Fluxional behaviour of potentially bidentate phenanthroline, naphthyridine, and phthalazine ligands in palladium complexes

Abstract

The synthesis of a series of palladium complexes, cis-[PdCl(PEt3)2L][Y]; L = 1,10-phenanthroline, 1,8-naphthyridine, or phthalazine; Y = BF4− or ClO4−; is reported. Variable temperature 1H and 31P nmr spectra are discussed in terms of square planar structures in which the heterocyclic ligands are essentially monodentate and fluxional with the palladium exchanging between the two nitrogen atoms. Above ca. −10 °C a dissociative exchange mechanism operates in all three complexes and, when L = 1,10-phenanthroline or 1,8-naphthyridine, exchange continues at lower temperatures by an intramolecular process.