Facile Synthesis of Silver(I)−Carbene Complexes. Useful Carbene Transfer Agents

[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 Ag^I−Ag^I contact (2.956 Å). FAB/mass spectrometry and molar conductivity measurements indicate the existence of ligand-unsupported Ag^I−Ag^I interactions in the gas phase and acetonitrile solution. ¹³C NMR studies suggest that the two Bimy ligands in 1 are fluxional in solution.