Abstract
: Metallo-carbynes grafted on mesoporous fibrous silica are active towards alkane metathesis. We are comparing the activity of well-defined grafted pre-catalysts (equivalent to Si-O-)W(equivalent to CCMe3)(i-CH2CMe3)(2), (equivalent to Sii-Oi-)W(equivalent to CH)(i-CH3)(2)and (equivalent to Sii-Oi-)Mo(equivalent to CCMe3)(i-CH2CMe3)(2)for Ring Opening Metathesis Polymerization ofcyclo-octene and metathesis ofcyclo-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 towardscyclo-alkanes andcyclo-olefins. In one case, withcyclo-alkanes they give a metallo-carbene alkyl and in the other case withcyclo-olefins they give a bis-carbene.