title: 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.
abstract: Oxygenation of a diiron(II) complex, [Fe(II)(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.
authors.affiliation: Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, USA.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Cranswick
authors.forename: Katlyn K
authors.initials: KK
authors.lastname: Meier
authors.forename: Xiaopeng
authors.initials: X
authors.lastname: Shan
authors.forename: Audria
authors.initials: A
authors.lastname: Stubna
authors.forename: Jószef
authors.initials: J
authors.lastname: Kaizer
authors.forename: Mark P
authors.initials: MP
authors.lastname: Mehn
authors.forename: Eckard
authors.initials: E
authors.lastname: Münck
authors.forename: Lawrence
authors.initials: L
authors.lastname: Que
mesh_terms: D000818:Animals; D056831:Coordination Complexes / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D005296:Ferrous Compounds / Q000737:chemistry*; D006801:Humans; D019159:Nonheme Iron Proteins / Q000737:chemistry; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D017601:Oxygen Compounds / Q000737:chemistry*; D011522:Protons; D013057:Spectrum Analysis
chemical_list: D056831:Coordination Complexes; D005290:Ferric Compounds; D005296:Ferrous Compounds; D019159:Nonheme Iron Proteins; D017601:Oxygen Compounds; D011522:Protons; D010100:Oxygen