Syntheses, structures, and characterization of new lead(II)-tellurium(IV)-oxide halides: Pb3Te2O6X2 and Pb3TeO4X2 (X = Cl or Br)

Article abstract of DOI:10.1021/ic025750j

The syntheses, structures, and characterization of four new lead(II)-tellurium(IV)-oxide halides, Pb₃Te₂O₆X₂ and Pb₃TeO₄X₂ (X = Cl or Br) are reported. The materials are synthesized by solid-state techniques, using Pb₃O₂Cl₂ or Pb₃O₂Br₂ and TeO₂ as reagents. The compounds have three-dimensional structural topologies consisting of lead-oxide halide polyhedra connected to tellurium oxide groups. In addition, the Pb²⁺ and Te⁴⁺ cations are in asymmetric coordination environments attributable to their stereoactive lone pair. We also demonstrate that Pb₃Te₂O₆X₂ and Pb₂TeO₄X₂ can be interconverted reversibly through the loss or addition of TeO₂. X-ray data: Pb₃Te₂O₆Cl₂, monoclinic, space group C2/m (No. 12), a = 16.4417(11) A, b = 5.6295(4) A, c = 10.8894(7) A, β= 103.0130(10)°, Z = 4; Pb₃Te₂O₆Br₂, monoclinic, space group C2/m (No. 12), a = 16.8911(8) A, b = 5.6804(2) A, c = 11.0418(5) A, β = 104.253(2)°, Z = 4; Pb₃TeO₄Cl₂, orthorhombic, space group Bmmb (No. 63), a = 5.576(1) A, b = 5.559(1) A, c = 12.4929(6) A, Z = 4; Pb₃TeO₄Br₂, orthorhombic, space group Bmmb (No. 63), a = 5.6434(4) A, b = 5.6434(5) A, c = 12.9172(6) A, Z = 4.

Full text of DOI:10.1021/ic025750j

Inorg. Chem. 2003, 42, 205−209
Syntheses, Structures, and Characterization of New
Lead(II)−Tellurium(IV)−Oxide Halides: Pb3Te2O X and Pb3TeO X (X )
6 2
4 2
Cl or Br)
Yetta Porter and P. Shiv Halasyamani*
Department of Chemistry, UniVersity of Houston, 4800 Calhoun BouleVard,
Houston, Texas 77204-5003
Received May 24, 2002
The syntheses, structures, and characterization of four new lead(II)−tellurium(IV)−oxide halides, Pb3Te2O X and
6
2
Pb3TeO X (X ) Cl or Br) are reported. The materials are synthesized by solid-state techniques, using Pb3O Cl2
4
2
2
or Pb3O Br2 and TeO as reagents. The compounds have three-dimensional structural topologies consisting of
2
2
lead−oxide halide polyhedra connected to tellurium oxide groups. In addition, the Pb2+ and Te4+ cations are in
asymmetric coordination environments attributable to their stereoactive lone pair. We also demonstrate that Pb3-
Te2O X and Pb2TeO X can be interconverted reversibly through the loss or addition of TeO . X-ray data: Pb3-
6
2
4
2
2
Te2O Cl2, monoclinic, space group C2/m (No. 12), a ) 16.4417(11) Å, b ) 5.6295(4) Å, c ) 10.8894(7) Å, â )
6
103.0130(10)°, Z ) 4; Pb3Te2O Br2, monoclinic, space group C2/m (No. 12), a ) 16.8911(8) Å, b ) 5.6804(2) Å,
6
c ) 11.0418(5) Å, â ) 104.253(2)°, Z ) 4; Pb3TeO Cl2, orthorhombic, space group Bmmb (No. 63), a ) 5.576(1)
4
Å, b ) 5.559(1) Å, c ) 12.4929(6) Å, Z ) 4; Pb3TeO Br2, orthorhombic, space group Bmmb (No. 63), a )
4
5.6434(4) Å, b ) 5.6434(5) Å, c ) 12.9172(6) Å, Z ) 4.
PbO and the corresponding lead halide in air at 500 °C for 1 day.
