Characterization and reactivity study of non-heme high-valent iron–hydroxo complexes

A terminal Fe(III)OH complex, [Fe(III)(L)(OH)](2−) (1), has been synthesized and structurally characterized (H(4)L = 1,2-bis(2-hydroxy-2-methylpropanamido)benzene). The oxidation reaction of 1 with one equiv. of tris(4-bromophenyl)ammoniumyl hexachloroantimonate (TBAH) or ceric ammonium nitrate (CAN) in acetonitrile at −45 °C results in the formation of a Fe(III)OH ligand radical complex, [Fe(III)(L˙)(OH)](−) (2), which is hereby characterized by UV-visible, (1)H nuclear magnetic resonance, electron paramagnetic resonance, and X-ray absorption spectroscopy techniques. The reaction of 2 with a triphenylcarbon radical further gives triphenylmethanol and mimics the so-called oxygen rebound step of Cpd II of cytochrome P450. Furthermore, the reaction of 2 was explored with different 4-substituted-2,6-di-tert-butylphenols. Based on kinetic analysis, a hydrogen atom transfer (HAT) mechanism has been established. A pK(a) value of 19.3 and a BDFE value of 78.2 kcal/mol have been estimated for complex 2.