Abstract
The monosiloxy surface complexes [( SiO)Mo( NAr)(=CHC-Me2R')(OR)] (R' = Me or Ph: OR = OtBu, OCMe(CF3)(2) or OAr) are obtained by grafting onto SiO2-(700) either symmetric Mo-alkylidene derivatives [Mo( NAr)(=CHCMe2R')(OR)(2)] Or asymmetric derivatives, that is, with two different pendant ligands, one amido and one alkoxy/aryloxy, [Mo( NAr)(=CHCMe2R')(OR)(NC6H8)]. ne formation of these complexes was confirmed by mass-balance analysis, and infrared (IR) and NMR spectroscopies. These systems are highly efficient catalyst precursors for the metathesis of acyclic alkenes; the best results were seen when OR = OCMe-(CF3)(2). Nevertheless, they display poor performances in ring-closing metathesis, possibly due to the rigidity of the metal center (as evidenced by NMR spectroscopy), which therefore slows the rate of the metathesis.