NMR, INFRARED AND RAMAN-SPECTROSCOPY STUDY OF ZR(IV) COMPLEXATION BY ACETIC-ACID IN AQUEOUS-SOLUTION

The complexation of Zr(IV) by acetic acid has been studied by NMR, infrared and Raman spectroscopy in zirconium oxide chloride aqueous solutions. We have shown that only one type of acetate complex is formed and this could be characterized by the position of the nu (C-C) stretching band of the acetic acid group complexed to the metal. The 956 cm-1 band position was independent of the analytical concentration [Zr]0, the ratio [CH3COOH]0/[Zr]0 and the acidity of solutions. The proton NMR spectrum confirmed that the complex does not contain double bridging hydroxide groups. The zirconium atoms are probably attached by simple oxo bridges and some H2O molecules are replaced by acetate. This complexation is probably achieved by chelating mode; each acetate group is bound to one zirconium atom. The complexation reaction was not complete because there always remained free acetic acid in solution. Raman spectroscopy and C-13 NMR have been applied to determine the stoichiometry of the acetate complex of zirconium in aqueous solution. These two techniques afforded proof that this complex contains one acetate group for each atom of zirconium.