Discrete Singular Metallophilic Interaction in Stable Large 12-Membered Binuclear Silver and Gold Metallamacrocycles of Amido-Functionalized Imidazole and 1,2,4-Triazole-Derived N-Heterocyclic Carbenes.

Metallophilic interactions were observed in four pairs of 12-membered metallamacrocyclic silver and gold complexes of imidazole-derived N-heterocyclic carbenes (NHCs), [1-(R 1 )-3-N-(2,6-di-(R 2 )-phenylacetamido)-imidazol-2-ylidene] 2 M 2 [R 1 = p -MeC 6 H 4 , R 2 = Me, M = Ag ( 1b ) and Au ( 1c ); R 1 = Me, R 2 = i -Pr, M = Ag ( 2b ) and Au ( 2c ); R 1 = Et, R 2 = i -Pr, M = Ag ( 3b ) and Au ( 3c )], and a 1,2,4-triazole-derived N-heterocyclic carbene (NHC), [1-( i -Pr)-4-N-(2,6-di-( i -Pr)-phenylacetamido)-1,2,4-triazol-2-ylidene] 2 M 2 [M = Ag ( 4b ) and Au ( 4c )]. The X-ray diffraction, photoluminescence, and computational studies indicate the presence of metallophilic interactions in these complexes, which are significantly influenced by the sterics and the electronics of the N-amido substituents of the NHC ligands. The argentophilic interaction in the silver 1b - 4b complexes was stronger than the aurophilic interaction in the gold 1c - 4c complexes, with the metallophilic interaction decreasing in the order 4b > 1b > 1c > 4c > 3b > 3c > 2b > 2c . The 1b - 4b complexes were synthesized from the corresponding amido-functionalized imidazolium chloride 1a - 3a and the 1,2,4-triazolium chloride 4a salts upon treatment with Ag 2 O. The reaction of 1b - 4b complexes with (Me 2 S)AuCl gave the gold 1c - 4c complexes.