Novel Rhodium and Iridium Complexes Coordinated to C3-Symmetric Tris-NHC Ligands Based on a 1,3,5-Triphenylbenzene Core. Electronic and Catalytic Properties

A series of novel tris-azolium salt precursors based on 1,3,5-triphenylbenzene have been prepared. These salts exhibit fluorescence emission in the 320-420 nm region. The coordination of these salts to [MCl(COD)](2) (M = Rh, Ir) was carried out in the presence of KHMDS and allowed the formation of the corresponding tris-NHC complexes of Rh and Ir in high yield. The electronic properties of the new complexes were analyzed by means of cyclic voltammetry and IR spectroscopy of the related carbonylated species. The catalytic activity of the trirhodium complex toward the addition of arylboronic acids to cyclohexen-2-one has been evaluated and compared to the activity shown by a related monometallic complex.