Reaction of triazolium precursors [MIC(CH ) - H ]I (n=1-3) with potassium hexamethyldisilazane (KHMDS) and AuCl(SMe ) generates the gold(I) complexes of the type MIC(CH ) ⋅AuI. Visible light exposure of the latter complexes promotes a spontaneous disproportionation process rendering gold(III) complexes of the type [{MIC(CH ) } ⋅AuI ] I . Both the Au and Au complex series were tested in the catalytic hydrohydrazination of terminal alkynes using hydrazine as nitrogen source.

Treatment of tris-azolium precursor 1 with palladium acetate under thermal conditions provided a CCC-pincer palladium­(II) complex (2) bearing three NHCs (one imidazolylidene and two triazolylidenes) and one iodide ligand. Further treatment of complex 2 with an excess of AgSbF6 generates tris­(carbene) dicationic palladium complex 3 in which the iodine ligands are exchanged with SbF6 anions and the metal center is stabilized by one acetonitrile ligand. Complexes 2 and 3 were tested in several cross coupling reactions showing high conversions under low catalyst loadings and mild reaction conditions. Additionally, complexes 2 and 3 performed well in the hydrosilylation of terminal alkynes with good selectivity toward the E-isomer.

Reaction of (NHC)­Au–X (X = halide) complexes with 2- or 4-mercaptopyridine under basic conditions allows for the preparation of a series of (NHC)­AuI–mercaptopyridine complexes 1–4 in high yields. All complexes have been fully characterized by means of 1H and 13C NMR spectroscopy, melting point, and elemental analysis. Single crystals of complexes 1–3 were obtained, and the solid-state structures display a linear Au­(I) center with coordination to the NHC ligand and the sulfur atom of the mercaptopyridine moiety. Interestingly, weak γ-anagostic C–H···Au interactions are found in complexes 1–3 regardless of the relative N or S position in the mercaptopyridine. Taking advantage of the free pyridine nitrogen, reaction of complexes 1 and 2 with palladium allyl chloride dimer permits the isolation of heteronuclear Au/Pd complexes 5 and 8 featuring a bridging ambidentate mercaptopyridine ligand. Further reactivity of complexes 1–3 toward B­(C6F5)3 produces complexes 6, 7, and 9, which display frustrated Lewis pair reactivity with the activation of a H–F bond.

A series of hydroxyl functionalized PEPPSI complexes have been used as highly active catalyts for the Suzuki coupling of aryl chlorides/amides with boronic acids.

The synthesis and biological effects on the nematodeCaenorhabditis elegansof chrysin functionalized Au(i)–NHC complexes are reported.