Treatment of Ru(PPh3)(3)HCl with the pincer phosphines 9,9-dimethyl-4,5-bis(diphenylphosphino)xanthene (xantphos), bis(2-diphenylphosphinophenyl)ether (DPEphos), or (Ph2PCH2CH2)(2)O affords Ru(P-O-P)(PPh3)HCl (xantphos, la; DPEphos, 1b; (Ph2PCH2CH2)(2)O, 1c). The X-ray crystal structures of 1a-c show that all three P-O-P ligands coordinate in a tridentate manner through phosphorus and oxygen. Abstraction of the chloride ligand from 1a-c by NaBAr4F (BAr4F = B(3,5-C6H3(CF3)(2))(4)) gives the cationic aqua complexes [Ru(P-O-P)(PPh3)(H2O)NBAr4F (3a-c). Removal of chloride from la by AgOTf yields Ru(xantphos)(PPh3)H(OTf) (2a), which reacts with water to form [Ru(xantphos)(PPh3)(H2O)H](OTf). The aqua complexes 3a-b react with O-2 to generate [Ru(xantphos)(PPh3)(eta(2)-O-2)H]BAr4F (5a) and [Ru(DPEphos)(PPh3)(eta(2)-O-2)H]BAr4F (5b). Addition of H-2 or N-2 to 3a-c yields the thermally unstable dihydrogen and dinitrogen species [Ru(P-O-P)(PPh3)(eta(2)-H-2)H]BAr4F (6a -c) and [Ru(P-O-P)(PPh3)(N-2)H]BAr4F (7a-c), which have been characterized by multinuclear NMR spectroscopy at low temperature. Ru(PPh3)(3)HCl reacts with 1,1'-bis(diphenylphosphino)ferrocene (dppf) to give the 16-electron complex Ru(dppf)(PPh3)HCl (1d), which upon treatment with NaBAr4F, affords [Ru(dppf){(eta(6)-C6H5)PPh2}H]BAr4F (8), in which the PPh3 ligand binds eta(6) through one of the PPh3 phenyl rings. Reaction of 8 with CO or PMe3 at elevated temperatures yields the 18-electron products [Ru(dppf)(PPh3)(CO)(2)H]BAr4F (9) and [Ru(PMe3)(5)H]BAr4F (10).