Crystal Structure and Absorption Spectra of Triguanidinium Bis(N-methyliminodiacetato)dioxoneptunate(V) {C(NH2)3}3[NpO2(mida)2

Abstract

This paper is a continuation of our on-going program for studying the structure and properties of pentavalent neptunium compounds with organic ligands containing several electron-donating atoms. Previously, we studied the neptunium(V) complexes with anions of pyridinecarboxylic acids, polypyridines, and found that the Np ion coordinates the oxygen and nitrogen atoms of heterocyclic ligands to form stable chelate rings [1‐3]. As is known, neptunium(V) in weak acid and basic aqueous solutions forms stable complexes with aliphatic polyaminoacetic acids (complexones). The compositions and stability constants were determined for the Np complexes with the anions of the following acids: iminodiacetic (H 2 ida), N -methyliminodiacetic (H 2 mida), ethylenediaminetetraacetic (H 4 edta), diethylenetetraminepentaacetic, and N -hydroxyethyliminodiacetic. It was noted that the complexes of pentavalent actinides in solutions are less stable than the complexes of hexavalent actinides with the same ligands [4‐6]. However, only neptunium(V) ethylenediaminetet