The powder X-ray diffraction patterns for Pb3O2Cl2 and Pb3O2Br2
matched those previously reported.2-4
Introduction
The interest in synthesizing new mixed-metal oxide halide
materials exists not only for their potential ion-exchange
behavior but also for their optical properties as well as
interesting crystal chemistry. We have previously reported
that a low-temperature (160 °C) aqueous method can be
employed for the synthesis of new metal oxide halides.1
Specifically, we synthesized and characterized Pb3(SeO3)(SeO2-
OH)Cl3 and Pb3(SeO3)2Cl2 utilizing this reflux technique and
demonstrated that an irreversible transformation occurs
between the two materials with the loss of HCl. In this paper,
we report the syntheses, structures, and characterization of
new Pb(II)-Te(IV)-oxide halides, Pb3Te2O6X2 and Pb3-
TeO4X2 (X ) Cl or Br). In addition, we demonstrate that a
reversible transformation occurs between the two materials
through the loss or addition of TeO2.
Synthesis. Single crystals of Pb3Te2O6Cl2 were grown by
combining Pb3O2Cl2 (0.2658 g, 3.67 × 10-4 mol) and TeO2 (0.2342
g, 1.47 × 10-3 mol) in a fused silica tube that was subsequently
evacuated and sealed. The mixture was heated at 550 °C for 1 day
and cooled at a rate of 6 °C h-1 to room temperature. A few clear
colorless crystals were observed (roughly 2% of the bulk powder).
Bulk, polycrystalline Pb3Te2O6Cl2 was synthesized by combining
Pb3O2Cl2 (0.3466 g, 4.79 × 10-4 mol) and TeO2 (0.1529 g, 9.58
× 10-4 mol). The mixture was introduced into a fused silica tube
that was subsequently evacuated and sealed. The tube was heated
to 575 °C for 1 day and then furnace cooled to room temperature.
An off-white powder was recovered.
The other phases, Pb3Te2O6Br2, Pb3TeO4Cl2, and Pb3TeO4Br2,
were synthesized as polycrystalline powders. All attempts to grow
single crystals were unsuccessful. Each material was synthesized
by combining stoichiometric amounts of Pb3O2Br2 (Pb3O2Cl2) with
TeO2. The mixtures were introduced into separate fused silica tubes
Experimental Section
Reagents. PbO (99.9+ %, Aldrich), PbCl2 (99%, Alfa Aesar),
and TeO2 (99.9% Aldrich) were used as received. Pb3O2Cl2 and
Pb3O2Br2 were synthesized by heating a stoichiometric mixture of
(2) Vincent, H.; Perrault, G. Bull. Soc. Fr. Mineral. Cristallogr. 1971,
94, 323.
(3) Berdonosov, P. S.; Dolgikh, V. A.; Popovkin, B. A. Mater. Res. Bull.
1996, 31, 717.
* To whom correspondence should be addressed. E-mail: psh@uh.edu.
(1) Porter, Y.; Halasyamani, P. S. Inorg. Chem. 2001, 40, 2640.
(4) Pasero, M.; Vacchiano, D. Neues Jahrb. Mineral., Monatsh. 2000,
563-569.
10.1021/ic025750j CCC: $25.00 © 2003 American Chemical Society
Published on Web 12/05/2002
Inorganic Chemistry, Vol. 42, No. 1, 2003 205

Porter and Halasyamani
Table 1. Crystallographic Data for Pb3Te2O6Cl2
Table 2. Atomic Coordinates for Pb3Te2O6Cl2
fw
1043.67
atom
x
y
z
Ueqa (Å2)
space group
a (Å)
b (Å)
C2/m (No. 12)
16.4417(11)
5.6295(4)
10.8894(7)
103.013(10)
982.02(11)
4
Pb(1)
Pb(2)
Pb(3)
Te(1)
Te(2)
Cl(1)
Cl(2)
O(1)
0.26200(6)
0.02126(6)
0.16092(7)
0.10312(10)
0.37188(10)
0.3179(4)
-0.0410(5)
0.1309(8)
0.0000
0.3935(13)
0.2913(9)
0.0000
0.0000
0.5000
0.5000
0.5000
0.5000
0.5000
0.263(3)
0.288(4)
0.5000
0.262(3)
0.20191(9)
0.20025(9)
0.39346(10)
0.05086(15)
0.40736(15)
0.0993(6)
0.3016(8)
0.1830(12)
0.0000
0.0113(4)
0.0108(4)
0.0145(4)
0.0088(4)
0.0088(4)
0.0166(14)
0.0252(17)
0.016(3)
c (Å)
â (deg)
V (Å3)
Z
temp (°C)
λ (Å)
25.0(2)
0.71073
O(2)
O(3)
O(4)
0.024(5)
0.018(2)
0.018(2)
F (g cm-3
µ (cm-1)
R(F)a
)
7.059
0.5810(19)
0.3859(13)
576.65 cm-1
0.0617
Rw(F2)b
0.158
a Ueq is defined as one-third of the trace of the orthogonalized Uij tensor.
a R ) Σ||Fo| - |Fc||/Σ|Fo|. b Rw ) [Σw(|Fo | - |Fc |)2/Σw(Fo )2]1/2
.
