Alkene Epoxidation Catalyzed by Ti-Containing Polyoxometalates: Unprecedented beta-Oxygen Transfer Mechanism

Identifier:  imarina:3665547

Handle: https://hdl.handle.net/20.500.11797/imarina3665547

Authors:  Jiménez-Lozano, P; Skobelev, IY; Kholdeeva, OA; Poblet, JM; Carbó, JJ

Abstract:
A DFT study revealed that the mechanism of alkene epoxidation with hydrogen peroxide catalyzed by Ti-containing polyoxometalates (POMs) depends on the Ti coordination environment: For rigid and hindered Ti centers, the unprecedented ¿-oxygen transfer from the titanium hydroperoxo species becomes favored over the ¿-oxygen one. Improving the model for catalyst description, the calculations were able to reproduce the Arrhenius activation energy values determined in kinetic studies. Unlike protonation, the possible ion-pairing between POMs and countercations has a minor effect on the electrophlicity of the catalyst and, consequently, on the activity of epoxidation.