The Flexibility of Tetra(N‐Heterocyclic Carbene) Ligands Controls the Nuclearity and Geometry of Polynuclear M I ‒NHC Assemblies

Abstract A series of tetrakisimidazolium salts bearing two di(phenylimidazolium)amine groups linked by differently substituted anthracenes has been prepared. These are H 4 ‐ 1a (PF 6 ) 4 (anthracene bridge), H 4 ‐ 1b (PF 6 ) 4 (phenyl‐anthracene‐phenyl bridge), H 4 ‐ 1c (PF 6 ) 4 (anthracene‐phenyl bridge), and H 4 ‐ 1d (PF 6 ) 4 (anthracene‐phenyl‐anthracene bridge). X‐ray crystallography showed that those ligand precursors having the di(phenylimidazolium)amine connected directly to the anthracene experience restricted rotation about the N─C anthracene bond. Depending on their flexibility, the reaction of the tetrakisimidazolium salts with Ag 2 O followed by transmetalation with [AuCl(THT)] yielded octanuclear ([Au 8 ( 1a ) 4 ](PF 6 ) 8 ), tetranuclear ([Au 4 ( 1b ) 2 ](PF 6 ) 4 ), hexanuclear ([Au 6 ( 1c ) 3 ](PF 6 ) 6 ), or octanuclear ([Au 8 ( 1d ) 4 ](PF 6 ) 8 ) assemblies, demonstrating the direct bonding strategy can be employed for the selective synthesis of polynuclear poly‐NHC (NHC = N‐heterocyclic carbene) metallosupramolecular assemblies.