Dinuclear Gold(I) Chloride Complexes of 1,4-Bis(diphenylphosphinyl)butane and 1,5-Bis(diphenylphosphinyl)pentane: A Conformational Study

[1,4-Bis(diphenylphosphinyl)butane]digold dichloride 1 and [1,5-bis(diphenylphosphinyl)-pentane]digold dichloride 2 have been prepared from R₂SAuCl (R = CH₂CH₂OH) and the corresponding bidentate phosphines Ph₂P(CH₂)ηPPh₂ (η = 4 or 5) in good yields. The structures of the compounds have been determined by single crystal X-ray diffraction (1·CH₂C1₂: space group P1, Z = 2; 2-0.5 CH₂Cl₂:space group C2/c, Z = 8). While the monomers [Ph₂P(CH₂)₅PPh₂] (AuCl)₂ are associated through intermolecular Au…Au contacts (3.323Å) to form a chain-like structure, the crystal lattice of 1·CH₂Cl₂ features independent [Ph₂P(CH₂)₄PPh₂](AuCl)₂ molecules which show no intra- or intermolecular Au…Au interactions. This exceptional behaviour can be rationalized on the basis of efficient packing of solvent molecules and molecules 1 with a particularly favourable conformation, which cannot be altered by weak Au(d¹⁰)-Au(d¹⁰) interactions.