In-situ approach for the synthesis of bromide-bridged mercury(II) N-heterocyclic carbene complexes

The study was designed to synthesize bromide-bridged mercury(II) symmetric and non-symmetric N-heterocyclic carbene complexes. The preparation of benzimidazolium salts (4–6) was accomplished by symmetrical and non-symmetrical substitution on benzimidazole. The salts were subjected to an in-situ process for metallation to get [Hg(II)-NHC] complexes [(HgBr-NHC)(µ2Br)2] (7–9) by reacting benzimidazolium salts (4–6) with mercury(II) acetate at room temperature. Compounds were characterized by elemental analyses, FT-IR and NMR spectroscopy. Single crystals of 7 and 8 were analyzed by X-ray crystallographic technique which showed tetrahedral dinuclear complexes with two bridging bromides. An attempt to explore the feasibility of redox transmetallation approach (RTM) for synthesis of ytterbium complexes was also carried out by reacting 7–9 with ytterbium powder under inert atmosphere. The products were metallic mercury, benzimidazolium salts, and ytterbium bromide instead of ytterbium complexes.