Mechanistic Insights into Unusual Reactions by High -Valent Iron Intermediates
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High-valent non-heme iron(III)-hydroperoxo and iron(IV)-oxo units are proposed as key oxidizing intermediates in many biological iron dependent oxygenases. The oxidant, iron(IV)-oxo species were proposed as active oxidant in several catalytic cycles. In recent years, emphasis on the evaluation of the kinetic and mechanistic insights into the reactivity of iron(IV)-oxo, iron(III)- hydroperoxo and other high-valent isolabal intermediates have increased. In the present work, the reactivity studies towards halide oxidation, Soxidation, C-H activation with high-valent iron(III)-hydroperoxo, iron(IV)-oxo and iron(IV)-imido species supported by penta-dentate ligands have been evaluated. These reactivity studies provide remarkable insights into the mechanistic pathway of these intermediates. Iron(III)-hydroproxo and iron(IV)-oxo complexes were compared in halide oxidation and observed that iron(III)-hydroproxo were efficient oxidizing species. In comparison of Iron(IV)-oxo and iron(IV)-imido complexes towards Soxidation and C-H activation, a conflicting results were observed. For Soxidation reactions, iron(IV)-imido complexes were a better oxidants as compared to iron(IV)-oxo. On the contrary, for C-H activation a complete reversal of the reactivity was observed where in iron(IV)-oxo species were more reaction than iron(IV)-imido complexes. Finally, the reactivity of iron(IV)-oxo complexes were evaluated for the oxidation of one of the most difficult pollutant (dibenzothiophene) and its thermodynamic parameters were evaluated..
Supervisor: Chivukula V. Sastri