Pb6Co9(TeO6)5

Christine Artner; Matthias Weil

doi:10.1107/S1600536812037038

. 2012 Aug 31;68(Pt 9):i71. doi: 10.1107/S1600536812037038

Pb₆Co₉(TeO₆)₅

Christine Artner ^a, Matthias Weil ^a,^*

PMCID: PMC3435567 PMID: 22969440

Abstract

Pb₆Co₉(TeO₆)₅, hexalead(II) nonacobalt(II) pentatellurate(VI), is isotypic with its nickel(II) analogue. The asymmetric unit contains two Pb atoms (site symmetries .2., ..2), four Co atoms (..2, ..2, 3.., 3.2) two Te atoms (..2, 3..) and six O atoms (all in general positions), with the Te and Co sites in octahedral coordination environments. The crystal structure can be subdivided into two types of layers parallel to (001). The first layer at z ≃ 0.25 is made up of edge-sharing [CoO₆] and [TeO₆] octahedra, with 1/6 of the octahedral holes not occupied. The second layer, situated at z ≃ 0, consist of an alternating arrangement of Pb^II atoms and of double octahedra that are made up from face-sharing [CoO₆] and [TeO₆] octahedra. The two types of layers are linked together through corner-sharing of [CoO₆] and [TeO₆] octahedra. The Pb^II atoms are situated in the cavities of the framework and are stereochemically active with one-sided [4]- and [6]-coordinations, respectively.

Related literature

For the isotypic nickel analogue, see: Wedel et al. (1998 ▶). Reviews on the crystal chemistry of oxotellurates(VI) and of the geometry of [Co^IIO₆] polyhedra are given by Levason (1997 ▶) and Wildner (1992 ▶), respectively. For Pb₅TeO₈, see: Artner & Weil (2012 ▶). For the bond-valence method, see: Brown (2002 ▶).

Experimental

Crystal data

Pb₆Co₉(TeO₆)₅
M _r = 2891.51
Hexagonal,
a = 10.3915 (1) Å
c = 13.6273 (2) Å
V = 1274.37 (3) Å³
Z = 2
Mo Kα radiation
μ = 50.89 mm⁻¹
T = 293 K
0.07 × 0.06 × 0.05 mm

Data collection

Bruker APEXII CCD diffractometer
Absorption correction: numerical (HABITUS; Herrendorf, 1997 ▶) T _min = 0.123, T _max = 0.200
45686 measured reflections
2262 independent reflections
1908 reflections with I > 2σ(I)
R _int = 0.068

Refinement

R[F ² > 2σ(F ²)] = 0.025
wR(F ²) = 0.056
S = 1.09
2262 reflections
81 parameters
Δρ_max = 2.96 e Å⁻³
Δρ_min = −2.59 e Å⁻³
Absolute structure: Flack (1983 ▶), 882 Friedel pairs
Flack parameter: 0.134 (10)

Data collection: APEX2 (Bruker, 2004 ▶); cell refinement: SAINT (Bruker, 2004 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ATOMS for Windows (Dowty, 2006 ▶); software used to prepare material for publication: publCIF (Westrip, 2010 ▶).

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536812037038/br2208sup1.cif

e-68-00i71-sup1.cif^{(24.3KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812037038/br2208Isup2.hkl

e-68-00i71-Isup2.hkl^{(111.4KB, hkl)}

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

Table 1. Selected bond lengths (Å).

Te1—O2	1.906 (5)
Te1—O6	1.991 (4)
Te2—O5	1.917 (6)
Te2—O3	1.937 (7)
Te2—O1ⁱ	1.939 (5)
Co1—O5ⁱⁱ	2.004 (6)
Co1—O6	2.262 (5)
Co2—O2	2.090 (6)
Co2—O3ⁱⁱⁱ	2.090 (8)
Co2—O1	2.108 (6)
Co3—O3	2.107 (4)
Co4—O2	2.067 (7)
Co4—O1^iv	2.071 (4)
Co4—O5^v	2.116 (7)

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) ; (v) .

