Coordination diversity of Ag(I) and Hg(II) towards symmetrically and non-symmetrically substituted imidazol-2-ylidenes: Synthesis, crystal structures, nitrile reactivity, and Hofmann-type elimination studies

Two mesityl bridged bis-1H-imidazolium salts having bromide/hexafluorophosphate counter ions have been prepared, compared with similar ortho-xylyl bridged salts and characterized by various spectral and X-ray diffraction techniques. The salt having 2-cyanoethyl substituents undergoes hydrolysis to produce compartmental 1H-imidazolium salts. Further, these salts are involved in the Hofmann-type elimination to produce bis-imidazole and Ag(I)- and Hg(II)-coordination compounds when treated with Ag2O and Hg(OAc)(2) in different ratios. Furthermore, a 3-nitrile-substituted imidazolium salt was prepared and treated with the aforementioned metal sources to evaluate the elimination reaction. However, it forms stable N-heterocyclic carbene (NHC) complex without eliminating any of the cyano-substitutions. Both, imidazolium salts and Ag(I)- and Hg(II)-coordination/NHC complexes have been characterized by H-1 and, C-13 NMR, FTIR spectral, and elemental and single crystal X-ray diffraction analyses. (c) 2012 Elsevier Ltd. All rights reserved.