Solid and solution structures of ternary gold(I) complexes with triphenylphosphine and nitrogen-containing ligands

A series of gold(I) complexes [Au(PPh3)L]ClO4 (L = pyridine 1a, 2,6-dimethylpyridine 1b, 2,6-di-tert-butylpyridine 1c, quinoline 1d, acridine 1e, benzo[h]quinoline 1f, naphthyridine 2a, 1,10-phenanthroline 2b, 2,2′-biquinoline 2c, di-2-pyridyl ketone 2d, di-2-pyridylamine 3a or 2-(2-pyridyl)benzimidazole 3b) were prepared by reaction of L with [Au(PPh3)(ClO4)] which was synthesized in situ. All complexes were characterized by IR, UV/VIS and 1H NMR spectroscopy. The crystal and molecular structures of 1b, 2a and 3b were investigated by single-crystal X-ray diffraction techniques. The gold(I) is co-ordinated to one nitrogen atom and one phosphine atom. Detailed 1H NMR studies suggested that linear two-co-ordinated structures persist in solution and further that all the complexes [Au(PPh3)L]ClO4, (2a–2d), are fluxional species in which the co-ordination site of gold(I) rapidly exchanges between two nitrogen atoms of the ligand.