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The main building units of the title compound, dimercury(II) selenite(IV) oxide hydrate, are strongly distorted [Hg1O6] and [Hg2O7] polyhedra, and a pyramidal SeIVO3 group. Slightly corrugated hexagonal rings made up of six [Hg1O6] octahedra spread parallel to the ab plane and are connected via [Hg2O7] polyhedra parallel and perpendicular to this direction, which results in a three-dimensional arrangement with channels propagating parallel to the c axis. The SeIVO3 groups are situated below and above the rings and bridge both types of Hg atoms. The non-bonding orbitals are stereochemically active and protrude into the channels of the three-dimensional network. Additional water mol­ecules are located at the centres of the channels and show weak interactions with the SeIV lone pairs and the O atoms of the SeIVO3 groups.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270102018152/sk1593sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270102018152/sk1593Isup2.hkl
Contains datablock I

Comment top

Numerous compounds within the system Hg—Se—O(—H), with different oxidation states of both Hg and Se, are compiled in standard textbooks about mercury (Gmelin, 1969), of which only a few have been crystallographically characterized, including α-HgSeO3 (Koskenlinna & Valkonen, 1995), Hg3(HSeO3)2(SeO3)2 (Koskenlinna & Valkonen, 1996a), Hg2(SeO3)2·H2O (Koskenlinna & Valkonen, 1996b), HgSeO4·H2O (Stålhandske, 1978) and Hg2SeO4 (Dorm, 1969).

In a recent project intended to provide more detailed knowledge of the crystal chemistry of this structure family, various compounds, some already described in the Gmelin textbook and some new, were prepared and structurally analyzed. These compounds were three polymorphs of mercury(I) selenite(IV), α-, β- and γ-Hg2SeO3 (Weil, 2002a), two new modifications of mercury(II) selenite(IV), β- and γ-HgSeO3 (Weil, 2002b), the mixed-valent seleniumIV/VI compound Hg3Se3O10 (Weil & Kolitsch, 2002), and the seleniumIV/-II compound Hg4Se4O9 (Weil, 2002b), as well as the mercury(II) selenites(VI), HgSeO4, Hg2SeO5 and Hg3SeO6 (Weil, 2002c). The title compound is the first basic mercury(II) selenite(IV) obtained so far and is composed of two crystallographically inequivalent HgII cations, one SeIVO32- pyramid, one oxidic O atom and an additional water molecule, corresponding to the formula HgSeO3·HgO.1/6H2O.

The two Hg atoms are surrounded by six and seven O atoms to form a strongly distorted [Hg1O6] octahedron and a [Hg2O7] polyhedron, whose intrapolyhedral geometry might be decribed as intermediate between a monocapped trigonal prism and a pentagonal bipyramid (Fig. 1). Although both polyhedra exhibit comparable mean Hg—O distances of 2.490 Å for Hg1—O and 2.453 Å for Hg2—O, the crystal chemical situation is quite different. [Hg1O6] shows an explicit linear coordination, with two short axial distances (mean axial Hg1—O 2.074 Å) and four considerably longer equatorial distances (mean equatorial Hg1—O 2.698 Å). Such a tetragonal flattened octahedron is a frequently observed coordination figure within the unique crystal chemistry of HgII oxo-compounds. In [Hg2O7], the Hg atom is also virtually linearly coordinated by the two closest bonded O atoms, O1 and O4, with a mean distance of 2.264 Å, and augmented by the remaining O atoms at longer distances, with a mean of 2.528 Å. Compared with [Hg1O6], these mean distances are significantly longer and shorter, respectively.

The selenite(IV) group displays the well known pyramidal geometry, with a mean Se—O distance of 1.692 Å and a mean O—Se—O angle of 100.2°. This is similar to the bond-length distribution observed for other mercury selenites(IV) and various metal selenites(IV) compiled in the most recent review of this structural family (Verma, 1999).

A characteristic feature of the present structure is the corrugated hexagonal rings built of six corner-sharing [Hg1O6] octahedra, with short Hg—O distances to the bridging O atoms and longer distances to the equatorial O atoms (Fig. 1). The Hg—O—Hg angle of 115.0 (2)° indicates a slight deviation from the ideal hexagonal geometry. Similar rings are found in the compounds Hg3XO6 with X = S (Weil, 2001), Se (Weil, 2002c) and Cr (Hansen et al., 1995). However, in this latter structure type, the rings are condensed to form infinite two-dimensional cationic nets with a composition of [Hg3O2]2+ and disordered XO4 tetrahedra situated in the interstices of the nets. In the title compound, the isolated rings spread parallel to the ab plane and are connected via the [Hg2O7] polyhedra parallel and perpendicular to this direction (Fig. 2 and 3). This arrangement leads to a three-dimensional framework with channels running parallel to the c axis, as depicted in Fig. 2.

