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Acta Crystallogr Sect E Struct Rep Online. 2010 February 1; 66(Pt 2): i7.
Published online 2010 January 16. doi:  10.1107/S1600536809053604
PMCID: PMC2979979

Pb3Te2O6Br2

Abstract

Single crystals of the title compound, trilead(II) bis­[tellurate(IV)] dibromide, have been grown under hydro­thermal conditions. The structure is isotypic with that of the chloride analogue, Pb3Te2O6Cl2, and consists of three Pb, two Te, two Br and four O atoms in the asymmetric unit. Except for two of the O atoms, all atoms are located on mirror planes. The Pb3Te2O6Br2 structure can be described as being built up from 2[Pb3Te2O6]2+ layers extending parallel to (20An external file that holds a picture, illustration, etc.
Object name is e-66-000i7-efi1.jpg) and Br anions between the layers. Cohesion of the structure is accomplished through Pb—Br contacts of two of the three lead atoms, leading to highly asymmetric coordination polyhedra. The lone-pair electrons of both TeIV and PbII atoms are stereochemically active and point towards the anionic halide layers.

Related literature

For reports and structures of other compounds in the system PbX 2—PbO—TeO2, where X = Br, Cl, see: Pb3TeO4 X 2 (Charkin et al., 2006 [triangle]; Porter & Halasyamani, 2003 [triangle]); Pb3Te2O6 X 2 (Porter & Halasyamani, 2003 [triangle]). The crystal chemistry of oxotellurate(IV) compounds has been reviewed by Dolgikh (1991 [triangle]) and Zemann (1971 [triangle]). For other oxotellurates(IV) prepared under hydro­thermal conditions, see: Weil & Stöger (2007 [triangle], 2008a [triangle],b [triangle]).

Experimental

Crystal data

  • Pb3Te2O6Br2
  • M r = 1132.59
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is e-66-000i7-efi2.jpg
  • a = 16.9151 (9) Å
  • b = 5.6813 (3) Å
  • c = 11.0623 (6) Å
  • β = 104.046 (1)°
  • V = 1031.3 (1) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 62.14 mm−1
  • T = 296 K
  • 0.18 × 0.10 × 0.04 mm

Data collection

  • Bruker APEXII CCD diffractometer
  • Absorption correction: numerical (HABITUS; Herrendorf, 1997 [triangle]) T min = 0.06, T max = 0.41
  • 3758 measured reflections
  • 1371 independent reflections
  • 1338 reflections with I > 2σ(I)
  • R int = 0.030

Refinement

  • R[F 2 > 2σ(F 2)] = 0.048
  • wR(F 2) = 0.107
  • S = 1.15
  • 1371 reflections
  • 73 parameters
  • Δρmax = 7.41 e Å−3
  • Δρmin = −6.41 e Å−3

Data collection: APEX2 (Bruker, 2008 [triangle]); cell refinement: SAINT (Bruker, 2008 [triangle]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: ATOMS (Dowty, 2006 [triangle]); software used to prepare material for publication: SHELXL97.

Table 1
Comparative geometrical parameters (Å) for selected bond lengths in Pb3Te2O6 X 2 compounds (X = Br, Cl)

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809053604/br2129sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809053604/br2129Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Acknowledgments

Financial support of the FWF (Fonds zur Förderung der wissenschaftlichen Forschung), project P19099-N17, is gratefully acknowledged.

supplementary crystallographic information

Comment

Single crystals growth of Pb3Te2O6Cl2 and Pb3Te2O6Br2 was studied during a recent project intended to elaborate hydrothermal formation conditions of oxotelluraTeIV compounds (Weil & Stöger, 2007; 2008a,b). Both Pb3Te2O6X2 (X = Br, Cl) compounds have been prepared previously by solid state techniques (Porter & Halasyamani, 2003). Whereas for the chloride compound a full structure analysis was undertaken at that time, for the isotypic bromide compound only lattice parameters were reported. Here we present details of the Pb3Te2O6Br2 structure determined from single-crystal X-ray data.

