Model Studies of Methyl CoM Reductase: Methane Formation via CH3鈥揝 Bond Cleavage of Ni(I) Tetraazacyclic Complexes Having Intramolecular Methyl Sulfide Pendants

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• 作者：Jun-ichi Nishigaki ; Tsuyoshi Matsumoto ; Kazuyuki Tatsumi
• 刊名：Inorganic Chemistry
• 出版年：2012
• 出版时间：May 7, 2012
• 年：2012
• 卷：51
• 期：9
• 页码：5173-5187
• 全文大小：750K
• 年卷期：v.51,no.9(May 7, 2012)
• ISSN：1520-510X

文摘

The Ni(I) tetraazacycles [Ni(dmmtc)]⁺ and [Ni(mtc)]⁺, which have methylthioethyl pendants, were synthesized as models of the reduced state of the active site of methyl coenzyme M reductase (MCR), and their structures and redox properties were elucidated (dmmtc, 1,8-dimethyl-4,11-bis{(2-methylthio)ethyl}-1,4,8,11-tetraaza-1,4,8,11-cyclotetradecane; mtc, 1,8-{bis(2-methylthio)ethyl}-1,4,8,11-tetraaza-1,4,8,11-cyclotetradecane). The intramolecular CH₃鈥揝 bond of the thioether pendant of [Ni^I(dmmtc)](OTf) was cleaved in THF at 75 掳C in the presence of the bulky thiol DmpSH, which acts as a proton source, and methane was formed in 31% yield and a Ni(II) thiolate complex was concomitantly obtained (Dmp = 2,6-dimesityphenyl). The CH₃鈥揝 bond cleavage of [Ni^I(mtc)]⁺ also proceeded similarly, but under milder conditions probably due to the lower potential of the [Ni^I(mtc)]⁺ complex. These results indicate that the robust CH₃鈥揝 bond can be homolytically cleaved by the Ni(I) center when they are properly arranged, which highlights the significance of the F430 Ni environment in the active site of the MCR protein.