Tetraxenonogold(II), gold tetraxenide(II) or AuXe2+ 4 is a cationic complex with a square planar configuration of atoms. It is found in the compound AuXe2+ 4(Sb 2F− 11) 2 (tetraxenonogold(II) undecafluorodiantimonate), which exists in triclinic and tetragonal crystal modifications. The AuXe2+ 4 ion is stabilised by interactions with the fluoride atoms of the counterion. The Au−Xe bond length is 274 pm. Tetraxenonogold(II) is unusual in that it is a coordination complex of xenon, which is weakly basic. It is also unusual in that it contains gold in the +2 oxidation state. It can be produced by reduction of AuF3 by xenon in the presence of fluoroantimonic acid. The salt crystallises at low temperature. Four xenon atoms bond with the gold(II) ion to make this complex. 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. Several related compounds containing gold(III)–xenon and gold(I)–xenon bonds have since been isolated. A compound containing a mercury–xenon bond [HgXe]2+[Sb2F11]–[SbF6]– (xenonomercury(II) undecafluorodiantimonate hexafluoroantimonate) has also been isolated.