The asymmetric unit of the Pb3Te2O6X2 structure contains three Pb, two Te, two X and four O atoms. Except two of the O atoms, all other atoms are located on mirror planes. The Pb3Te2O6X2 structure type can be described as being built up from 2[Pb3Te2O6]2+ layers extending parallel to (201) and X- anions between the layers. The tellurium atoms in the cationic layer are surrounded by four (Te1) and three (Te2) oxygen atoms in distorted tetrahedral (Te1) and trigonal-pyramidal (Te2) environments, respectively. Under an additional contribution of the lone electron pairs to the stereochemistry of the two TeIV atoms, the corresponding Ψ-oxopolyhedra can be considered as distorted TeO4E square pyramids (Te1) and TeO3E tetrahedra (E designates the lone electron pair). These kinds of TeOx polyhedra are frequently observed for various oxotelluraTeIV structures (Dolgikh, 1991; Zemann, 1971). The Te1O4 group forms Te12O6 dimers via edge-sharing, whereas the Te2O3 group is isolated in the layers. Both oxotelluraTeIV units are surrounded by lead atoms. Four O atoms are bonded to Pb1, five O atoms to Pb2 and eight O atoms to Pb3. For both Pb3Te2O6X2 structures the respective Te—O and Pb—O distances are very similar (Table 1). The main difference between the Pb3Te2O6X2 structures pertains to the distances of the lead atoms to the X atoms that are situated between the cationic layers. As expected, the Pb—X distances are about 0.1 to 0.15 Å longer for the Br compound (Table 1). The layered character of the Pb3Te2O6X2 structure type with alternating layers parallel to (201) is also reflected by the differences of the lattice parameters for the Br and the Cl analogues. While the lengths of the b-axes are very similar (5.6813 (3) (Br) versus 5.6295 (4) Å (Cl)), a and c differ notedly (16.9151 (9) versus 16.4417 (11) Å, and 11.0623 (6) versus 10.8894 (7) Å) due to the different ionic radii of Br- and Cl-. The coordination of the halogen atoms in the neighbouring anionic layer to the lead atoms augments the coordination polyhedra of Pb1 and Pb2 to an overall coordination of [Pb1O4X4], [Pb2O5X3] and [Pb3O8X].

All TeOx and PbOxXy polyhedra in the structure are highly irregular. The lone-pair electrons of both TeIV and PbII atoms are stereochemically active and point towards the anionic halide layers (Fig. 1). Similar TeOx and PbOxXy polyhedra are observed for the Pb3TeO4X2 structures (Charkin et al., 2006) that show a lower TeO2 content in comparison with the Pb3Te2O6X2 structures.

Experimental

All chemicals used were of analytical grade and employed without further purification. 1 mmol PbBr2 (0.367 g) and 1 mmol TeO2 (0.160 g) were placed in a Teflon inlay that was filled with a hydrous NH4OH solution (10%wt) to two-thirds of its volume. The inlay was placed in a steel autoclave and heated at 493 K for four weeks. The reaction product consisted of small colourless crystals of the title compound with rod-like habit and a maximum edge lengths of 0.2 mm. Experiments under similar conditions but with with PbCl2 instead of PbBr2 led to crystals of the isotypic compound Pb3Te2O6Cl2.

Refinement

The structure was solved using direct methods. For better comparison with the isotypic structure of Pb3Te2O6Cl2 (Porter & Halasyamani, 2003), the atomic coordinates of the Cl analogue were taken as starting parameters for refinement. The highest remaining peak in the final difference Fourier map is 0.80 Å from Pb2 and the deepest hole is 0.57 Å from the same atom.

Lattice parameters of Pb3Te2O6Br2 based on the present single-crystal study agree reasonably well with those of the powder diffraction data provided by Porter & Halasyamani (2003): a = 16.8911 (8), b = 5.6804 (2), c = 11.0418 (5) Å, β = 104.253 (2)°.

Figures

Fig. 1.
The crystal structure of Pb3Te2O6Br2 in projection along [010]. Te atoms are given as red, Pb as blue, O atoms as white and Br atoms as green ellipsoids at the 74% probability level.

