The dication complex trans(O,S)-[Ru(bpy)(dmso-O)2(dmso-S)2](OTf)2 [1·(OTf)2; bpy = 2,2′-bipyridyl; dmso = dimethyl sulfoxide; OTf– = CF3SO3 –] was obtained from the reaction of cis(Cl),cis(S)-[RuCl2(bpy)(dmso-S)2] with Ag(OTf) in DMSO. The crystal structure of 1·(OTf)2 revealed two labile dmso-O ligands and two less-labile dmso-S ligands positioned cis to each other. In DMSO, the equatorial dmso-O in 12+ equilibrates with its linkage isomer dmso-S to fac(S)-[Ru(bpy)(dmso-O)(dmso-S)3]2+ [1iso 2+] ([1iso 2+]/[12+] = 3:97 at 298 K and 33:67 at 373 K). The linkage isomerization kinetic parameters, determined by 1H NMR, were ΔH = 22(1) kJ mol–1 and ΔS = 52(2) J mol–1 K–1. The two O-bonded dmso ligands of 1·(OTf)2 were easily solvolyzed in MeCN to form trans(NMeCN,S)-[Ru(bpy)(MeCN)2(dmso-S)2](OTf)2 [2·(OTf)2]. Moreover, the reaction of 1·(OTf)2 with 1,10-phenanthroline (phen) in acetone afforded cis-[Ru(bpy)(phen)(dmso-S)2](OTf)2 [3·(OTf)2] in very good yield (95 %) and excellent purity.