Catalytic oxidation of dibenzothiophene and thioanisole by a diiron(III) complex and hydrogen peroxide

•Synthesis and characterization of a new diiron(III) complex.•Quantitative oxidation of thioanisole using 1,3 equivalent of H2O2 with respect to the substrate (100 turnovers).•Efficient oxidation of DBT catalyzed by a diiron(III) complex with H2O2 (80 turnovers).•Isotope labelling experiments demonstrate the implication of a metal centred iron-oxo intermediate.

One diiron(III) complex of the dinucleating ligand HPTP (N,N,N′,N′-tetrakis(2-pyridylmethyl)-2-hydroxy-1,3-diaminopropane) and one mononuclear iron(III) complex of the BPMEN ligand (N,N′-dimethyl-N,N′-bis-2-pyridinylmethyl)-1,2-ethanediamine) have been synthesized and characterized by X-ray diffraction analysis, high resolution mass spectrometry, and electronic absorption spectroscopy. The diiron(III) complex reacts with hydrogen peroxide to generate a short lived blue intermediate comparable to the previously described μ-peroxo-diiron(III) intermediate, obtained from the interaction of the corresponding HPTP diiron(II) complex with dioxygen. Both mononuclear and dinuclear iron complexes were tested for the catalytic oxidation of sulphides with H2O2, and the diiron complex showed good activity for the oxidation of dibenzothiophene (DBT), a fuel contaminant naturally present in crude oil. It catalyzed the total conversion of DBT into the corresponding sulfone via the formation of the sulfoxide, in acetonitrile at room temperature.

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