Uranium hexachloride

Uranium hexachloride has an octahedral geometry, with point group Oh. Its lattice (dimensions: 10.95 ± 0.02 Å x 6.03 ± 0.01 Å) is hexagonal in shape with three molecules per cell; the average theoretical U-Cl bond is 2.472 Å long (the experimental U-Cl length found by X-ray diffraction is 2.42 Å), and the distance between two adjacent chlorine atoms is 3.65 Å. ==Chemical properties==

is stable up to temperatures between 120 °C and 150 °C. The decomposition of results in a solid phase transition from one crystal form of to another more stable form. It decomposes as follows: : The activation energy for this reaction is about 40 kcal per mole. Solubility is not a very soluble compound. It dissolves in to give a brown solution. It is slightly soluble in isobutyl bromide and in fluorocarbon (). Reaction with hydrogen fluoride When treated with liquid hydrogen fluoride (HF) at room temperature, produces uranium pentafluoride|. : ==Synthesis==

Uranium hexachloride is efficiently prepared from uranium hexafluoride by halide exchange using boron trichloride according to the following idealized equation: The is converted to , which in turn reacts with the excess to form . It requires a substantial amount of heat for the reaction to take place; the temperature range is from 65 °C to 170 °C depending on the amount of reactant (ideal temperature 100 °C - 125 °C). The reaction is carried out in a closed gas-tight vessel (for example a glovebox) that can withstand the pressure that builds up. Step 1: Step 2: Overall reaction: This metal hexahalide also form upon combining and at 350 °C.{{cite journal|title=The Electronic Structure of UCl6: Photoelectron Spectra and Scattered Wave Xα Calculations|year=1979|last1=Thornton|first1=G.|last2=Edelstein|first2=N. Step 1: Step 2: Overall Reaction: ==References==