REACTIVITY OF METAL COMPLEXES WITH RADICALS

This review presents the results of studies on the reactivity of metal complexes with short-lived radicals (primarily peroxyl radicals) and metal complexes (mainly Cu(II) ions) with chelating nitroxide radicals. The reactions of newly synthesized paramagnetic ligands – Schiff bases derived from ortho-hydroxyaromatic aldehydes and two nitroxide radicals, 2,2,5,5-tetramethyl-3-amino-pyrrolidine-1-oxide and 2,2,6,6-tetramethyl-piperidine-4-amino-1-oxide – are discussed. It has been shown that in the derivative of the five-membered pyrrolidine radical, the radical center becomes part of the coordination sphere of the Cu(II) ion and is reduced to hydroxylamine. Ultimately, this leads to the formation of binuclear complexes with strong antiferromagnetic interactions between the Cu(II) ions. At room temperature, the resulting binuclear complexes interact with chloroform to abstract HCl and, with pyridine in the presence of oxygen, form paramagnetic mononuclear Cu(II) complexes. Separate sections of the review are devoted to catalytic oxidation reactions of alcohols and other substrates using metal complexes with nitroxide radicals (mainly TEMPO) as catalysts. Additionally, the catalytic reactions of metal complexes with phenoxyl radicals, which serve as biochemical models of the enzyme galactose oxidase, are discussed