NOVEL LUMINESCENT POLYNUCLEAR GOLD(I) PHOSPHINE COMPLEXES - SYNTHESIS, SPECTROSCOPY, AND X-RAY CRYSTAL-STRUCTURE OF [AU3(DMMP)2]3+ [DMMP = BIS(DIMETHYLPHOSPHINOMETHYL)METHYLPHOSPHINE]

Reaction of K[AuCl4] with bis(dimethylphosphinomethyl) methylphosphine (dmmp) in the presence of thiodiglycol (2,2'-thiodiethanol) in methanol yielded [Au3 (dmmp)2]3+, which was isolated as its perchlorate salt. The X-ray crystal structure of [Au3(dmmp)2] [ClO4]3 has been determined: monoclinic, space group P2(1)/n, a = 12.880(3), b = 14.210(1), c = 21.208(2) angstrom, beta- = 106.25(1)-degrees, Z = 4, R = 0.047 for 2 927 observed Mo-K-(alpha) data. The Au-Au-Au bond angle of 136.26(4)-degrees is greatly distorted from rectilinear geometry, with intramolecular Au ... Au distances of 2.981 (1) and 2.962(1) angstrom. Excitation of a degassed acetonitrile solution of [Au3(dmmp)2]3+ at 300-370 nm resulted in dual phosphorescence (lambda- = 467 nm, tau-0 = 1.6 +/- 0.2 mu-s; lambda- = 580 nm, tau-0 = 7.0 +/- 0.5 mu-s). A comparison between the electronic absorption and emission spectra of [Au3(dmmp)2]3+ and [Au2(dmpm)2]2+ [[dmpm = bis(dimethylphosphino)methane] has been made. The assignment of the lowest electronic excited state in the P2Au)n system has been suggested to be 3[(d-delta*) (p-sigma)]. The excited-state redox potentials of [Au3(dmmp)2]3+* and [Au2(dmpm)2]2+* have been determined through oxidative quenching experiments with a series of pyridinium acceptors of variable reduction potential.