Unexpected Coordination Modes of Bisphosphoramides with Lanthanum(III) and Thorium(IV) Salts: Synthesis, Structural Characterization, Stability, and Extraction Studies

摘要

A series of bisphosphoramides of the type R2P(O) NHCH2CH2NHP(O)R2 (L) (where R=n-butyl, n-hexyl, n-octyl, ethoxy, phenyl) is synthesized in two-steps by Atherton-Todd reaction of ethylenediamine and H-phosphonate derived from the reaction of diethylphosphite and the Grignard reagent. These ligands were employed in the preparation of La(III) and Th(IV)complexes of the general type [LaCl3(L)2]n and [Th- (NO3)4Th(IV)2]. Notably, La(III) complexes of bisphosphoramides are found as infinite coordination polymers with bridging phosphine oxide ligands in an intermolecular fashion. In contrast, Th(IV) complexes are formed with two chelating bisphosphoramide ligands around the metal center intramolec- ularly. All these ligands and the corresponding metal com- plexes are characterized by spectroscopic and analytical data. The single-crystal X-ray analyses of lanthanum and thorium complexes each confirm the coordination modes. Further, these ligands were evaluated to check the extraction behavior with Am(III), U(VI), Th(IV), and Pu(IV) as a function of nitric acid concentration.