The preparation and structure of chain and sheet mercury compounds

Abstract This paper is a review of the preparation and structures of the polymercury cations Hg32+ and Hg32+, the mercury chain compounds, Hg3-δAsF6, Hg3-δSbF6, Hg3-δ NbF6 and Hg3_δTaF6, and the mercury layer compounds Hg3NbF6 and Hg3TaF6. The chain compounds Hg3-δMF6 are hard, golden yellow insoluble crystals with a shiny metallic appearance that have linear chains of mercury atoms parallel to the a and b axes of a tetragonal cell. They are non-stoichiometric because the Hg-Hg distance is not com mensurate with the tetragonal lattice of AsF6− octahedra. The layer compounds have a silver colour with a distinct metallic lustre, but they are quite soft. They have sheets of hexagonally close-packed mercury atoms separated by a layer of NbF6− or TaF6− octahedra. In contrast to the chain compounds the layer compounds are stoichiometric. The interconversion of the chain and layer compounds is described and discussed.