Influence of N-donor bases and the solvent in oxodiperoxomolybdenum catalysed olefinepoxidation with hydrogen peroxide in ionic liquids

Abstract

Biphasic catalytic olefin epoxidation systems consisting of oxodiperoxomolybdenum catalysts in 1-n-alkyl-3-methylimidazolium hexafluorophosphate ionic liquid (IL) media with aqueous hydrogen peroxide oxidant were optimised by tuning the molecular structure of the IL and employing N-heterocyclic donor base additives to inhibit hydrolysis and enhance the activity of the catalyst. The latter study was only made possible by the solubilising properties of the IL media. Of the bases investigated, pyrazoles were identified as the most efficient additive species and the best results were obtained using 3,5-dimethylpyrazole. Immobilisation of the catalyst in the IL allowed for very efficient catalyst recycling. Finally, the compound [MoO(O₂)₂(3-Mepz)₂] (3-Mepz = 3-methylpyrazole) was characterised and its structure determined by X-ray crystallography.