Preparation,Thermal Behaviour and Crystal Structure of the Basic Mercury(II) Tetraoxotellurate(VI), Hg2TeO5, and Redetermination of the Crystal Structure of Mercury(II) Orthotellurate(VI), Hg3TeO6

Single crystals of Hg₂TeO₅ were obtained as dark‐red parallelepipeds by reacting stoichiometric amounts of Hg(NO₃)₂ · H₂O and H₆TeO₆ under hydrothermal conditions (250 °C, 10d). The crystal structure (space group Pna2₁, Z = 4, a = 7.3462(16), b = 5.8635(12), c = 9.969(2)Å, 1261 structure factors, 50 parameters, RF² > 2σ(F²)] = 0.0295) is characterized by corner‐sharing TeO₆] octahedra forming isolated chains TeO_4/1O_2/2] which extend parallel to 100]. The two crystallographically independent Hg atoms are located in‐between the chains and interconnect the chains via common oxygen atoms. Amber coloured single crystals of Hg₃TeO₆ were prepared by heating a mixture of Hg, HgO and TeO₃ together with small amounts of HgCl₂ as mineralizer in an evacuated and sealed silica glass tube (520 °C). The previously reported crystal structure has been re‐investigated by means of single crystal X‐ray data which reveal a symmetry reduction from Ia3¯d to Ia3¯ (Z = 16, a = 13.3808(6) Å, 609 structure factors, 33 parameters, RF² > 2σ(F²)] = 0.0221). The crystal structure is made up of a body‐centred packing of TeO₆] octahedra with the Hg atoms situated in the interstices of this arrangement. Upon heating, both title compounds decompose in a one‐step mechanism under formation of TeO₂ and loss of the appropriate amounts of elementary mercury and oxygen.