THE CRYSTAL STRUCTURES OF THE MERCURY(II)-PERIODATES HgH₃IO₆ AND Hg₃(H₂IO₆)₂ AND THE NEW MERCURY(II)-OXIDE-SILVER-NITRATE AgHg₂NO₅

Thomas Mormann and Wolfgang Jeitschko

Anorganisch-Chemisches Institut, Universität Münster, Wilhelm-Klemm-Straße 8, D-48149 Münster, Germany
E-mail: mormann@nwz.uni-muenster.de

Keywords: Crystal Structure, Periodates, Mercuryoxides

The compounds HgH₃IO₆ and Hg₃(H₂IO₆)₂ have been prepared by Siebert and Fuckert [1]. The crystal structures, however, have not been reported at that time. We have determined the crystal structures of both compounds from four-circle X-ray diffractometer data of single-crystals. Both compounds crystallize with new structure types. The crystal structure of HgH₃IO₆ has been solved for a triclinic cell, space group P1, a = 480.6(2) pm, b = 530.9(2) pm, c = 560.8(2) pm, a = 65.35(2)°, b = 76.45(1)° , g = 63.76(2)°, Z = 1, R = 0.045 for 2673 structure factors and 50 variable parameters. In this structure I(OH)₃O₃ octahedra are linked via mercury atoms in nearly linear O-Hg-O arrangement, thus forming infinite chains (Fig. 1).

Fig. 1. The crystal structure of HgH₃IO₆.

The structure of Hg₃(H₂IO₆)₂ is monoclinic: P2₁/c, a = 853.7(2) pm, b = 1219.6(3) pm, c = 935.5(2) pm, b = 90.89(1)°, Z = 4 , R = 0.038 for 2029 F values and 98 variables. In this structure the (OH)₂IO₄ octahedra are condensed with nearly linear O-Hg-O bridges to infinite chains extending along the b axis. These chains are linked in the other two translation directions via mercury atoms, which obtain tetrahedral oxygen coordination (Fig. 2).

Fig. 2. The crystal structure of Hg₃(H₂IO₆)₂. The chains Hg-O-[I(OH)₂O₂]-O-Hg-O-[I(OH)₂O₂]- extend along the b direction. They are linked in the a and c directions via tetrahedrally coordinated Hg(II) atoms. The terminal OH groups of the (OH)₂IO₄ octahedra are omitted for clarity.

The crystal structure of the new compound AgHg₂NO₅ was determined from single-crystal X-ray diffractometer data: Pnma, a = 619.7(2) pm, b = 669.9(2) pm, c = 1265.2(4) pm, Z = 4, R = 0.026 for 586 F values and 33 variables. The compound may be represented by the formula 2HgO AgNO₃. The mercury(II) atoms together with oxygen form zig-zag chains with linear mercury coordination. The oxygen atoms of these chains are linked via silver atoms. The oxygen atoms of the nitrate groups form weak bonds to the metal atoms (Fig. 3).

Fig. 3. The structure of AgHg₂NO₅. In the left-hand part of the figure chains of mercury oxide linked via silver atoms are emphasized. The right-hand part shows all atoms in a projection along the shortes translation period (a).

1. H. Siebert and M. Fuckert, Z. Anorg. Allg. Chem. 433 (1977) 224-228.