GILDING PRIMARY AMINES - FORMATION OF ORGANOTRIS(TRIPHENYLPHOSPHINEAURIO)AMMONIUM TETRAFLUOROBORATES [AUPPH3)3-NR]+BF4- - CRYSTAL-STRUCTURES WHERE R= BU(T) OR C6H11

Tris(triphenylphosphineaurio)oxonium tetrafluoroborate was found to be a powerful aurating reagent for primary amines RNH2 (R = Me, Et, Pr(n), Pr(i), Bu(t), cyclohexyl, CH2Ph or Ph). Stable, colourless organotris(triphenylphosphineaurio)ammonium tetrafluoroborates are formed in high yields. The products have been characterized by analytical and spectroscopic data, including Au-197 Mossbauer spectroscopy for [(AuPPh3)3NBu(t)]+BF4- and single-crystal X-ray analysis of this compound and that where R = cyclohexyl. The ammonium nitrogen atoms have been located at the centre of a distorted tetrahedron in both cases, with Au-N-Au angles smaller than the tetrahedral value and Au...Au contacts near 3.0 angstrom indicating attractive forces between the gold atoms ('aurophilicity').