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

摘要

The discrete multinuclear Ag-NHC complexesAgn(1)n)(X)n;(n = 3 or 4,X = BF4,PF6),synthesized from a bis-NHC ligand 1 and Ag1 ions via multili-gand self-assembly,were observed to be in equilibrium between two forms(tri-and tetranuclear)in solution on the NMR timescale,which is unprecedented in C_(NHC)-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 Ag~I with other coinage metals(Au~I and Cu~I)was found to alter the phenomenon entirely:a slow exchange from the tetra-to trinuclear species was noticed for the Au~I complexes(4a,b),whereas no such process was detected in case of the Cu1 complexes(5a,b).