Hexafluoroplatinates
Platinum hexafluoride can gain an electron to form the hexafluoroplatinate anion, PtF6-. It is formed by reacting platinum hexafluoride with relatively uncationisable elements and compounds, for example with xenon to form "XePtF6" (actually a mixture of XeFPtF5, XeFPt2F11, and Xe2F3PtF6), known as xenon hexafluoroplatinate. The discovery of this reaction in 1962 proved that noble gases form chemical compounds. Previous to the experiment with xenon, PtF6 had been shown to react with oxygen to form +−, dioxygenyl hexafluoroplatinate.
Read more about this topic: Platinum Hexafluoride