Acknowledgments

The X-ray centre of the Vienna University of Technology is acknowledged for providing access to the single-crystal diffractometer.

supplementary crystallographic information

Comment

Single crystals of the title compound, Pb₆Co₉(TeO₆)₅, were serendipitously obtained as a minority phase during phase formation studies in the system Pb^II/Co^II/Te^VI/O intended on crystal growth of cubic Pb₂CoTeO₆.

The crystal structure of Pb₆Co₉(TeO₆)₅ is isotypic with its nickel analogue (Wedel et al., 1998). The two Te(VI) and the four Co(II) atoms are in slightly distorted octahedral coordination environments with mean bond lengths of ¯d(Te—O) = 1.940 Å and ¯d(Co—O) = 2.105 Å, both in good agreement with literature data for oxotellurates (Levason, 1997) and for [CoO₆] octahedra (Wildner, 1992). The two lead(II) atoms exhibit coordination numbers of four and six. The crresponding Pb—O, Te—O and M—O (M = Co, Ni) bond lengths are very similar in the two isotypic structures.

The crystal structure of Pb₆Co₉(TeO₆)₅ can be described in terms of (001) layers A at z≈ 0.25 and B at z≈ 0 that stack alternately along [100] (Fig. 1). In layer A [TeO₆] and [CoO₆] octahedra share edges with 1/6 of the octahedral holes at the 2c and 2d positions, both with site symmetry 3.2, not occupied. The corresponding vacancies, denominated as X1 at the 2d position and as X2 at the 2c position, have different sizes. X1 has a diagonal diameter of 4.1076 (8) Å whereas X2 is somewhat larger with a diagonal diameter of 4.3258 (8) Å. This difference might be correlated with the size of the surrounding octahedra. Whereas the smaller X1 vacancy is encircled by a ring of six [CoO₆] octahedra, the larger X2 is encircled by a ring of three [CoO₆] and three slightly smaller [TeO₆] octahedra (Fig. 2). Layer B consists of double octahedra that are made up from face-sharing [CoO₆] and [TeO₆] octahedra, and by surrounding lead(II) atoms (Fig. 3). Adjacent A and B layers are linked together above and below the X1 and X2 vacancies through corner-sharing of [CoO₆] and [TeO₆] octahedra.

The resulting [Co₉Te₅O₃₀]^12- framework anion leaves space for the stereochemically active lead(II) cations. The oxygen coordination of the two Pb²⁺ cations is one-sided, with a [4]-coordination for Pb1 and a [6]-coordination for Pb2, if only Pb—O distances less than 2.75 Å are taken into account. The two cations share a common edge (O6—O6') with the lone pair electrons E pointing towards opposite directions. However, a bond valence calculation (Brown, 2002) shows a significant contribution of the four additional Pb—O distances for each of the two Pb atoms if interactions up to 3.5 Å are considered. Inclusion of these bonds increases the bond valence sum at Pb1 from 1.61 valence units (vu) to 1.83 vu and at Pb2 from 1.64 to 1.96 vu. The bond valence sum at O3 is also raised from 1.60 to 1.80 vu. Therefore the overall coordination of Pb1 might be described as [4 + 4] and that of Pb2 as [6 + 4] (Fig. 4).

Experimental

1.281 (5.7 mmol) PbO, 0.216 g (2.9 mmol) CoO and 0.914 g (5.7 mmol) TeO₂ were mixed and thoroughly ground and heated in an alumina crucible under atmospheric conditions during 6 h to 1023 K and held at that temperature for 48 h. Then the furnace was shut-off. Several crystal phases could be identified from the cooled reaction mixture by single-crystal diffraction: Dark blue isometric crystals of Pb₂CoTeO₆, dark-red (nearly black) block-like crystals of Pb₅TeO₈ (Artner & Weil, 2012), colourless crystals of α-Al₂O₃ and dark red crystals of Pb₆Co₉(TeO₆)₅ with a block-like shape.