Synthesis, spectroscopy and crystal structures of [Au2{μ-Ph2PN(Et)PPh2}2][SbF6]2 and [Au3Cl2 {μ-Ph2PN(Et)PPh2)2]PF6

Treatment of [Au(MeCN)(2)]SbF6 in acetonitrile with bis(diphenylphosphino)ethylamine (dppa) afforded a colourless crystalline material characterised as [Au-2(mu-dppa)(2)][SbF6](2). An X-ray diffraction study confirmed that the two ligands bridge the two gold atoms with a Au ... Au 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 characterised as [Au3Cl2(mu-dppa)(2)]PF6. A crystal structure determination revealed a cation of C-2 symmetry, comprising a bent chain of three gold atoms (Au ... Au ... Au = 167.5(8)degrees, Au ... Au =3.037(1) Angstrom), with each pair of adjacent gold atoms bridged by a diphosphazane ligand and with the coordination at the outer gold atoms completed by a chloride ligand. This compound luminesces extremely weakly in acetonitrile but does emit strongly at 485 nm when irradiated in the solid state. The luminescence displayed by both compounds is attributed to the presence of a substantial intramolecular interaction between the gold atoms, but ligand effects appear to be more important in determining the emissive energies. (C) 1998 Elsevier Science Ltd. All rights reserved.