Synergistic Effects of Tris(4-isopropyltropolonato)cobalt(III) on the Extraction of Lanthanum(III) and Lutetium(III) with Acetylacetone into Benzene

The synergistic effects of tris(4-isopropyltropolonato)cobalt(III) (Co(ipt)(3)) on the extraction of lanthanum(III) and lutetium(III) with acetylacetone (Hacac) into benzene were investigated. A synergistic enhancement of the extraction of trivalent lanthanides was found in the presence of Co(ipt)(3). From equilibrium analysis, it was found that Ln(acac)(3) forms a 1:1 adduct, i.e., a binuclear complex, with the Co(ipt)(3) in benzene. The adduct formation constants (beta(s,l)) of Ln(acac)(3) with Co(ipt)(3) in benzene were determined, discussed, and compared with those reported previously. The beta(s,l) values in the Ln(acac)(3) system became smaller than those in the Ln(tta)(3) system. The Lewis acidity of the Ln chelate had a significant effect on the adduct formation in the La(III) system and a relatively small effect in the Lu(III) system.