AN INDIRECT APPROACH TO SYNERGISTIC EXTRACTION MECHANISMS - SPECTROSCOPY OF INDIUM(III) LIPOPHILIC COMPLEXES EXTRACTABLE FROM PERCHLORATE MEDIUM BY 2 1-PHENYL-3-METHYL-4-ACYL-PYRAZOL-5-OLS AND TRI-N-OCTYLPHOSPHINE OXIDE

With the aim of improving our knowledge about the extraction of indium from perchlorate media, by 1-phenyl-3-methyl-4-acyl-pyrazol-5-ols, "HL" (HPMBP: acyl = benzoyl, HPMTP: acyl = thenoyl) and their mixtures with tri-n-octylphosphine oxide, "TOPO", in toluene, synthetic and extraction organic phases, and extractable complexes, have been studied by phosphorus-31 and proton NMR, and IR spectroscopy. NMR measurements show that the reaction InL3(H2O)2BAR + 2 TOPOBAR reversible InL3(TOPO)2BAR + 2 H2O generally assumed to describe the synergistic effect, does not occur in homogeneous organic phases, which implies an interfacial mechanism for the synergistic extraction. In the extracted complexes, L- behave in all cases as a bidentate o o- ligand. However, while the three chelate rings of InL3(H2O)2 are identical, there are only two chelate rings in InL3(TOPO)2, the (In<--O = C(acyl)) bond of the third acylpyrazololato ligand being weak. The two phosphine oxide - indium bonds also noticeably differ from one another. Taking into account this unique structure of the extracted complex, a possible mechanism is proposed for the synergistic extraction.