Dimerization of a mononuclear gold(I) complex to its corresponding dinuclear complex containing a cyclophane-NHC ligand

A new mononuclear AuI-NHC complex dimerizes into its corresponding dinuclear AuI-NHC complex slowly in solution at room temperature. In the solid state, the dinuclear AuI-NHC appears to adopt a square planar geometry, while a linear shaped coordination has been measured in solution. [Display omitted] A mononuclear AuI-NHC complex was synthesized in good yield via the reaction of KAuCl4 with an imidazolium-linked cyclophane salt in the presence of a mild base. The new complex was fully characterized by 1H and 13C NMR spectroscopy and mass spectrometry. The 1H NMR studies, supported by DFT analysis, show how the mononuclear AuI-NHC complex dimerizes to its corresponding dinuclear AuI-NHC analogue slowly in solution (DMSO or CH3CN). The thermodynamic properties show a distinctive preference for dinuclear Au formation over that of the monomer. We have also discussed the unconventional structural contrast between the experimental and computational geometrical analysis of the dinuclear AuI-NHC complex.