Aerobic Oxidative Dehydrogenations Catalyzed by the Mixed-Addenda Heteropolyanion PV₂Mo₁₀O₄₀^5-: A Kinetic and Mechanistic Study

The aerobic oxidative dehydrogenation of α-terpinene to p-cymene catalyzed by the mixed-addenda heteropolyanion PV₂Mo₁₀O₄₀^5- has been used to investigate the oxidation mechanism catalyzed by this class of compounds. The kinetics of the reaction show it to be zero order in α-terpinene, first order in dioxygen, and second order in the heteropolyanion catalyst. The kinetic results along with the use of UV-vis, ESR, ³¹P NMR, and IR spectroscopy have enabled the formulation of a reaction scheme involving the formation of a stable substrate-catalyst complex in the catalyst reduction (substrate oxidation) stage and a μ-peroxo catalyst intermediate in the catalyst reoxidation stage where dioxygen is reduced to water in a four-electron redox reaction.