Synthetic strategy of diflurophosphate-bridged bimetallic N-heterocyclic carbene complexes: Synthesis, structures and photoluminescence of picolyl-substituted alkylbenzimidazolylidene ligands

Starting from the proligands 1-methyl-3-picolylbenzimidazoliumhexaflurophosphate (1) and 1-benzyl-3-picolylbenzimidazoliumhexaflurophosphate (2) Ag(I)–NHC complexes, 1-methyl-3-picolylbenz-imidazolylidenesilver(I)hexaflurophosphate (3) and 1-benzyl-3-picolylbenzimidazolylidenesilver(I)hexaflurophosphate (4) have been synthesized. PO2F2 bridged Ag(I)-bimetallic system (5 and 6) developed from 3 and 4 after treatment of AgPF6 and water. 1-Methyl-3-picolyl-benzimidazolylidene-gold(I)hexaflurophosphate(7) and 1-benzyl-3-picolylbenzimidazolylidenegold(I)hexaflurophosphate (8) have been synthesized by Ag–carbene transmetallation method. Further reaction of AgPF6 with 7 and 8 build up the heterobimetallic Ag(I)–Au(I) systems (9 and 10); significantly, PO2F2 unit holds two heterobimetallic Ag(I)–Au(I) units together. Solid state structures of 3, 5, 8 and 9 have been determined by X-ray diffraction studies. Closed shell d10–d10 interactions are ascertained by the luminescence of bimetallic systems 7–10 upon irradiation of UV light.