THE ELECTRONIC-STRUCTURE OF ANIONIC HALIDE-COMPLEXES OF ELEMENT-105 IN AQUEOUS-SOLUTIONS AND THEIR EXTRACTION BY ALIPHATIC-AMINES

To study the complex formation of group 5 elements (Nb, Ta, Ha, and ps eudoanalog Pa) in aqueous HCl solutions of medium and high concentrati ons the electronic structures of anionic complexes of these elements [ MCl6]-, [MOCl4]-, [M(OH)2Cl4]-, and [MOCl5]2- have been calculated usi ng the relativistic Dirac-Slater Discrete-Variational Method. The char ge density distribution analysis has shown that tantalum occupies a sp ecific position in the group and has the highest tendency to form the pure halide complex, [TaCl6]-. This fact along with a high covalency o f this complex explains its good extractability into aliphatic amines. Niobium has equal trends to form pure halide [NbCl6]- and oxyhalide [ NbOCl5]2- species at medium and high acid concentrations. Protactinium has a slight preference for the [PaOCl5]2- form or for the pure halid e complexes with coordination number higher than 6 under these conditi ons. Element 105 at high HCl concentrations will have a preference to form oxyhalide anionic complex [HaOCl5]2- rather than [HaCl6]-. For th e same sort of anionic oxychloride complexes an estimate has been done of their partition between the organic and aqueous phases in the extr action by aliphatic amines, which shows the following succession of th e partition coefficients: P(Nb) < P(Ha) < P(Pa).