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Z. Naturforsch. 2014, 69b, 665 – 673
doi:10.5560/ZNB.2014-4063
The Mixed-valent Mercury(I/II) Compounds Hg3(HAsO4)2 and Hg6As2O10
Matthias Weil
Institute for Chemical Technologies and Analytics, Division of Structural Chemistry, Vienna University of Technology, Getreidemarkt 9/164-SC, A-1060 Vienna, Austria
Reprint requests to Prof. Dr. Matthias Weil. Fax: ++43-1-58801-17199. E-mail: mweil@mail.zserv.tuwien.ac.at
Received March 17, 2014 / published online June 7, 2014
The mixed-valent mercury compounds Hg3(HAsO4)2 (= HgIIHgI2(HAsO4)2) and Hg6As2O10 (= HgI2HgII2(AsO4)2 ·2HgIIO) were obtained from the reaction of (Hg3)3(AsO4)4 with arsenic acid (60 wt-%) carried out at 65 °C and as a by-product under hydrothermal conditions, respectively. The crystal structure of Hg3(HAsO4)2 (Z = 2, C2/c, a = 13.010(3), b = 8.149(2), c = 9.496(3) Å, β =126.864(4)°, 1427 structure factors, 64 parameters, R [F2 > 2 σ(F2)] = 0.0272; wR (all F2) = 0.0490) contains a centrosymmetric O–Hg–Hg–O unit (d(Hg–Hg) = 2.5226(8) Å, d(Hg–O) = 2.141(5) Å), ∠(Hg–Hg–O) = 167.68(13)) and an Hg2+ cation that is located on a twofold rotation axis showing an almost linear coordination to two O atoms (d(Hg–O) = 2.059(5) Å; ∠(O–Hg–O) = 177.3(2)). The O–Hg–Hg–O and O–Hg–O units are linked by AsO3OH tetrahedra resulting in the formation of chains extending parallel to [102]. Strong hydrogen bonding (d(O···O) = 2.523(6) Å) between AsO3OH tetrahedra of neighbouring chains is observed. The crystal structure of Hg6As2O10 (Z = 2, P21/n, a = 6.94750(10), b = 8.9837(2), c = 8.9966(2) Å, β =98.1630(10)°, 4842 structure factors, 83 parameters, R [F2 > 2 σ(F2)] = 0.0269, wR (all F2) = 0.0577) contains an O–Hg–Hg–O unit (d(Hg–Hg) = 2.5337(3) Å, d(Hg–O) = 2.181(3) Å, ∠(Hg–Hg–O) = 168.05(10)) and two O–Hg–O units (d(Hg–O) = 2.048(3), 2.072(3) Å, ∠(O–Hg–O) = 168.78(15); 2.149(4), 2.150(3) Å, 166.65(12)) that are linked into a three-dimensional framework structure with As atoms of the AsO4 tetrahedra in the voids. An alternative structural description of Hg6As2O10 is presented under consideration of oxygen-centred [OHg4] tetrahedra.
Key words: Mercury, Mixed Valence, Arsenate, Crystal Structure
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