Crystal data

Pb3Te2O6Br2F(000) = 1872
Mr = 1132.59Dx = 7.295 Mg m3
Monoclinic, C2/mMo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yCell parameters from 4771 reflections
a = 16.9151 (9) Åθ = 2.5–32.2°
b = 5.6813 (3) ŵ = 62.14 mm1
c = 11.0623 (6) ÅT = 296 K
β = 104.046 (1)°Rod, colourless
V = 1031.3 (1) Å30.18 × 0.10 × 0.04 mm
Z = 4

Data collection

Bruker APEXII CCD diffractometer1371 independent reflections
Radiation source: fine-focus sealed tube1338 reflections with I > 2σ(I)
graphiteRint = 0.030
ω– and [var phi]–scansθmax = 27.9°, θmin = 1.9°
Absorption correction: numerical (HABITUS; Herrendorf, 1997)h = −22→15
Tmin = 0.06, Tmax = 0.41k = −7→7
3758 measured reflectionsl = −13→14

Refinement

Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.048w = 1/[σ2(Fo2) + (0.0166P)2 + 250.8836P] where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.107(Δ/σ)max < 0.001
S = 1.15Δρmax = 7.41 e Å3
1371 reflectionsΔρmin = −6.41 e Å3
73 parametersExtinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
0 restraintsExtinction coefficient: 0.00021 (2)

Special details

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)

xyzUiso*/Ueq
Pb10.26158 (6)0.00000.21028 (8)0.0178 (2)
Pb20.02616 (6)0.00000.19788 (9)0.0250 (3)
Pb30.16368 (6)0.50000.39320 (8)0.0217 (3)
Te10.10510 (10)0.50000.04764 (16)0.0233 (4)
Te20.37019 (9)0.50000.41467 (14)0.0141 (3)
Br10.31858 (15)0.50000.0993 (2)0.0205 (5)
Br2−0.03969 (16)0.50000.3103 (3)0.0313 (6)
O10.1315 (8)0.263 (3)0.1840 (11)0.028 (3)
O20.00000.294 (5)0.00000.059 (7)
O30.3884 (15)0.50000.5887 (17)0.040 (5)
O40.2909 (7)0.262 (2)0.3877 (10)0.017 (2)

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
Pb10.0224 (5)0.0150 (4)0.0161 (4)0.0000.0048 (3)0.000
Pb20.0258 (5)0.0204 (5)0.0253 (5)0.000−0.0004 (4)0.000
Pb30.0190 (4)0.0261 (5)0.0191 (4)0.0000.0026 (3)0.000
Te10.0224 (8)0.0186 (8)0.0236 (8)0.000−0.0046 (6)0.000
Te20.0117 (6)0.0124 (7)0.0177 (7)0.0000.0025 (5)0.000
Br10.0208 (11)0.0220 (11)0.0183 (11)0.0000.0039 (9)0.000
Br20.0202 (12)0.0236 (13)0.0525 (18)0.0000.0131 (12)0.000
O10.032 (7)0.026 (7)0.023 (6)−0.010 (6)0.005 (5)0.002 (5)
O20.031 (11)0.062 (18)0.09 (2)0.0000.028 (13)0.000
O30.051 (13)0.046 (14)0.011 (8)0.000−0.014 (8)0.000
O40.019 (5)0.016 (6)0.018 (5)−0.007 (5)0.009 (4)−0.001 (4)

Geometric parameters (Å, °)

