Novel ligands for the separation of trivalent lanthanides and actinides - Tetrakis(phosphane sulfide) and -(phosphinic acid) cavitands

Cavitands with phosphane sulfide moieties 4 and 8a,b were prepared in good yields from their phosphane oxide analogues, as more stable alternatives fo r the dithiophosphinic acids used at present. The cavitands 7a and 7b with flexible butoxyphosphane oxide Ligating sites are more efficient than cavit and 3 having rigid methylphosphane oxide groups as was studied with Eu-III picrate extractions. Due to the absence of an ionic functionality in the ph osphane sulfides 4 and 8a,b Am-III and EUIII are not extracted, not even in the presence of synergents (e.g. TBP, TOPO, HDNNS). Cavitand 10 with phosp hinic acid groups efficiently extracts Eu-III in 1:1 or 2:1 complexes, depe nding 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 Eu-III is preferentially extracted over Am-III with a se paration factor S-Eu/Am up to 5.