Preparation of Chromium(III) and Cobalt(III) Complexes with l-Leucine-N,N-diacetic Acid

Abstract

Abstract l-Leucine-N,N-diacetic acid (abbreviated as LDA) and the complexes thereof were prepared as follows: K[Cr(OH)(lda)(H2O)]·3H2O (violet) (I), [Cr(lda)(H2O)2] (bluish violet) (II), [Cr(lda)(H2O)2]·2H2O (grayish violet) (III), (enH2)1⁄2[Cr(OH)(lda)(H2O)2] (green) (IV), [Cr(lda)(o-phen)]·2H20 (brownish orange) (V), K[Cr(lda)(acac)]·H2O (blackish violet) (VI) and K[Co(OH)(lda)(H20)]·H2O (bluish violet) (VII), where lda, en, o-phen and acac are the abbreviations of l-leucine-N,N-diacetate ion, ethylenediamine, o-phenanthroline and acetylaceto-nate ion, respectively. Except for Complex IV, LDA behaves as a quadridentate ligand. In Complex IV, it acts as a terdentate one. It was found from electronic absorption spectra that in Complex I, LDA behaves as a quadridentate in a solid state and as a terdentate ligand in an aqueous solution, whereas in cobalt(III) complex VII corresponding to I, LDA behaves as a quadridentate. Stepwise liberation of the coordinated water molecules in Complexes II and III could be detected by means of Derivatograph. Complex VII showed “Dehydration-Dimerization Reaction” upon being heated.