The well-defined molecular rhenium complexes CH3ReO3 and (CH3)3SiOReO3 are adsorbed onto oxide surfaces with their structures largely intact. Interactions between each molecular complex and Lewis acid sites on the surface of the solid support confer metathesis activity. The nature of the activation process was studied using a combination of spectroscopy (IR, solid-state NMR, XPS), active site counting, and kinetics. In the case of CH3ReO3, the mechanism involves support-induced tautomerization of the pre-existing methyl ligand, while the inorganic perrhenate ester requires activation by an olefin. There are two deactivation pathways with different rates. The surface hydroxyl groups, both acidic and basic, alter the structure of the grafted sites cause rapid deactivation. Over time, mobility on the surface causes active sites to encounter hydroxyl groups leading to deactivation.

Well-defined olefin metathesis catalysts by the activation of molecular rhenium complexes on solid supports

2019 Spring National Meeting

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