Reactions of xenon fluorides

Much of the chemistry of the xenon fluorides centers on their reactions with aqueous solutions. Owing to its greater ionic character, the reaction of XeF2 with water is much slower than those of XeF4 and XeF6. In fact, XeF2 can be dissolved in water to produce relatively stable solutions. The slow hydrolysis reaction of XeF2 can be shown as follows  

In basic solution, the reaction is rapid and is represented by the equation 

The reaction of XeF4 with water is extremely vigorous, and it occurs as a result of a disproportionation reaction that is similar to that of the halogens  

In this process, Xe(IV) reacts to produce Xe(VI) and Xe(0). The oxide, Xe03, is a dangerously explosive compound. Hydrolysis of XeF6 also produces this oxide as a product of the following reaction  

However, this reaction appears to take place in two steps as shown by the following equations  

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Xenon also forms many fluoroanions and their salts, mostly prepared from xenon tetrafluoride and hexafluoride. Such compounds include Na+XeFs and Cs" XeF7- formed by reactions of xenon fluorides with sodium fluoride or cesium fluoride. The dicesium xenon octafluoride, Cs2XeFs, is a stable yellow solid that decomposes above 400°C. 

C. Reactions of Xenon Fluorides with Aromatic Molecules. 842... 

The pure, crystalline chromium (V) oxide trifluoride can be prepared by the reaction of xenon(II) difluoride and chromium (VT) dioxide difluoride [7788-96-7], also known as chromyl fluoride, Cr02F2 (56) ... 

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],... 

Many of the reactions that xenon fluorides undergo are similar in some ways to those of interhalogens. However, the xenon halides differ markedly in terms of their reactivity, with XF2 being much less reactive than either XeF4 or XeF6. The difluoride reacts only slowly with water,... 

Phosphorus trifluoride has been used as a reactant gas in calorimetry to act as a fluorine acceptor rather than donor. The heats of formation of xenon fluorides have been calculated from the reaction heats (137) ... 

Heats of formation for a complete set of Group VILA fluorides are unavailable, but a set of xenon fluoride cations, isoelectronic with iodine fluorides, exhibits the alternating pattern expected for odd- and even-electron molecules. The original energy-level diagram for stepwise fluorine dissociation is shown in Fig. 5. The tabulated values were derived from the ionization energies of XeF and the threshold values for XeFJ — XeF, - + F, where n is even (27), together with heats of formation obtained by reaction calorimetry (137). 

Bartlett prepared xenon difluoride by the reaction of xenon with silver fluoride in hydrofluoric acid in the presence of boron trifluoride ... 

The case with which highly expl Xe03 may be formed at room temp by reaction of Xe fluorides with moisture has been strongly emphasized (Refs 2, 3 4). Xenon trioxide, Xe03, is a wh sol comparable in deton sensitivity to nitrogen triiodide and in expl force to TNT Refs 1) N. Bartlett P.R. Rao, Science 139, 506 (1963) 2) D.F. Smith, JACS 85, 816... 

The reaction of xenon difluoride with a series of cis- and trans-phenyl substituted alkenes was examined in detail. 1,1-Diphenylethene, l,1-diphenyl-2-fluoroethene and 1.1-diphenyl-propene form vicinal 1,2-difluoro derivatives in 65 95% yield in dichloromethane solution with hydrogen fluoride as the catalyst.29-32 Two possible mechanisms were discussed.33... 

Xenon reacts directly with fluorine to form fluorides. Other compounds of Xe can be prepared by reactions using xenon fluorides as starting materials, which fall into four main types ... 

In 1962, Neil Bartlett produced a reaction of xenon, the first reported reaction of any noble gas. Later it was found that fluorine reacts directly with xenon to give one of three xenon fluorides, depending on temperature and pressure. Because all the products and the reactants are colorless, the easiest way to tell that a reaction is occurring is the drop in the total pressure of the system as the number of moles of gas decreases. For example,... 

The first synthesis of XeFe was also reported in 1962. All syntheses are best carried out in nickel or monel reaction vessels. From the equilibrium constants for the formation of xenon fluorides, " it is evident that an excess of fluorine is necessary to minimize the formation of Xep4. In addition, the reaction temperature should be as low as possible, yet consistent with a reasonable reaction rate. In the presence of Nip2 as catalyst the activation energy for the xenon-fluorine reaction is lowered and the reaction proceeds rapidly at 393 K, in contrast to 523 K without catalyst. 

Xe02p2 was observed in the early mass spectra of xenon fluorides and can be obtained by hydrolysis of XeFe. The best method for its preparation in macroscopic quantities is by the reaction of XeOs and XeOp4. The XeOp4 and Xep2 impurities may be removed by fractional distillation. Xenon dioxide difluoride forms colorless crystals at room temperature, which have a vapor pressure between that of XeOs and XeOp4 and melts at 303.95 K to give a colorless liquid. It can decompose to Xep2 and O2. 

CsHXe04 has been prepared by the reaction of xenon trioxide with aqueous cesium hydroxide in the presence of fluoride ion. The role of the fluoride ion in the preparation of CsHXe04 is not clear, but it seems that it prevents the formation of perxenate. In the absence of the fluoride ion, xenon trioxide and cesium hydroxide form a mixed perxenate and xenate salt. CsHXe04 is stable in air. 

REACTIONS OF THE OXIDES OF NITROGEN 5.8 REACTIONS WITH XENON FLUORIDES... 

A simple model predicts that the ease of removal of a fluoride ion from a xenon fluoride molecule should decrease in the order XeF > Xe 4 > Xep6, as the oxidation number and positive charge on the xenon atom rise. That the actual sequence is XeFe > Xep2 > Xep4, was first indicated by comparative Studies of reactions of the fluorides with acceptors, and was later confirmed by enthalpy measurements for the processes ... 

With the exception of the reactions of xenon with the powerful flu-orinating agent PtF6 and its relatives, all of the chemistry of xenon has been derived from reactions of the binary fluorides. 

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