Tungsten -dibromide dioxide

The tube is sealed under vacuum and placed in a temperature gradient of 400/40°C. until the bromine has completely reacted. After this preliminary firing, the reaction tube is placed in a temperature gradient of 450/325°C. for 15 hours. The crude product is purified by a second sublimation. The more volatile impurities, WOBr4 and WBr5, are separated in the usual way, which leaves behind pure crystalline tungsten(VI) dibromide dioxide. The product yield is 15 g. (97%). Anal. Calcd. for W02Br2 W, 48.95 Br, 42.53 O, 8.52. Found W, 48.78 Br, 41.58 O, 8.65. 

Tungsten(VI) dibromide dioxide is sensitive to atmospheric moisture. It yields a clear, colorless solution in dilute and concentrated solutions of ammonia or sodium hydroxide. No reaction is observed with hot or cold concentrated hydrochloric acid, or dry organic solvents. 

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. 

U02Br2 URANIUM DIBROMIDE DIOXIDE 1749 W(CO)6[g] TUNGSTEN HEXACARBONYL (GAS) 1790... 

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