Synthesis, Structure, and Reactivity of [RuCl(PP)L]PF₆ (PP = (PPh₃)₂, Ph₂P(CH₂)₄PPh₂; L = P(py)₃, PPh(py)₂, py = 2-pyridyl). The “Missing” P,N,N‘-Coordination Mode for 2-Pyridylphosphines

The complexes [RuCl(PPh₃)₂(P,N,N‘-PPh_3-x(py)_x)]PF₆ (x = 2, 1b; 3, 1c; py = 2-pyridyl) were isolated from the reaction of RuCl₂(PPh₃)₃ with 1 equiv of PPh_3-x(py)_x and NH₄PF₆ in acetone. Crystals of 1b (C₅₂H₄₃ClF₆N₂P₄Ru) are monoclinic, a = 17.795(2), b = 11.375(4), and c = 23.343(2) Å, β = 97.012(8)°, Z = 4, space group P2₁/c; those for 1c (C₅₁H₄₂ClF₆N₃P₄Ru) are monoclinic, a = 17.812(1), b = 11.353(2), and c = 23.391(1) Å, β = 97.738(5)°, Z = 4, space group P2₁/c. The isomorphous structures were solved by the Patterson method and were refined by full-matrix least-squares procedures to R = 0.036 and 0.033 (R_w = 0.035 and 0.031) for 7690 and 8121 reflections with I ≥ 3σ(I), respectively. The P,N,N‘-coordination mode for 2-pyridylphosphines is previously unreported. The P,N-coordinated complexes cis-RuCl₂(dppb)(PPh_3-x(py)_x) (x = 1−3; dppb = Ph₂P(CH₂)₄PPh₂) were made by isomerization of the corresponding trans-dichloro isomers, which are themselves synthesized from RuCl₂(dppb)(PPh₃). The cis complexes in CHCl₃ or CH₂Cl₂ dissociate chloride reversibly with formation of P,N,N‘-coordinated PPh_3-x(py)_x species, which were isolated as [RuCl(dppb)(PPh_3-x(py)_x)]PF₆ (x = 2, 3). Reactions of CO with the species containing the strained P,N,N‘-coordination mode lead to displacement of a coordinated pyridyl and formation of the P,N-coordinated complexes [RuCl(CO)(PP)(PPh_3-x(py)_x)]PF₆ (PP = (PPh₃)₂, x = 2, 3; and PP = dppb, x = 2, 3). The CO reactions are partially reversible. Solution structures of the complexes were determined by NMR, IR, and UV−visible spectroscopies and conductivity.