Grafted metallo-carbynes as bifunctional pre-catalysts for ROMP of cyclo-octene and cyclic alkane metathesis

Abstract

Abstract: Metallo-carbynes grafted on mesoporous fibrous silica are active towards alkane metathesis. We are comparing the activity of well-defined grafted pre-catalysts (≡Si−O−)W(≡CCMe3)(i−CH2CMe3)2, (≡Sii−Oi−)W(≡CH)(i−CH3)2 and (≡Sii−Oi−)Mo(≡CCMe3)(i−CH2CMe3)2 for Ring Opening Metathesis Polymerization of cyclo-octene and metathesis of cyclo-octane. This comparison is because olefins are assumed to be intermediate products in alkane metathesis. The three pre-catalysts are active in cyclo-octane metathesis, and give the higher, and lower cyclic homologues. However, with cyclo-octene the three catalysts give polyoctenamer by classical ROMP. It is assumed that the metallo-carbynes react differently towards cyclo-alkanes and cyclo-olefins. In one case, with cyclo-alkanes they give a metallo-carbene alkyl and in the other case with cyclo-olefins they give a bis-carbene.