The elusive structures of pentakis[(triphenylphosphine)gold]ammonium(2+) bis[tetrafluoroborate(1-)]

{Pentakis[(triphenylphosphine)gold(I)]ammonium(2+)} bis[(tetrafluoroborate)(1-)] was prepared from {tetrakis[(triphenylphosphine)gold(I)]-ammonium(1+)} [tetrafluoroborate(1-)] and [(triphenylphosphine)gold(I)] tetrafluoroborate in hexamethyl phosphoric triamide and tetrahydrofuran at 20 degrees C in 53% yield and crystallized from dichloromethane as the new solvate {[(Ph3P)AU](5)N}(3) [BF4](6) [CH2Cl2]4 The crystal structure of this product has been determined by single-crystal X-ray methods [monoclinic, P2(I)/n, a 34.200(3), b = 15.285(1), c = 53.127(3) Angstrom, beta = 107.262(2)degrees, V = 26521(3) Angstrom(3), Z = 12, at 153 K]. The lattice contains three independent trinuclear dications that have no crystallographically imposed symmetry and are mutually similar in their molecular structure. The geometry of the [Au5N] core with pentacoordinate nitrogen atoms is intermediate between trigonal-bipyramidal and square pyramidal with severe distortions to minimize the Au-Au distances along some of the edges of the polyhedra. The three structures are thus different from that found previously in the tetrahydrofuran solvate {[(Ph3P)AU](5)N}(BF4)(2)(C4H8O)(2), where the geometry of the same trinuclear dication is closer to the trigonal-bipyramidal reference model. The new results are discussed in the light of the structures of tetra(gold)ammonium cations in salts of the type {[(Ph3P)Au](4)N}X-+(-) and of related tetra-, penta-, and hexacoordinate poly(gold)phosphonium, -arsonium, -sulfonium, and -selenonium cations.