Pincer Phosphine Complexes of Ruthenium: Formation of Ru(P−O−P)(PPh3)HCl (P−O−P = xantphos, DPEphos, (Ph2PCH2CH2)2O) and Ru(dppf)(PPh3)HCl and Characterization of Cationic Dioxygen, Dihydrogen, Dinitrogen, and Arene Coordinated Phosphine Products

Treatment of Ru(PPh3)3HCl with the pincer phosphines 9,9-dimethyl-4,5-bis(diphenylphosphino)xanthene (xantphos), bis(2-diphenylphosphinophenyl)ether (DPEphos), or (Ph2PCH2CH2)2O affords Ru(P−O−P)(PPh3)HCl (xantphos, 1a; DPEphos, 1b; (Ph2PCH2CH2)2O, 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 NaBAr4 F (BAr4 F = B(3,5-C6H3(CF3)2)4) gives the cationic aqua complexes [Ru(P−O−P)(PPh3)(H2O)H]BAr4 F (3a−c). Removal of chloride from 1a 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 O2 to generate [Ru(xantphos)(PPh3)(η2-O2)H]BAr4 F (5a) and [Ru(DPEphos)(PPh3)(η2-O2)H]BAr4 F (5b). Addition of H2 or N2 to 3a−c yields the thermally unstable dihydrogen and dinitrogen species [Ru(P−O−P)(PPh3)(η2-H2)H]BAr4 F (6a−c) and [Ru(P−O−P)(PPh3)(N2)H]BAr4 F (7a−c), which have been characterized by multinuclear NMR spectroscopy at low temperature. Ru(PPh3)3HCl reacts with 1,1′-bis(diphenylphosphino)ferrocene (dppf) to give the 16-electron complex Ru(dppf)(PPh3)HCl (1d), which upon treatment with NaBAr4 F, affords [Ru(dppf){(η6-C6H5)PPh2}H]BAr4 F (8), in which the PPh3 ligand binds η6 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)2H]BArF 4 (9) and [Ru(PMe3)5H]BAr4 F (10).