Novel Mixed Coordination of N and C Donors to Gold–Gold Centers

Mixed-ligand gold(I) compounds featuring N and C connectivity from two dissimilar ligands, a formamidinate and a phosphorus ylide, are obtained by the reaction of a dinuclear gold(I) formamidinate with a phosphorus ylide in toluene solution under Schlenk conditions. When the reaction conditions such as polarity, basicity, and gold to ylide ratio are varied, a series of structures are produced, where the formamidinate (f = N,N′-bis(2,6-dimethylphenyl)methanimidamide) invariably bridges gold(I) centers. The aurophilic distances of Au(I)···Au(I) range around 3.00 Å, whereas the ylide (dimethyldiphenylphosphonium, [H2y]+) is monocoordinated as [Hy]. This produces open dinuclear species, with two terminal Hy's as the cation [Au2f(Hy)2]+ (1), with the nitrate anion or terminal Hy and chloride anion in [Cl-Au2f(Hy)] (2), or Hy and phenyl in [Ph-Au2f(Hy)] (3). The activation of the ylide ligand by base liberates the phenyl group which produces 3. A related cationic mononuclear moiety [Au(Hf)(Hy)] (4), with neutral amidinate and ylide, is produced from the neutral amidine upon reaction with [Au(THT)Cl] in a THF solution of ylide. These new compounds have been characterized by X-ray crystal structures, 1H NMR, IR, and elemental analysis.