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 beta-mercaptoethylamine, HS(CH2)(2)NH2, 1,4-diaminobutane, H2N(CH2)(4)NH2, and n-butyl- and n-octylamine, CH3(CH2)(n)NH2 (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 Angstrom, indicating significant bonding, which is probably the main driving force for the clustering of seemingly closed-shell (d(10)) gold(I) metal atoms.