Self-Assembly of Benzimidazole-Derived Tris-NHC Ligands and Ag^I-Ions to Hexanuclear Organometallic Cages and Their Unusual Transmetalation Chemistry

Multi-ligand self-assembly to attain the AgI-N-heterocyclic carbene (NHC)-built hexanuclear organometallic cages of composition [Ag6(3 a,b)4](PF6)6 from the reaction of benzimidazole-derived tris(azolium) salts [H3-3 a,b](PF6)3 with Ag2O was achieved. The molecular structures of the cages were established by X-ray diffraction studies along with NMR and MS analyses. The existence of a single assembly in solution was supported by diffusion-ordered spectroscopy (DOSY) 1H NMR spectra. Further, transmetalation reactions of these self-assembled complexes, [Ag6(3 a,b)4](PF6)6, with CuI/AuI-ions provided various coinage metal-NHC complexes having diverse molecular compositions, which included the first example of a hexanuclear CuI-dodecacarbene complex, [Cu6(3 b)4](PF6)6.