A gas-phase study on the cyclometallation of a series of Cp*Ir(III) complexes bearing bidentate pyrimidine ligands

Abstract A concerted approach of synthesis and gas phase experiments characterizes the relative cyclometallation barriers of a series of cationic h5-Cp* iridium(III) compounds. The common feature of the investigated compounds is a bidentate N,N’-donor ligand possessing a pyridine site functionalized with a 5-butylpyrimidin-2-yl ring in the 2-position. In addition, the pyridine ring was functionalized with electron-donating or -withdrawing groups. The compounds were characterized by means of NMR and IR spectroscopy and elemental analysis. For the measurements of the relative barriers of the cyclometallation, collision-induced dissociation (CID) experiments were carried out, which revealed a clear dependence of the relative barriers from the nature and the position of the substituents at the pyridine ring could be worked out.