Novel Ligands for the Separation of Trivalent Lanthanides and Actinides-Tetrakis(phosphane sulfide) and -(phosphinic acid) Cavitands

摘要

Cavitands with phosphane sulfide moieties 4 and 8a, b were prepared in good yields from their phosphane oxide analogues, as more stable alternatives for the dithiophosphinic acids used at present. The cavitands 7a and 7b with flexible butoxyphosphane oxide ligating sites are more efficient than cavitand 3 having rigid methylphosphane oxide groups as was studied with Eu~(III) picrate extractions. Due to the absence of an ionic functonality in the phosphane sulfides 4 and 8a, b Am~(III) and Eu~(III) are not extracted, not even in the presence of synergents (e.g. TBP, TOPO, HDNNS). Cavitand 10 with phosphinic acid groups efficiently extracts Eu~(III) in 1:1 or 2:1 complexes, depending on the metal-to-ligand concentration ratio (extraction constants K_(ex)~1=3.9.10~(-5) M~2 and K_(ex)~2=1.9.10~2 M, respectively). Furthermore, in the case of 10 Ei~(III) is preferentially extracted over Am~(III) with a separation factor S_(Eu/Am) up to 5.