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

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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 ligands in the aqueous phase is recognized from the extraction curves. No explanation can be given at the moment for the poor extractability of the most stable tris-complexes among those studied.
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