Noble Metal Complexes of a Bis-Caffeine Containing NHC Ligand

N-Heterocyclic carbenes (NHCs) have seen more and more use over the years. The go-to systems that are usually considered are derivatives of benzimidazole or imidazole. Caffeine possesses an imidazole unit and was already utilized as a carbene-type ligand; however, its use within a tridentate bis-NHC system has-to the best of our knowledge-not been reported so far. The synthesis of the ligand is straightforward and metal complexes are readily available via silver-salt metathesis. A platinum(II) and a palladium(II) complex were isolated and a crystal structure of the former was examined. For the Pt(II) complex, luminescence is observed in solid state as well as in solution.

Automated summary

N-Heterocyclic carbenes (NHCs) are widely used compounds, with benzimidazole and imidazole derivatives being commonly used. Caffeine, which contains an imidazole unit, has been used as a carbene-type ligand before, but its use in a tridentate bis-NHC system has not been reported. The ligand can be synthesized easily, and metal complexes can be obtained through silver-salt metathesis. Platinum(II) and palladium(II) complexes were successfully isolated, and the crystal structure of the platinum complex was analyzed. Luminescence was observed in both the solid state and solution for the Pt(II) complex.