Uranium tetrabromide

Uranium pentabromide [13775-16-1], UBr, is unstable toward reduction and the pentaiodide is unknown. Two synthetic methods utilized for the production of UBr involve the oxidation of uranium tetrabromide [13470-20-7], UBr, by Br2 or by bromination of uranium turnings with Br2 in acetonitrile. The metastable pentabromide is isostmctural with the pentachloride, being dimeric with edge-sharing octahedra U2Br2Q. 

The actinide tetrachloride-DMA complexes cover quite a range of stoichiometry (22,24,27) and the behavior of protactinium tetrachloride is intermediate between that observed for thorium and uranium tetrachloride (Table XI). PaCl4 2.5 DMA is isostructural with the y-modifica-tion of the other 1 2.5 complexes and with PaBr4 2.5 DMA (24). However, the uranium tetrabromide complex, UBi 4 2.5 DMA, possesses a different structure. The 1 5 tetrabromide-DMA complexes (Th to U inclusive) are isostructural (24). 

Double bromides of the type RjUBre, similar to the corresponding chlorides, have been prepared by passing uranium tetrabromide vapour over the heated alkali bromides. The potassium and sodium salts, KgUBrg and NajUBr, are green crystalline substances, hygroscopic, but less so than uranium tetrabromide. 

Aluminum bromide and iodide, however, have special utility in the conversion of oxides to the corresponding halides. Prigent (66) has reported that UOj heated with carbon tetrabromide at 165° forms UBr4. Uranium tetrabromide has also been prepared by reaction of uranium dioxide with a tenfold excess of carbon tetrabromide at 175° and subliming away the UBr4 formed (22). 

TII2 TITANIUM DIIODIDE 1685 UBr4[g] URANIUM TETRABROMIDE (GAS) 1730... 

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

Uranium forms two stable fluorides, UF4 and UFe. When metal is heated with fluorine gas, hexafluoride, UFe, is produced. Heating powdered metal with hydrogen fluoride gas at 350°C yields tetrafluoride, UF4. Powdered metal is obtained by thermal decomposition of trihydride, UH3. Uranium combines with chlorine at elevated temperature (at about 500°C) to form a mixture of various chlorides namely, the tetrachloride, UCI4, pentachloride, UCI5, and hexachloride,UCl6. Heating the metal with bromine vapor at 650°C forms tetrabromide, UBr4. Uranium also forms tri-and pentabromides. With... 

Protactinium pentabromide is appreciably more stable than uranium pentabromide, which decomposes to the tetrabromide at 160°C (116). It is moisture-sensitive and hydrolyzes rapidly on the addition of water. The few known complexes are discussed later. 

Tetrachloride and tetrabromide complexes are known for thorium, protactinium, uranium, neptunium, and plutonium. These are similarly produced by halide-based oxidation of metals or hydrides, or by halogenation of oxides. A common structural type is reported for most compounds. The reported structure of thorium tetrachloride reveals that the coordination geometry about the metal is dodecahedral.The compounds are generally volatile and can be sublimed. The gas-phase electron diffraction structure of suggests that the molecule is... 

Ezhov, Yu. S., Akishin, P. A., Rambidi, N. G., Electron-diffraction study of uranium and thorinm tetrahalides in the gas phase. II. Uranium and thorinm tetrachlorides and tetrabromides, Zh. Strukt. Khim., 10, (1969), 571, inRnssian. Cited on page 202. 

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