(NH4)2[UO2Cl4]·2H2O, a new uranyl tetra-chloride with ammonium charge-balancing cations

Abstract

A new uranyl tetra-chloride salt with chemical formula, (NH₄)₂[UO₂Cl₄]·2H₂O, namely, di-ammonium uranyl tetra-chloride dihydrate, 1, was prepared and crystallized via slow evaporation from a solution of 2 M hydro-chloric acid. As confirmed by powder X-ray diffraction, the title compound crystallizes with an ammonium chloride impurity that formed as a result of the breakdown of a triazine precursor. The (UO₂Cl₄)^2- dianion is charge balanced by ammonium cations, while an extensive hydrogen-bond network donated from structural water mol-ecules stabilize the overall assembly. Compound 1 adds to the extensive collection of actinyl tetra-chloride salts, but it represents the first without an alkali cation for purely inorganic compounds. Diffuse reflectance and luminescence spectra show typical absorption and emission behavior, respectively, of uranyl materials.

Keywords: X-ray diffraction; ammonium; crystal structure; optical properties; uranyl tetra­chloride.