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Published on: June 8, 2022
A comparison of neptunyl(V) and neptunyl(VI) solution coordination: the stability of cation-cation interactions
S Skanthakumar1, Mark R Antonio, L Soderholm
1Heavy Elements and Separation Sciences Group, Argonne National Laboratory, Argonne, IL 60439, USA.
Abstract:
The solution coordination environments of pentavalent and hexavalent Np are studied by high-energy X-ray scattering. Np5+ and Np6+ both exist as the neptunyl moiety coordinated with five equatorial waters at Np-O distances of 2.46(2) and 2.37(2) A, respectively. NpO2(2+) also has a second coordination sphere of 6-10 waters at 4.37(3) A. The NpO2+ scattering is complicated by the presence of scattering at about 4.2 A that is attributed to Np-Np cation-cation interactions. The analysis of changing intensity of this peak as a function of Np concentration is used to determine a stability constant of Keq=0.74(9) M(-1) for the dimeric complex.
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