Abstract
Grafting of [Mo(NAr)(=CHCMe2R)(CH(2)t(3)Bu)(2)], 1-R (R = Me or Ph) on the surface silanols of SiO2-(700) gives 2-R through the electrophilic cleavage of the Mo-C sigma-bond according to labelling (GUMS 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 pKa >= 9. Finally, the surface complex 2-R (R = Me or Ph) is a highly efficient olefin metathesis catalyst.