Oxygen Anion-Radical Complexes with Mo(VI) on MoO_x/SiO₂ Catalysts and Their Role in the Oxidation of Methane to Methanol

Oxygen anion radicals \({O}_{2}^{-\cdot }\) $O_2^{-·}$ coordinated with one Mo(VI) have been identified in MoO_x/SiO₂ samples enriched with ⁹⁵Mo isotope. It is shown that unpaired electron is mainly localized on the oxygen ion (g_z = 2.017, g_y = 2.004, g_x = 1.999; A_x(⁹⁵Mo) = 6.1, A_y(⁹⁵Mo) = 6.0, A_z(⁹⁵Mo)=9.1 G; ∆H_x = ∆H_y = 2,2 G and ∆H_z = 2,6 G). Using a special freezing technique, peroxide radicals (CH₃OO^·), which are the products of the reaction of the methyl radical with molecular oxygen in the gas phase, have been identified. The oxidation pathways of methane to methanol with participation of the oxygen ion radicals coordinated directly by Mo(VI) are discussed.