Di-mesoionic carbene-bridged complexes of Rh2, Ir2, and RhIr: A stepwise metalation strategy for the synthesis of di-MIC-bridged mixed-metal systems

Article abstract of DOI:10.1021/om300423z

A meta-substituted benzene-bridged ditriazolium salt has been prepared using copper-catalyzed azide-alkyne cycloaddition (CuAAC or click chemistry) and methylation protocols. Metalation of this dicationic species by basic-ligand-containing [Rh(μ-OMe)(COD)]₂ and [Ir(μ-OMe)(COD)] ₂ precursors provides homobimetallic complexes of Rh and Ir bridged by a 1,2,3-triazol-5-ylidene-type di-mesoionic carbene (di-MIC) via an internal-base strategy. By using only ¹/₂ equiv of the internal-base precursor, mononuclear MIC-anchored/pendent- triazolium intermediates have been isolated, in which only one end of the ditriazolium salt has been deprotonated and attached to Rh or Ir. Reaction of these pendent intermediates with another ¹/₂ equiv of an internal-base precursor affords either the aforementioned homobimetallic products or an analogous di-MIC-bridged, mixed-metal Ir/Rh complex.