Noble gases xenon fluorides

Since the discovery of the first noble gas compound, Xe PtF (Bartlett, 1962), a number of compounds of krypton, xenon, and radon have been prepared. Xenon has been shown to have a very rich chemistry, encompassing simple fluorides, XeF2> XeF, and XeF oxides, XeO and XeO oxyf luorides, XeOF2> XeOF, and Xe02 2 perxenates perchlorates fluorosulfates and many adducts with Lewis acids and bases (Bartlett and Sladky, 1973). Krypton compounds are less stable than xenon compounds, hence only about a dozen have been prepared KrF and derivatives of KrF2> such as KrF+SbF, KrF+VF, and KrF+Ta2F11. The chemistry of radon has been studied by radioactive tracer methods, since there are no stable isotopes of this element, and it has been deduced that radon also forms a difluoride and several complex salts. In this paper, some of the methods of preparation and properties of radon compounds are described. For further information concerning the chemistry, the reader is referred to a recent review (Stein, 1983). 

Among the noble gas fluorides, the binary fluorides of xenon have received the most attention as fluorinating agents. Krypton fluorides seem to be more exotic novelties than real reagents. 

There are currently two approaches to the problem of bonding in noble gas compounds. Neither is completely satisfactory, but between the two they account adequately for the properties of these compounds. The first might be termed a valence bond approach. It would treat the xenon fluorides by means of expanded valence shells through promotion uf electrons lo the SJ orbitals ... 

Xenon is much more reactive, forming a number of different fluorides, fluorocations, fluoroanions, oxides, and oxofluorides. The first noble gas compound to be discovered contained xenon— the orange/yeUow solid Xe+LPtFel" discovered by Bartlett 12) in 1962. The oxidation... 

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,... 

For xenon fluorides and oxides, for example, the same models can be apphed as for interhalogen and halogen oxy species. Furthermore, the very successful valence shell electron pair repulsion (VSEPR) rules for molecule and ion shapes are as effective for noble gas compounds and their relatives as for classical octet compounds. 

Malm, Bone, and Holt, The Hydrolysis of Xenon Fluorides and the Isolation of Stable Xenates , H. H. Hyman, ed. Noble Gas Compounds , University of Chicago Press (1963). 

Diatomic noble gas ions and diatomic hydride ions involving argon have been observed since the i930 s 11 and [ArN]+ 50) and [Arl]+ S1) were observed in collision experiments in mass spectrometers in 1960. However, none of these species were isolable as stable solids. Following the discovery of stable krypton and xenon fluorides and, in particular, recognition of the enhanced stability of [KrF]+ and [XeF]+ in crystalline solids, there has been renewed interest in the possibility of obtaining other related species. 

Since Bartlett s discovery, many other noble gas compounds have been made. All involve very electronegative elements. Most are compounds of Xe, and the best characterized compounds are xenon fluorides. Oxygen compounds are also well known. Reaction of Xe with F2, an extremely strong oxidizing agent, in different stoichiometric ratios produces xenon difluoride, Xep2 xenon tetrafluoride, XeF and xenon hexafluoride, XeFg, all colorless crystals (Table 24-3). 

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