Spectroscopically distinct sites present in methyltrioxorhenium grafted onto silica-alumina, and their abilities to initiate olefin metathesis

Solid-state NMR and infrared (IR) measurements are combined with computational analysis to examine the structures of major sites formed by grafting C[H.sub.3]Re[O.sub.3] onto amorphous silica-alumina and their relationships with olefin metathesis activity of this material. The results have suggested simple modifications in catalyst preparation, which has led to higher selectivity, less leaching and efficient use of the Re complex.