Chemical properties of element 105 in aqueous solution: Extraction of the fluoride-, chloride-, and bromide complexes of the group-5 elements into analiphatic amine

Previously, the halide complex formation of the group-5 elements had been s tudied in mixed HCl/HF solutions by their extraction into triisooctyl amine (TiOA). The extraction sequence Ta > Nb > 105 > Pa was observed, while the oretical calculations performed for the pure chloride system predict the re versed sequence of extraction. To verify this experimentally, new batch ext raction experiments for Nb, Ta, and Pa from pure HCl-, HBr-, and HF solutio ns were performed with various aliphatic amines. Based on these results, ne w reversed-phase micro chromatographic column separations were elaborated u sing the quaternary ammonium salt Aliquat 336 on an inert support in the co mputer-controlled chromatography apparatus ARCA II. In the system Aliquat 3 36(F-)/HF, after feeding of the activity onto the column in 0.5 M HF, eleme nt 105 did not elute in 4 M HF (Pa fraction) but showed a higher distributi on coefficient (>570), close to that of Nb land Ta). In the system Aliquat 336(Cl-)/ HCl, after feeding onto the column in 10 M HCl, element 105 showe d a distribution coefficient in 6 M HCl (similar to 438) close to that of N b establishing the extraction sequence Pa > Nb greater than or equal to 105 > Ta. Exactly this sequence has been predicted theoretically based on rela tivistic calculations of the electronic structure of hydrolzed species of N b, Ta, Pa, and element 105, and of their various complexes formed in HCl so lutions, i.e. by explicitly considering the competition between hydrolysis and complex formation. In this way, the extraction sequence fluorides much greater than chlorides > bromides for the group-5 halide complexes is also correctly predicted.