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

Abstract

[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.