Page 335 - Arrow Pushing in Inorganic Chemistry A Logical Approach to the Chemistry of the Main Group Elements

8.11 KRYPTON DIFLUORIDE 315

3KrF + Xe → XeF + 3 Kr (8.57)
2 6
∘
At 60 C, the gold-containing salt decomposes to yield the molecular fluoride Au F :
2 10
+ −
2KrF AuF 6 → Au F + 2Kr + 2F 2 (8.58)
2 10
The molecular structure of Au F is as follows:
2 10
F + F
− −
F F F
Au Au
F F
F
F + F
+
KrF transfers a fluoride ion to strong Lewis acids such as SbF , forming the KrF cation:
2
5
+ −
KrF + SbF → KrF SbF 6 (8.59)
5
2
+
The KrF cation is one of the strongest oxidants known. As mentioned in Section 7.8, it
+
oxidizes ClF and BrF to ClF + and BrF , respectively:
5 5 6 6
+ − + −
XF + KrF SbF → XF SbF + Kr (X = Cl, Br) (8.60)
5 6 6 6
Recall that, unlike iodine, chlorine and bromine do not form uncharged XF molecules.
7
REVIEW PROBLEM 8.9

Suggest a mechanism for the above reaction leading to XF 6 + salts.

REVIEW PROBLEM 8.10

Use of the teflate ligand permitted the synthesis of the first species containing a
krypton–oxygen bond (Sanders, J. C. P.; Schrobilgen, G. J. J. Chem. Soc., Chem.
Comm. 1989, 1576–1578). The synthesis involved the interaction of KrF and
2
∘
B(OTeF ) at low temperature (−90 to −112 C) in SO ClF as solvent:
5 3
2
3KrF + 2B(OTeF ) → 3Kr(OTeF ) + 2BF 3
2
5 3
5 2
Because of thermal instability, the product, krypton “diteflate,” could be spectroscop-
ically characterized only in solution. Suggest a mechanism for this reaction.