Syntheses and structure of 2-diphenylphosphinomethylenide-6-diphenylphosphino methylene-pyridine complexes of palladium(II) and platinum(II); crystal structures of [PtCl(2-(CHPPh2)-6-(CH2PPh2) pyridine)] and [Pd(COOMe)(2-(CHPPh2)-6-(CH2PPh2)pyridine)].

The reactions of the palladium(II) and platinum(II) complexes of formula M(pnp)Cl2 (M ? Pd, Pt; pnp = 2,6-bis(diphenylphosphinomethyl)pyridine) and Pt(dppf)Cl2 (dppf = 1,1?-bis(diphenylphosphinomethyl)ferrocene) with NaOMe in methanol under CO at room temperature and atmospheric pressure has been investigated. In contrast with the behaviour of the Pd(dppf)Cl2 complex, which gives the corresponding bis-methoxycarbonyl compound, the terdentate ligand of the M(pnp)Cl2 complexes is nucleophilically attacked by the methoxide ion to lose a proton and yield complexes of formula [MXC5H3N(CHPPh2)(CH2PPh2)] (M ? Pt, X ? Cl, COOMe; M ? Pd, X ? COOMe), which have been characterized by chemical and spectroscopic means. The crystal structures of [PtCl2-(CHPPh2)-6-(CH2PPh2)pyridine] (1) and [Pd(COOMe)2-(CHPPh2)-6-(CH2PPh2)pyridine] (2) have been determined by X-ray diffaction. In both complexes the terdentate anionic ligand chelates the metal to form two five-membered rings, and the P?C and C?C bond lengths in one of the chelate rings is in agreement with an sp2 hybridization of the formally anionic methylenidic carbon and with a large delocalization in the ring.