Treatment of [{Ru(P(OCH3)(3))(2)(CH3CN)(3)}(2)(mu -S-2)](CF3SO3)(4) (1), which is prepared by the reaction of [{RuCl(P(OCH3)(3))(2)}(2)(mu -S-2)(mu -Cl)(2)] (2) with 4 equiv of AgCF3SO3, with terminal alkenes such as I-pentene, allyl ethyl ether, allyl phenyl ether, 1,4-hexadiene, and 3-methyl-1-butene, resulted in the formation of complexes carrying a C3S2 five-membered ring, [{Ru(P(OCH3)(3))(2)(CH3CN)(3)}(2){mu -(SCH2CH2CRRS)-R-1-S-2}](CF3SO3)(4) (3, R-1 = CH2CH3, R-2 = H, 40%; 4, R-1 = OCH2CH3, R-2 = H, 60%; 5, R-1 = OC6H5, R-2 = H, 73%; 6, R-1 = CH=CHCH3, R-2 = H, 48% 7, R-1 = R-2 = CH3, 40%). Reaction of 1 with methylenecycloalkanes was found to give several different types of products, depending on the ring size of the substrates. A trace of [{Ru(P(OCH3)(3))(2)(CH3CN)(3)}(2){mu -SCH-(CH2CH2)CH(CH3)S}](CF3SO3)(4) (9) having a C2S2 four-membered ring to bridge the two Ru atoms was obtained by the reaction of I with methylenecyclobutane, whereas the reaction with methylenecyclohexane gave [{Ru(P(OCH3)(3))(2)(CH3CN)(3)}(2){mu -S(CH2(C=CHCH2CH2CH2CH2)S)}(CF3SO3)(3) (10) in 69% yield via C-S bond formation and elimination of a proton. Throughout these reactions with alkenes giving a variety of products, the activation of the allylic C-H bond is always the essential and initial key step.