The Chromium(III) Complexes with β-Aminoethylsulfonic-N,N-diacetic Acid and Aspartic-N,N-diacetic Acid

Abstract

Abstract The following chromium (III) complexes with the β-aminoethylsulfonic-N,N-diacetic acid (AEDA) and aspartic-N,N-diacetic acid (ASDA) were newly prepared; K3[Cr(aeda)2]·4H2O (pale red) (I), [Cr(OH)(Haeda)(o-phen)]·2H2O (orange) (II) and [Cr(Hasda)(H2O)2]·H2O (reddish purple) (III). From the results of spectral measurments, it was found that AEDA acts as a quadridentate ligand as well as a terdentate one in an aqueous solution, but only as a terdentate ligand in a crystal state, and that the coordinating ability of the oxygen atom of sulfonic radical in AEDA is weaker than that of carboxylic radical in ammoniapropionicdiacetic acid (APDA). In Complex III, ASDA behaved as a quadridentate ligand rather than as a quinquedentate. Complexes II and III showed some interesting thermal decomposition processes. The former lost one mole of water at 110°C from the hydrogen atom in free sulfonic acid radical and the coordinated OH group, accompanied with the increase of coordination number of AEDA from 3 to 4. In the latter, one mole of crystalline water was lost first, and then the carboxylic acid bound to the methylene group at β-position in the ligand was decomposed to liberate carbon dioxide, and the coordinated asda was changed into apda.