Grubbs Catalysts Immobilized on Mesoporous Molecular Sieves via Phosphine and Pyridine Linkers

Hybrid catalysts for olefin metathesis were prepared by the immobilization of Ru alkylidenes (Grubbs catalysts) on mesoporous molecular sieves SBA-15 and MCM-41 having, the surface modified with molecules bearing dicyclo-hexylphosphine (PCy2) and pyridine end groups. Hybrid catalysts with Ru attached to the surface via PCy2 ligands exhibited higher activity and stability than those with Ru attached via pyridine ligands. The former catalysts exhibited a high activity in a series of metathesis reactions (RCM, ROMP, and cross-metathesis) reaching turnover numbers (TONs) from 200 to 2000 and being reusable several times. The filtration tests for all catalysts suggested that the solid catalysts were responsible for catalytic activity during the reactions. Only low Ru leaching was observed. A positive effect of the pore size of the support on catalyst activity was observed for the metathesis of methyl oleate.