2
2
2
Table 3. Summary of Crystallographic Powder X-ray Diffraction and
Refinement Data for Pb3Te2O6Cl2 and Pb3TeO4Cl2
that were subsequently evacuated and sealed. For Pb3Te2O6Br2 (Pb3-
TeO4Cl2 and Pb3TeO4Br2) the tubes were heated to 575 °C (650
°C) for 1 day and cooled at a rate of 6 °C h-1 to room temperature.
With Pb3Te2O6Br2 (Pb3TeO4Cl2 and Pb3TeO4Br2) off-white (yellow)
polycrystalline powders were recovered.
Pb3Te2O6Cl2
Pb3TeO4Cl2
a (Å)
b (Å)
c (Å)
16.4349(5)
5.6255(1)
10.8802(3)
103.050(1)
979.94(1)
C2/m (No. 12)
1380
2.55
0.131
0.167
0.104
5.576(1)
5.559(1)
12.4929(6)
Single-Crystal Structure Determination. The structure of Pb3-
Te2O6Cl2 was determined by standard crystallographic methods.
For Pb3Te2O6Cl2 a colorless column (0.04 mm × 0.08 mm × 0.20
mm) was used for single-crystal measurements. Room-temperature
intensity data were collected on a Siemens SMART diffractometer
equipped with a 1K CCD area detector using graphite- monochro-
mated Mo KR radiation. A hemisphere of data was collected using
a narrow-frame method with scan widths of 0.30° in ω and an
exposure time of 25 s/frame. The first 50 frames were remeasured
at the end of the data collection to monitor instrument and crystal
stability. The maximum correction applied to the intensities was
<1%. The data were integrated using the Siemens SAINT program,5
with the intensities corrected for Lorentz, polarization, air absorp-
tion, and absorption attributable to the variation in the path length
through the detector faceplate. ψ-scans were used for the absorption
correction on the hemisphere of data. The data were solved and
refined using SHELXS-97 and SHELXL-97, respectively.6,7 All
calculations were performed using the WinGX-98 crystallographic
software package.8 Crystallographic data, atomic coordinates, and
thermal parameters for Pb3Te2O6Cl2 are given in Tables 1 and 2.
Powder Diffraction and Crystal Structure Refinement. The
X-ray powder diffraction data were collected on a Scintag XDS2000
diffractometer at room temperature (Cu KR radiation, θ-θ mode,
flat plate geometry) in the 2θ range 3-110° with a step size of
0.02° and a step time of 10 s. The diffraction patterns were analyzed
using the Rietveld9 method with the FULLPROF program.10 An
asymmetry correction was applied to the low-angle reflections. The
scale was refined initially, followed in subsequent iterations by the
zero point error, cell constants, peak shape parameters, atomic
parameters, and overall isotropic temperature factors. For Pb3Te2O6-
Cl2, a powder refinement was undertaken attributable to the
somewhat large errors observed in the single-crystal refinement.
â (deg)
V (Å3)
space group
observns
ø2
385.9(1)
Bmmb (No. 63)
352
3.25
0.169
0.215
0.119
0.087
a
Rp
b
Rwp
c
Rexp
d
RBragg
0.069
b
2
2 1/2
a Rp ) Σ|Io - Ic|/ΣIo. Rwp ) [Σw|Io - Ic| /ΣwIo ]
. .
c Rexp ) Rwp/(ø2)1/2
d RBragg ) Σ|Ik(obs) - Ik(calc)|/ΣIk(obs) , where Io and Ic are the observed and
calculated integrated intensities, Ik is the Bragg intensity, and w is the weight
derived from an error propagation scheme during the process of the least-
squares refinement.
