Dataset Information

Observation of Radical Rebound in a Mononuclear Nonheme Iron Model Complex.

ABSTRACT: A nonheme iron(III) terminal methoxide complex, [FeIII(N3PyO2Ph)(OCH3)]ClO4, was synthesized. Reaction of this complex with the triphenylmethyl radical (Ph3C•) leads to formation of Ph3COCH3 and the one-electron-reduced iron(II) center, as seen by UV-vis, EPR, 1H NMR, and Mössbauer spectroscopy. These results indicate that homolytic Fe-O bond cleavage occurs together with C-O bond formation, providing a direct observation of the "radical rebound" process proposed for both biological and synthetic nonheme iron centers.

SUBMITTER: Pangia TM

PROVIDER: S-EPMC6047074 | biostudies-literature | 2018 Mar

REPOSITORIES: biostudies-literature

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Observation of Radical Rebound in a Mononuclear Nonheme Iron Model Complex.

Pangia Thomas M TM Davies Casey G CG Prendergast Joshua R JR Gordon Jesse B JB Siegler Maxime A MA Jameson Guy N L GNL Goldberg David P DP

Journal of the American Chemical Society 20180314 12

A nonheme iron(III) terminal methoxide complex, [FeIII(N3PyO2Ph)(OCH3)]ClO4, was synthesized. Reaction of this complex with the triphenylmethyl radical (Ph3C•) leads to formation of Ph3COCH3 and the one-electron-reduced iron(II) center, as seen by UV-vis, EPR, 1H NMR, and Mössbauer spectroscopy. These results indicate that homolytic Fe-O bond cleavage occurs together with C-O bond formation, provid ...[more]

PMID: 29537258

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Project description:Redox-inactive metal ions that function as Lewis acids play pivotal roles in modulating reactivities of oxygen-containing metal complexes in a variety of biological and biomimetic reactions, including dioxygen activation/formation and functionalization of organic substrates. Mononuclear nonheme iron(III)-peroxo species are invoked as active oxygen intermediates in the catalytic cycles of dioxygen activation by nonheme iron enzymes and their biomimetic compounds. Here, we report mononuclear nonheme iron(III)-peroxo complexes binding redox-inactive metal ions, [(TMC)FeIII(O2)]+-M3+ (M3+ = Sc3+ and Y3+; TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane), which are characterized spectroscopically as a 'side-on' iron(III)-peroxo complex binding a redox-inactive metal ion, (TMC)FeIII-(?,?2:?2-O2)-M3+ (2-M). While an iron(III)-peroxo complex, [(TMC)FeIII(O2)]+, does not react with electron donors (e.g., ferrocene), one-electron reduction of the iron(III)-peroxo complexes binding redox-inactive metal ions occurs readily upon addition of electron donors, resulting in the generation of an iron(IV)-oxo complex, [(TMC)FeIV(O)]2+ (4), via heterolytic O-O bond cleavage of the peroxide ligand. The rates of the conversion of 2-M to 4 are found to depend on the Lewis acidity of the redox-inactive metal ions and the oxidation potential of the electron donors. We have also determined the fundamental electron-transfer properties of 2-M, such as the reduction potential and the reorganization energy in electron-transfer reaction. Based on the results presented herein, we have proposed a mechanism for the reactions of 2-M and electron donors; the reduction of 2-M to the reduced species, (TMC)FeII-(O2)-M3+ (2'-M), is the rate-determining step, followed by heterolytic O-O bond cleavage of the reduced species to form 4. The present results provide a biomimetic example demonstrating that redox-inactive metal ions bound to an iron(III)-peroxo intermediate play a significant role in activating the peroxide O-O bond to form a high-valent iron(IV)-oxo species.

Dataset Information

Observation of Radical Rebound in a Mononuclear Nonheme Iron Model Complex.

Publications

Observation of Radical Rebound in a Mononuclear Nonheme Iron Model Complex.

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