ABSTRACT
Reaction of 1,3,4,6-tetra-O-acetyl-N-(2-hydroxy)-naphthylidene glucosamine (HL(Ac)) with uranyl acetate in ethanol leads to formation of dinuclear [(UO2)2(L)2] (1). In a second step 1 is quantitatively transferred into the trinuclear oxo-bridged complex [(UO2)3(µ3-O)(L)3]2- (22-) via deprotonation and coordination of a water molecule. This transformation was followed by NMR and UV/Vis spectroscopy and it proved possible to selectively introduce 18O into the µ3-bridge.
ABSTRACT
Effective receptors for the separation of Li+ from a mixture with other alkali metal ions under mild conditions remains an important challenge that could benefit from new approaches. In this study, it is demonstrated that the 4-phosphoryl pyrazolones, HL2 -HL4 , in the presence of the typical industrial organophosphorus co-ligands tributylphosphine oxide (TBPO), tributylphosphate (TBP) and trioctylphosphine oxide (TOPO), are able to selectively recognise and extract lithium ions from aqueous solution. Structural investigations in solution as well as in the solid state reveal the existence of a series of multinuclear Li+ complexes that include dimers (TBPO, TBP) as well as rarely observed trimers (TOPO) and represent the first clear evidence for the synergistic role of the co-ligands in the extraction process. Our findings are supported by detailed NMR, MS and extraction studies. Liquid-liquid extraction in the presence of TOPO revealed an unprecedented high Li+ extraction efficiency (78 %) for HL4 compared to the use of the industrially employed acylpyrazolone HL1 (15 %) and benzoyl-1,1,1-trifluoroacetone (52 %) extractants. In addition, a high selectivity for Li+ over Na+ , K+ and Cs+ under mild conditions (pH â¼8.2) confirms that HL2 -HL4 represent a new class of ligands that are very effective extractants for use in lithium separation.
