Synthesis and characterization of new iridium(III) complexes containing the fragment [Cp*IrCl2] and the ligands 2- and 4-aminobenzonitryl and 2- and 4-aminopyridine

Abstract

We report the synthesis and characterization of six new iridium(III) complexes of stoichiometry, [Ir(Cp*Cl2(2abn)] (1), [Cp*Cl2Ir(µ-2abn)IrCl2Cp*] (2), [IrCp*Cl2(4abn)] (3), [Cp*Cl2Ir(µ-4abn)IrCl2Cp*] (4), [IrCp*Cl2(2-ampy)] (5) and [IrCp*Cl2(4-ampy)] (6) (Cp* =pentamethylcyclopentadienyl anion; 2- and 4abn = 2- and 4-aminobenzonitrile, respectively; 2- and 4-ampy = 2- and 4-aminopyridine, respectively). The new compounds have been prepared from [(IrCp*Cl)(µ-Cl)]2 by the addition of the ligands in appropriate proportions in dichloromethane and then precipitated using hexane. They have been characterized by C, H, N elemental analyses, thermogravimetric analysis, infrared spectroscopy,1H and 1H-1H Cosy nuclear magnetic resonance spectroscopy, high-resolution mass spectrometry (ESI), and in the case of 1 and 5, by single-crystal X-ray diffraction, confirming the proposed structure. To the best of our knowledge, 1 is the first reported crystal structure of a neutral Cp*Ir complex with a benzonitrile-based ligand coordinated through the -CN group. The cytotoxic behavior of all compounds was studied against HeLa cells, but no measurable biological activity could be established.