New iridium complexes having functional 8-quinolinolato ligands have been synthesized. By single-crystal X-ray analysis, it was revealed that these new complexes had coordinatively unsaturated structure (five-coordinate trivalent iridium: 16e(-) complex). Furthermore, one of the new complexes exhibited high catalytic activity for the dehydrogenative oxidation of various aromatic and aliphatic secondary alcohols in aqueous media to give the corresponding ketones in good to excellent yields.