Stability Constants of Cadmium(Ii) Complexes With Some Amino Acids and Phthalate System : A Polarography Study

Sudesh Kumar Singh and C. P. Singh Chandel

Department of Chemistry, University of Rajasthan, Jaipur- 302 004 (India)

The reduction of cadmium (II) in the presence of phthalate and some amino acids (Alanine, Glycine, Aspartic acid and Glutamic acid) has been carried out electrochemically. The reduction of all the systems has been found to be reversible and diffusion controlled, involving two electrons. The stability constants of mixed-ligand complexes MXY, MXY2 and MX2Y have been evaluated by the method of Schaap and McMasters. The statistical and electrostatic effect have also been discussed by using these stability constants. For the comparison of the simple and mixed complexes, the mixing constants (Km) and the stabilization constants (Ks) are measured. The positive values of the mixing constants and stabilization constants show that the ternary complexes are more stable than the binary complexes. For the comparison of the stability Dlog K are measured. The Dlog K values are higher than statistical values which again proves that the ternary complexes are more stable than expected from statistical reasons.

Stability constants; mixed-ligand complexes; polarography