The peaks were indexed on a monoclinic cell, with the refinements
of the unit cell constants performed using a least-squares method.
The structural refinements were carried out in space group C2/m
(No. 12) with a starting model based on the single-crystal data. A
total of 44 parameters, including 13 profile parameters, were used
in the refinement. For Pb3TeO4Cl2 the peaks were indexed on an
orthorhombic cell, with refinement of the unit cell constants
performed by a least-squares method. The structural refinements
were carried out in space group Bmmb (No. 63) with a starting
model based on the structure of orthorhombic PbBiO2Cl. To model
Pb3TeO4Cl2 with the orthorhombic PbBiO2Cl structure, statistical
disorder must occur between the Pb2+ and the Te4+ cations. A
variety of disorder models are possible; however, the model that
gave the best fit to the data and made the most chemical sense is
to statistically disorder Pb(2) and Te(1) (vide infra). In addition,
although the unit cell is metrically tetragonal, refinements using
higher symmetry tetragonal space groups resulted in large errors.
A total of 20 parameters, including 12 profile parameters, were
used in the refinement. The results of the powder refinements,
atomic coordinates, thermal parameters, and bond distances are
given in Tables 3-5. Pb3Te2O6Br2 and Pb3TeO4Br2 are isostructural
with Pb3Te2O6Cl2 and Pb3TeO4Cl2, respectively. Tables 6 and 7
gives the refined unit cell, space group, hkl, dobs, dcalc, Iobs, and Icalc
for Pb3Te2O6Br2 and Pb3TeO4Br2, respectively.
(5) SAINT, version 4.05 ed.; Siemens Analytical X-ray Systems, Inc.:
Madison, WI, 1995.
(6) Sheldrick, G. M. SHELXS-97-A program for automatic solution of
crystal structures; University of Goettingen: Goettingen, Germany,
1997.
(7) Sheldrick, G. M. SHELXL-97-A program for crystal structure refine-
ment; University of: Goettingen: Goettingen, Germany, 1997.
(8) Farrugia, L. J. WinGX: An integrated system of publically available
windows programs for the solution, refinement, and analysis of single-
crystal X-ray diffraction data. J. Appl. Crystallogr. 1998, 32, 837.
(9) Rietveld, H. M. J. Appl. Crystallogr. 1969, 2, 65.
(10) Rodriguez, J. C. FULLPROF Program: RietVeld Pattern Matching
Analysis of Powder Patterns; ILL: Grenoble, France, 1990.
Infrared Spectroscopy. Infrared spectra were recorded on a
Matteson FTIR 5000 spectrometer in the 400-4000 cm-1 range,
with the sample pressed between two KBr pellets.
Thermogravimetric Analysis. Thermogravimetric measure-
ments were carried out on a TGA 2950 thermogravimetric analyzer
(TA Instruments). The samples were contained within platinum
206 Inorganic Chemistry, Vol. 42, No. 1, 2003

Lead(II)-Tellurium(IV)-Oxide Halides
a
Table 4. Fractional Atomic Coordinates, Isotropic Temperature Factors
Table 7. Powder XRD Data for Pb3TeO4Br2
(Å2), and Occupancies for Pb3TeO4Cl2
h
k
l
dcalc
dobs
Icalc
Iobs
atom
x
y
z
U
eq (Å2)
occ
0
1
1
0
1
0
0
0
1
0
2
2
1
1
0
2
4
0
0
1
1
2
1
0
2
1
3
2
0
2
1
3
0
2
0
2
2
1
3
0
5
6
4
6
1
6
6
4
7
3
8
6
0
8
6.459
3.812
2.927
2.822
2.169
2.153
2.125
1.995
1.768
1.712
1.711
1.697
1.675
1.649
1.615
1.463
1.411
1.401
6.490
3.822
2.932
2.826
2.171
2.156
2.128
1.997
1.768
1.722
1.713
1.699
1.677
1.650
1.617
1.469
1.412
1.402
4
19
100
21
2
6
6
18
2
8
7
4
7
16
1
7
3
1
5
18
100
18
2
7
7
22
3
6
6
5
6
18
4
15
3
1
Pb(1)
Pb(2)
Te(1)
Cl(1)
O(1)
0.00000
0.00000
0.00000
0.00000
0.767(3)
0.2500
0.2500
0.2500
0.2500
0.0000
0.39063(19)
0.09796(23)
0.09796(23)
0.74746(114)
0.00000
0.02504(9)
0.0219(1)a
0.0219(1)a
0.0123(30)
0.0116(58)
1.0
0.5
0.5
1.0
1.0
a These atoms were constrained to have the same atomic coordinates
and thermal parameters.
