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)₆Au₅]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 Auä bonding, as suggested by the structure of its arsenic analogue.