Kotseruba V. Liquid-phase oxidation of dibenzyl ether and cyclohexene in the presence of 3d metals polynuclear carboxylates

Object of investigation: reactions of organic compounds liquid-phase oxidation by air oxygen catalyzed by the complexes of transitional metals. Aim of research: to find the alternative routes of dibenzyl ether (DBE) and cyclohexene (СН) liquid-phase oxidation, and mechanisms of activating of corresponding substrates and intermediates, depending on composition of metalocomplex catalysts and terms of reaction. Methods: formal kinetics, gas-liquid chromatography, potentiometric and volumetric analysis, X-ray structure analysis. Theoretical and practical results: liquid-phase oxidation of DBE and СН by air oxygen and decomposition of corresponding hydroperoxides in the presence of Co(II,III), Cu(II), Ni(II), Fe(II,III), Cr(III), Mn(II,III), Pd(II) and Zn(II) mono- and polynuclear carboxylates have been studied. It is shown, that factors of benzyl СН-bond activation in DBE and its hydroperoxide will be the similar. Polynuclear complexes-intermediates of Cu, Co and Pd, which are the first examples of stable complexes with coordinated DBE oxidized to benzoic acid, are separated and identified by X-ray structure analysis. At CH liquid-phase oxidation by air in the presence of Co, Cr, Fe and Ni hexacarboxylates, formed CH hydroperoxide is main "key" intermediate, "providing" the alternative catalytic cycles of CH transformation to cyclohexenol and cyclohexenone, realized on a the same "catalytic center".