Determination of spin inversion probability, H-tunneling correction and regioselectivity in the two-state reactivity of nonheme iron(IV)-oxo complexes

Abstract

We show by experiments that nonheme FeIVO species react with cyclohexene to yield selective hydrogen atom transfer (HAT) reactions with virtually no C=C epoxidation. Straightforward DFT calculations reveal, however, that C=C epoxidation on the S = 2 state possesses a low energy barrier and should contribute substantially to the oxidation of cyclohexene by the nonheme FeIVO species. By modeling selectivity of this two-site reactivity, we show that an interplay of tunneling and spin inversion probability (SIP) reverses the apparent barriers and prefers exclusive S = 1 HAT over mixed HAT and C=C epoxidation on S = 2. The model enables us to derive an SIP value by combining experimental and theoretical results.