Krypton compound

The known compounds of krypton are limited to the +2 oxidation state, and the list includes the following  

Krypton difluoride KrF2 exists in two forms in the solid state a-KrF2 and /3-KrF2, whose crystal structures are shown in Fig. 17.5.8. Specifically, a-KrF2 

The Kr-F bond length in a-KrF2 is 189.4 pm and is in excellent agreement with those determined for /3-KrF2,189 pm, by X-ray diffraction and for gaseous KrF2 by electron diffraction, 188.9 pm. The interatomic F- F distance between collinearly orientated KrF2 molecules is 271 pm in both structures. 

Greenwood and A. Earnshaw, Chemistry of the Elements, 2nd edn., Butterworth-Heinemann, Oxford, 1997. 

G Massey, Main Group Chemistry, 2nd edn., Wiley, Chichester, 2000. 

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Naturally occurring krypton contains six stable isotopes. Seventeen other unstable isotopes are now recognized. The spectral lines of krypton are easily produced and some are very sharp. While krypton is generally thought of as a rare gas that normally does not combine with other elements to form compounds, it now appears that the existence of some krypton compounds is established. Krypton difluoride has been prepared in gram quantities and can be made by several methods. A higher fluoride of krypton and a salt of an oxyacid of krypton also have been... 

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). 

Kroll process, 13 84-85 15 337 17 140 in titanium manufacture, 24 851-853 Kroll zirconium reduction process, 26 631 KRW gasifier, 6 797-798, 828 Krypton (Kr), 17 344 commercial, 17 368t complex salts of, 17 333-334 doubly ionized, 14 685 hydroquinone clathrate of, 14 183 in light sources, 17 371-372 from nuclear power plants, 17 362 physical properties of, 17 350 Krypton-85, 17 375, 376 Krypton compounds, 17 333-334 Krypton derivatives, 17 334 Krypton difluoride, 17 333, 336 uses for, 17 336... 

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 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. 

Ketone peroxides, 198 Ketoximinosilanes, 199 Kinetics and instability, 199 Kjeldahl method, 199 Kondratiev cycles, 199 Krypton compounds, 200... 

No krypton compounds appear to thermodynamically stable, but KrF2 can be made from the elements in an electric discharge at very low temperatures, and a few compounds of the cationic species [KrF]+ and [Kr2F3]+ are also known. As the ionisation energy of Kr is higher than that of Xe, the lower stability of krypton compounds is expected from the bonding models shown in structures 1 and 2, where Xe carries a formal positive charge. 

Krypton Compounds with Bonds to Oxygen and Nitrogen... 

Kr(OTeF5)2 is the first krypton compound containing a krypton-oxygen bond. It was prepared by the reaction between KrF2 and B(OTeFs)3 at 183-161 K in SO2CIF as solvent. ... 

For many years, krypton was thought to be completely inert. Then, in the early 1960s, it was found to be possible to make certain compounds of the element. English chemist Neil Bardett (1932—2008) found ways to combine noble gases with the most active element of all, fluorine. In 1963, the first krypton compounds were made—krypton difluoride (KrF2) and krypton tetrafluoride (KrF4). Other compounds of krypton have also been made since that time. FFowever, these have no commercial uses. They are only laboratory curiosities. 

One might have expected oxo-anions [16] of Kr(VI) or Kr(VIII) (Br04 was prepared in 1968), but the only well-characterized krypton compounds are the rather unstable linear molecule FKrF and the Kr(II) salts such as KrF SbFg and KrF" AuFg containing an octahedral 5d gold(V) complex anion. There are good reasons to believe from quantum mechanical calculations (see Sect. 4.3 of... 

Xe, the lower stability of krypton compounds is expected from the bonding models shown in structures 1 and 2, where Xe carries a formal positive charge. 

The existence of krypton and xenon compounds inevitably raises the question as to whether noble-gas chemistry might be extended to argon. The increasing range of krypton compounds that have been synthesized over the last 10 years, and in particular the recent observation of Kr-0 and Kr-N species, will undoubtedly further stimulate interest in this area. 

In 1962 the first chemical noble gas compound, formulated as XePtFg, was synthesized by Neil Bartlett. This result spurred intense research activity and led to the discovery of numerous xenon and krypton compounds. In 2000 the formation of the first argon compound, argon fluorohydride (HArF), was reported by Leonid Khriachtchev and colleagues, see also Argon Cavendish, Henry Helium Krypton Neon Ramsay, William Ruthereord, Ernest Soddy, Frederick Strutt, John Xenon. 

The only known krypton compound for which data are available is Krp2... 

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