a
Table 5. Selected Bond Distances (Å) for Pb3Te2O6Cl2 and
Pb3TeO4Cl2
b
Pb3Te2O6Cl2
Pb(1)-O(1)
Pb(1)-O(4)
Pb(1)-Cl(1)
Pb(1)-Cl(2)
Pb(2)-O(1)
Pb(2)-O(2)
Pb(2)-O(3)
Te(1)-O(1)
Te(1)-O(2)
2.586(14) × 2
2.447(15) × 2
3.237(12)
Pb(2)-Cl(2)
Pb(3)-O(1)
Pb(3)-O(4)
Pb(3)-O(4)
Pb(3)-O(3)
Pb(3)-Cl(2)
3.270(12) × 2
2.600(14) × 2
2.544(16) × 2
2.778(15) × 2
2.985(15) × 2
3.244(12)
3.176(12)
2.374(14) × 2
2.677(13) × 2
2.48(2)
a Refined unit cell a ) 5.6434(4) Å, b ) 5.6434(5) Å, and c )12.9172(6)
Å and space group Bmmb (No. 63).
1.938(13) × 2
Te(2)-O(3)
Te(2)-O(4)
1.84(2)
1.861(16) × 2
2.044(12) × 2
Pb3TeO4Cl2
Pb(1)-O(1)
Pb(1)-Cl(1)
2.452(12) × 4
Pb(1)-Cl(1)
3.305(12) × 2
2.257(12) × 4
3.271(12) × 2
Pb(2)/Te(2)-O(1)
a Single-crystal data. b Powder diffraction data.
a
Table 6. Powder XRD Data for Pb3Te2O6Br2
h
k
l
dcalc
dobs
Icalc
Iobs
2
-2
0
-4
3
-4
1
-2
4
-3
-1
4
-5
1
0
-6
-2
0
5
-4
0
-1
4
-4
1
0
0
0
0
1
0
1
0
0
1
1
0
1
1
2
0
0
0
1
0
2
1
0
2
1
2
0
1
2
1
0
2
2
3
1
2
3
2
1
3
0
1
4
4
1
4
2
4
3
1
4
2
8.186
7.446
5.351
4.182
3.935
3.723
3.645
3.612
3.543
3.479
3.088
2.922
2.899
2.866
2.840
2.815
2.751
2.675
2.608
2.545
2.509
2.476
2.411
2.350
2.321
2.258
8.231
7.486
5.369
4.190
3.941
3.723
3.651
3.625
3.458
3.484
3.092
2.925
2.903
2.870
2.843
2.826
2.758
2.678
2.612
2.543
2.510
2.480
2.414
2.352
2.322
2.259
2
13
5
9
10
1
27
2
1
3
14
5
8
10
1
26
1
1
8
9
100
43
97
4
50
2
1
1
4
2
2
1
2
3
2
1
100
42
92
4
47
3
1
1
4
2
1
1
2
3
2
1
Figure 1. Ball-and-stick diagram of Pb3Te2O6Cl2 in the a-c plane.
forming PbO4Cl4(Br4), PbO5Cl3(Br3), and PbO8Cl(Br) groups
for Pb(1), Pb(2), and Pb(3), respectively, whereas the Te4+
cations are only bonded to oxygen forming TeO4 and TeO3
groups for Te(1) and Te(2), respectively. Both Pb2+ and Te4+
are in highly asymmetric coordination environments attribut-
able to their stereoactive lone pair. The lone pairs point into
the layer, between the halide anions. The Pb-O and Pb-Cl
bond distances range 2.447(15)-2.994(15) and 3.236(12)-
3.270(12) Å, respectively, whereas the Te-O bond distances
range 1.84(2)-2.044(12) Å. The closest Te-Cl contacts are
at a distance of greater than 3.2 Å. Bond valence sums11,12
for Pb2+ range from 1.83 to 2.19 and for Te4+ are 3.89 and
4.18.
