Metal complexes of salicylhydroxamic acid: Equilibrium studies and synthesis

The complex formation equilibria involved in the binary and ternary systems of M(II)-SHAM and M(II)-SHAM-L [M = Cu, Ni, Co, Zn, Cd, Mn, Hg, Ca or UO2; SHAM = salicylhydroxamic acid; L = the ligating agent, N-(2-acetamido)iminodiacetic acid (ADA), iminodiacetic acid (IDA) or nitrilotriacetic acid (NTA)] were investigated by the potentiometric technique at 25 degrees C and ionic strength 0.1 M NaNO3. The results indicate the formation of 1:1 and 1:2 (metal ion:ligand) SHAM complexes. The formation of mixed-ligand complexes followed a stepwise mechanism, whereby an ML complex was first formed, followed by the ligation of SHAM. The relative stability of the mixed-ligand complex was compared with that of the binary complex. The concentration distribution of the complexes possibly formed in solution was evaluated. Solid complexes of SHAM were prepared and characterized by microanalysis, conductivity, i.r., electronic and n.m.r. spectroscopies, and magnetic susceptibility measurements.