METAL-COMPLEXES OF GLUTAMIC ACID-GAMMA-HYDROXAMIC ACID (GLU-GAMMA-HA)(N-HYDROXYGLUTAMINE) IN AQUEOUS-SOLUTION

Stability constants and assumptions concerning the bonding mode are su mmarized for the complexes formed in aqueous solution in nickel(II)-, copper(II)-, zinc(II)- and iron(III)-L-glutamic acid-gamma-hydroxamic acid (Glu-gamma-ha) systems and nickel(II)-, copper(II)- and zinc(II)- acetohydroxamic acid-alpha-alanine ternary systems as models. Mononucl ear species have been found with bidentate co-ordination of the HA- (m onoprotonated) and tridentate co-ordination of the A2- (deprotonated) form of Glu-gamma-ha under the conditions employed. Co-ordination of t he hydroxamate and carboxylate oxygens is proposed in the case of iron (III). Complexes with different bonding modes existing in equilibria a re formed with nickel(II) and copper(II), while preference for co-ordi nation via hydroxamate oxygens and amino-N is found with zinc(II).