Vinylsilanes and/or allylsilanes are formed upon silylation of terminal alkenes with R3' SiCl in the presence of a Grignard reagent and a catalytic amount of [Cp2 ZrCl2 ] [Eq. (a)]. The reaction also proceeds under mild conditions when silylsulfides (X=SPh), silylselenides (X=SePh), and silyltellurides (X=TePh) are used in place of chlorosilanes (X=Cl). R″=alkyl, aryl, alkylsilyl; R'=Me, Et, nPr; R=CH2 R″, aryl, H.