The SeO3 pyramids are situated above and below the rings and bridge both Hg atoms. The lone-pair electrons of the SeIV atom groups are stereochemically active and protrude into the channels of the three-dimensional network. At the centres of the channels, additional water molecules are located which show only very weak interactions with the remaining O atoms (H2O—O > 3.7 Å) and the non-bonding orbitals of the SeIV atoms. The presence of water molecules is confirmed by complementary IR spectroscopic measurements of the yellow crystals obtained from the precipitation reaction.

Atoms O1—O4 are four-coordinate. Atom O4 is surrounded by four Hg atoms forming a slightly distorted [OHg4] tetrahedron, whereas all other O atoms have one Se and three Hg atoms as coordination partners. The corresponding [OSeHg3] tetrahedra are strongly distorted from the ideal geometry.

Results from the bond-valence sum (BVS) calculations, using the parameters provided by Brese & O'Keeffe (1991), are in accordance with the expected values, with Hg1 2.094, Hg2 2.034, Se 4.144, O1 2.131, O2 1.943, O3 1.919 and O4 2.280.

Experimental top

Precipitation of a slightly acidified Hg2(NO3)2 solution with an excess of selenic acid solution (both Merck, p·A.) produced a dark brown polycrystalline material, the X-ray powder diffraction pattern of which revealed Hg2SeO4 (Dorm, 1969) as the main phase. Some weak additional reflections could not be assigned to any known phase within this system. Hydrothermal treatment of this material in demineralized water at 453 K in a 10 ml capacity Teflon-lined steel autoclave resulted in a very few amber-coloured hexagonal crystals of HgSeO3·HgO.1/6H2O, in addition to other crystalline phases that are being investigated further. In an alternative procedure, single crystals of HgSeO3·HgO.1/6H2O were obtained during a precipitation experiment. A small beaker was filled with an Hg(Ac)2 solution (Sigma-Aldrich, >99%; Ac is acetate), which was acidified with an excess of acetic acid. This beaker was then placed in a larger container which was carefully filled with demineralized water. After adding a selenous acid solution (Merck, p·A.) to the large container, this apparatus was set aside in a dark room. After several days, colourless single crystals of α- and β-HgSeO3 (Weil, 2002b) were observed at the bottom of the large container. Besides a few crystals of these two polymorphs, yellow needle-shaped crystals of HgSeO3·HgO.1/6H2O with an edge length of up to 2 mm had formed in the small beaker with the Hg(Ac)2 solution. For the present structure analysis, a hydrothermally grown crystal was used. The yellow crystals obtained from the precipitation experiment exhibited no significant differences of lattice constants or structural parameters after refinement, compared with the hydrothermally grown crystals.

Refinement top

The crystal shape was optimized by minimizing the internal Ri-value of selected reflections [I>20σ(I)] using the program HABITUS (Herrendorf, 1993–1997). The habit so derived was used for the numerical absorption correction. After location and refinement of the framework structure, an obvious electron density of ca 11 e° A-3 was found at the inversion centre (Wyckoff position 3 a) which was assigned to the O atom of a water molecule. The H atoms of this molecule were not located. The highest difference peak is then 0.84 Å from Se and the deepest hole is 1.09 Å from Hg.

