Reaction of [RuCl₂(DMSO)₄] 1 with (2,6-dimethoxyphenyl)diphenylphosphine (MDMPP) in acetone–CH₂Cl₂ at reflux gave t,c,c-[RuCl₂(MDMPP-κ²P,O)₂] 2. Reaction with bis(2,6-dimethoxyphenyl)phenylphosphine (BDMPP) afforded the phosphonium salt containing a ruthenium(II) anion, [BDMPP(CH₂Cl)][RuCl₃(DMSO)₃] 3b, [BDMPP(CH₂Cl)][RuCl(DMSO)₂{PPh(C₆H₃OMe-6-O-2)₂-κ³P,O,O′)] 4b and [BDMPP(CH₃)][RuCl (DMSO)₂{PPh(C₆H₃OMe-6-O-2)₂-κ³P,O,O′)] 4d [BDMPP(CH₂Cl) = {2,6-(MeO)₂C₂H₃}₂PhP(CH₂Cl), BDMPP(CH₃) = {2,6-(MeO)₂C₆H₃}₂PhP(CH₃)]; complexes 4 contain tridentate P,O,O′ co-ordination in which two methoxy groups of BDMPP were demethylated. These structures were confirmed by X-ray analyses. Tris(2,6-dimethoxyphenyl)phosphine (TDMPP) reacted with 1 to give 3c [TDMPP(CH₂Cl)][RuCl₃(DMSO)₃] [TDMPP(CH₂Cl) = {2,6-(MeO)₂ C₆H₃}₃P(CH₂Cl)]. Complex 2 reacted with xylyl or mesityl isocyanide to give mer-[RuCl₂(MDMPP-P)(RNC)₃] 5. Reaction with CO afforded [RuCl₂(MDMPP-P)(MDMPP-κ²P,O)(CO)] 6 and an insoluble unidentified complex. The structure of 6 was confirmed by an X-ray analysis; one MDMPP group acts as a P,O bidentate ligand, the other as a monodentate ligand, and a CO ligand occupies the trans position to an oxygen atom. Two Cl and two P atoms were located at mutually trans positions. The phosphonium salt [BDMPP(CH₂Cl)]Cl, derived from CH₂Cl ₂ and BDMPP, reacted with 1 to afford 3b. The reaction of 3b with BDMPP gave 4b and 4d. The reaction pathways are discussed.