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

摘要

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 degreesdegreesC, 10d). The crystal structure (space group Pna2(1), Z = 4, a = 7.3462(16), b = 5.8635(12), c = 9.969(2) Angstrom, 1261 structure factors, 50 parameters, R[F-2 > 2sigma(F-2)] = 0.0295) is characterized by corner-sharing [TeO6] octahedra forming isolated chains (1)(infinity)[TeO4/O-1(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 degreesC). 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) over bard to Ia (3) over bar (Z = 16, a = 13.3808(6) Angstrom, 609 structure factors, 33 parameters, R[F-2 > 2sigma(F-2)] = 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. [References: 23]