Aromatic hydroxylation by molecular oxygen performed by mononuclear benzoato iron(II) complexes and preparation of new iron(III) complex with two minus ligand

A novel oxygen insertion reaction by molecular oxygen into an aromatic C–H bond in benzoato iron(II) complexes [FeII{HB(3-Ph-5-Mepz)3}(η1-O2CC6H4-p-X)(3-Ph-5-MepzH)] (2a (X = Cl), 2b (X = H), and 2c (X = OMe)) is described. The structures of the hydroxylated complexes (3a (X = Cl), 3b (X = H), and 3c (X = OMe)) were determined by X-ray crystallography and other spectroscopic characterizations were performed; one of the phenyl rings in the hydrotris(pyrazolyl)borate ligand was hydroxylated. A new purple colored iron(III) complex (4), which was obtained by the reaction of 3a with base, is also characterized.