Preparation, Thermal Behaviour and Crystal Structure of the Basic Mercury(II) Tetraoxotellurate(VI), Hg 2 TeO 5 , and Redetermination of the Crystal Structure of Mercury(II) Orthotellurate(VI), Hg 3 TeO 6

Single crystals of Hg 2 TeO 5 were obtained as dark‐red parallelepipeds by reacting stoichiometric amounts of Hg(NO 3 ) 2 · H 2 O and H 6 TeO 6 under hydrothermal conditions (250 °C, 10d). The crystal structure (space group Pna 2 1 , Z = 4, a = 7.3462(16), b = 5.8635(12), c = 9.969(2)Å, 1261 structure factors, 50 parameters, R [ F 2 > 2 σ ( F 2 )] = 0.0295) is characterized by corner‐sharing [TeO 6 ] octahedra forming isolated chains   ∞ 1 [TeO 4/1 O 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 Hg 3 TeO 6 were prepared by heating a mixture of Hg, HgO and TeO 3 together with small amounts of HgCl 2 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 Ia 3¯ d to Ia 3¯ ( Z = 16, a = 13.3808(6) Å, 609 structure factors, 33 parameters, R [ F 2 > 2 σ ( F 2 )] = 0.0221). The crystal structure is made up of a body‐centred packing of [TeO 6 ] 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 TeO 2 and loss of the appropriate amounts of elementary mercury and oxygen.