Strong Radical Character of the Catecholate Ligand of Catecholato(pyridine)iron Complexes Involved in the Catecholdioxygenase-model Reaction

Abstract

Abstract Five-coordinated catecholato(pyridine)iron complexes were isolated from the THF solution of the iron complex used for the catecholdioxygenase model reaction. Formation and structure of species with a catecholate ligand having a strong radical character in the pyridine solution were shown spectroscopically, especially by the large down-field shift of the methyl resonance of 4-methylcatecholate complex in 2H NMR and by the large band at >1000 nm in electronic spectra. Effect of Et4NCl on the spectra indicated that the complexes are in equilibrium with the the chloride-pyridine ligand exchange.