SYNTHESES, MOLECULAR-STRUCTURES, AND SPECTROSCOPY OF GOLD(III) DITHIOLATE COMPLEXES

Two Au(III) dithiolate complexes, [Au(dbbpy)(tdt)]PF6 and Au(eta(2)-C, N-ppy)(tdt), (dbbpy = 4,4'-di-tert-butyl-2,2'-bipyridine; tdt 3,4-tolu enedithiolate; ppy C-deprotonated 2-phenylpyridine), have been prepare d and structurally characterized by X-ray crystallography. The complex es have low-energy absorption bands that exhibit mild solvatochromism (lambda(max) = 444 nm (epsilon, 2310 M-1 cm(-1)) in CH2Cl2 and 406 nm( epsilon, 3170 M-1 cm(-1)) in DMSO) and are tentatively assigned to a c harge-transfer-ta-diimine transition. This transition occurs at higher energy than the analogous charge-transfer transition in related Pt(LI ) complexes (e.g., Pt(dbbpy)(tdt), lambda(max) = 563 nm (epsilon, 7200 M-1 cm(-1)). Whereas neither Au(III) complex is emissive, their respe ctive dichloride precursors, [Au-(dbbpy)Cl-2]PF6 and Au(eta(2)-C,N-ppy )Cl-2, luminesce in low-temperature glass matrixes from an excited sta te that is tentatively assigned as intraligand pi-pi. The neutral com plex, Au(eta(2)-C,N-ppy)(tdt), is mon easily oxidized (E-ox = 0.925 V vs 1.589 V (vs NHE)) and less easily reduced (E-red = -1.339 V vs -0.2 55 V (vs NHE)) than the cationic complex, [Au(dbbpy)(tdt)]PF6. Both di thiolate complexes exhibit approximately square planar coordination. Y ellow crystals of [Au(dbbpy)(tdt)]PF6 (C25H30AuF6N2PS2) are triclinic, space group P (1) over bar (No. 2), with a = 7.1977(2) Angstrom, b = 11.7292(1) Angstrom, c = 17.5820(5) Angstrom, alpha = 104.537(2)degree s, beta = 96.592(2)degrees, gamma = 102.455(2)degrees, V = 1380.41(6) Angstrom(3), Z = 2, and final R = 0.050 (R-w = 0.1062) for 3446 unique reflections. Orange crystals of Au(eta(2)-C,N-ppy)(tdt) (C18H14AuNS2) are monoclinic, space group P2(1)/c (No. 14), with a = 8.852(1) Angst rom, b = 11.726(2) Angstrom, c = 15.499(5) Angstrom, beta = 101.34(2)d egrees, V = 1577.5(6) Angstrom(3), Z = 4, and final R = 0.0438 (R-w = 0.0759) for 3685 unique reflections. A structural trans effect in Au(e ta(2)-C,N-ppy)(tdt) results in a significantly longer Au-S distance (c a. 0.1 Angstrom) trans to the Au-C bond than that trans to the Au-N bo nd. In the solid state, the [Au(dbbpy)(tdt)](+) cations are arranged i n stacks with alternating intermolecular Au ... Au separations of 3.60 and 3.75 Angstrom while the Au((eta(2)-C,N-ppy)(tdt) molecules form s tacks with an intermolecular Au ... Au separation of 3.81 Angstrom.