Uranium hexachloride

A suitable vacuum line is depicted in W. L. Jolly and J. E. Drake, Inorganic Syntheses, 7, 34 (1963). 

Although there are a number of reported methods for preparing uranium hexachloride, most of them can be grouped under two types.(1) Uranium hexachloride can be prepared by further chlorination of lower uranium chlorides. This type includes those preparations in which a uranium oxide is the starting material, since a lower uranium chloride is normally formed as an intermediate in these chlorination reactions. (2) Uranium hexachloride is formed in the thermal decomposition of uranium pentachloride. Neither method yields uranium hexachloride in a very pure form. Uranium/chlorine ratios of 1 5.8 to 5.9 are normally the best encountered. 

The procedure described below, which uses a metathetical reaction between uranium hexafluoride and boron trichloride (trichloroborane), is the only preparation available which gives pure uranium hexachloride. It is also a significant improvement on previous methods because of the ease with which it can be conducted and its excellent yields (approaching 100%). 

The apparatus used is shown diagrammatically in Fig. 14. The vacuum line is made from f-in. nickel or Monel tubing. The metal valves can be of the bel- 

Inorganic Syntheses, Volume XVI Edited by Fred Basolo Copyright 1976 by McGraw-Hill, Inc. 

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The hexachloride, uranium hexachloride [13763-23-0], UCl, is best prepared by chlorination of UCl [10026-10-5] with SbCl. An alternative preparative approach is the disproportionation UCl [13470-21 -8] to UCl and UCl under reduced pressure. The obvious disadvantage of the second method is contamination by UCl, however, sublimation is a possible purification technique. Isostmctural with the hexafluoride, the hexachloride is monomeric with an octahedral arrangement of the chlorine atoms around the uranium center. 

Uranium halide complexes, 25 437-439 physical constants for, 25 4371 Uranium hexachloride, 25 439 Uranium hexafluoride, 11 845, 859, 25 438 Uranium hydrocarbyl complexes,... 

Tungsten tetrabromide oxide, 0294 Uranium hexachloride, 4192 Uranium hexafluoride, 4375 Vanadium dichloride, 4118... 

In chronic-duration feeding studies, no adverse effects on the respiratory system were reported in 1-year studies of dogs given oral doses of 31 mg U/kg/day as uranium tetrachloride, 3,790 mg U/kg/day as uranium hexachloride, 8 mg U/kg/day as uranyl fluoride, or 4,407 mg U/kg/day as uranium dioxide (Maynard and Hodge 1949 Maynard et al. 1953). In 2-year studies, the respiratory system was unaffected in dogs and rats given 2 mg U/kg/day as uranyl nitrate hexahydrate and in rats given 12,141 mg U/kg/day as uranium dioxide, 664 mg U/kg/day as uranyl nitrate hexahydrate,... 

After about 30 min the reaction ceases. At this stage the boron trifluoride and the excess boron trichloride must be removed. One way is to open valve 1 and pump them into the vacuum system (which should have a liquid-nitrogen scavenger trap). It is a considerable advantage of the preparative method that all the reagents and products, except uranium hexachloride, are volatile. 

If for some reason excess boron trichloride is not used and unreacted uranium hexafluoride remains, it also is volatile and is removed from the uranium hexachloride at this stage. The residue is essentially pure uranium hexachloride. The uranium hexachloride is in its purest form immediately following the preparation. Attempts to sublime the compound invariably decrease its purity, as there is always some thermal decomposition. 

Uranium hexachloride is a black solid melting at 177.5°. Since it is hygroscopic and reacts vigorously with water, it should be handled only in dry-boxes. The crystal structure has been determined hexagonal symmetry, space group D a-C7> (m, n = 3), with an almost perfect octahedron of chlorine atoms around each uranium atom. Uranium hexachloride can be sublimed at 75-100° at low pressures, but normally some thermal decomposition results. The ultraviolet-visible spectrum of gaseous uranium hexachloride has been determined. No fine structure was observed in the spectrum. Because previously available preparative methods were inadequate, there has been very little study of the chemistry of uranium hexachloride. It reacts with hydrogen... 

Another unsuccessful attempt has been made to prepare AmFe, by fluorinating Am203 in the presence of PtFe (100). Complexes of UFe such as Na2UF8 (d3), NH4UF7 (102) and NOUF7 (56) are now known, but the complexing behavior of neptunium and plutonium hexafluorides and uranium hexachloride has scarcely been investigated. 

Ti02[A] TITANIUM DIOXIDE (ANATASE) 1693 UCI6 URANIUM HEXACHLORIDE 1737... 

A parallel body of a regular octahedron embracing six pieces of magnet in symmetry represents uranium hexachloride, UClg, and... 

Fig. 15. Hexagonal and trigonal crystals of convex models of molecules, (a) corresponding to uranium hexachloride, (b) to wolfram hexachloride.

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