Determination of Spin Inversion Probability, H‑Tunneling
Correction, and Regioselectivity in the Two-State Reactivity of Nonheme
Iron(IV)-Oxo Complexes
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Abstract
We show by experiments that nonheme
Fe<sup>IV</sup>O species react
with cyclohexene to yield selective hydrogen atom transfer (HAT) reactions
with virtually no CC epoxidation. Straightforward DFT calculations
reveal, however, that CC epoxidation on the <i>S</i> = 2 state possesses a low-energy barrier and should contribute substantially
to the oxidation of cyclohexene by the nonheme Fe<sup>IV</sup>O species.
By modeling the 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 <i>S</i> = 1
HAT over mixed HAT and CC epoxidation on <i>S</i> = 2. The model enables us to derive a SIP value by combining experimental
and theoretical results