Syntheses and structures of 2-diphenylphosphinomethylenide-6-diphenylphosphinomethylenepyridine complexes of palladium(II) and platinum(II); crystal structures of [PtCl2-(CHPPH 2)-6-(CH 2PPh 2)pyridine] and [Pd(COOMe)2-(CHPPh 2)-6-(CH 2PPh 2)pyridine

Abstract

The reactions of the palladium(II) and platinum(II) complexes of formula M(pnp)Cl 2 (M  Pd, Pt; pnp = 2,6-bis(diphenylphosphinomethyl)pyridine) and Pt(dppf)Cl 2 (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)Cl 2 complex, which gives the corresponding bis-methoxycarbonyl compound, the terdentate ligand of the M(pnp)Cl 2 complexes is nucleophilically attacked by the methoxide ion to lose a proton and yield complexes of formula [MXC 5H 3N(CHPPh 2)(CH 2PPh 2)] (M  Pt, X  Cl, COOMe; M  Pd, X  COOMe), which have been characterized by chemical and spectroscopic means. The crystal structures of [PtCl2-(CHPPh 2)-6-(CH 2PPh 2)pyridine] ( 1) and [Pd(COOMe)2-(CHPPh 2)-6-(CH 2PPh 2)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 sp 2 hybridization of the formally anionic methylenidic carbon and with a large delocalization in the ring.