Epoxidation Of Cyclooctene Catalyzed By Early Transition Metal Mixed-addendum Keggin Typed Polyoxometalates

Epoxides are one of the most valuable building blocks that can be used as intermediates and precursors for chemical production. The most important way is to make the formation of epoxide olefin by oxidant. Hydrogen peroxide is cheap, environmentally clean and easy to handle. H₂O₂ is an adduct of H₂ and O₂ that is also viewed as an adduct of an O atom and an H₂O molecule. Therefore, the oxidation of alkenes with aqueous hydrogen peroxide is very attractive from the viewpoint of industrial production and synthetic organic chemistry.Recently, the catalytic function of polyoxometallates （POMs） has attracted much attention because their acidic and redox properties can be controlled at atomic or molecular levels. The study found that POMs have efficient catalytic activity for olefin epoxidation reaction, is a kind of good catalyst for the oxidation of olefins.In this paper, we studyed the epoxidation of cyclooctene with H₂O₂ catalyzed by [PTi₂W₁₀O₄₀]^7- and [H₂PTi₂W₁₀O₄₀]^5- . They are showed efficient activity for the epoxidation of cyclooctene with H₂O₂, and the active intermediate of [PTi₂W₁₀O₃₈（O₂）₂]^7- containing the peroxide group is generated during during the reaction. Furthermore, after the addition of acid, it is found that conversion of cyclooctene is dramatically enhanced. This paper also studied the catalytic activity of [SiW9（CNbO₂）3O37]^7- and [GeW9（NbO₂）3037]^7- for the epoxidation of cyclooctene. The results showed that [SiW9（NbO₂）3O37]^7- and [GeW9（NbO₂）3O37]^7- have the catalytic activity for the epoxidation of cyclooctene. Under acidic conditions, the catalytic activity of [GeW9（NbO₂）3O37]^7- will be significantly improved. Therefore, the stability of the peroxo-species is changed by the addition of H+, which improves the activity of the peroxide species, and is more favorable for the catalytic reaction.