Gold Clustering at the Terminal Functions of Long-Chain Thiols and Amines

Treatment of 1,6-hexanedithiol with 4/3 mol equiv of tris[(triphenylphosphino)aurio(I)]oxonium tetrafluoroborate and sodium tetrafluoroborate affords (n-hexane-1,6-dithiolato)tetrakis-[(triphenylphosphine)gold(I)] bis(tetrafluoroborate) (1). The analogous reactions with β-mercaptoethylamine, HS(CH₂)₂NH₂, 1,4-diaminobutane, H₂N(CH₂)₄NH₂, and n-butyl- and n-octylamine, CH₃(CH₂)_nNH₂ (n = 3 or 7), give the corresponding penta- (2), hexa- (3), and trinuclear (4, 5) complexes, respectively. The crystal structures of compounds 3 and 5 have been determined by single-crystal X-ray diffraction studies. In the hexanuclear complex 3, three gold atoms are bonded to each nitrogen, putting each of these atoms at the apex of an NAu₃ pyramid. There are no intra- or intermolecular interactions between the gold centers of different nitrogen atoms. The trinuclear complex 5 features the unfolded aliphatic chain at the apex of such a pyramid. In both compounds the gold atoms show close contacts of 3.0 ± 0.1 Å, indicating significant bonding, which is probably the main driving force for the clustering of seemingly closed-shell (d¹⁰) gold(I) metal atoms.