Functional Model of Compound II of Cytochrome P450: Spectroscopic Characterization and Reactivity Studies of a FeIV–OH Complex

Herein, we show that the reaction of a mononuclear FeIII(OH) complex (1) with N-tosyliminobenzyliodinane (PhINTs) resulted in the formation of a FeIV(OH) species (3). The obtained complex 3was characterized by an array of spectroscopic techniques and represented a rare example of a synthetic FeIV(OH) complex. The reaction of 1with the one-electron oxidizing agent was reported to form a ligand-oxidized FeIII(OH) complex (2). 3revealed a one-electron reduction potential of −0.22 V vs Fc+/Fc at −15 °C, which was 150 mV anodically shifted than 2(Ered= −0.37 V vs Fc+/Fc at −15 °C), inferring 3to be more oxidizing than 2. 3reacted 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 2and 3was compared and showed that 3is 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 2and 3using decamethylferrocene (Fc*) revealed a higher ketof 3than 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 FeIII(OMe) complex (4) was synthesized and thoroughly characterized, including X-ray structure determination. The reaction of 4with PhINTs resulted in the formation of a FeIV(OMe) species (5), revealing the presence of two FeIVspecies with isomer shifts of −0.11 mm/s and = 0.17 mm/s in the Mössbauer spectrum and showed FeIV/FeIIIpotential at −0.36 V vs Fc+/Fc couple in acetonitrile at −15 °C. The reactivity studies of 5were investigated and compared with the FeIV(OH) complex (3).