Tungsten VI Tetrabromide Oxide

The crude product contains a small amount of the less volatile tungsten(VI) dibromide dioxide as an impurity, which can be separated by sublimation at 120°C. under dynamic vacuum (10-3 torr). A yield of approximtely 15 g. (96%) of pure tungsten(VI) tetrabromide oxide is obtained after sublimation. Large crystals can be obtained by sublimation of the purified product in another tube with 1 mg. of bromine per milliliter of tube volume in a temperature gradient of 220/160°C. Anal. Calcd. for WOBr4 W, 35.40 Br, 61.52 O, 3.08. Found W, 35.37 Br, 61.56 O, 3.08. 

Tungsten(VI) tetrabromide oxide is a dark-brown crystalline compound, which is obtained in the form of needles or flakes. It is extremely sensitive to atmospheric moisture, decomposes rapidly in water, which leaves a gray-green precipitate, and is completely dissolved in solutions of ammonia or sodium hydroxide, which form clear, colorless solutions. It is slightly soluble in concentrated hydrochloric acid, dioxane (yellow solution), 2-methoxyethanol (colorless solution), and acetone (green solution). It has a melting point of 322°C., as determined by D.T.A. 

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