Tungsten Tetrafluoride Oxide

Submitted by WILLIAM W. WILSON and KARL O. CHRISTE Checked by ROLAND BOUGONt 

Tungsten tetrafiuoride oxide is a white hygroscopic solid (mp 104.7 at 25 torr, bp 185.9°) which can be sublimed readily. It is soluble in HF and in propylene carbonate. The F NMR spectrum in propylene carbonate solution consists of a singlet at 65.2 ppm downfield from external CFCla, with two satellites with 7wf = 69 Hz.  

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VCI3 VANADIUM TRICHLORIDE 1768 WOF4 TUNGSTEN TETRAFLUORIDE OXIDE 1813... 

VCI4 VANADIUM TETRACHLORIDE 1769 WOF4[g] TUNGSTEN TETRAFLUORIDE OXIDE (GAS) 1814... 

In agreement with earlier work, tellurium tetrafluoride oxide dimer has been found to be strongly oxygen-bridged, in sharp contrast to tungsten tetrafluoride oxide, which is weakly fluorine-bridged in the solid state but which readily dissociates to a square-pyramidal monomer. Despite variable-temperature i.r. and Raman studies, no trace of reversible equilibria involving a terminal Te—O bond was detected... 

Tungsten tetrabromide oxide, 0294 Undecaamminetetraruthenium dodecaoxide, 4598 Xenon difluoride dioxide, 4322 Xenon tetrafluoride oxide, 4346 Zinc ethylsulfinate, 1711... 

F4OW, Tungsten fluoride oxide, 24 37 F4SE, Selenium tetrafluoride, 24 28 FsCJH, Benzene, pentafluoro-cobalt complexes, 23 23-25 lithium and thallium complexes, 21 71,... 

The oxide tetrafluorides and dioxide difluorides of molybdenum and tungsten are the most studied transition-metal oxide fluorides, and their preparation and properties are discussed separately below. 

Preparation of uranium metal. As discussed previously, some nuclear power plant reactors such as the UNGG type have required in the past a nonenriched uranium metal as nuclear fuel. Hence, such reactors were the major consumer of pure uranium metal. Uranium metal can be prepared using several reduction processes. First, it can be obtained by direct reduction of uranium halides (e.g., uranium tetrafluoride) by molten alkali metals (e.g., Na, K) or alkali-earth metals (e.g.. Mg, Ca). For instance, in the Ames process, uranium tetrafluoride, UF, is directly reduced by molten calcium or magnesium at yoO C in a steel bomb. Another process consists in reducing uranium oxides with calcium, aluminum (i.e., thermite or aluminothermic process), or carbon. Third, the pure metal can also be recovered by molten-salt electrolysis of a fused bath made of a molten mixture of CaCl and NaCl, with a solute of KUFj or UF. However, like hafnium or zirconium, high-purity uranium can be prepared according to the Van Arkel-deBoer process, i.e., by the hot-wire process, which consists of thermal decomposition of uranium halides on a hot tungsten filament (similar in that way to chemical vapor deposition, CVD). 

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