N-Functionalised heterocyclic dicarbene complexes of silver: Synthesis and structural studies

A range of new diimidazolium salts, held together by an alkyl unit and bearing alcohol pendant arms on their nitrogen, was synthesized. A short modular reaction pathway leads to the N-heterocyclic carbene (NHC) precursors, differing by the flexibility of the bridge, the steric bulk of substituents in α-position of the OH groups and the anions. Treatment of diimidazolium salts with Ag2O yields AgI(carbene)2 complexes. The related trimethylene-bridged bis-NHC silver complexes 6 and 7 were crystallised with di-tosylate and di-hexafluorophosphate anions, respectively. Their X-ray structures revealed dimeric species, involving two ligands with different arrangements around the Ag cations, leading to crossed and parallel conformations.

A series of alcohol functionalised diimidazolium salts bridged by an alkyl arm was synthesized, using a modular strategy. The corresponding silver–carbene complexes were obtained. X-ray structures of two dinuclear Ag(I) complexes, involving a trimethylene-bridged bis-carbene ligand and non-coordinating anions TsO− or PF6−, showed crossed and parallel conformations, respectively.Figure optionsDownload as PowerPoint slide