Silver(I) N-heterocyclic carbenes with long N-alkyl chains

Silver(I) N-heterocyclic carbene complexes (Ag(I)-NHCs) with long N-alkyl side chains formulated as (a) ion pairs, (b) halide-bridged neutral complexes, and (c) disilver tetrahalide anion bridged tetranuclear complexes were obtained by the reaction of benzimidazolium and imidazolium halide salts with Ag2O. Interestingly, when excess Ag2O was used, Ag nanoparticles were formed along with Ag(I)-NHCs. Crystal structures of Ag(I)-NHC complexes including both long and short N-alkyl chains were determined. The diversity of the solid-state structures depended on the halide ions, chain length, carbene cores, and crystallization conditions. The Ag(I)-NHCs of long alkyl chains did not show liquid crystal properties but did so when mixed with their corresponding imidazolium salts. These organic-inorganic hybrids were good single-source precursors for silver nanomaterials.