corresponding dioxo complexes along an assumed O-O bond cleavage reaction coordinate. Fragment molecular orbital (FMO) and Walsh diagram analyses clarify the bonding and orbital interactions. While the π(g)* orbitals of O2 are initially occupied by two electrons, in the first dioxygen binding step two other electrons are effectively transferred from the 't(2g)' block to O2 to form O22-. To cleave the dioxygen O-O bond, it is necessary further to fill the σ(u)* orbital (high lying and unoccupied in the peroxide). The computations suggest that the μ-ν1:ν1-O2 mode is more effective for electron transfer from the d-block orbitals to the σ(u)*. Our calculations indicate that a C(3v)- or D(2d)-distorted methane can be activated if a coordinatively unsaturated iron, which has been proposed to exist in the diamond Fe2(μ- O)2 core of intermediate Q of methane monooxygenase, is generated. The complex is suggested to include a five-coordinate carbon species with an Fe- CH4 bond. We propose possible concerted reaction pathways for the conversion of methane to methanol on the supposed diiron active site of methane monooxygenase. Inversion at a five-coordinate carbon species is suggested to reasonably occur in an initially formed complex of methane and a model of intermediate Q, leading to inversion of stereochemistry at a labeled carbon center.
AB - Two possible mechanisms for dioxygen cleavage on non-heme diiron enzyme models are studied with an approximate molecular orbital method, the extended Huckel method. Diiron peroxo model complexes with different μ-η1:η1-O2 and μ-η2:η2-O2 binding modes are distorted to corresponding dioxo complexes along an assumed O-O bond cleavage reaction coordinate. Fragment molecular orbital (FMO) and Walsh diagram analyses clarify the bonding and orbital interactions. While the π(g)* orbitals of O2 are initially occupied by two electrons, in the first dioxygen binding step two other electrons are effectively transferred from the 't(2g)' block to O2 to form O22-. To cleave the dioxygen O-O bond, it is necessary further to fill the σ(u)* orbital (high lying and unoccupied in the peroxide). The computations suggest that the μ-ν1:ν1-O2 mode is more effective for electron transfer from the d-block orbitals to the σ(u)*. Our calculations indicate that a C(3v)- or D(2d)-distorted methane can be activated if a coordinatively unsaturated iron, which has been proposed to exist in the diamond Fe2(μ- O)2 core of intermediate Q of methane monooxygenase, is generated. The complex is suggested to include a five-coordinate carbon species with an Fe- CH4 bond. We propose possible concerted reaction pathways for the conversion of methane to methanol on the supposed diiron active site of methane monooxygenase. Inversion at a five-coordinate carbon species is suggested to reasonably occur in an initially formed complex of methane and a model of intermediate Q, leading to inversion of stereochemistry at a labeled carbon center.
UR - http://www.scopus.com/inward/record.url?scp=0031576666&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0031576666&partnerID=8YFLogxK
U2 - 10.1021/ja9726419
DO - 10.1021/ja9726419
M3 - Article
AN - SCOPUS:0031576666
VL - 119
SP - 12311
EP - 12321
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 50
ER -