Preparation and Crystal Structures of the Hydrous Mercury Tellurates, Hg II (H 4 Te VI O 6 ) and Hg I 2 (H 4 Te VI O 6 )(H 6 Te VI O 6 )·2H 2 O

Single crystals of Hg II (H 4 Te VI O 6 ) (colourless to light‐yellow, rectangular plates) and Hg I 2 (H 4 Te VI O 6 )(H 6 Te VI O 6 )·2H 2 O (colourless, irregular) were grown from concentrated solutions of orthotelluric acid, H 6 TeO 6 , and respective solutions of Hg(NO 3 ) 2 and Hg 2 (NO 3 ) 2 . The crystal structures were solved and refined from single crystal diffractometer data sets (Hg II (H 4 Te VI O 6 ): space group Pna 2 1 , Z = 4, a =10.5491(17), b = 6.0706(9), c = 8.0654(13)Å, 1430 structure factors, 87 parameters, R [ F 2 > 2 σ ( F 2 )] = 0.0180; Hg I 2 (H 4 Te VI O 6 )(H 6 Te VI O 6 )·2H 2 O: space group P 1¯, Z = 1, a = 5.7522(6), b = 6.8941(10), c = 8.5785(10)Å, α = 90.394(8), β = 103.532(11), γ = 93.289(8)°, 2875 structure factors, 108 parameters, R [ F 2 > 2 σ ( F 2 )] = 0.0184). The structure of Hg II (H 4 Te VI O 6 ) is composed of ribbons parallel to the b axis which are built of [H 4 TeO 6 ] 2— anions and Hg 2+ cations held together by two short Hg—O bonds with a mean distance of 2.037Å. Interpolyhedral hydrogen bonding between neighbouring [H 4 TeO 6 ] 2— groups, as well as longer Hg—O bonds between Hg atoms of one ribbon to O atoms of adjacent ribbons lead, to an additional stabilization of the framework structure. Hg I 2 (H 4 Te VI O 6 )(H 6 Te VI O 6 )·2H 2 O is characterized by a distorted hexagonal array made up of [H 4 TeO 6 ] 2— and [H 6 TeO 6 ] octahedra which spread parallel to the bc plane. Interpolyhedral hydrogen bonding between both building units stabilizes this arrangement. Adjacent planes are stacked along the a axis and are connected by Hg 2 2+ dumbbells ( d (Hg—Hg) = 2.5043(4)Å) situated in‐between the planes. Additional stabilization of the three‐dimensional network is provided by extensive hydrogen bonding between interstitial water molecules and O and OH‐groups of the [H 4 TeO 6 ] 2— and [H 6 TeO 6 ] octahedra. Upon heating Hg I 2 (H 4 Te VI O 6 )(H 6 Te VI O 6 )·2H 2 O decomposes into TeO 2 under formation of the intermediate phases Hg II 3 Te VI O 6 and the mixed‐valent Hg II Te IV/VI 2 O 6 .