Stability Of 2-Carboxyphenylhydrazoacetoacetanilide,and 2-Carboxyphenylhydrazobenzoylacetone Complexes of Rare-Earth Elements in Mixed Solvents

The overall stability constants of the 1:1 and 2:1 2-Carboxyphenylhydrazoacetoacetanilide (2-CPHAAA) and 2-Carboxyphenylhydrazobenzoylacetone (2-CPHBA) rare-earth chelates, were determined by a potentiometric method. The variation of the overall stability constants, “log β” with atomic number, of the lanthanide was ascribed to different degrees of dehydration of the cations. The 2-CPHBA ligand exhibited less affinity for rare earth cations than 2-CPHAAA. The correlation of “log β” versus the basicity of the ligands showed that 2-CPHAAA and 2-CPHBA form the same type of chelate in polar solvents but differ in non polar solvents.