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.

Graphical abstractA 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 full-size imageDownload as PowerPoint slide