Mononuclear Nonheme High-Spin (S=2) versus Intermediate-Spin (S=1) Iron(IV)–Oxo Complexes in Oxidation Reactions

Mononuclear nonheme high-spin (S=2) iron(IV)–oxo species have been identified as the key intermediates responsible for the C−H bond activation of organic substrates in nonheme iron enzymatic reactions. Herein we report that the C−H bond activation of hydrocarbons by a synthetic mononuclear nonheme high-spin (S=2) iron(IV)–oxo complex occurs through an oxygen non-rebound mechanism, as previously demonstrated in the C−H bond activation by nonheme intermediate (S=1) iron(IV)–oxo complexes. We also report that C−H bond activation is preferred over C=C epoxidation in the oxidation of cyclohexene by the nonheme high-spin (HS) and intermediate-spin (IS) iron(IV)–oxo complexes, whereas the C=C double bond epoxidation becomes a preferred pathway in the oxidation of deuterated cyclohexene by the nonheme HS and IS iron(IV)–oxo complexes. In the epoxidation of styrene derivatives, the HS and IS iron(IV) oxo complexes are found to have similar electrophilic characters.