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)] tetrafluorobora te 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 b een determined by single-crystal X-ray methods [monoclinic, P2(I)/n, a 34.2 00(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 indepe ndent trinuclear dications that have no crystallographically imposed symmet ry and are mutually similar in their molecular structure. The geometry of t he [Au5N] core with pentacoordinate nitrogen atoms is intermediate between trigonal-bipyramidal and square pyramidal with severe distortions to minimi ze the Au-Au distances along some of the edges of the polyhedra. The three structures are thus different from that found previously in the tetrahydrof uran solvate {[(Ph3P)AU](5)N}(BF4)(2)(C4H8O)(2), where the geometry of the same trinuclear dication is closer to the trigonal-bipyramidal reference mo del. 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 re lated tetra-, penta-, and hexacoordinate poly(gold)phosphonium, -arsonium, -sulfonium, and -selenonium cations.