A highly unusual compound of four xenon atoms bound to a gold atom.
“Tetraxenonogold(II) is unusual in that it is a compound of the notoriously inert atoms xenon and gold. It is also unusual in that it uses xenon as a transition metal ligand, and in that it contains gold in the +2 oxidation state. It can be produced by reduction of AuF3 in the presence of fluoroantimonic acid (the strongest superacid) and xenon, and crystallised at low temperature.
It was the first description of a compound between a noble gas and a noble metal. It was first described in 2000 by Konrad Seppelt and Stefan Seidel.”