471
Z. Kristallogr. NCS 215 (2000) 4 7 1 ^ 7 2
© by Oldenbourg Wissenschaftsverlag, München
Crystal structure of mercury(II) metaarsenate(V), HgAs206
Th. J. Mormann and W. Jeitschko*
Universität Münster, Anorganisch-Chemisches Institut, Wilhelm-Klemm-Straße 8, D-48149 Münster, Germany
Received April 17, 2000, CSD-No. 409490
Experimental details
The lattice constants were determined from Guinier powder data
using Cu K a i radiation and a-quartz (a = 491.30 pm, c =
540.46 pm) as an internal standard. The positional parameters
have been standardized using the program STRUCTURE TIDY
[1].
Discussion
The mercury metaarsenate HgAs2C>6 has already been reported
by Magneli [2] to be isotypic with PbSb2C>6. The structure of the
latter compound has been refined recently [3]. A structure refinement of H g A s 2 0 6 is reported here for the first time. Both the mercury and the arsenic atoms are octahedrally coordinated by
oxygen atoms. The six Hg—O distances of 235.9(6) pm compare
well with that of 238 pm calculated from the radii given by Shannon for six-coordinated Hg(II) and three-coordinated oxygen [4].
The AsOa octahedra share edges, thus forming two-dimensionally infinite nets extending perpendicular to the trigonal axis.
The mercury atoms are situated in between these As2C>6 sheets.
The six As—O distances of 182.7(4) pm are in good agreement
with the As—O distances of 183.3(5) pm in P b A s 2 0 6 [5],
183.3(2) pm in CaAs 2 06 [5], and the average As—O distance of
181.8(4) pm in AS2O5 [6], respectively. The angles in the nearly
trigonal planar oxygen coordination amount to 100.0(3)° for
A s - O - A s and 2x 126.7(2)° for H g - O - A s .
Table 1. Data collection and handling.
Crystal:
Abstract
As 2 Hg0 6 , trigonal, P3\m (No. 162), a = 4.8502(4) A,
c = 4.9853(7) A, V= 101.6 A 3 , Z = 1, Rgt(F) = 0.037,
wRlef(F2) = 0.103, T = 293 K.
Source of material
H g A s 2 0 6 was prepared by heating 0.3 g of a mixture of yellow
mercury(II) oxide HgO and arsenic pentoxide AS2O5 with the
molar ratio 1:1 in an evacuated silica tube for 7 days at 833 K. An
energy dispersive X-ray fluorescence analysis for elements
heavier than sodium revealed only mercury and arsenic.
colorless, hexagonal,
size 0.045 x 0.066 x 0.082 mm
Wavelength:
Mo K a radiation (0.71073 Â)
H:
540 cm" 1
Diffractometer, scan mode:
Enraf-Nonius CAD4, co/20
29max:
59.64°
N(hkl)measured, N(hkl)„nique. 848, 122
Criterion for /0bs, N(hkl)gt:
/obs > 2 a(/obs), 122
N(param)rermti'.
9
Programs:
SHELXL-97 [7], DIAMOND [8]
Table 2, Atomic coordinates and displacement parameters (in  2 ).
Atom
Site
x
y
O
6k
0.380(1)
0
'
z
U¡m
0.296(1)
0.004(1)
* Correspondence author (e-mail: [email protected])
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472
Mercury(II) metaarsenate(V)
Table 3. Atomic coordinates and displacement parameters (in  2 ).
Atom
Site
x
y
z
Un
U22
Í/33
C/12
U13
Í/23
Hg
As
la
2d
0
1/3
0
2/3
0
1/2
0.0073(7)
0.0023(8)
U\\
Uu
0.0054(8)
0.005(1)
1/2Un
\t2Uu
0
0
0
0
References
1. Gelato, L. M.; Parthé, E.: STRUCTURE TIDY - a Computer Program to
Standardize Crystal Structure Data. J. Appl. Crystallogr. 20 (1987)
139-143.
2. Magneli, A.: The Crystal Structure of Lead Metaantimonate and
Isomorphous Compounds. Ark. Kemi, Mineral. Geol. 15B (1941) 1-6.
3. Hill, R. J.: Structure of PbSbzOs and Its Relationship to the Crystal Chemistry of PbÛ2 in Antimonial Lead-Acid Batteries. J. Solid State Chem. 71
(1987) 12-18.
4. Shannon, R. D.: Revised Effective Ionic Radii and Systematic Studies of
Interatomic Distances in Halides and Chalcogenides. Acta Crystallogr.
A32 (1976) 751-767.
5. Losilla, E. R.; Aranda, M. A. G.; Ramirez, F. J.; Bruque, S.: Crystal Structure and Spectroscopic Characterization of MAS2O6 (M = Pb, Ca). Two
Simple Salts with AsOé Groups. J. Phys. Chem. 99 ( 1995) 12975-12979.
6. Jansen, M.: Die Kristallstruktur von AS2O5, eine neue Raumnetzstruktur.
Z. Anorg. Allg. Chem. 441 (1978) 5-12.
7. Sheldrick, G. M.: SHELXL-97 - A Program System for the Solution and
Refinement of Crystal Structures. University of Göttingen, Germany
1997.
8. Brandenburg, K.; Bemdt, M.; Bergerhoff, G.: DIAMOND - Visuelles
Informationssystem für Kristallstrukturen. University of Bonn, Germany
1999.
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