Pb1—O42.415 (11)Pb3—O4viii2.555 (12)
Pb1—O4i2.415 (11)Pb3—O42.555 (12)
Pb1—O1i2.617 (14)Pb3—O12.617 (13)
Pb1—O12.617 (14)Pb3—O1viii2.617 (13)
Pb1—Br2ii3.274 (3)Pb3—O4ix2.788 (11)
Pb1—Br1iii3.3287 (13)Pb3—O4v2.788 (11)
Pb1—Br13.3287 (13)Pb3—O3v2.995 (8)
Pb1—Br1iv3.364 (3)Pb3—O3x2.995 (8)
Pb2—O12.360 (13)Pb3—Te23.4432 (17)
Pb2—O1i2.360 (13)Te1—O1viii1.989 (13)
Pb2—O3v2.451 (18)Te1—O11.989 (13)
Pb2—O2vi2.704 (19)Te1—O22.085 (17)
Pb2—O22.704 (19)Te1—O2xi2.085 (17)
Pb2—Br23.3955 (17)Te2—O31.874 (19)
Pb2—Br2iii3.3955 (17)Te2—O41.879 (11)
Pb2—Br1vii3.415 (3)Te2—O4viii1.879 (11)
O4—Pb1—O4i76.0 (5)O1—Te1—O280.4 (6)
O4—Pb1—O1i116.3 (4)O1viii—Te1—O2xi80.4 (6)
O4i—Pb1—O1i74.9 (4)O1—Te1—O2xi126.3 (5)
O4—Pb1—O174.9 (4)O2—Te1—O2xi68.2 (14)
O4i—Pb1—O1116.3 (4)O3—Te2—O495.5 (6)
O1i—Pb1—O169.7 (6)O3—Te2—O4viii95.5 (6)
O1—Pb2—O1i78.6 (7)O4—Te2—O4viii92.3 (7)
O1—Pb2—O3v77.6 (5)Te1—O1—Pb2116.3 (6)
O1i—Pb2—O3v77.6 (5)Te1—O1—Pb1119.9 (6)
O1—Pb2—O2vi108.5 (4)Pb2—O1—Pb1105.0 (5)
O1i—Pb2—O2vi62.2 (4)Te1—O1—Pb3106.4 (6)
O3v—Pb2—O2vi136.2 (5)Pb2—O1—Pb3105.4 (5)
O1—Pb2—O262.2 (4)Pb1—O1—Pb3101.9 (4)
O1i—Pb2—O2108.5 (4)Te1—O2—Te1xi111.8 (14)
O3v—Pb2—O2136.2 (5)Te1—O2—Pb2vi120.87 (15)
O2vi—Pb2—O276.4 (10)Te1xi—O2—Pb2vi100.36 (16)
O4viii—Pb3—O464.0 (5)Te1—O2—Pb2100.36 (16)
O4viii—Pb3—O1104.3 (4)Te1xi—O2—Pb2120.87 (15)
O4—Pb3—O172.7 (4)Pb2vi—O2—Pb2103.6 (10)
O4viii—Pb3—O1viii72.7 (4)Te2—O3—Pb2v154.3 (13)
O4—Pb3—O1viii104.3 (4)Te2—O4—Pb1124.8 (5)
O1—Pb3—O1viii61.9 (6)Te2—O4—Pb3100.8 (5)
O1viii—Te1—O185.1 (8)Pb1—O4—Pb3109.7 (4)
O1viii—Te1—O2126.3 (5)

Symmetry codes: (i) x, −y, z; (ii) x+1/2, y−1/2, z; (iii) x, y−1, z; (iv) −x+1/2, −y+1/2, −z; (v) −x+1/2, −y+1/2, −z+1; (vi) −x, −y, −z; (vii) x−1/2, y−1/2, z; (viii) x, −y+1, z; (ix) −x+1/2, y+1/2, −z+1; (x) −x+1/2, −y+3/2, −z+1; (xi) −x, −y+1, −z.

Table 1 Comparative geometrical parameters (Å) for selected bond lengths in Pb3Te2O6X2 compounds (X = Br, Cl)

DistanceX= Br (this work)X= Cl (Porter & Halasyamani, 2003)
Pb1—O42.415 (11)2.447 (15)
Pb1—O12.617 (14)2.586 (14)
Pb1—X2i3.274 (3)3.176 (12)
Pb1—X13.3287 (13)3.237 (12)
Pb1—X1ii3.364 (3)3.247 (12)
Pb2—O12.360 (13)2.374 (14)
Pb2—O3iii2.451 (18)2.48 (2)
Pb2—O22.704 (19)2.677 (13)
Pb2—X23.3955 (17)3.270 (12)
Pb2—X1iv3.415 (3)3.276 (13)
Pb3—O42.555 (12)2.544 (16)
Pb3—O12.617 (13)2.600 (14)
Pb3—O4v2.788 (11)2.777 (17)
Pb3—O3iii2.995 (8)2.986 (16)
Pb3—X23.338 (21)3.244 (12)
Te1—O11.989 (13)1.938 (13)
Te1—O22.085 (17)2.044 (12)
Te2—O31.874 (19)1.84 (2)
Te2—O41.879 (11)1.861 (16)

Symmetry codes: (i) x+1/2, y-1/2, z; (ii) -x+1/2, -y+1/2, -z; (iii) -x+1/2, -y+1/2, -z+1; (iv) x-1/2, y-1/2, z; (v) -x+1/2, y+1/2, -z+1.

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BR2129).

References

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