Synergistic Extraction of Rare Earth Ions with Acidic Chelating Reagents and a Metal (III)-Tropolone Chelat As a Neutral Ligand

研究了三（4-异丙基托泊洛酮）钴（III）（Co（ipt）_3）和三（乙酰丙酮）钴（III）（Co（acac）_3）对β-二酮萃取稀土离子（RE）的影响。在噻吩甲酰三氟丙酮（Htta）或六氟乙酰丙酮（Hhfa）-甲苯体系中，加入这些钴（Ⅲ）螯合物，尤其是Co（ipt）_3，可显著增强Hhfa-甲苯体系萃取稀土的能力。这是由钴（III）螯合物引起的协同效应。根据平衡分析，协同作用归因于RE（A）_3与钴（III）螯合物在有机相中形成1：1的加合物，并测定了加合物形成常数β_*。β_* 值随稀土离子半径的减小而减小，使轻稀土和重稀土的β_* 值有很大的差别。用电子吸收和红外吸收等光谱学方法解释了这种差别。红外光谱表明，轻稀土螯合物如Nd（Eta）_3与Co（ipt）_3的配位水分子发生了位移;因此，Co（ipt）_3直接与稀土螯合物的中心金属配位。另一方面，重稀土的加合物的形成归因于Co（ipt）_3与稀土螯合物中的配位水分子之间的氢键作用。结果表明，钴（Ⅲ）-ipt络合物作为络合配体对稀土萃取有协同增效作用。

Effect of cobalt (III) chelates such as tris (4-isopropyltropolonato)cobalt (III)(Co (ipt)_3) and tris (acetylacetonato) cobalt (III)(Co (acac)_3) for comparison on the extraction of rare earth ions (RE) with β-diketones (HA) has been studied. The extraction of RE with thenoyltrifluoroacetone (Htta) or hexafluoroacetylacetone (Hhfa) in benzene or toluene was remarkably enhanced by the addition of those cobalt (III) chelates, especially Co (ipt)_3 in the Hhfa-toluene system. This is the synergistic effect caused by the cobalt (III) chelates. From the equilibrium analysis, the synergism was ascribed to the formation of a 1 : 1 adduct of RE (A)_3 with the cobalt (III) chelate in the organic phase and the adduct formation constant (β_*) was determined. The β_* values decreased with decrease in the ionic radius of RE and gave the large differentce between light and heavy RE.Some spectroscopic studies such as electronic absorption and infrared absorption were performed to explain such difference in β_* From the IR spectra, the displacement of the coordinated water molecules of the light RE chelates such as Nd (Eta)_3 with Co (ipt)_3 was observed ; therefore, the direct coordination of Co (ipt)_3, toward the central metal of the RE chelate. On the other hand, the adduct formation of heavy RE was ascribed to the hydrogen bonding between Co (ipt)_3 and the coordinated water molecules of the RE chelates. It was proved that the coordinately saturated cobalt (III)-ipt chelate acts as a complex ligands and causes the synergistic enhancement of the extraction of RE.