Synthesis and characterization of silver and gold NHC complexes: Crystal structures and mass spectral studies

Mononuclear silver and gold complexes [Ag(BzlCy)(Cl)] (1) and [Au(BzlCy)(Cl)] (2) were synthesized starting from the N-heterocyclic carbene (NHC) BzlCy∙HCl (1,3-Dicyclohexylbenzimidazolium chloride) and characterized by NMR and ESI-MS spectral studies. Molecular structures of complexes [Ag(BzlCy)(Cl)] (1) and [Au(BzlCy)(Cl)] (2·THF) were determined by X-ray crystallography. Formation of different species of these complexes 1 and 2 in gas phase was investigated by electrospray ionization mass spectrometry in positive mode and compared with solution formulation. To better understand the nature of NHC complexes and their reactivity with phenyl acetylene in gas phase, we synthesized a negatively charge tag gold complex [Au(SBzlCy)(Cl)] starting from SBzlCy∙HCl which prepared by the sulphonation of BzlCy. We investigated the formation of intermediate species [Au(SBzlCy)(PhC≡C)] by the coordination of phenyl acetylene to the charge-tag gold complex in gas phase. We compared the stability of these NHC complexes and also investigated the decomposed mixture by electrospray ionization.