The Mixed-Metal Oxochromates(VI) Cd(HgI2)2(HgII)3O4(CrO4)2, Cd(HgII)4O4(CrO4) and Zn(HgII)4O4(CrO4)—Examples of the Different Crystal Chemistry within the Zinc Triad

The three mixed-metal oxochromates(VI) Cd(HgI2)2(HgII)3O4(CrO4)2, Cd(HgII)4O4(CrO4), and Zn(HgII)4O4(CrO4) were grown under hydrothermal conditions. Their crystal structures were determined from single-crystal X-ray diffraction data. The crystal-chemical features of the respective metal cations are characterised, with a linear coordination for mercury atoms in oxidation states +I and +II, octahedral coordination spheres for the divalent zinc and cadmium cations and a tetrahedral configuration of the oxochromate(VI) anions. In the crystal structures the formation of two subunits is apparent, viz. a mercury-oxygen network and a network of cadmium (zinc) cations that are directly bound to the oxochromate(VI) anions. An alternative description of the crystal structures based on oxygen-centred polyhedra is also given.