A Revised Structure Model for the UCl 6 Structure Type, Novel Modifications of UCl 6 and UBr 5 , and a Comment on the Modifications of Protactinium Pentabromides

Synthesis and crystal structure of triethylammonium hexabromidouranate(IV) dichloromethane monosolvate

Triethylammonium hexabromidouranate(IV) dichloromethane monosolvate, [(C2H5)3NH]2[UBr6]·CH2Cl2, was obtained in the form of dark-brown crystals from the reaction of uranium pentabromide with NEt3 and ethylene glycol in dichloromethane at low temperature. During the progress of the reaction, the reduction of uranium(V) to uranium(IV) was observed, whose associated oxidation product could not be identified. The uranium atom of the [UBr6]2– anion is coordinated by six bromido ligands in the shape of an octahedron. Between cations, anion and solvent molecules of crystallization, numerous C—H...Hal hydrogen-bond-like interactions are present, leading to a three-dimensional network structure.

Rerefinement of the crystal structure of trichloridosulfonium(IV) hexachloridouranate(V), (SCl3)[UCl6]

Single crystals of trichloridosulfonium(IV) hexachloridouranate(V) were obtained from the reaction of uranium(IV) chloride with an excess of disulfur dichloride and studied by single-crystal X-ray diffraction. In comparison with the structure model reported previously [Sawodny et al. (1983). Z. Anorg. Allg. Chem. 499, 81–88.], the lattice parameters and fractional atomic coordinates were determined to a much higher precision, leading overall to an improved structure model. The ionic compound contains trigonal–pyramidal (SCl3)+ cations and slightly distorted octahedral [UCl6]− anions. The structure was refined as an inversion twin with a twin ratio of 4.4:1.