The reactivity of Ni(II) toward aspartic and glutamic monohydroxamates

The formation of complexes of Ni(II) with aspartic and glutamic acid hydroxamates was determined by potentiometric methods at I = 0.15 M NaCl and T = 25°C. The equilibrium study of Ni(II) with ASX or GLX revealed that the predominant species formed in solution were (M:L:H+): (1:1:0), (1:1:1), (2:1:0), and (2:1:1) in the whole pH range (∼3–11). The formation of polymeric species was not observed. The octahedral structures were predicted in which the ligands act as tridentate ligands. The kinetics of complex formation between Ni(II) with ASX system as well as Ni(II) with GLX were also studied in a wide pH range. The observed rate constants for the Ni(II)‐hydroxamates were found to be dependent on the total concentration of hydroxamates at a given pH through the following relations: kobs = Y0 + Z(TASX) and kobs = Y0 + Z(TGLX) + W(TGLX)2. The trans effect of the hydroxyl group present in the reacting species of Ni(OH)+ as well as a ring closure resulted from ligand chelation are introduced as explanations for the rate constants obtained for the reactions of Ni(II) with ASX or GLX. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 540–552, 2006