Grafting mechanism and olefin metathesis activity of well-defined silica-supported Mo imido alkyl alkylidene complexes

摘要

Grafting of [Mo(NAr)(=CHCMe2R)(CH2tBu)2], 1-R (R = Me or Ph) on the surface silanols of SiO_(2-(700)) gives 2-R through the electrophilic cleavage of the Mo—C σ-bond according to labelling (GC/MS and solid-state NMR) and reactivity studies (monitoring initiation). Similarly, molecular silanol derivatives react with 1-Ph also to give directly the monosiloxy derivatives. Therefore, surface or molecular silanols have reactivities similar to alcohols and phenols having pK_a ≥ 9. Finally, the surface complex 2-R (R = Me or Ph) is a highly efficient olefin metathesis catalyst.