The PtP(C6H11)3(C2H4)2 mediated activation of aldehyde CH bonds via chelate-assisted oxidative addition reactions

Hydrocarbon solutions of PtPCy₃(C₂H₄)₂ (Cy = cyclohexyl) react rapidly with 8-quinolinecarboxaldehyde (1 equiv.) to yield tricyclohexylphosphine quinolinecarboxyl platinum hydride (1) and CH₂CH₂ (2 equiv.). Compound 1 reacts with CCl₄ in hydrocarbons to give PtPCy₃(NC₉H₆CO)Cl (2) and CHCl₃. The compound PtPCy₃(C₂H₄)₂ also reacts with Ph₂P(C₆H₄-o-CHO) and Ph₂As(C₆H₄-o-CHO) to give PCy₃PtPh₂P(C₆H₄-o-CO)(H) (3) and PCy₃PtPh₂As(C₆H₄-o-CO)(H) (4), respectively. Compounds 1, 2, 3, and 4 were characterized by infrared and ¹H NMR spectra, and the crystal structure of 3 was determined by X-ray diffraction. Crystals of 3 are monoclinic, with space group P2₁/n and Z = 4 with the unit cell dimensions a 9.7936(17), b 14.844(35), c 23.530(64) Å, β 91.817 (18)°, and V 3419.09(1.36) ų. The structure is refined to final discrepancy factors of R = 0.055, and R_w = 0.064. The molecular structure of 3 is that ligating atoms are in a plane containing Pt. The position of the hydride was not located crystallographically, but the ¹H NMR spectrum of 3, supports the presence of a terminal hydride that is cis to the carbonyl. The IR band of 3 at 2023 cm^?1 which is assigned to ν(PtH), and the hydride cleavage reaction of 1 with CCl₄, provide evidence for the PtH bond.