Other compounds of xenon

   Members of a series of compounds of the type FXeA where, for example, A^- is [OClO₃]^- , [OSO₂F]^-,[OTeF₅]^- or [O₂CCF₃]^- have been prepared by the highly exothermic elimination of HF between XeF₂ and HA. Further loss of HF leads to XeA₂ (e.g. equation 1.1). Elimination of HF also drives the reaction of XeF₂ with HN(SO₃F)₂ to yield FXeN(SO₃F)₂, a relatively rare example of Xe^_N bond formation.

            (1.1)

(1.1)

   Xenon–carbon bond formation is now quite well exemplified, and many products contain fluorinated aryl substituents, e.g.(C₆F₅CO₂)Xe(C₆F₅), [(2,6-F₂C₅H₃N)XeC₆F₅]‏ (Figure 1.1a), [(2,6-F₂C₆H₃(Xe][BF₄] (Figure 1.1b), [(2,6-F₂C₆H₃)Xe][CF₃SO₃] and [(MeCN)Xe(C₆F₅)] ‏.

Fig. 1.1 The structures (X-ray diffraction) of (a) [(2,6-F₂C₅H₃N)Xe(C₆F₅)]⁺‏ in the [AsF₆]^- salt [H.J. Frohn et al. (1995) Z. Naturforsch., Teil B, vol. 50, p. 1799] and (b) [(2,6-F₂C6H₃)Xe][BF₄] [T. Gilles et al. (1994) Acta Crystallogr., Sect. C, vol. 50, p. 411]. Colour code: Xe, yellow; N, blue; B, blue; C, grey; F, green; H, white.

   The degree of interaction between the Xe centre and non-carbon donor (i.e. F, O or N) in these species varies. Some species are best described as containing Xe in a linear environment (e.g. Figure 1.1a) and others tend towards containing an [RXe]‏⁺ cation (e.g. Figure 1.1b). The compounds C₆F₅XeF and (C₆F₅)₂Xe are obtained using the reactions in scheme 1.2. Stringent safety precautions must be taken when handling such compounds; (C₆F₅)₂Xe decomposes explosively above 253 K.

   (1.2)

   The [C₆F₅XeF₂]⁺‏ ion (formed as the [BF₄]^- salt from C₆F₅BF₂ and XeF₄) is an extremely powerful oxidativefluorinating agent, e.g. it converts I₂ to IF₅. Compounds containing linear C^_Xe^_Cl units are recent additions to xenon chemistry, the first examples being C₆F₅XeCl (equation 1.3) and [(C₆F₅Xe)₂Cl]‏ (equation 1.4 and structure 1.2).

   (1.3)

                 (1.4)

(1.2)

  Compounds containing metal–xenon bonds have been known only since 2000. The first example was the square planar [AuXe₄]²⁺‏ cation (av. Au^_Xe = 275 pm). It is produced when AuF₃ is reduced to Au(II) in anhydrous HF/SbF₅ in the presence of Xe (equation 1.5).

                           (1.5)

   Removal of Xe from [AuXe₄][Sb₂F₁₁]₂ under vacuum at 195K leads to [cis-AuXe₂][Sb₂F₁₁]₂. The cis-description arises as a result of Au_F_Sb bridge formation in the solid state (diagram 1.3). The trans-isomer of [AuXe₂]^2‏+ is formed by reacting finely divided Au with XeF₂ in HF/ SbF₅ under a pressure of Xe, but if the pressure is lowered, the product is the Au(II) complex [XeAuFAuXe][SbF₆]₃.

(1.3)

   The ‏2 oxidation state is rare for gold. The acid strength of the HF/SbF₅ system can be lowered by reducing the amount of SbF₅ relative to HF. Under these conditions, crystals of the Au(III) complex 1.4 (containing trans-[AuXe₂F]₂‏) are isolated from the reaction of XeF₂, Au and Xe.

(1.4)

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