The alpha-C-H bonds of 3-methyl-2-butanone, 3-pentadone, and 2-methyl-3-pentanone were activated on the sulfur center of the disulfide-bridged ruthenium dinuclear complex [{RuCl(P(OCH3)(3))(2)}(2)(mu-S-2)(mu-Cl)(2)] (1) in the presence of AgX (X = PF6, SbF6) with concomitant formation of C-S bonds to give the corresponding ketonated complexes [{Ru(CH3CN)(2)(P(OCH3)(3))(2)}(mu-(SSCHRCOR2)-C-1){Ru(CH3CN)(3)(P(OCH3)(3))(2)}]X-3 ([5](PF6)(3), R-1 = H, R-2 = CH(CH3)(2), X = PF6; [6](PF6)(3), R-1 = CH3, R-2 = CH2CH3, X = PF6; [7](SbF6)(3), R-1 = CH3, R-2 = CH(CH3)(2), X = SbF6). For unsymmetric ketones, the primary or the secondary carbon of the alpha-C-H bond, rather than the tertiary carbon, is preferentially bound to one of the two bridging sulfur atoms. The alpha-C-H bond of the cyclic ketone cyclohexanone was cleaved to give the complex [{Ru(CH3CN)(2)(P(OCH3)(3))(2)}(mu-SS-1-cyclohexanon-2-yl){Ru(CH3CN)(3)(P(OCH3)(3))(2)}](SbF6)(3) ([8](SbF6)(3)). And the reactions of acetophenone and p-methoxyacetophenone, respectively, with the chloride-free complex [( Ru(CH3CN)(3)(P(OCH3)(3))(2)}(2)(mu-S-2)](4+) (3) gave [{Ru(CH3CN)(2)(P(OCH3)(3))(2)}(mu-SSCH2COAr){Ru(CH3CN)(3)(P(OCH3)(3))(2)}](CF3SO3)(3) ([9](CF3SO3)(3), Ar = Ph; [10](CF3SO3)(3), Ar = p-CH3OC6H4) The relative reactivities of a primary and a secondary C-H bond were clearly observed in the reaction of butanone with complex 3, which gave a mixture of two complexes, i.e., [{Ru(CH3CN)(2)(P(OCH3)(3))(2)}(mu-SSCH2COCH2-CH3{Ru(CH3CN)(3)(P(OCH3)(3))(2)}](CF3SO3)(3)) {Ru(CH3CN)(3)(P(OCH3)(3))(2)}](CF3SO3)(3) ([11](CF3SO3)(3)) and [{Ru(CH3CN)(2)(P(OCH3)(3))(2)}(mu-SSCH2COCH2-CH3){Ru(CH3CN)(3)(P(OCH3)(3))(2)}](CF3SO3)(3) ([12](CF3SO3)(3)), in a molar ratio of 1:1.8. Complex 12 was converted to 11 at room temperature if the reaction time was prolonged. The relative reactivities of the alpha-C-H bends of the ketones were deduced to be in the order 2 degrees > 1 degrees > 3 degrees, on the basis of the consideration of contributions from both electronic and steric effects. Additionally, the C-S bonds in the ketonated complexes were found to be cleaved easily by protonation at room temperature. The mechanism for the formation of the ketonated disulfide-bridged ruthenium dinuclear complexes is as follows: initial coordination of the oxygen atom of the carbonyl group to the ruthenium center, followed by addition of an cc-C-H bond to the disulfide bridging ligand, having S=S double-bond character, to form a C-S-S-H moiety, and finally completion of the reaction by deprotonation of the S-H bond.