A new catalytic route for synthesis of unsaturated organosilicon compounds with vinylic functionality (R'O)(3)SiCH CH(CH2)(a)SR (where R = t-Bu. Ph. R'=Me, Et, Me3Si n= 0, 1), based on cross -metathesis of vinyltrialkoxy- and vinyltris(trimethylsiloxy)silanes with vinyl and allyl, t-butyl (phenyl) sulfides catalyzed by the second generation Grubbs catalyst Cl-2(PCy3)(1,3-dimesityl-4,5-dihydroimidazol-2-ylidene)Ru(=CHPh)(II) is reported. The silylative coupling reactions of the substrates performed in the presence of Ru-H(III) and Ru-Si(IV) Give no products which is explained by formation of the ruthenium sulfide species Ru-S-t-Bu that appear to be catalytically inactive towards the silylative coupling reactions since there is no insertion of olefin into Ru-S bond. (C) 2004 Elsevier B.V. All rights reserved.