COORDINATION SELECTIVITY IN THE REACTION OF ALUMINUM(III) WITH 8-HYDROXY-7-[(8 ' -HYDROXY-3 ', 6 ' -DISULFO-1 ' -NAPHTHYL) AZO] QUINOLINE-5-SULFONIC ACID

Abstract Studies have been made on the coordination behavior of aluminum(III) with 8-hydroxy-7-[(8 ' -hydroxy-3 ', 6 ' -disulfo-1 ' -naphthyl)azo]quinoline-5-sulfonic acid (H5hns)1 which is capable of acting as a bidentate or a terdentate ligand. The ligand serves as an O-N-O terdentate one with coordination of the azo nitrogen atom to form a mono-hns complex, [Al(hns)(H2 O)3]2-, which involves two fused six-membered chelate rings. Formation of the complex proceeds through three different pathways from a kinetic viewpoint, i.e., reactions of [Al(H2O)6]3+ with Hhns4-, [Al(OH)(H2O)5]2+ with H2 hns3-, and [Al(OH)(H2 O)5]2+ with Hhns4-. The coordination mechanism is discussed.