A new ligand BDNA [1,8-bis(diphenylphosphinomethyl)naphthalene] and three ruthenium complexes containing the new ligand, Ru 2 Cl 4 (BDNA) 2 1, RuHCl(CO)(PPh 3 )(BDNA) 2, and RuH 2 (CO)(PPh 3 )(BDNA) 3, have been synthesized. Their compositions and structures were characterized by 31 P{ 1 H}-NMR, 1 H-NMR, and elemental analysis. Molecular structure of 3 was also confirmed by single-crystal X-ray diffraction. The crystal belonged to the triclinic crystal system, P1̄ space group, a=10.7450(7), b=12.7100(7), c=18.1390(13) Å, α=89.558(6), β=83.117(2), γ=80.859(5)°, V=2428.0(3) Å 3 , and Z=2. The hydrogenation results of citral and cinnamaldehyde revealed that complex 2 had good catalytic activity and complex 3 had the high selectivity for the hydrogenation of CO bond in α,β-unsaturated aldehydes to form the corresponding allylic alcohols. In the presence of complex 3, very high selectivities of 99.5 and 95.1% were obtained for the hydrogenation of the carbonyl group in citral and cinnamaldehyde, respectively.