A neptunium chloride complex that contains neptunium in the (V) and (VI) valence states

A cubic phase of a neptunium chloride complex was obtained by x-ray diffraction and was found to be isomorphous with the cubic modification of Cs/sub 2/AmOCl/sub 4/, but the interpretation of it as Cs/sub 2/NpO/sub 2/Cl/sub 4/ (by analogy with Cs/sub 2/AmO/sub 2/Cl/sub 4/) was questionable. In this connection this report investigates the conditions of synthesis, the composition, and the properties of the cubic modification of the neptunium chloride complex with cesium. Comparison of the results for Cs/sub 7/Np(V)O/sub 2/(Np(VI)O/sub 2/)/sub 2/Cl/sub 12/ with those for the cubic modification of Cs/sub 2/AmO/sub 2/Cl/sub 4/ indicated that the data on the cubic americium chloride complex requires a critical review. The cubic americium chloride complex should more likely be considered as a single compound that contains both Am(V) and Am(VI). Likewise, the comparison of the electron spectra of Cs/sub 2/NpO/sub 2/Cl/sub 4/ and Cs/sub 3/NpO/sub 2/Cl/sub 4/ discloses fine differences that prevent one from considering the spectrum of the cubic phase as a superposition of the spectra of Cs/sub 2/NpO/sub 2/Cl/sub 4/ and Cs/sub 3/NpO/sub 2/Cl/sub 4/. Moreover, comparison of the electron spectra shows unambiguously that tetravalent neptunium is absent from the cubic phase.