xenone Oxides

   Equations 1.1 and 1.2 showed the formation of XeO₃ by hydrolysis of XeF₄ and XeF₆. Solid XeO₃ forms colourless crystals and is dangerously explosive (∆_fH^o)298K(= ‏402 kJ mol^-1). The solid contains trigonal pyramidal molecules (1.1). Xenon trioxide is only weakly acidic and its aqueous solution is virtually non-conducting. Reactions of XeO₃ and MOH (M = K, Rb, Cs) produce xenates (equation 1.3) which slowly disproportionate in olution (equation 1.4).

       (1.1)

                                (1.2)

   (1.1)

                                                         (1.3)

      (1.4)

   Aqueous [XeO₆]^4-  is formed when O₃ is passed through a dilute solution of XeO₃ in alkali. Insoluble salts such as Na₄XeO₆.8H₂O and Ba₂XeO₆ may be precipitated, but perxenic acid ‘H₄XeO₆ (a weak acid in aqueous solution) has not been isolated. The perxenate ion is a powerful oxidant and is rapidly reduced in aqueous acid (equation 1.5); oxidations such as Mn(II) to [MnO₄]^- occur instantly in acidic media at 298 K.

      (1.5)

    Xenon tetraoxide is prepared by the slow addition of concentrated H₂SO₄ to Na₄XeO₆ or Ba₂XeO₆. It is a pale yellow, highly explosive solid (∆_fH^o(298K) = 642 kJ mol^-1) which is a very powerful oxidizing agent.  Tetrahedral XeO₄ molecules (1.3) are present in the gas phase.

(1.3)