Equilibrium Study of Mixed Complexes of Uranyl Ion with Pyridine Carboxylic Acids as Primary and Some Dicarboxylic Acids as Secondary Ligands

Department of Chemistry, Marathwada University, Aurangabad-431 004

Department of Chemistry, Georgia State University, University Plaza, Atlanta, Georgia-30302, U. S. A.

Manuscript received 20 February 1979, accepted 6 October 1979

Equlibrium constants of the binary and ternary complexes of UO\(_2^{3+}\) with pyridine carboxylic acids and some dicarboxylic acids have been investigated by \(p\)H titration method at 30° and µ =0.1 M (NaClO₄). Pyridine carboxylic acids used are picolinic, quinolinic, dipicolinic and dicarboxylic acids are malic, maleic, chlorosuccinic, dimercapto succinic, methylmalonic and dimethylmaionic, UO\(_2^{2+}\), forms 1 : 1 and 1: 2 binary bis complexes with all the ligand acids except maleic, chlorosuccink and dimercapto succinic.

Ternary chelates of UO\(_2^{2+}\) pyridine carboxylic-secondary acid systems have been studied. Binary stabilities are explained on the ring size effect and nature of subs­tituent in the parent acids. Equilibrium constants of ternary complexes were utilized to discuss the preferential formation of ternary complexes over binary. The values of K_2\(YX\) and \(\beta\)_\(XY\) depend on the basicities of the secondary ligands and 1 : 1 binary stabilities of the metal chelates respectively.