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

Abstract

[Ag(Et 2 -Bimy) 2 ][AgBr 2 ] ( 1; Et 2 -Bimy = diethylbenzimidazol-2-ylidene) was obtained readily from the reaction of [Et 2 -BimyH]Br with Ag 2 O. Compound 2, [Ag(Et 2 -Bimy) 2 ]PF 6, was prepared by the reaction of [Et 2 -Bimy]PF 6 with Ag 2 O under basic phase transfer catalysis conditions. Both compounds 1 and 2 are good carbene transfer agents. Thus, Pd(Et 2 -Bimy) 2 Cl 2, Au(Et 2 -Bimy)Br, and [Au(Et 2 -Bimy) 2 ]PF 6 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(Et 2 -Bimy) 2 ] + and [AgBr 2 ] - 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. 13 C NMR studies suggest that the two Bimy ligands in 1 are fluxional in solution.