-4
a Refined unit cell a ) 16.8911(8) Å, b ) 5.6804(2) Å, c )11.0418(5)
Å, and â ) 104.253(2)° and space group C2/m (No. 12).
crucibles and heated at a rate of 2 °C min-1 from room temperature
to 900 °C in flowing nitrogen.
Results and Discussion
The isostructural materials Pb3Te2O6Cl2 and Pb3Te2O6Br2
have three-dimensional structural topologies consisting of
lead-oxide halide polyhedra linked to tellurium-oxide
groups (see Figures 1and 2). In both materials the Pb2+
cations are linked to both oxygen and chloride (bromide)
(11) Brown, I. D.; Altermatt, D. Acta Crystallogr. 1985, B41, 244.
(12) Brese, N. E.; O’Keeffe, M. Acta Crystallogr. 1991, B47, 192.
Inorganic Chemistry, Vol. 42, No. 1, 2003 207

Porter and Halasyamani
Table 8. Infrared Spectroscopy Data (cm-1) for Pb3Te2O6X2 and
Pb3TeO4X2 (X ) Cl or Br)
ν(Pb-O)
ν(Te-O)
ν(Te-O-Pb)
Pb3Te2O6Cl2
Pb3Te2O6Br2
Pb3TeO4Cl2
Pb3TeO4Br2
701
696
534
522
509
499
750
746
669
659
661
653
636
632
628
613
422
416
439
441
to Pb3Te2O6Cl2, the closest Te-Cl contacts are greater than
3.2 Å. The relationship between the stoichiometries of
PbBiO2Cl and Pb3TeO4Cl2 may be understood as follows.
If the formula of PbBiO2Cl is “doubled”, “Pb2Bi2O4Cl2” is
obtained. If the two Bi3+ cations are replaced by one Te4+
and one Pb2+ cation, “Pb2(PbTe)O4Cl2” ≡ Pb3TeO4Cl2 may
be formulated. As stated earlier the Te4+ can be disordered
over both Pb2+ sites, without any detriment to the refinement.
However, this would result in larger, chemically unreason-
able, Te-O bond lengths (ca. 2.452(12) Å). Thus, we
decided to statistically disorder Pb(2) and Te(1) resulting in
four equal Te-O bonds distances of 2.257(12) Å (see Tables
4 and 5).
Infrared Spectroscopy. The infrared spectra for Pb3Te2O6-
Cl2, Pb3Te2O6Br2, Pb3TeO4Cl2, and Pb3TeO4Br2 revealed a
host of Pb-O, Te-O, and Te-O-Pb vibrations. Table 8
summarizes the infrared data. The additional Pb-O and
Te-O stretches observed in Pb2Te2O6X2 compared with Pb2-
TeO4X2 are attributable to the different coordination environ-
ments of the Pb2+ and Te4+ cations in the materials. In
Pb2Te2O6X2 the Pb2+ are in 8- and 9-fold coordination
environments, whereas in Pb2TeO4X2 the Pb2+ is only in an
8-fold environment. Similarly for Te4+, in Pb2Te2O6X2 the
Te4+ are in 3- and 4-fold environments, whereas in Pb2-
TeO4X2 the Te4+ is only in a 3-fold environment. All of the
assignments are consistent with those previously reported.17-19
Thermogravimetric Measurements. For Pb3Te2O6Cl2
(Pb3Te2O6Br2), the TGA measurements revealed one transi-
tion between 560 and 750 °C corresponding to a weight loss
of 15.57% (14.21%). The weight loss is consistent with the
following reaction:
Figure 2. Ball-and-stick diagram of Pb3Te2O6Cl2 in the b-c plane.
Pb3Te2O6X2 f Pb3TeO4X2 + TeO2v
Here X ) Cl or Br. The calculated weight loss for this
reaction for Pb3Te2O6Cl2 (Pb3Te2O6Br2) is 15.29% (14.09%).
For Pb3TeO4Cl2 (Pb3TeO4Br2), the TGA measurements also
revealed one transition between 650 and 850 °C correspond-
ing to a weight loss of 31.46% (37.62%). The weight loss is
consistent with the following reaction:
Figure 3. Ball-and-stick diagram of Pb3TeO4Cl2 in the b-c plane. Note
the large, clear spheres are statistically disordered between Pb2+ and Te4+
.
