N,S-containing soft ligands for extractive separation of f-metals: synthesis and unexpected inverse selectivity

A number of heterocycle-based bis(phosphine sulfides) have been synthesized from the corresponding phosphine oxides using phosphorus(v) sulfide in good to excellent yields, for one representative compound the molecular structure has been determined by single crystal X-ray diffraction. The compounds obtained were tested as extractants for f-metals both in nitric acid and ammonium nitrate media, distribution coefficients and selectivity factors have been determined for an Am/Eu pair.