Protonation of a Peroxodiiron(III) Complex and Conversion to a Diiron(III/IV) Intermediate: Implications for Proton-Assisted O鈥揙 Bond Cleavage in Nonheme Diiron Enzymes

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• 作者：Matthew A. Cranswick ; Katlyn K. Meier ; Xiaopeng Shan ; Audria Stubna ; J贸szef Kaizer ; Mark P. Mehn ; Eckard M眉nck ; Lawrence Que ; Jr.
• 刊名：Inorganic Chemistry
• 出版年：2012
• 出版时间：October 1, 2012
• 年：2012
• 卷：51
• 期：19
• 页码：10417-10426
• 全文大小：494K
• 年卷期：v.51,no.19(October 1, 2012)
• ISSN：1520-510X

文摘

Oxygenation of a diiron(II) complex, [Fe<sup>IIsup><sub>2sub>(渭-OH)<sub>2sub>(BnBQA)<sub>2sub>(NCMe)<sub>2sub>]<sup>2+sup> [2, where BnBQA is N-benzyl-N,N-bis(2-quinolinylmethyl)amine], results in the formation of a metastable peroxodiferric intermediate, 3. The treatment of 3 with strong acid affords its conjugate acid, 4, in which the (渭-oxo)(渭-1,2-peroxo)diiron(III) core of 3 is protonated at the oxo bridge. The core structures of 3 and 4 are characterized in detail by UV鈥搗is, M枚ssbauer, resonance Raman, and X-ray absorption spectroscopies. Complex 4 is shorter-lived than 3 and decays to generate in 20% yield of a diiron(III/IV) species 5, which can be identified by electron paramagnetic resonance and M枚ssbauer spectroscopies. This reaction sequence demonstrates for the first time that protonation of the oxo bridge of a (渭-oxo)(渭-1,2-peroxo)diiron(III) complex leads to cleavage of the peroxo O鈥揙 bond and formation of a high-valent diiron complex, thereby mimicking the steps involved in the formation of intermediate X in the activation cycle of ribonucleotide reductase.