Thermodynamic and Kinetic Studies of Mononuclear Non-Heme High-Valent (FeO)²⁺ Complexes

Mononuclear nonheme high-valent (FeO)²⁺ complexes participate in many enzymatic oxidation-reduction cycles in a living body and play a key role in organic synthesis. The concept of molecular ID (molecular identities) was proposed and applied in our previous work; it covers all thermodynamic data for compounds containing an active carbon-hydrogen bond: oxidation potential, hydride anion affinity, proton affinity, and hydrogen atom affinity. To facilitate quantitative analysis of the physical organic chemistry and molecular biology properties of (FeO)²⁺ complexes, the molecular identities and reaction thermodynamic platform of representative complexes were established based on the thermodynamic data, such as (N4Py)(FeO)²⁺ and (Bn-TPEN)(FeO)²⁺, and their kinetic characteristics. Finally, the findings of this study are as follows: first, the reaction between (N4Py)(FeO)²⁺ and hydride donors 1/2 (Scheme 1) followed a one-step hydride anion transfer mechanism. The reactions between (N4Py)(FeO)²⁺ and hydride donors 3 (Scheme 1) and between (Bn-TPEN)(FeO)²⁺ and hydride donors 1 followed the hydrogen atom-electron transfer mechanism. Second, by comparison of high-valent (RuO)²⁺ complexes and organic hydride acceptors, the essential laws in selecting the reaction mechanism were obtained to determine the reaction mechanism of this study. Third, the reaction between (N4Py)(FeO)²⁺ and 1 followed the electron-proton-electron transfer mechanism under acidic conditions.