Alkene Epoxidations Catalyzed by Mo(VI) Supported on Imidazole-Containing Polymers: I. Synthesis, Characterization, and Activity of Catalysts in the Epoxidation of Cyclohexene

Polystyrene resins functionalised with hydroxylpropyl aminomethyl pyridine, pyridyl imidazole, and carboxybenzimidazole, polyglycidyl methacrylate resins functionalised with aminomethyl pyridine and pyridyl imidazole, and a polybenzimidazole resin have all been loaded with Mo(VI). The resulting polymer metal complexes have been activated by treatment with t-butylhydroperoxide, then used as catalysts in the liquid-phase epoxidation of cyclohexene using t-butylhydroperoxide. Polymers containing the imidazole group were particularly active, and unlike the other species did not require preactivation to induce high activity. The complexes formed with the imidazole-containing polymers appear to be monometallic species, whereas the other polymer ligands yield oxybridged bimetallic species. This accounts for the major difference in activity recorded. Possible structures for the catalysts are proposed based on information in the literature.