Ryokichi Murai

Formation and two-phase distribution equilibria of cobalt(II) and zinc(II) complexes with β-diketones in several solvent extraction systems

Abstract The equilibrium constants for the complex formation of cobalt(II) and zinc(II) with several β-diketones in 1M sodium perchlorate solution ( β n ), the two-phase distribution constants of the bis-chelates of these metals between carbon tetrachloride and the above aqueous solution ( Kdm ), and the adduct formation of the bis-chelates with trioctylphosphine oxide (TOPO) in the organic phase ( β n ( org ) ) have been determined at 25°C. The distribution constants of the bis-zinc(II) chelates were also determined when the solvent was hexane, chloroform or benzene. The weaker the acidity of the ligand the higher the β n value for these complexes. The relationship, log Kdm = 2 log Kd + C , where Kd is the distribution constant of the extractant is obeyed for each of the zinc(II) chelates when the solvent is different. The Kdm values of the metal chelates with the same ligand are always lower for cobalt(II) than for zinc(II), and among the series of bis-chelates of the same metal ion, there is a tendency for β n ( org ) of TOPO adducts to be higher when the β 2 is lower, but the stability order of the adducts of a set of cobalt(II) and zinc(II) chelates with the same β-diketone is not always the same.

SOLVENT EXTRACTION EQUILIBRIA OF TRIS(BENZOYL- TRIFLUOROACETONATO)COMPLEX OF COBALT(II) AND NICKEL(II) AS ION-PAIRS WITH TETRABUTYLAMMONIUM

Abstract Solvent extraction of cobalt(Il) and nickel(II) in aqueous 1 mol dm−3 NaCl solutions with benzoyltrifluoro-acetone(Hbfa) in carbon tetrachloride has been measured in the absence and presence of tetrabutylammonium(tba+). In the absence of tba+, M(bfa)2 species is extracted and the extraction of cobalt(II) is better in the higher Hbfa concentration range but in the presence, M(bfa)3 −tba+ type ion-pair is extracted and the extraction of nickel-(II) is always better. This is explained in terms that although the bis-nickel(II) complex is more stable, it is much more strongly hydrated than the bis-cobalt(II) complex and consequently its extraction is hindered but in the tris-complexes such a large difference of the hydration may not occur and the more stable nickel(II) complex is extracted better.

SOLVENT EXTRACTION OF ZINC(II) ANIONIC g-DIKETONATE COMPLEXES AS ION-PAIRS WITH TETRABUTYLAMMONIUM IONS

ABSTRACT Solvent extraction equilibria of zinc(II)with five 6-diketones(HA)in carbon tetrachloride-aqueous 1 mol dm−3NaN03systems are studied in the absence and presence of tetrabutylammonium ions(tba+The distribution data of zinc(II)in the absence of tba+ are explained in terms of extractions of uncharged ZnA2 complex from the aqueous phase where the ZnA+, ZnA2and ZnA3complexes are formed, and those in the presence of tba+ in terms of extraction of the ZnA3~tba+ ion-pairs in addition to the uncharged one. The extraction of the ZnA3-tba+species is better with hexafluoroacetylacetone than with trifluoroacetyl-acetone. It is better when the extractant is benzoyltri-fluoroacetone than when it is trifluoroacetylacetone and this is explained in terms of a greater increase in the hydrofobic character by formation of the tris-complex from the bis-complex with the larger ligand. However, the extraction with acetylacetone and benzoylacetone is not affected by though the formation of the tris-chelate with these lig...

Solvent extraction equilibria of bis-Hg(II) benzoylacetonate and benzoyltrifluoroacetonate complexes and their adducts with trioctylphosphine oxide

Abstract The solvent extraction equilibria of Hg(II) in 1 mol dm−3 (Na, H)ClO4 with benzoylacetone and benzoyltrifluoroacetone in carbon tetrachloride containing trioctylphosphine oxide (TOPO) have been measured at 25°C. The stability constants of the complexes in the aqueous phase, the two-phase partition constants, and the adduct formation constants with TOPO of the bis-complexes have been computed from the data. It is concluded that Hg(II) forms very stable β-diketonates and the bis-complexes form stable TOPO adducts in the organic phase. However, the partition constants of the bis-complexes are much lower than those of many other metal ions and this is the reason for the poor extraction of Hg(II) with these reagents.