Pb3TeO4Cl2 and Pb3TeO4Br2 also have three-dimensional
structural topologies with lead-oxide halide polyhedra linked
to tellurium oxide groups (see Figure 3). The materials are
isostructural with orthorhombic PbBiO2Cl13 and PbSbO2Cl
(Nadorite).14-16 The Pb-O bond distances are 2.452(12) Å
with Pb-Cl bond distances of 3.274(12) and 3.305(12) Å,
whereas the Te-O bond distances are 2.252(12) Å. Similar
Pb3TeO4X2 f Pb2TeO4 + PbCl2v
Here X ) Cl or Br. The calculated weight loss for this
reaction for Pb3TeO4Cl2 (Pb3TeO4Br2) is 31.81% (37.72%).
One of the most interesting aspects of the reported
materials is their interconvertibility. As demonstrated by the
TGA measurements, when Pb3Te2O6Cl2 is heated above 560
(13) Gillberg, M. ArkiV Mineral. Geol. 1961, 2, 565.
(17) Brooker, M. H.; Irish, D. E. J. Chem. Phys. 1970, 53, 1083.
(18) Bart, J. C. J.; Petrini, G. Z. Z. Anorg. Allg. Chem. 1984, 509, 183.
(19) Nakamoto, K. Infrared and Raman Spectra of Inorganic and Coor-
dination Compounds, 5th ed.; John Wiley & Sons: 1997.
(14) Sillen, L. G.; Melander, L. Z. Kristallogr. 1941, 103, 420.
(15) Giuseppetti, G.; Tadini, C. Period. Mineral. 1973, 42, 335.
(16) Porter, Y.; Halasyamani, P. S. Z. Naturforsch. 2002, 57b, 360.
208 Inorganic Chemistry, Vol. 42, No. 1, 2003

Lead(II)-Tellurium(IV)-Oxide Halides
of TeO2 between Pb3Te2O6Cl2 and Pb3TeO4Cl2.
Pb3Te2O6Cl2 {-TeO , 560 °C} Pb3TeO4Cl2
2
+TeO2, 600 °C
Conclusion. We have reported the synthesis and charac-
terization of four new mixed-metal oxide halide materials,
Pb3Te2O6X2 and Pb3TeO4X2 (X ) Cl or Br). All of the
materials have three-dimensional structural topologies, with
lead-oxide halide polyhedra linked to tellurium-oxide
groups. The stereoactive lone pairs on the Pb2+ and Te4+
point into the layer, between the halide anions. Interestingly,
the materials may be interconverted through the loss or
addition of TeO2. Synthetically, we prepared all the reported
materials by a combination of an oxide halide, Pb3O2X2 (X
) Cl or Br), and an oxide, TeO2. This suggests that other
three-dimensional materials are possible. We are pursuing
this avenue of synthetic research and will be reporting on
the new materials shortly.
Acknowledgment. We wish to thank the reviewers for
perceptive criticism of an earlier version of the manuscript.
We thank the Robert A. Welch Foundation for support. We
wish to acknowledge the Center for Materials Chemistry at
the University of Houston (CMC-UH) for support. This work
was also supported by the NSF-Career Program through
Grant DMR-0092054, and an acknowledgment is made to
the donors of the Petroleum Research Fund, administered
by the American Chemical Society, for partial support of
this research. P.S.H. is a Beckman Young Investigator.
Figure 4. Schematic structural representation of the interconversion
between Pb3Te2O6Cl2 and Pb3TeO4Cl2. The circled atoms indicate where
TeO2 may be lost, or added, during the transformation.
°C, the material loses TeO2 and forms Pb3TeO4Cl2. Interest-
ingly, when Pb3TeO4Cl2 is combined with TeO2 and heated
in an evacuated and sealed quartz tube at 600 °C for 12 h,
Pb3Te2O6Cl2 is re-formed. The interconversion, which also
occurs with the bromine analogues, indicates a great deal of
stability in the lead(II)-tellurium(IV)-oxide “sheets”. The
aforementioned reaction is outlined below, and Figure 4 gives
a schematic structural representation of the loss, or addition,
Supporting Information Available: Refined powder X-ray
diffraction patterns for Pb3Te2O6Cl2 and Pb3TeO4Cl2 and a CIF for
Pb3Te2O6Cl2. This material is available free of charge via the
Internet at http://pubs.acs.org.
IC025750J
Inorganic Chemistry, Vol. 42, No. 1, 2003 209