Sc³⁺-Promoted O–O Bond Cleavage of a (μ-1,2-Peroxo)diiron(III) Species Formed from an Iron(II) Precursor and O₂ to Generate a Complex with an Fe^IV₂(μ-O)₂ Core

Abstract

Soluble methane monooxygenase (sMMO) carries out methane oxidation at 4 °C and under ambient pressure in a catalytic cycle involving the formation of a peroxodiiron(III) intermediate (<b>P</b>) from the oxygenation of the diiron(II) enzyme and its subsequent conversion to <b>Q</b>, the diiron(IV) oxidant that hydroxylates methane. Synthetic diiron(IV) complexes that can serve as models for <b>Q</b> are rare and have not been generated by a reaction sequence analogous to that of sMMO. In this work, we show that [Fe^II(Me₃NTB)(CH₃CN)](CF₃SO₃)₂ (Me₃NTB = tris((1-methyl-1<i>H</i>-benzo[d]imidazol-2-yl)methyl)amine) (<b>1</b>) reacts with O₂ in the presence of base, generating a (μ-1,2-peroxo)diiron(III) adduct with a low O-O stretching frequency of 825 cm^-1 and a short Fe···Fe distance of 3.07 Å. Even more interesting is the observation that the peroxodiiron(III) complex undergoes O-O bond cleavage upon treatment with the Lewis acid Sc³⁺ and transforms into a bis(μ-oxo)diiron(IV) complex, thus providing a synthetic precedent for the analogous conversion of <b>P</b> to <b>Q</b> in the catalytic cycle of sMMO.