Reagent-Regulated Oxidative O-Demethylation of a Ferrous Complex Stabilized by a Tetradentate N Ligand with a Methoxyphenyl Substituent

A ferrous complex FeIILOMeCl2, 1, where LOMe is 2-methoxy-N,N-bis(pyridin-2-ylmethyl) aniline, has been synthesized and studies on its structure, spectral properties, and reactivity have been carried out. The complex has rich spectral properties and shows a well-defined paramagnetic 1H NMR spectrum with sharp and hyperfine shifted signals, which were assigned with the help of a combination of 1H–1H COSY and T1 and T2 relaxation time measurements. Though stable to air, complex 1 underwent oxidation in the presence of AgClO4, which resulted in the formation of a symmetric diferric oxo complex [(LOMeFeIIICl)2O](ClO4)2, 2. However, on reaction with strong oxidants such as tBuOOH, complex 1 yielded a mixture of an unsymmetric diferric oxo complex LOMeFeIIIClOFeIIICl3, 3, and a mononuclear ferric complex LO–FeIIICl2, 4, with a modified phenoxide ligand LO–, which is formed as a result of the demethylation of LOMe during oxidation. The factors affecting O-demethylation were studied and a possible mechanistic pathway involving a high-valent iron-oxo species is proposed.