Hexafluoride hydrolysis

Rhenium hexafluoride [10049-17-9J, ReF, is a pale yeUow soHd at 0°C, but a Hquid at ambient temperature. In the presence of moisture it hydroly2es rapidly forming HF, Re02, and HRe04 (see Rheniumand rhenium compounds). It is not safe to store ReF in a glass trap or glass-lined container. Leaks in the system can initiate hydrolysis and produce HF. The pressure buildup causes the system to burst and an explosion may result. 

Although uncontrolled reaction of xenon hexafluoride and moisture produces explosive xenon trioxide, controlled action by progressive addition of limited amounts of water vapour with agitation to a frozen solution of the hexafluoride in anhydrous hydrogen fluoride at —196° C to give xenon oxide tetrafluoride or xenon dioxide difluoride is safe [1], Controlled hydrolysis in solution in hydrogen fluoride is, however, described as hazardous [2],... 

The hexafluoride is a very powerful oxidizing agent reacting violently with most oxidizable substances. Reaction with liquid water is violent forming HF, oxygen, lower fluorides of platinum, and other products. In vapor phase hydrolysis occurs more smoothly. 

Careful hydrolysis of xenon hexafluoride produces xenon teuafluoride oxide ... 

Complete hydrolysis of xenon hexafluoride or hydrolysis or disproportionation of xenon tetmfluoride produces the tnoxide ... 

Selenium hexafluoride, SeFg, the only clearly defined hexahalide, is formed by reaction of fluorine with molten selenium, It is more reactive than the corresponding sulfur compound, SFs, undergoing slow hydrolysis. Selenium forms tetrahalides with fluorine, chlorine, and bromine, and dihalides with chlorine and bromine. However, other halides can be found in complexes, e.g,. treatment of the pyridine complex of SeF/i in ether solution with HBr yields (py)2SeBrc Selenium tetrafluoride also forms complexes with metal fluorides, giving MSeF complexes with the alkali metals. 

Two further points merit attention. PuPe is a very volatile substance, like the other actinide hexafluorides (mp 51.5 °C bp 62.15 °C) very reactive (it undergoes controlled hydrolysis to PUO2F2 and PUOF4), it tends to be decomposed by its own a-radiation, and is best kept in the gaseous state (resembling NO2 in appearance). 

XeOp4 was first detected as an impurity by mass spectrometry among the xenon fluorides prepared by thermal methods. It was obtained in macroscopic quantities by the partial hydrolysis of xenon hexafluoride (equation 7). Umeacted XeFe and HF formed in the reaction are removed... 

Bostick WD, McCulla WH, Pickrell PW. 1985. Sampling, characterization, and remote sensing of aerosols formed in the atmospheric hydrolysis of uranium hexafluoride. J Environ Sci Health, Part A A20 369-393. 

Leach LJ, Gelein RM, Panner BJ, et al. 1984. The acute toxicity of the hydrolysis products of uranium hexafluoride (UE6) when inhaled by the rat and guinea pig. Pinal report. ISS K/SUB-81-9039-3. NTIS... 

Morrow PE, Leach LJ, Smith FA, et al. 1982b. Metabolic fate and evaluation of injury in rats and dogs following exposure to the hydrolysis products of uranium hexafluoride. Implications for a bioassay program related to potential releases of uranium hexafluoride. Govt Rep Announce Ind, Issue 11. NTIS/NUREG/CR-2268. 

In view of the instability of the trioxide it is interesting to speculate on the stability of the oxyfluorides. Xenon oxide tetrafluoride should be an exothermic compound since the atomic heat of formation using average bond energies of 32 kcal. and 17 kcal. respectively for Xe-F and Xe-O is —160 kcal. mole-. The combined heat of atomization of four fluorine atoms (4 x 18.3 kcal.) and one oxygen atom (59.2 kcals.), 132.4 kcal., is less than this. Xenon dioxide difluoride, by such considerations, should be endothermic. It is of interest that xenon oxide tetrafluoride is easily made by controlled hydrolysis of xenon hexafluoride and is a thermally stable entity (m.p. —28) whereas xenon dioxide difluoride has been observed only mass spectrometrically < >. 

Xenon difluoride dissolves in water, yielding a solution which contains undissociated XeFa molecules which have a half-life of about 7 hours at 0°. It eventually hydrolyzes to yield the expected products, xenon, hydrogen fluoride, and oxygen. The hydrolysis reactions of the tetrafluoride and hexafluoride are somewhat more complicated. The addition of the stoichiometric amount of water to the hexafluoride results in the formation of xenon oxide tetrafluoride. Hydrolysis of either fluoride with an excess of water or acid yields in solution a stable xenon(VI) species, which has been shown to be hydrated xenon trioxide. Removal of the excess water leaves xenon trioxide as a solid residue. Inasmuch as this solid is an extremely sensitive explosive, such solutions must be handled with care. 

Hydrolysis of xenon hexafluoride or tetrafluoride with a sodium hydroxide solution results in the precipitation of a stable xenon (VIII) salt, sodium perxenate, Na4XeOe, which on heating does not decompose until around 300°. Similar hydrolysis with potassium hydroxide can yield a yellow precipitate which is a mixed potassium perxenate-xenon trioxide salt, and is explosive even when damp. With more concentrated base, the much more stable hydrated perxenate may be isolated. 

Xenon hexafluoride hydrolyzes in excess dilute acid or water to produce XeOa [Xe(VI)] in solution. Hydrolysis with strong base results in the precipitation of a perxenate salt [Xe(VIlI)]. Xenon hexafluoride is a fairly strong fluorinating agent, and it forms addition compounds w ith other fluorides such as BF3, AsFs, SbFs, and alkali metal fluorides. 

The xenon hexafluoride for this synthesis is best prepared by reaction of xenon with an excess of fluorine at 300° in a nickel or Monel apparatus. Extremely pure XeFs is not required. Xenon hexafluoride attacks glass, and should be stored in a nickel or Monel container until ready for use. The hydrolysis reaction is violent, and if more than a hundred milligrams of XeFe is to be hydrolyzed, special safety precautions must be taken. Face shields, heavy gloves, and a sturdy plastic explosion barrier between the hydrolysis apparatus and the experimenter are strongly recommended. No more than about 3 g. of XeFg should be hydrolyzed in one batch. 

Molybdenum hexafluoride, MoFj (mp 17 °C, bp 35 °C) [528], and molybdenum oxychloride, M0OCI3, which is prepared by the partial hydrolysis of molybdenum pentachloride [528], are suitable for the recovery of ketones from their dimethylhydrazones and tosylhydrazones under very mild conditions [525]. 

Uranium hexafluoride /77S5-87-5/ M 352.0, b 0 /17.4mm, 56.2 /765mm, m 64.8 , pK s 1.68 (for hydrolysis of U" " " to UOH " ). Piuify uranium hexafluoride by fractional distillation to remove HF. Also purify it by low-temperature trap-to-trap distillation over pre-dried NaF [Anderson Winfield... 

Preparation by hydrolysis of either xenon tetrafluoride or xenon hexafluoride. Oxidizing action,2 Xenic acid reacts readily with u/c-diols in neutral or alkaline solution the products are xenon (gas) and carboxylic acids. 

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