Azide complexes, trivalent actinide

The emphasis of work by French researchers has been the use of soft-donor extractants and complexants to enhance actinide/lanthanide group separation (Vitorge 1985, Musikas et al. 1980, Musikas 1985). The relative stability constants for lanthanide and actinide azide complexes reported by Musikas etal. (1980) suggest that hydrazoic acid could function as a useful reagent for this separation. This is confirmed in a later report for Am/Eu separation (Musikas 1985) in which americium extraction is suppressed by complex formation with azide. The separation factors are not very different from those reported by Sekine (1965) using SCN as the complexant in TBP extraction. However, Choppin and Barber (1989) find that, while the trivalent actinide-azide stability constants are somewhat larger than those of the trivalent lanthanides, the complexation enthalpies calculated from the temperature coefficient of the / s do not support the existence of a covalent bonding contribution. 

Azide complexes. The aqueous trivalent actinide and lanthanide azides complexes were examined by two techniques ... 

This paper reports the results of investigations of the complex formation between actinide or lanthanide ions and azide or orthophenanthroline. The aim of this work was first to confirm whether these relatively soft ligands give complexes of different stabilities with the trivalent lanthanide and actinide ions, as a consequence of the broader extension of 5f orbitals as compared with 4f. Secondly, we attempted to use the results in actinide chemical separation processes. 

Orthophenanthroline complexes. As azides exhibit greater chemical affinity for trivalent actinide ions, we tried to check this behavior with a bidentate ligand. We chose 1-10 ghenantro-line which has two nitrogen donors at 2.75 A from each... 

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