Neil Bartlett observed that $\mathrm{PtF}_6$ reacts with $\mathrm{O}_2$ to yield an ionic solid,$\mathrm{O}_2^{+}\,\mathrm{PtF}_6^{-}$.Here, $\mathrm{O}_2$ gets oxidised to $\mathrm{O}_2^{+}$ by $\mathrm{PtF}_6$.Since the first ionisation enthalpy of Xe(1170 kJ mol$^{-1}$) is fairly close tothat of $\mathrm{O}_2$ molecule (1175 kJ mol$^{-1}$), Bartlett thought that $\mathrm{PtF}_6$should alsooxidise Xe. When Xe and $\mathrm{PtF}_6$ were mixed, a rapid reaction took place anda red solid with the formula, $\mathrm{Xe}^{+}\mathrm{PtF}_6^{-}$was obtained.$\mathrm{Xe} + \mathrm{PtF}_6 \xrightarrow{278\,\text{K}} \mathrm{Xe}^{+} [\mathrm{PtF}_6]^{-}$