Perxenate

Oxides. Two oxides of xenon are known xenon trioxide [13776-58-4], XeO, and xenon tetroxide [12340-14-6], XeO (Table 1). Xenon trioxide is most efftcientiy prepared by the hydrolysis of XeE (47) or by the reaction of XeE with HOPOE2 (48). The XeO molecule has a trigonal pyramidal shape Xe—O, 176(3) pm (49), and XeO is tetrahedral with Xe—O, 173.6(2) pm (50). Xenon tetroxide is prepared by the interaction of concentrated sulfuric acid with sodium or barium perxenate, Na XeO, Ba2XeO ( )- Both oxides are thermodynamically unstable, explosive soHds which must be... 

Xenates and Perxenates. Alkali metal xenates of composition MHXe04-1.5H20, where M is sodium, potassium, mbidium, or cesium, have been prepared by free2e-dryiQg mixtures of xenon trioxide and the corresponding metal hydroxides ia 1 1 molar ratios. The xenates are unstable, explosive solids. 

The aeid potential is exeeeded only by fluorine (p. 804), perxenate (p. 901), atomie O, the OH radieal, and a few other sueh potent oxidants. Deeomposition is rapid in aeid solutions but the allotrope is much more stable in alkaline solution. At 25° the half-life of O3 in 1 M NaOH is 2min eorresponding times for 5 m and 20 m NaOH are 40 min and 83 h respeetively. 

However, although some salts have been isolated, alkaline solutions are not stable and immediately, if slowly, begin to disproportionate into Xe (perxenates) and Xe gas by routes such as ... 

Xenon Tetroxide. Xe04, mw 195.30, colorl gas, mp -40° (explds). Prepn is by reacting sodium perxenate with coned sulfuric acid. Compd is v unstable... 

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). 

With the oxidation state of Xe in perxenates being +8, they are, as expected, very strong oxidizing agents. 

Pervaporation systems, 15 798 Perxenates, 17 326 Perylene Green (Yellow), colorant for plastics, 7 374t Perylene pigments, 19 443 commercial, 19 444t Perylene Red... 

As mentioned above, xenon trioxide is an endothermic compound which explodes violently at the slightest provocation. Aqueous solutions are stable but powerfully oxidizing. These solutions are weakly acidic ( xenic acid ) and contain molecular XeOj When these solutions are made basic. HXeO ions are formed and alkali hydrogen xenates, MHXe04, may be isolated from them. Hydrogen xenale ions disproportionate in alkaline solution to yield perxenates ... 

Xenate solutions may also be oxidized directly to perxenate with ozone. Solid perxenates are rather insoluble and are unusually stable for xenon-oxygen compounds Most do not decompose until healed above 200 eC. X-ray crystallographic structures have been determined for several perxenates. and they have been found to contain the octahedral XeC ion. which persists in aqueous solution (possibly with proionation to HXeOj"). 

Treatment of a perxenate salt with concentrated sulfuric acid results in the most unusual xenon letroxide ... 

Salts containing the octahedral Xe(VIII) perxenate ion Xe04-g are known, and by the action of acid the tetrahedral xenon teroxide Xe04 is formed. 

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