Copper(II) and nickel(II) complexes with oxime analogues of amino acids. Potentiometric, spectroscopic and X-ray studies of complexes with 2-cyano-2-(hydroxyimino)acetic acid and its ethane-1,2-diamine derivative

Abstract

2-Cyano-2-(hydroxyimino)acetic acid was found to be an effective ligand for Cu²⁺ and Ni²⁺ ions over a very broad pH range. Potentiometric and spectroscopic data indicate the formation of dimeric complexes with Cu²⁺ ions and the first X-ray evidence for dimer formation is obtained. Conjugation of the oximic moiety with ethane-1,2-diamine leads to another very effective family of chelating agents, although metal ion co-ordination may induce amide bond hydrolysis as indicated by the crystal structure.