Functional Model of Compound II of Cytochrome P450: Spectroscopic Characterization and Reactivity Studies of a...

Herein, we show that the reaction of a mononuclear Fe^III(OH) complex (1) with N-tosyliminobenzyliodinane (PhINTs) resulted in the formation of a Fe^IV(OH) species (3). The obtained complex 3 was characterized by an array of spectroscopic techniques and represented a rare example of a synthetic Fe^IV(OH) complex. The reaction of 1 with the one-electron oxidizing agent was reported to form a ligand-oxidized Fe^III(OH) complex (2). 3 revealed a one-electron reduction potential of -0.22 V vs Fc⁺/Fc at -15 °C, which was 150 mV anodically shifted than 2 (E_red = -0.37 V vs Fc⁺/Fc at -15 °C), inferring 3 to be more oxidizing than 2. 3 reacted spontaneously with (4-OMe-C₆H₄)₃C^• to form (4-OMe-C₆H₄)₃C(OH) through rebound of the OH group and displayed significantly faster reactivity than 2. Further, activation of the hydrocarbon C-H and the phenolic O-H bond by 2 and 3 was compared and showed that 3 is a stronger oxidant than 2. A detailed kinetic study established the occurrence of a concerted proton-electron transfer/hydrogen atom transfer reaction of 3. Studying one-electron reduction of 2 and 3 using decamethylferrocene (Fc*) revealed a higher k_et of 3 than 2. The study established that the primary coordination sphere around Fe and the redox state of the metal center is very crucial in controlling the reactivity of high-valent Fe-OH complexes. Further, a Fe^III(OMe) complex (4) was synthesized and thoroughly characterized, including X-ray structure determination. The reaction of 4 with PhINTs resulted in the formation of a Fe^IV(OMe) species (5), revealing the presence of two Fe^IV species with isomer shifts of -0.11 mm/s and = 0.17 mm/s in the Mössbauer spectrum and showed Fe^IV/Fe^III potential at -0.36 V vs Fc⁺/Fc couple in acetonitrile at -15 °C. The reactivity studies of 5 were investigated and compared with the Fe^IV(OH) complex (3).