Structural chemistry of tetrachloride complexes of uranyl (review)

Abstract The paper systematizes and discusses the structures of uranyl tetrachloride complexes with inorganic and protonated organic cations, which were investigated by single-crystal X-ray structure analysis. The crystallochemical structural features of the analyzed compounds were determined. In the studied crystal structures of the UO 2 2+ tetrachloride complexes, the coordination polyhedron of the hexavalent uranium atom has a tetragonal-bipyramidal (flattened octahedral) structure with the oxygen atoms of the uranyl group located at the apical vertices of the tetragonal-bipyramidal polyhedron. In the presence of free Cl − ions and/or free neutral molecules containing acceptor atoms in the structures of the uranyl tetrachloride complexes that are not bound to the U atom, the cations do not interact with the donor Cl atoms of the anion, but form hydrogen bonds with free chlorine ions and acceptor atoms of free molecules.