Preparation and crystal structures of the hydrous mercury tellurates, Hg-II((H4TeO6)-O-VI) and Hg-2(1)((H4TeO6)-O-VI)((HTeO6)-Te-6-O-VI)center dot 2H(2)O

摘要

Single crystals of Hg-II((H4TeO6)-O-VI) (colourless to light-yellow, rectangular plates) and Hg-2(I)((H4TeO6)-O-VI)((H6TeO6)-O-VI)(.)2H(2)O (colourless, irregular) were grown from concentrated solutions of orthotelluric acid, H6TeO6, and respective solutions of Hg(NO3)(2) and Hg-2(NO3)(2). The crystal structures were solved and refined from single crystal diffractometer data sets (Hg-II((H4TeO6)-O-VI): space group Pna2(1), Z = 4, a =10.5491(17), b = 6.0706(9), c = 8.0654(13) Angstrom, 1430 structure factors, 87 parameters, R[F-2 > 2sigma(F-2)] = 0.0180; Hg-2(I)((H4TeO6)-O-VI)((H6TeO6)-O-VI)(.)2H(2)O: space group P (1) over bar, Z = 1, a = 5.7522(6), b = 6.8941(10), c = 8.5785(10) Angstrom, alpha = 90.394(8), beta = 103.532(11), gamma = 93.289(8)degrees, 2875 structure factors, 108 parameters, R[F-2 > 2sigma(P)] = 0.0184). The structure of Hg-II((H4TeO6)-O-VI) is composed of ribbons parallel to the b axis which are built of [H4TeO6](2-) anions and Hg2+ cations held together by two short Hg-O bonds with a mean distance of 2.037 Angstrom. Interpolyhedral hydrogen bonding between neighbouring [H4TeO6](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-2(I)((H4TeO6)-O-VI)((H6TeO6)-O-VI)(.)2H(2)O is characterized by a distorted hexagonal array made up of [H4TeO6](2-) and [H6TeO6] 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) Angstrom) 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 [H4TeO6](2-) and [H6TeO6] octahedra. Upon heating Hg-2(I)((H4TeO6)-O-VI)((H6TeO6)-O-VI)(.)2H(2)O decomposes into TeO2 under formation of the intermediate phases (Hg3TeO6)-Te-II-O-VI and the mixed-valent (HgTe2O6)-Te-II-O-IV/VI.