Protonation of a peroxodiiron(III) complex and conversion to a diiron(III/IV) intermediate: Implications for proton-assisted O-O bond cleavage in nonheme diiron enzymes

Matthew A. Cranswick, Katlyn K. Meier, Xiaopeng Shan, Audria Stubna, Jószef Kaizer, Mark P. Mehn, Eckard Münck, Lawrence Que

Research output: Contribution to journalArticlepeer-review

33 Scopus citations

Abstract

Oxygenation of a diiron (II) complex, [FeII 2 ( μ - OH)2(BnBQA)2(NCMe)2]2+ [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 (μ-oxo)(μ-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-vis, Mössbauer, 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 Mössbauer spectroscopies. This reaction sequence demonstrates for the first time that protonation of the oxo bridge of a (μ-oxo)(μ-1,2-peroxo)diiron(III) complex leads to cleavage of the peroxo O-O 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.

Original languageEnglish (US)
Pages (from-to)10417-10426
Number of pages10
JournalInorganic chemistry
Volume51
Issue number19
DOIs
StatePublished - Oct 1 2012

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