[Ag(Et2-Bimy)2][AgBr2] (1; Et2-Bimy = diethylbenzimidazol-2-ylidene) was obtained readily from the reaction of [Et2-BimyH]Br with Ag2O. Compound 2, [Ag(Et2-Bimy)2]PF6, was prepared by the reaction of [Et2-Bimy]PF6 with Ag2O under basic phase transfer catalysis conditions. Both compounds 1 and 2 are good carbene transfer agents. Thus, Pd(Et2-Bimy)2Cl2, Au(Et2-Bimy)Br, and [Au(Et2-Bimy)2]PF6 were obtained in high yields using 1 and 2 as carbene sources. The byproduct AgBr or AgCl can be reused to generate 1 under basic phase transfer catalysis conditions. The crystal structure of compound 1 revealed that linear [Ag(Et2-Bimy)2]+ and [AgBr2]- groups were associated through a short AgI−AgI contact (2.956 Å). FAB/mass spectrometry and molar conductivity measurements indicate the existence of ligand-unsupported AgI−AgI interactions in the gas phase and acetonitrile solution. 13C NMR studies suggest that the two Bimy ligands in 1 are fluxional in solution.

A series of gold(I)−carbene complexes of the type [Au(R2-bimy)L] (R = Et, Me; bimy = benzimidazol-2-ylidene; L = Cl, Br, I, bimy, thiophenolate, phenylacetylide) have been prepared. These carbene complexes are luminous in acetonitrile solution and in the solid state with long lifetimes at room temperature. Multiple emissions have been observed for different R and L. The crystal structure of [Au(Me2-bimy)Cl] shows a relatively short intermolecular AuI−AuI contact of 3.1664(10) Å and an intermolecular ring π−π interaction with a ring−ring distance of 3.45 Å. The structure of [Au(Et2-bimy)Cl], however, shows only intermolecular ring−ring interactions with a distance of 3.53 Å. Crystal structure data suggest that bimy is a high-trans-influence ligand.

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Gold(I) carbene complexes of the type [Au(NHC)Cl], where NHC represents N-heterocyclic carbenes, have been synthesized. Two crystal structures of this type show that the molecules are stacked to form a linear polymer with Au‚‚‚Au interactions. Luminous [Au(NHC)(cbz)] (cbz ) carbazolate) were synthesized from [Au(NHC)Cl]. The crystal structure of one of this series indicates that the carbene and cbz rings are coplanar and two molecules are arranged pairwise in a head-to-tail fashion. While all the compounds prepared exhibit high-energy emission bands at ∼400 nm, [Au(NHC)Cl] complexes display additional low-energy emission bands at 580-650 nm, which are attributed to Au-centered transitions involving Au‚‚‚Au interactions. On the other hand, the low-energy emission bands of the [Au(NHC)(cbz)] complexes, which appear at 584-592 nm with fine structures, are likely to arise from the transitions involving mainly carbazolate tuned by Au, as also suggested by the density functional calculations. Crystal structures of Au(I)-dicarbenes are also reported.