Functional Model of Compound II of Cytochrome P450: Spectroscopic Characterization and Reactivity Studies of a Fe^IV-OH Complex

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 degrees C, which was 150 mV anodically shifted than 2 (E-red = -0.37 V vs Fc(+)/Fc at -15 degrees C), inferring 3 to be more oxidizing than 2. 3 reacted spontaneously with (4-OMe-C6H4)(3)C-center dot to form (4-OMe-C6H4)(3)C(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 Mossbauer spectrum and showed Fe-IV/Fe-III potential at -0.36 V vs Fc(+)/Fc couple in acetonitrile at -15 degrees C. The reactivity studies of 5 were investigated and compared with the Fe-IV(OH) complex (3).