Xenon—oxygen bonds

Following Bartlett s discovery of xenon hexafluoroplatinate(VI), xenon and fluorine were found to combine to give several volatile, essentially covalent fluorides, and at least one fluoride of krypton has been obtained. From the xenon fluorides, compounds containing xenon-oxygen bonds have been made much of the known chemistry of xenon is set out in Figure 12.1. 

Inasmuch as the energy of a xenon-oxygen bond is only about 88 kJ/mole ( ), F atoms should be able to extract oxygen from such molecules as XeOij and XeOFij. These reactions do not, however, appear to have been investigated. 

In 1979, Lagow and co-workers reported the first evidence for a compound with a bond between xenon and carbon, namely Xe(CF3)2 (90). While the evidence for this compound still receives much scrutiny, the groups of Frohn and Naumann independently synthesized the first definitive examples of compounds with a xenon-carbon bond (91-96). Until recently all of the examples of xenon-carbon bonds were cationic species. However, earlier this year Frohn reported the preparation, characterization, and structure of C6F5Xe02CC6F5, the first truly covalent compound with not only a xenon-carbon bond, but a xenon-oxygen bond as well (97). 

The shapes of the Xe03 and Xe04 molecules are correctly predicted by VSEPR theory when two of the eight xenon electrons are used to form each xenon-oxygen bond. 

In the past 40 years, compounds have been isolated in which xenon is bonded to several nonmetals (N, C, and Cl) in addition to fluorine and oxygen. In the year 2000, it was reported [Science, Volume 290. page 117) that a compound had been isolated in which a metal atom was bonded to xenon. This compound is a dark red solid stable at temperatures below -40°C it is believed to contain the [AuXe4F+ cation. 

On page 835 it is stated that xenon forms bonds with only the most electronegative elements such as the very active fluorine and oxygen. How can you reconcile this with Ihe formation of the Xc—Xe bond in Xe Winr Rethink Problem 5.15.J... 

All xenon-oxygen compounds are very strongly oxidising, and some decompose explosively. Compounds with Xe O bonds attaching polyatomic groups are known, and weak Xe N and Xe C bonds can also be formed, as in Xe(CF3)2, which decomposes rapidly at room temperature. 

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. 

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