Xenon hexafluoroplatinate is the product of the reaction of platinum hexafluoride with xenon, in an experiment that proved the chemical reactivity of the noble gases. This experiment was performed in 1962 by Neil Bartlett at the University of British Columbia, who formulated the product as "Xe+[PtF6]−", although subsequent work suggests that Bartlett's product was probably a salt mixture and did not in fact contain this specific salt.
Structure The material described originally as "xenon hexafluoroplatinate" is probably not Xe+[PtF6]−. The main problem with this formulation is "Xe+", which would be a radical and would dimerize or abstract a fluorine atom to give XeF+. Thus, Bartlett discovered that Xe undergoes chemical reactions, but the nature and purity of his initial mustard yellow product remains uncertain. Further work indicates that Bartlett's product probably also contained products of further oxidation by PtF6, platinum(V) derivatives PtF5, [XeF]+[PtF5]−, and [XeF]+[Pt2F11]−. The title "compound" is a salt, consisting of an octahedral anionic fluoride complex of platinum and various xenon cations.
It has been proposed that the platinum fluoride forms a negatively charged polymeric anion with xenon fluoride cations. A preparation of "XePtF6" by reaction of XeF2 and PtF4 in anhydrous HF solution results in a solid which has been characterized as a polymeric or oligomeric anion associated with XeF+. Such F-bridged polymeric chains and tetrameric ring with pendant XeF+ units have been observed in the crystal structures of the analogous compounds XeCrF6 (XeF2∙CrF4) and XeMnF6 (XeF2∙MnF4), respectively. These structures could serve as structural models for XePtF6.
Preparation Xenon hexafluoroplatinate is prepared from xenon and platinum hexafluoride (PtF6) as gaseous solutions in SF6. The reactants are combined at 77 K and slowly warmed to allow for a controlled reaction.
Discovery
In 1962, Neil Bartlett, together with his graduate student Derek Lohmann, discovered that a mixture of platinum hexafluoride gas and oxygen formed a red solid. The red solid turned out to be dioxygenyl hexafluoroplatinate, Bartlett noticed that the ionization energy for O2 (1175 kJ mol−1), was very close to the ionization energy for Xe (1170 kJ mol−1) – "Immediately, I realized that the heavier noble gases had ionization potentials like that of O2 [...]." He then asked his colleagues to give him some xenon "so that he could try out some reactions". He later recounted the discovery:
Although, as discussed above, the product was probably a mixture of several compounds, Bartlett's work was the first proof that compounds could be prepared from a noble gas. Since Bartlett's observation, many well-defined compounds of xenon have been reported including XeF2, XeF4, and XeF6.
See also Hexafluoroplatinate Xenon hexafluororhodate
References