The synthesis and characterization of a range of Pt(II) and Ru(II) complexes containing the new 2-pyridyldi-phosphine ligand, d(py)pcp = (py)(2)P(CH(CH2)(3)CH)P(py)(2) (made as a racemate) and the previously reported d(py)pe = (py)(2)P(CH2)(2)P(py)(2) are given (py =2-pyridyl). The Pt complexes made were cis-PtX2(d(py)pcp) (X = Cl (1), I (2)), cis-PtX2(d(py)pe) (X = Cl (3), I (4)), [Pt(d(py)pcp)(2)][PF6](2) (5), and [Pt(d(py)pe)(2)][PF6](2) (6); these all contain P,P-bonded diphosphine ligand, as evidenced by P-31 NMR data and by crystallographic data in the case of 2 and 3. The X-ray structure of d(py)pe is also reported. The complexes RuX2(P,P,N-d(py)pcp)(PPh3) have cis-halogens and a P,P,N-bonding mode of the pyridyldiphosphine (which incorporates a four-membered P,N-chelate ring) with either a mer-arrangement (in 7a, X = Cl) or a fac-arrangement of the three P donor atoms (in 7b (X = Cl), 8 (X = Br), 9 (X = I)); cis-RuCl2(dppb)(P,N-PPh2(py)) (12) (dppb = Ph-2(CH2)(4)PPh2) is included because it has a donor set corresponding to that in 7b. Use of the purely P,P donor Ph2P(CH(CH2)(3)CH)PPh2 (dppcp), made as a racemate, affords trans-RuCl2(dppcp)(2) (10) and trans-RuCl2(dppcp)(dppb) (II). Crystallographic data for 7a, 7b, and 12 are reported together with the NMR data for all the Ru complexes. Preliminary results show that the Ru complexes 7b, 8, and 9 are effective precursors for catalytic H-2-hydrogenation of aldimines.