Synthesis, structure, characterization and one pot catalytic activity of half-sandwich iridium(III) complexes

A series of stable mononuclear half-sandwich iridium(III) complexes of the general formula [(eta 5-C5Me5)Ir(L)Cl] (BPh4) has been synthesized in dry methanol using different imino pyridine ligands (L1-L6) and [(eta 5C5Me5)2Ir2(mu -Cl)2Cl2] in a 2:1 molar ratio. All complexes were fully characterized by melting point, CHN analysis, FT-IR, UV-visible, 1H NMR, 13C NMR spectroscopy and mass spectrometry. The structure of complex 3 [(eta 5C5Me5)Ir(L3)Cl](BPh4) was determined by single crystal X-ray structure analysis, showing a chelating coordination mode of the imino pyridine L3. One pot organic transformations of aldehyde to amide were carried out by complexes 1-6 in toluene at 110 degrees C in the presence of hydroxyl amine hydrochloride and sodium bicarbonate. The catalytic activity of complex 3 was found to be excellent, showing high conversion with catalytic turnover frequency up to 500.