Ligand topology effect on the reactivity of a mononuclear nonheme iron(IV)-oxo complex in oxygenation reactions

Mononuclear nonheme iron(IV)-oxo complexes with two different topologies, cis-α-[Fe ^IV(O)(BQCN)] ²⁺ and cis-β-[Fe ^IV(O)(BQCN)] ²⁺, were synthesized and characterized with various spectroscopic methods. The effect of ligand topology on the reactivities of nonheme iron(IV)-oxo complexes was investigated in C-H bond activation and oxygen atom-transfer reactions; cis-α-[Fe ^IV(O)(BQCN)] ²⁺ was more reactive than cis-β-[Fe ^IV(O)(BQCN)] ²⁺ in the oxidation reactions. The reactivity difference between the cis-α and cis-β isomers of [Fe ^IV(O)(BQCN)] ²⁺ was rationalized with the Fe ^IV/III redox potentials of the iron(IV)-oxo complexes: the Fe ^IV/III redox potential of the cis-α isomer was 0.11 V higher than that of the cis-β isomer.