FORMATION-CONSTANTS OF BINARY AND TERNARY COMPLEXES OF YTTRIUM(III) WITH AROYLHYDRAZONE SCHIFF-BASES AS SECONDARY LIGANDS AND AMINOPOLYCARBOXYLIC ACIDS AS PRIMARY LIGANDS

The formation constants of complexes of yttrium(III) with 2-hydroxy-1- naphthalidene benzoyl hydrazone (NABHZ) and 2-hydroxy-1-naphthalidene salicyloyl hydrazone (NASAZ) has been studied in 75% v/v dioxane-water at different temperatures. The formation constants are in the order l og K1 > log K2 > log K3 for both the ligands. The formation of binary complexes is favoured by enthalpy and, entropy changes. The ternary co mplexes with NTA, HEDTA and EDTA as primary ligands are also studied. The stabilities at the ternary step are lower than log K(ML3)ML2 for t he ligands. The negative enthalpy changes are larger in the ternary st ep whereas entropy changes are negative. The ternary step constants ar e in the order log K(MNTAL)M TA > log K(MHEDTAL)MHEDTA > log K(MEDTAL) MEDTA for both the ligands.