Theoretical Study of the Oxidation of Methane to Methanol by the [CuIICuII(μ-O)2CuIII(7-N-Etppz)]1+ Complex

Yan Fang Liu* 

The Key Laboratory of Biobased Materials, The Qingdao Key Lab of Solar Energy Utilization and Energy Storage Technology, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, Shandong 266101, People’s Republic of China

Likai Du* 

Hubei Key Laboratory of Agricultural Bioinformatics, College of Informatics, Huazhong Agricultural University, Wuhan, 430070, People’s Republic of China

The reactivity patterns of a series of trivalent copper complexes have been studied to gain a better understanding of the chemical reactions occurring at the active site of particulate methane monooxygenase (pMMO). In this study, hybrid density functional theory is used to study the oxidation of methane to methanol mediated by the [CuIICuII(μ-O)2CuIII(7-N-Etppz)]1+ complex. Reaction mechanisms in different spin states were explored. Based on the calculated free-energy profile, a mechanism is suggested for the reaction of the oxidation of methane to methanol. The first step (1 → 2) is a hydrogen transfer to the bridged oxygen in the Cu2O2 core from the methane to form a methyl radical. The second step (2 → 3) is the radical recombination, in which the bridged hydroxyl rotates upward and exposes the oxygen moiety toward the methyl radical to form methanol. The radical recombination step is rate-limiting, with a calculated free-energy barrier of 19.6 kcal mol–1, which is in good agreement with the experimental value of 18.4 kcal mol–1. The mixed valent bis(μ-oxo)CuIICuIII species in the Cu3O4 core is directly responsible for the C–H activation of methane.

https://pubs.acs.org/doi/pdf/10.1021/acs.inorgchem.8b00054

Sunny Chanグループが以前報告した7員環と6員環骨格を持つ三核銅錯体を使って、別の人がメタンと反応するときの反応機構を計算科学を使って提唱しています。

Complex1のような混合原子価銅(II,II,III)ビス(µ-オキソ)錯体が活性種となりメタンの水素原子を引き抜くと言っています。

特に中西さんはチェックしておいた方がいいかと思います。