PHOSPHORUS-CENTERED GOLD CLUSTERS - A NOVEL PENTANUCLEAR SPECIES ([(PH3P)6AU5]P)2+

The reaction of tris[(triphenylphosphane)gold]oxonium tetrafluoroborate with phosphane gas in tetrahydrofuran leads to a mixture of products, one of which has now been isolated and identified as the complex {[(Ph3P)6Au]P}2+ (BF4-)2 (1). This cluster can be described as an adduct of [(Ph3PAu)4P]+ and [(Ph3P)2Au]+. CrystalS Of (1)2. (CH2Cl2)3 - Et2O contain two crystallographically independent formula units of very similar structure. The dications are centered by pentacoordinate phosphorus atoms in an irregular coordination geometry. In the crystal one of the five gold atoms is attached to two triphenylphosphane ligands, while the other four bear only one such ligand. In solution rapid ligand exchange renders the ligands equivalent on the NMR time scale. This stoichiometry and structure of 1 are indicative of the strong basicity of the [(Ph3PAu)4p]+ cation probably owing to its square-pyramidal structure with strong Au ... Au bonding, as suggested by the structure of its arsenic analogue.