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

Identifier:  PC:1758

Handle: https://hdl.handle.net/20.500.11797/PC1758

Authors:  Josep M. Poblet; Pablo Jiménez-Lozano; Igor Y. Skobelev; Oxana A. Kholdeeva; Jorge J. Carbó

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 ß-oxygen transfer from the titanium hydroperoxo species becomes favored over the ß-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.