The imidazolium cation 1,3,7,9-tetramethylxanthinium methyl sulfate (1a) is obtained by the reaction of caffeine with dimethyl sulfate. The anion exchange of la gives 1,3,7,9-tetramethylxanthinium hexafluorophosphate (1b). Ligand 1a reacts with Ag 2O in water to yield an N-heterocyclic carbene (NHC) silver(I) complex (2a). Similarly, ligand 1b reacts with Ag 2O in DMSO to yield NHC silver(I) complex 2b in high yield. A carbene transfer reaction of 2b with [Rh(COD)Cl]2 gives NHC Rh(I) complex 3. All compounds were characterized by 1H NMR, 13C NMR, and mass spectrometry. The solid-state structures of 1b, 2b, and 3 were determined by X-ray crystallography.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry