Self-Assembly of a Bis-NHC Ligand and Coinage Metal Ions: Unprecedented Metal-Driven Chemistry between the Tri- and Tetranuclear Species.

The discrete multinuclear AgI -NHC complexes [Agn (1)n )](X)n ; (n=3 or 4, X=BF4 , PF6 ), synthesized from a bis-NHC ligand 1 and AgI ions via multiligand self-assembly, were observed to be in equilibrium between two forms (tri- and tetranuclear) in solution on the NMR timescale, which is unprecedented in CNHC -donor based chemistry. The existence of both the species was confirmed by various studies such as NMR (1 H, VT, 2D-DOSY) and ESI-MS analysis along with concentration studies. Importantly, replacing AgI with other coinage metals (AuI and CuI ) was found to alter the phenomenon entirely: a slow exchange from the tetra- to trinuclear species was noticed for the AuI complexes (4 a, b), whereas no such process was detected in case of the CuI complexes (5 a, b).

Self-Assembly of Benzimidazole-Derived Tris-NHC Ligands and AgI -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 Ag2 O 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) 1 H 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 .