Synthesis of propargyl-functionalized NHC gold complexes

A series of propargyl functionalized N-heterocyclic carbene gold(I) complexes have been synthesized from the corresponding imidazolium salts with tetrabutylammonium acetylacetonate in the presence of a gold(I) precursor in a onepot reaction. Several complexes of different stoichiometries are described: [AuBr(NHC)], [Au(NHC)2]Br and [Au(C6F5) (NHC)], and many of these have been characterized by Xray diffraction studies. Aurophilic interactions are present in the compounds bearing less sterically hindered carbenes, and secondary interactions such as hydrogen bonds, π-π stacking, or weak contacts of the gold center with the carbon of the propargyl unit have also been found. These complexes possess a high degree of water solubility, which makes them potentially useful for the synthesis of biologically active compounds or as gold catalysts in water. Activation of the propargyl unit in [AuBr(NHC)] complexes leads to the formation of interesting trimers with bridging bidentate C^C alkynyl-carbene ligands.