STABILITIES OF SCANDIUM(III)- AND YTTRIUM(III)-TIRON CHELATES AND THEIR HYDROLYTIC BEHAVIORS

摘要

The interactions of Sc3+ and Y3+ ions with disodium, 2-dihydroxybenzene-3,5-disulfonate (Na2H2L, where H2L~(2-) - Tiron) were investigated in aqueous solution by means of potentiometric and spectroscopic methods. The coordination of Tiron to Sc3+ andY3+ takes place through two phenolic oxygen atoms of catecholate ion in different stochiometries. Thus, the binding of Tiron to Sc3+ occurs either in 1 : 1 or 1 : 2 molar ratios; they have resulted by the formation of [ScL]~- and [ScL2]~(5-) type complexes, respectively. On the other hand, Y3+ ion behaves like Th4+ and Ln3+ ions toward Tiron. It forms [YL]~- type complex in 1 :1 molar ratio; but in 1 : 2 or in higher molar ratios only unique [Y-2L-3]-(6-)type complex formation takes place. The formationconstants of [ScL]~-, [ScL2]~(5-), [YL]~-, and [Y-2L-3]-(6-) complexes were determined by analysis of the potentiometric data in ionic medium of 0.1 M KNO3 or NaClO4 at 25°C. The hydrolytic reactions of Sc(III) and Y(III) complexes with Tiron were determined from potentiometric data and the formation constants of [ScL(OH)]~(2-) and [YL(OH)]~(2-)were also calculated.