PRIMARY AMINES AS NUCLEATION CENTERS FOR GOLD CLUSTERING, AND THE STRUCTURAL CHEMISTRY OF POLYGOLD AMMONIUM CATIONS

Treatment of tert-butylamine and benzylamine with [Au(PR'3)]BF4 led to the monoauration products [(R'3P)AuNH2R]+BF4- (R' = Me, R = Bu(t) 1a; R' = Me, R = CH2Ph 1b; R'3 = Ph2Me, R = Bu(t) 1c). The salts [{Au(PMe3)}3NR]+BF4- (R' = Me, R = Bu(t) 2a or CH2Ph 2b) derived from the same amines were obtained using the corresponding oxonium salt [{Au(PMe3)}3O]+BF4-. A diauration product [{Au(PMe3)}2NH(CH2Ph)]+BF4- 3 was generated upon slow hydrolytic degradation of 2b in solution. Treatment of NH(SiMe3)2 with [{Au(PMe3)}3O]+BF4- afforded both the tris- and tetra-aurated ammonium salts, [{Au(PMe3)}3NSiMe3]+BF4- 2c and [{Au(PMe3)}4N]+BF4- 4, depending on the reaction conditions. The cation of 2c is one of the very rare examples of silylammonium species. Compound 4 was also obtained from the oxonium salt and ammonia. All compounds have been characterized through analytical and spectroscopic data. The crystal structures of 1a, 1c and 3 have been determined by X-ray diffraction methods: 1c is a salt with monomeric gold ammonium cations, but 1a and 3 show supramolecular aggregation of the cations into dimers with short intercationic Au ... Au contacts.