The reactivity of the novel tridentate phosphine ligand N(CH(2)PCyp(2))(3) (N-triphos(Cyp), 2; Cyp = cyclopentyl) with various ruthenium complexes was investigated and compared that of to the less sterically bulky and less electron donating phenyl derivative N(CH2PPh2)(3) (N-triphos(Ph), 1). One of these complexes was subsequently investigated for reactivity toward levulinic acid, a potentially important biorenewable feedstock. Reaction of ligands 1 and 2 with the precursors [Ru(COD)(methylallyl)(2)] (COD = 1,5-cycloocatadiene) and [RuH2(PPh3)(4)] gave the tridentate coordination complexes [Ru(tmm){N(CH2PR2)(3)-kappa P-3}] (R = Ph (3), Cyp (4); tmm = trimethylenemethane) and [RuH2(PPh3){N(CH2PR2)(3)-kappa P-3}] (R = Ph (5), Cyp (6)), respectively. Ligands 1 and 2 displayed different reactivities with [Ru-3(CO)(12)]. Ligand 1 gave the tridentate dicarbonyl complex [Ru(CO)(2){N(CH2PPh2)(3)-kappa P-3}] (7), while 2 gave the bidentate, tricarbonyl [Ru(CO)(3){N(CH(2)PCyp(2))(3)-kappa P-2}] (8). This was attributed to the greater electron-donating characteristics of 2, requiring further stabilization on coordination to the electron-rich Ru(0) center by more CO ligands. Complex 7 was activated via oxidation using AgOTf and O-2, giving the Ru(II) complexes [Ru(CO)(2)(OTf){N(CH2PPh2)(3)-kappa P-3}(OTf) (9) and [Ru(CO3)(CO){N(CH2PPh2)(3)-kappa P-3}] (11), respectively. Hydrogenation of these complexes under hydrogen pressures of 3-15 bar gave the monohydride and dihydride complexes [RuH(CO2){N(CH2PPh2)(3)-kappa P-3}] (10) and [RuH2(CO){N(CH2PPh2)(3)-kappa P-3}] (12), respectively. Complex 12 was found to be unreactive toward levulinic acid (LA) unless activated by reaction with NH4PF6 in acetonitrile, forming [RuH(CO){MeCN){N-(CH2PPh2)(3)center dot kappa P-3}(PF6), (13) which reacted cleanly with LA to form [Ru(CO3)(CO){N(CH2PPh2)(3)-kappa P-3}{CH3CO(CH2)(2)CO2H-kappa O-2}]](PF6) (14). Complexes 3, 5, 7, 8, 11, and 12 were characterized by single-crystal X-ray crystallography.