Synthesis and characterization of a family of binuclear non-heme iron monooxygenase model compounds: Evidence for a “phenolate/amide carbonyl (PAC) shift” upon oxidation

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• 作者：Patrick J. Cappillino ; Paul C. Tarves ; Gerard T. Rowe ; Andrew J. Lewis ; Mark Harvey ; Corina Rogge ; Adonis Stassinopoulos ; Wayne Lo ; William H. Armstrong ; John P. Caradonna
• 关键词：Binuclear iron ; Non-heme iron ; Carboxylate shift ; sMMO ; Di-μ ; -alkoxy diferric ; Dioxygen activation
• 刊名：Inorganica Chimica Acta
• 出版年：2009
• 出版时间：15 May 2009
• 年：2009
• 卷：362
• 期：7
• 页码：2136-2150
• 全文大小：1214 K

文摘

A series of binuclear iron compounds has been synthesized using diamide, bis-phenolate ligands in which the carbon-linker between the amide nitrogen atoms has been varied. Two diferrous compounds in the series, along with their two-electron oxidized, di-μ-methoxy-bridged counterparts, have been crystallographically characterized, as have the di-μ-methoxy compounds (H₂Hbab = 1,2-bis(2-hydroxybenzamido) benzene, H₂Hbach = trans-1,2-bis(2-hydroxybenzamido) cyclohexane, H₂Hbame = 1,2-bis(2-hydroxybenzamido) ethane, H₂Hbap = 1,3-bis(2-hydroxybenzamido) propane, H₂Hbabn = 1,4-bis(2-hydroxybenzamido) butane, H₂Hbapen = 1,5-bis(2-hydroxybenzamido) pentane, N-MeIM = N-methylimidazole and OMe = methoxide). are structurally very similar to previously reported diferrous compounds of this family of ligands that have been shown to be active as oxygen atom transfer catalysts. Flexibility in the carbon-linker allows some variability in the orientation of the phenolate arms of the ligands in the diferric di-μ-methoxy compounds, but the Fe₂O₂ core remains largely unchanged across the series. Two-electron oxidation of the ferrous compounds in methanol shows a substantial ligand rearrangement that is consistent with other spectroscopic, electrochemical and kinetic investigations. The loss of both phenolate bridges upon oxidation is reminiscent of the “carboxylate shift” observed in binuclear non-heme enzymes and could provide insight into the driving force behind this family of compounds’ function as a catalyst.