Computing details top

Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens, 1996); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ATOMS (Dowty, 2000); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. The hexagonal six-membered ring in HgSeO3·HgO.1/6H2O, made up of six [Hg1O6] polyhedra, and the [Hg2O7] polyhedron, both with displacement ellipsoids drawn at the 74% probability level. Short Hg—O bonds of less than 2.2 Å are drawn as solid lines.
[Figure 2] Fig. 2. A projection of the crystal structure of HgSeO3·HgO.1/6H2O along [001]. For Hg1, only short Hg—O bonds of less than 2.2 Å, drawn as solid lines, are given.
[Figure 3] Fig. 3. A projection of the crystal structure of HgSeO3·HgO.1/6H2O along [010]. For Hg1, only short Hg—O bonds of less than 2.2 Å, drawn as solid lines, are given. H2O molecules have been omitted for clarity.
Dimercury(II) selenite(IV) oxide hydrate top
Crystal data top
H0.3333Hg2O4.1667SeDx = 7.923 Mg m3
Mr = 547.14Mo Kα radiation, λ = 0.71073 Å
Trigonal, R3Cell parameters from 4279 reflections
Hall symbol: -R 3θ = 2.5–29.9°
a = 15.3965 (6) ŵ = 74.68 mm1
c = 10.0549 (5) ÅT = 293 K
V = 2064.20 (15) Å3Spheroid, amber
Z = 180.13 × 0.10 × 0.10 mm
F(000) = 4098
Data collection top
Siemens SMART area-detector
diffractometer
1355 independent reflections
Radiation source: fine-focus sealed tube1147 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.065
ω scansθmax = 30.2°, θmin = 2.7°
Absorption correction: numerical
?
h = 2121
Tmin = 0.011, Tmax = 0.051k = 2121
9998 measured reflectionsl = 1413
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullH-atom parameters not refined
R[F2 > 2σ(F2)] = 0.022 w = 1/[σ2(Fo2) + (0.0166P)2 + 35.2262P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.054(Δ/σ)max = 0.001
S = 1.09Δρmax = 2.32 e Å3
1355 reflectionsΔρmin = 1.43 e Å3
67 parametersExtinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
0 restraintsExtinction coefficient: 8.3 (5) × 10-5
Primary atom site location: structure-invariant direct methods
Crystal data top
H0.3333Hg2O4.1667SeZ = 18
Mr = 547.14Mo Kα radiation
Trigonal, R3µ = 74.68 mm1
a = 15.3965 (6) ÅT = 293 K
c = 10.0549 (5) Å0.13 × 0.10 × 0.10 mm
V = 2064.20 (15) Å3
Data collection top
Siemens SMART area-detector
diffractometer
1355 independent reflections
Absorption correction: numerical
?
1147 reflections with I > 2σ(I)
Tmin = 0.011, Tmax = 0.051Rint = 0.065
9998 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0220 restraints
wR(F2) = 0.054H-atom parameters not refined
S = 1.09 w = 1/[σ2(Fo2) + (0.0166P)2 + 35.2262P]
where P = (Fo2 + 2Fc2)/3
1355 reflectionsΔρmax = 2.32 e Å3
67 parametersΔρmin = 1.43 e Å3
Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Hg10.10602 (2)0.26075 (2)0.00554 (2)0.01901 (10)
Hg20.41724 (2)0.05241 (2)0.03888 (3)0.01910 (10)
Se0.14711 (6)0.00803 (6)0.34892 (7)0.02141 (16)
O10.0856 (4)0.2371 (5)0.2631 (5)0.0261 (12)
O20.1284 (5)0.4285 (5)0.1269 (6)0.0368 (15)
O30.2083 (6)0.1058 (5)0.2446 (6)0.0452 (19)
O40.2437 (4)0.2748 (4)0.0518 (5)0.0176 (10)
OH20.00000.00000.00000.031 (3)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Hg10.01556 (15)0.02356 (17)0.01903 (15)0.01062 (12)0.00167 (9)0.00041 (10)
Hg20.01780 (16)0.02157 (16)0.01956 (15)0.01106 (13)0.00296 (9)0.00211 (9)
Se0.0206 (4)0.0226 (4)0.0241 (3)0.0131 (3)0.0006 (3)0.0013 (3)
O10.018 (3)0.034 (3)0.024 (3)0.011 (3)0.003 (2)0.009 (2)
O20.042 (4)0.040 (4)0.030 (3)0.022 (3)0.006 (3)0.011 (3)
O30.089 (6)0.029 (4)0.024 (3)0.034 (4)0.011 (3)0.008 (2)
O40.016 (3)0.016 (3)0.024 (3)0.010 (2)0.0004 (18)0.0000 (18)
OH20.028 (5)0.028 (5)0.036 (8)0.014 (3)0.0000.000
Geometric parameters (Å, º) top
Hg1—O42.074 (5)Se—O1vi1.710 (5)
Hg1—O4i2.074 (5)O1—Seviii1.710 (5)
Hg1—O12.613 (5)O1—Hg2iv2.284 (5)
Hg1—O3i2.634 (6)O1—Hg2ix2.550 (6)
Hg1—O22.718 (7)O2—Seii1.681 (6)
Hg1—O3ii2.828 (8)O2—Hg2ix2.556 (6)
Hg1—OH23.4974 (3)O2—Hg2viii2.601 (7)
Hg2—O4iii2.243 (5)O3—Hg2iv2.494 (6)
Hg2—O1iv2.284 (5)O3—Hg1iii2.634 (6)
Hg2—O4iv2.442 (5)O3—Hg1vii2.828 (8)
Hg2—O3iv2.494 (6)O4—Hg1iii2.074 (5)
Hg2—O1v2.550 (6)O4—Hg2i2.243 (5)
Hg2—O2v2.556 (6)O4—Hg2iv2.442 (5)
Hg2—O2vi2.601 (7)OH2—Hg1viii3.4974 (3)
Se—O2vii1.681 (6)OH2—O3x3.710 (7)
Se—O31.684 (6)
O4—Hg1—O4i176.60 (11)O4iv—Hg2—O3iv76.84 (17)
O4—Hg1—O180.67 (19)O4iii—Hg2—O1v98.13 (18)
O4i—Hg1—O1102.35 (19)O1iv—Hg2—O1v79.6 (2)
O4—Hg1—O3i96.3 (2)O4iv—Hg2—O1v116.64 (16)
O4i—Hg1—O3i80.4 (2)O3iv—Hg2—O1v161.14 (19)
O1—Hg1—O3i157.1 (2)O4iii—Hg2—O2v76.2 (2)
O4—Hg1—O299.4 (2)O1iv—Hg2—O2v86.7 (2)
O4i—Hg1—O283.3 (2)O4iv—Hg2—O2v162.6 (2)
O1—Hg1—O268.68 (18)O3iv—Hg2—O2v91.4 (2)
O3i—Hg1—O2133.9 (2)O1v—Hg2—O2v72.19 (19)
O4—Hg1—O3ii81.61 (19)O4iii—Hg2—O2vi82.95 (19)
O4i—Hg1—O3ii98.26 (19)O1iv—Hg2—O2vi110.0 (2)
O1—Hg1—O3ii116.86 (18)O4iv—Hg2—O2vi72.17 (17)
O3i—Hg1—O3ii84.7 (2)O3iv—Hg2—O2vi139.0 (2)
O2—Hg1—O3ii55.47 (17)O1v—Hg2—O2vi59.90 (18)
O4iii—Hg2—O1iv162.60 (17)O2v—Hg2—O2vi123.8 (2)
O4iii—Hg2—O4iv115.18 (16)Hg1—O4—Hg1iii115.0 (2)
O1iv—Hg2—O4iv80.67 (17)O2vii—Se—O3100.3 (4)
O4iii—Hg2—O3iv86.6 (2)O2vii—Se—O1vi98.7 (3)
O1iv—Hg2—O3iv90.4 (3)O3—Se—O1vi101.5 (3)
Symmetry codes: (i) xy, x, z; (ii) x+y+1/3, x+2/3, z1/3; (iii) y, x+y, z; (iv) x+2/3, y+1/3, z+1/3; (v) x+1/3, y1/3, z1/3; (vi) x+y, x, z; (vii) y+2/3, xy+1/3, z+1/3; (viii) y, xy, z; (ix) x1/3, y+1/3, z+1/3; (x) x, y, z.

