The synthesis and full characterization of a well-defined silica-supported :Si-O-W(Me)(5) species is reported. Under an inert atmosphere, it is a stable material at moderate temperature, whereas the homoleptic parent complex decomposes above -20 degrees C, demonstrating the stabilizing effect of immobilization of the molecular complex. Above 70 degrees C the grafted complex converts into the two methylidyne surface complexes [( SiO-)W( CH)Me-2] and [( SiO-)(2)W( CH)Me]. All of these silica-supported complexes are active precursors for propane metathesis reactions.