STABILITY CONSTANT FOR THORIUM(IV) COMPLEXES WITH S-(5-HYDROXY-3-METHYL-1-PHENYL-4-PYRAZOLYL)METHANE LIGANDS

Chelate stability constants of is(5-hydroxy-3-methyl-1-phenyl-4-pyrazo lyl)methane [ABPM] derivatives with thorium(IV) ion were determined by the potentiometric method at 30 degrees C and 0.1 mol dm(-3) (KNO3) i n 75% (v/v) dioxane-water solvent. The computation of the titration da ta indicated that four kinds of complexes [ThL](2+) [ThL(OH)](+), [ThL (2)] and [ThL(OH)(2)] were formed. The appropriate formation constants for all of the 1:1 species and 2:1 complexes have also been calculate d and probable ligand-bonding sites of the complexes were proposed. In addition, the applicability of the Hammett equation for correlation o f the stability constants of [Th(IV)-ABPM] complexes was discussed.