The Cesium Oxide Mercuride Cs18Hg8O6

Abstract

By reacting Cs with Cs2O and elemental mercury the new double salt Cs18Hg8O6 could be obtained. Its crystal structure (cubic, space group I23 with a=13.3920(10) Å, Z=2, R1=0.026/0.032 for I≥2σ(I)/all I, respectively) comprises isolated oxide anions in octahedral coordination by cesium cations next to the mercuride anion [Hg8]6−. This first isolated anion of mercury has cubic shape and is coordinated by cesium atoms capping the faces and the edges of the [Hg8]6− cube. The ionic character of the double salt is shown in DFT calculations of the electronic structure. Raman spectra show distinct features in the low energy region arising from the vibrations of the mercuride anion. Cs18Hg8O6 has very close structural analogies to the thallide oxide Cs18Tl8O6.