Oxidative defluorination reactivity of μ-nitrido diiron tetraphenylporphyrin complex

Abstract

Transformation of organofluorine compounds by oxidation pathways is rare in chemistry and biology since C-F bonds formed by the most electronegative element should react with electron-deficient oxidizing species. Recently, we have shown that [Formula: see text]-nitrido diiron phthalocyanine complexes efficiently catalyze oxidative defluorination of poly- and perfluoroaromatics by H2O2. Herein, we studied their more biologically relevant porphyrin counterpart, [Formula: see text]-nitrido diiron(III,IV) tetraphenylporphyrin complex (TPP)Fe[Formula: see text]N)Fe[Formula: see text](TPP) in stoichiometric and catalytic reactions with a series of fluorinated aromatic compounds under oxidation conditions. The addition of hexafluorobenzene to (TPP)Fe[Formula: see text]N)Fe[Formula: see text](TPP) in the presence of [Formula: see text]-butylhydroperoxide led to the formation of high-valent [Formula: see text]-nitrido diiron(IV,IV) porphyrin cation radical complex [TPP)Fe[Formula: see text] -N)Fe[Formula: see text](TPP[Formula: see text]]F2. This complex was isolated and its structural and electronic properties were investigated by spectroscopic methods (EXAFS, XANES, EPR, UV-vis). Replacement of [Formula: see text]BuOOH with H2O2oxidant resulted in the catalytic defluorination of selected heavily fluorinated aromatic compounds with high conversions (25–84%), TON (1768–3535), and defluorination degrees (71–84%). The scope of oxidative defluorination with (TPP)Fe[Formula: see text]N)Fe[Formula: see text](TPP) was extended to perfluorinated olefins exemplified by perfluoroallylbenzene. The perfluorinated double bond was more reactive compared with perfluorinated aromatic moiety providing C6F5CF2COOH and C6F5COOH products. The properties of [Formula: see text]-nitrido diiron tetraphenylporphyrin in homogeneous and heterogeneous catalytic defluorination were compared with those of its phthalocyanine counterpart.