Mechanistic analysis of the reaction between elemental sulfur or selenium and 1,3-dialkylimidazolium acetate ionic liquids, in the absence of an external base or solvent, affords evidence for the equilibrium presence of carbene species in these ionic liquids. It demonstrates the potential to control, through anion selection, the concentration of carbene in stable ionic liquids.
Rodriguez Martinez, H., Gurau, G., Holbrey, J., & Rogers, R. (2011). Reaction of elemental chalcogens with imidazolium acetates to yield imidazole-2-chalcogenones: direct evidence for ionic liquids as proto-carbenes. Chemical Communications, 47(11), 3222-3224. https://doi.org/10.1039/c0cc05223j