Synthese und Struktur von Graphit-Einlagerungsverbindungen des Quecksilber(II)-chlorids / Synthesis and Structure of the Graphite Intercalation Compounds of Mercuric Chloride

Abstract

Graphite intercalation compounds (GICs) of mercuric chloride have been synthesized by four different methods: via the vapour phase, from melts of pure HgCl2, from melts of HgCl2, and alkali metal chlorides, and from solutions in concentrated aqueous HCl. Compounds of stages 4, 3 and 2 were obtained, respectively. GICs prepared from solution always show staging disorder. Pure stage compounds of stage three and four exhibit the following repeat distances along the c⃗ axis: c(3) = 1632 pm; c(4) = 1968 pm. Further structural analysis is hindered by the disorder phenomena common to GICs. Rather surprisingly, monochromatic Laue photographs probing the in-plane order of the intercalate reveal that - regardless of the preparation method - the diffraction patterns of all compounds are identical. The main phase possesses a monoclinic in-plane lattice with cell dimensions: a = 390(4) pm, b = 412(4) pm, γ = 108.6(3)°. A structure which resembles certain features of the structure of pristine HgCl2 is proposed for this phase. Another unidentified phase seems to stabilize this structure in spite of different amounts of chlorine excess probably occurring in compounds prepared in different ways.