Preparation and Crystal Structure Analyses of Compounds in the Systems HgO/MXO4/H2O (M = Co, Zn, Cd; X = S, Se)

Abstract

AbstractDuring phase formation experiments under hydrothermal conditions (250 °C, 5d) in the systems HgO/MXO4/H2O (M = Co, Zn, Cd; X = S, Se), single crystals of the mercuric compounds (CdSO4)2(HgO)2H2O (I), (CdSeO4)2(HgO)2H2O (II), (CdSeO4)Hg(OH)2 (III), (CoSO4)2(HgO)2H2O (IV), (ZnSO4)2(HgO)2H2O (V), (ZnSeO4)2(HgO)2H2O (VI), and the mixed‐valent (ZnSeIVO3)(ZnSeVIO4)HgI2(OH)2 (VII) were obtained. The crystal structure determinations from X‐ray diffraction data revealed four unique structure types for these compounds. I and II crystallise isotypically in space group P2/n (a ≈ 7.85, b ≈ 6.28, c ≈ 10.5Å, β ≈ 102°), compound III crystallises in space group C2/m (a = 10.540(2), b = 9.0120(8), c = 6.1330(12)Å, β = 100.45(3)°), and the isotypic compounds IV, V and VI crystallise in space group Pbcm (a ≈ 6.15, b ≈ 11.3, c ≈ 13.1Å). Common with these three structure types are distorted octahedral [MO6] and tetrahedral XO4 building units which are organised in a layered assembly. Within the layers H bonding of OH groups or H2O molecules of the [MO6] octahedra leads to an additional stabilisation. Adjacent layers are separated by mercury atoms which are linearly bonded to two O atoms at short distances, forming either interconnecting [O‐Hg‐O] units which are part of [O‐Hg‐O]∞ zig‐zag chains, or single [HO‐Hg‐OH] units (realised in compound III). VII is the only compound with mercury in oxidation state +1. It crystallises in space group C2/m (a = 17.342(3), b = 6.1939(10), c = 4.4713(8)Å, β = 90.154(3)°) and is made up of Hg22+ dumbbells, [ZnO4(OH)2] octahedra, and statistically distributed SeVIO4 and SeIVO3 groups as the main building units.