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

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Abstract
The complexes [RuCl(PPh3)2(P,N,N‘-PPh3-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 PPh3-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 (Rw = 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)(PPh3-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 PPh3-x(py)x species, which were isolated as [RuCl(dppb)(PPh3-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)(PPh3-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.

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