SYNTHESIS, SPECTROSCOPY AND CRYSTAL-STRUCTURES OF [AU-2(MU-PH2PN(ET)PPH2)(2)][SBF6](2) AND [AU3CL2 (MU-PH2PN(ET)PPH2)(2)]PF6

Treatment of [Au(MeCN)(2)]SbF6 in acetonitrile with bis(diphenylphosph ino)ethylamine (dppa) afforded a colourless crystalline material chara cterised as [Au-2(mu-dppa)(2)][SbF6](2). An X-ray diffraction study co nfirmed that the two ligands bridge the two gold atoms with a Au ... A u separation of 2.838(2) Angstrom. The electronic absorption spectrum exhibits a band at 298 nm (epsilon(max), ca. 17000 dm(3) mol(-1) cm(-1 )) attributable to a p(sigma) double left arrow d(sigma) transition. The compound luminesces strongly in acetonitrile (lambda(max)=500nm). Treatment of HAuCl4. 2H(2)O with 2,2'-thioethanol in methanol followed by the ligand afforded a colourless crystalline material characterise d as [Au3Cl2(mu-dppa)(2)]PF6. A crystal structure determination reveal ed a cation of C-2 symmetry, comprising a bent chain of three gold ato ms (Au ... Au ... Au = 167.5(8)degrees, Au ... Au =3.037(1) Angstrom), with each pair of adjacent gold atoms bridged by a diphosphazane liga nd and with the coordination at the outer gold atoms completed by a ch loride ligand. This compound luminesces extremely weakly in acetonitri le but does emit strongly at 485 nm when irradiated in the solid state . The luminescence displayed by both compounds is attributed to the pr esence of a substantial intramolecular interaction between the gold at oms, but ligand effects appear to be more important in determining the emissive energies. (C) 1998 Elsevier Science Ltd. All rights reserved .