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 (1H, 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).