Experimental details

Crystal data
Chemical formulaH0.3333Hg2O4.1667Se
Mr547.14
Crystal system, space groupTrigonal, R3
Temperature (K)293
a, c (Å)15.3965 (6), 10.0549 (5)
V3)2064.20 (15)
Z18
Radiation typeMo Kα
µ (mm1)74.68
Crystal size (mm)0.13 × 0.10 × 0.10
Data collection
DiffractometerSiemens SMART area-detector
diffractometer
Absorption correctionNumerical
Tmin, Tmax0.011, 0.051
No. of measured, independent and
observed [I > 2σ(I)] reflections
9998, 1355, 1147
Rint0.065
(sin θ/λ)max1)0.709
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.022, 0.054, 1.09
No. of reflections1355
No. of parameters67
H-atom treatmentH-atom parameters not refined
w = 1/[σ2(Fo2) + (0.0166P)2 + 35.2262P]
where P = (Fo2 + 2Fc2)/3
Δρmax, Δρmin (e Å3)2.32, 1.43

Computer programs: SMART (Siemens, 1996), SAINT (Siemens, 1996), SAINT, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ATOMS (Dowty, 2000), SHELXL97.

Selected geometric parameters (Å, º) top
Hg1—O42.074 (5)Hg2—O4iv2.442 (5)
Hg1—O4i2.074 (5)Hg2—O3iv2.494 (6)
Hg1—O12.613 (5)Hg2—O1v2.550 (6)
Hg1—O3i2.634 (6)Hg2—O2v2.556 (6)
Hg1—O22.718 (7)Hg2—O2vi2.601 (7)
Hg1—O3ii2.828 (8)Se—O2vii1.681 (6)
Hg2—O4iii2.243 (5)Se—O31.684 (6)
Hg2—O1iv2.284 (5)Se—O1vi1.710 (5)
O4—Hg1—O4i176.60 (11)O2vii—Se—O3100.3 (4)
O4iii—Hg2—O1iv162.60 (17)O2vii—Se—O1vi98.7 (3)
Hg1—O4—Hg1iii115.0 (2)O3—Se—O1vi101.5 (3)
Symmetry codes: (i) xy, x, z; (ii) x+y+1/3, x+2/3, z1/3; (iii) y, x+y, z; (iv) x+2/3, y+1/3, z+1/3; (v) x+1/3, y1/3, z1/3; (vi) x+y, x, z; (vii) y+2/3, xy+1/3, z+1/3.
 

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