Noble gases xenon compounds

O O In the early 1960s, Neil Bartlett, at the University of British Columbia, was the first person to synthesize compounds of the noble gas xenon. A number of noble gas compounds (such as XeF2, XeF4, XeFe, and XeOs) have since been synthesized. Consider the reaction of xenon difluoride with fluorine gas to produce xenon tetrafluoride. 

Hydrazine can be stabilized by formation of an inclusion compound with hydroquinone.58 Uncomplexed anhydrous hydrazine can be explosive. Highly toxic dimethyl sulfate can be handled more easily as an inclusion compound with toxic 18-crown-6. Both of these toxic compounds could be avoided through the use of dimethyl carbonate (as described in Chap. 2). Reactive intermediates, such as benzyne, have been stabilized by generating them inside hosts.59 Even the noble gas xenon can be trapped reversibly by hosts such as a cryptophane, 4-ferf-butyl-calix[4]arene or a-cyclodextrin.60... 

Fig. 4.8 Representation of all non-equivalent bonds of the Ng2 C6o compound. The activation energies (in kcal mop ) corresponding to the Diels-Alder cycloaddition reaction between 1,3-butadiene and all non-equivalent bonds for all considered noble gas endohedral compounds. Ng2 Cjo has been represented on the right. A grey scale has been used to represent the different noble gases endohedral compounds black color is used to represent the helium-based fullerene, light grey for neon, medium grey for argon, dark grey for krypton, and white for xenon...

Stable noble-gas compounds have no industrial uses as of this writing but are frequently utilized in laboratories as fluorinating and oxidizing agents. Xenon difluoride and xenon tetrafluoride are relatively mild oxidative fluorinating agents and have been used for the preparation of phosphoms, sulfur, tellurium. 

The chemistry of xenon is much more extensive than that of any other noble gas. Only one binary compound of krypton. KrF2, has been prepared. It is a colorless solid that decomposes at room temperature. The chemistry of radon is difficult to study because all its isotopes are radioactive. Indeed, the radiation given off is so intense that it decomposes any reagent added to radon in an attempt to bring about a reaction. 

Xenon is the only noble gas known to form an extensive series of compounds... 

Stable noble gas compounds are restricted to those of xenon. Most of these compounds involve bonds between xenon and the most electronegative elements, fluorine and oxygen. More exotic compounds containing Xe—S, Xe—H, and Xe—C bonds can be formed under carefully controlled conditions, for example in solid matrices at liquid nitrogen temperature. The three Lewis structures below are examples of these compounds in which the xenon atom has a steric munber of 5 and trigonal bipyramidal electron group geometry. 

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). 

Stein, L., Noble Gas Compounds New Methods for Collecting Radon and Xenon, Chemistry 47, No. 9, 15-20 (1974). 

The difference in the ionization potentials of xenon and krypton (1170 versus 1351 kj/mol) indicates that krypton should be the less the reactive of the two. Some indication of the difference can be seen from the bond energies, which are 133 kj/mol for the Xe-F bond but only 50 kj/mol for the Kr-F bond. As a result, XeF2 is considerably more stable of the difluorides, and KrF2 is much more reactive. Krypton difluoride has been prepared from the elements, but only at low temperature using electric discharge. When irradiated with ultraviolet light, a mixture of liquid krypton and fluorine reacts to produce KF2. As expected, radon difluoride can be obtained, but because all isotopes of radon undergo rapid decay, there is not much interest in the compound. In this survey of noble gas chemistry, the... 

For convenience, the even rarer and less stable krypton compounds are also covered in this entry. All xenon compounds are very strong oxidants and many are also explosively unstable. For a now obsolete review, see [1]. A recent compact review of noble gas chemistry is found in [2], A series of alkali xenates, MH0Xe03.1.5H20 are unstable explosive solids. The equivalent fluoroxenates MFXe03are far more stable. Individually indexed compounds are ... 

As a noble gas that is mostly inert, xenon is nontoxic and noncombustible. Some of its compounds are toxic and potentially explosive, but there is little chance of coming into contact with them on a day-to-day basis. 

Accordingly, he mixed xenon and PtFe and obtained the orange-yellow solid of xenon hexafluoroplatinate—the first noble gas compound. (Although in fact, the compound turned out not to have the structure that Bartlett predicted because at room temperature the XePtFe reacts with another molecule of PtFe to give a product containing [XeF]"[PtFe]- and [PtFslF)... 

As stated above, noble gas chemistry is almost restricted to that of xenon, with a few krypton compounds of lower stability and with the chemistry of radon largely unexplored, due to the short half-lives of its isotopes. Two reviews1,6 give good coverage of more recent noble gas chemistry. 

According to Klimov (Ref 2) the tetrafluoride is resistant to deton. However, because of its high reactivity, very sensitive explns result from contact with flammable materials such as acet, polyethylene, wool, paper, sawdust, Al foil, ferric carbonyl, lubricants or styrene Refs 1) J.H. Holloway, Noble-Gas Chemistry , Methuen, London (1968), 95 ff 2) BD. Klimov et al, Explosion Hazard During Work With Fluorine Containing Xenon Compounds , Zh Prikl Khim (Leningrad) 42 (12), 2822-24 (1969) CA 72, 85784 (1970) 3) T.C. 

Thorough studies of solutions of xenon in boron trichloride and boron iribromide were undertaker. A phase study of the melting point of these systems sis a function of composition showed no evidence of compound formation. The Raman spectra of these mixtures are identical to those of pure BX, indicating no noble gas-boron trihalide interactions. 

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