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Noble-Gas Chemistry 461

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The corresponding HeF and NeF cations are predicted are already in their highest attainable oxidation states as is
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to be unstable. Experimental evidence for ArF in the gas exemplified by the fluorination of OsO 4 to cis-OsO 2 F 4 and
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phase has been obtained, leading to D o (ArF ) ≥ 1.655 eV TcO 2 F 3 to TcOF 5 by KrF 2 , and XeOF 4 to XeF by KrF .
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and confirming the instability of HeF and NeF in their Aqueous solutions of sodium perxenate and of xenon tri-
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electronic ground states. The electronegativity values as- oxide are intermediate in oxidizing strength and are useful
signed to the compound-forming noble gases (Ar, 3.2; Kr, for analyzing manganese and alcohols and carboxylic
2.9; Xe, 2.3; Rn, 2.1) and those predicted for the noble acids, respectively. Radon-222, an air contaminant in
gases which presently do not form compounds (He, 5.2; uranium mines, can be analyzed by means of oxidants that
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Ne, 4.5) suggest that the values for argon and krypton are form nonvolatile radon salts, e.g., O (dioxygenyl) cation
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rather close and that efforts to synthesize an ArF salt salts.
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are realistic. The ArF cation is expected to be an even
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stronger oxidant than KrF , making it an oxidizer of un-
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precedented strength. However, unlike KrF , which can SEE ALSO THE FOLLOWING ARTICLES
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only be synthesized from KrF 2 , any synthesis of an ArF +
salt cannot rely upon the difluoride precursor. Theoretical NOBLE METALS • PERIODIC TABLE (CHEMISTRY) • RARE
calculations also suggest that HC N ArF may be stable EARTH ELEMENTS AND MATERIALS
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(see Sections III.E and IV.C).
BIBLIOGRAPHY
VII. APPLICATIONS
Bartlett, N., and Sladky, F. O. (1973). The chemistry of krypton, xenon
Stable noble-gas compounds have no industrial uses and radon. In “Comprehensive Inorganic Chemistry” J. C. Bailar, Jr.,
at present but are frequently utilized in laboratories H. J. Emel´eus, R. Nyholm, and A. F. Trotman-Dickenson, eds.), Vol.
as fluorinating and oxidizing agents. Xenon difluoride 1, pp. 213–330, Pergamon, New York.
and xenon tetrafluoride are relatively mild oxidative Hyman, H. H., ed. (1963). “Noble Gas Compounds,” Univ. of Chicago
Press, Chicago.
fluorinating agents and have been used for the preparation
Laszlo, P., and Schrobilgen, G. J. (1988). Angew. Chem. Int. Ed. Engl.
of phosphorus, sulfur, tellurium, and silicon derivatives. 27, 479.
Xenon difluoride has proven to be a versatile and stable Schrobilgen, G. J., and Whalen, J. M. (1994). Helium-group gases, com-
fluorinating agent for use in synthetic organic chemistry. pounds. In “Kirk-Othmer Encyclopedia of Chemical Technology,” 4th
It has been used for the fluorination of alkenes in fluorode- ed., pp. 38–53, Chap. 13, Wiley, New York.
Schrobilgen, G. J. (1992). Lewis acid properties of noble gas cations. In
carboxylation and for the fluorination of thioethers and
“Synthetic Fluorine Chemistry,” (R. D. Chambers, G. A. Olah, and G.
aromatic and aliphatic compounds. Xenon hexafluoride K. S. Prakash, eds.), pp. 1–30, Chap. 1, Wiley, New York.
has been used to synthesize transition metal fluorides and Selig, H., and Holloway, J. H. (1984). Cationic and anionic complexes
oxofluorides, where the metal is in its highest oxidation of the noble gases. In “Topics in Current Chemistry” (F. L. Boschke,
ed.), Vol. 124, pp. 33–90, Springer-Verlag, Berlin.
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state, e.g., Xe 2 F AuF , TcO 2 F 3 . Krypton difluoride and Seppelt, K., and Lentz, D. (1982). Novel developments in noble gas
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11
its complex salts are extremely powerful oxidative fluo-
chemistry. In “Progress in Inorganic Chemistry” (S. J. Lippard, ed.),
rinating agents and can be used to oxidatively fluorinate pp. 167–202, Wiley, New York.
gold, silver, and halogen fluorides to their highest oxida- (1970). Edelgasverbindungen, In “Gmelins Handbuch der Anorganis-
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tionstates,e.g.,AuF 5 ,AgF ,ClF ,BrF (seeSectionIV). chen Chemie,” 8th ed., Main Supplement, Vol. 1, VCH, Weinheim/
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4 6 6
Krypton difluoride and XeF 6 have been used to form lan- New York.
ˇ Zemva, B. (1988). Croat. Chem. Acta 61, 163.
thanide(IV) fluorometallate complexes by the oxidation
ˇ Zemva, B. (1994). Noble gases: inorganic chemistry. In “Encyclopedia
of Ln(III) in anhydrous HF solvent. Krypton species can of Inorganic Chemistry,” (R. B. King, ed.), pp. 2660–2680, Vol. 5,
also be used to fluorinate oxocompounds of elements that Wiley, New York.