Polymorphism and variable structural dimensionality in the iron(III) phosphate oxalate system: A new polymorph of 3D [Fe2(HPO 4)2(C2O4)(H2O) 2]·2H2O and the layered ma

Article abstract of DOI:10.1039/b911757a

Two new iron (III) phosphate oxalates have been isolated under hydrothermal conditions as phase-pure samples and their crystal structures determined from single crystal X-ray diffraction. [Fe₂(HPO₄) ₂(C₂O_4<

Full text of DOI:10.1039/b911757a

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Polymorphism and variable structural dimensionality in the iron(III)
phosphate oxalate system: a new polymorph of 3D
[Fe2(HPO4)2(C2O4)(H2O)2]·2H2O and the layered material
[Fe2(HPO4)2(C2O4)(H2O)2]†
Zoe A. D. Lethbridge, Guy J. Clarkson, Scott S. Turner‡ and Richard I. Walton*
Received 16th June 2009, Accepted 17th August 2009
First published as an Advance Article on the web 3rd September 2009
DOI: 10.1039/b911757a
Two new iron (III) phosphate oxalates have been isolated under hydrothermal conditions as
phase-pure samples and their crystal structures determined from single crystal X-ray diffraction.
[Fe2(HPO4)2(C2O4)(H2O)2]·2H2O, I, is a polymorph of a known phase and differs in the local
arrangement of hydrophosphate, oxalate and coordinated water about iron, presenting a mer
orientation of three coordinated phosphates, rather than fac as previously seen. The structure of I is
three-dimensionally connected with similar network connectivity to the known phase but different
overall topology. [Fe2(HPO4)2(C2O4)(H2O)2], II, has a layered structure constructed from octahedral
Fe(III) centres coordinated by hydrophosphate, oxalate and water in a fac arrangement. The amount of
water used in synthesis is one of the key experimental parameters in stabilising one phase over the
other. Thermogravimetric analysis shows that both I and II ultimately collapse into dense tridymite
type FePO4 above 600 ◦C and variable temperature powder XRD shows that this occurs via crystalline
intermediate phases. Variable temperature magnetisation measurements show that both materials order
antiferromagnetically at low temperatures, with similar Ne´el temperatures (~29 K) despite their
long-range structural differences.
exist with other structural units (e.g. phosphate tetrahedra) in
Introduction
hybrid materials. The simplest dicarboxylate unit, the oxalate
anion, is a rigid unit that exhibits a range of co-ordination
behaviour. It often acts in a bis-bidentate configuration bridging
metal centres and oxalate is particularly effective in providing
electronic communication between paramagnetic metal centres
producing magnetic ordering and its use as a linker in hybrid
materials provides a route to multifunctional magnetic materials.6
A wide range of metal oxalate structures now exist, and oxalate
has also been combined with phosphate units to produce hybrid
materials giving even greater structural variety.7–9 Here oxalate
has been observed to act as a pillar between metal phosphate
layers, or it can be part of a layer linking metal phosphate ladders.
Other mixed anion frameworks have been reported combining,
for example, phosphate and acetate, phosphonate and oxalate and
bipyridyl and glutarate. Metals incorporated include vanadium,
iron, manganese, cobalt, (with the possibility of each in variable
oxidation states) zinc, aluminium and gallium.5 Use has been made
of amines in many of these syntheses, where the amine plays a role
of structure direction, space filling or charge balance, similar to
the templates often used in zeolite synthesis.
The study of hybrid organic-inorganic solids continues to be of
great interest because of the variety of solid-state structures that
can be produced, often with open frameworks that might have
applications due to their porosity. The combination of metal-
centred polyhedral units with organic ligands offers some scope
of design in synthesis by potentially providing choice in the
connectivity of an extended structure, by selection of a particular
organic ligand, and also by the selection of a metal with a
particular preferred coordination environment or specific chemical
property. The initial work in this area arose from the possibility of
preparing novel zeolite analogues,1 but currently the focus is in the
field of metal-organic framework (MOF) materials.2 These solids
have porosity that extend from the microporous to the mesoporous
with applications in gas purification, separation and shape-
selective catalysis,3 and several of these have extreme flexibility
in the solid state, giving them distinctly different properties from
traditional zeolite materials.4
Rao and co-workers have reviewed the use of carboxylate units
in MOFs and other hybrid structures.5 When polycarboxylate
anions are used, these units can act as bridging linkers between
metal centres or more complex inorganic groups, and may co-
In this paper we describe the synthesis and structural character-
isation of two new Fe(III) oxalate phosphate materials. Although
a variety of oxalate phosphates of transition metals have been
reported previously,7–9 our results illustrate the effect that subtle
changes in synthesis conditions can have on the material produced:
in this case permitting small changes in the local structure of
the metal or by adjusting the amount of extra-framework water,
that then give a material with a different extended structure. The
Department of Chemistry, University of Warwick, Gibbet Hill Road,
Coventry, CV4 7AL, UK. E-mail: r.i.walton@warwick.ac.uk
† CCDC reference numbers 736331 and 736332. For crystallographic data
in CIF or other electronic format see DOI: 10.1039/b911757a
‡ Present address: Chemical Sciences, University of Surrey, Guildford,
Surrey, UK GU2 7XH.
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results are potentially of relevance to the future ‘design’ of open
framework hybrid solids.
using the ratios from the work of Choudhury et al. and a steel
autoclave, failed to form this material. This suggests that the
water content of the reaction mixtures is crucial for obtaining
the desired product in hydrothermal synthesis. The water content
of these reactions is indeed low for hydrothermal synthesis and
II is observed to form with lower reagent water content than I
(compare reactions A, C, D and E in Table 2), which is consistent
with the different crystal water content of the two materials as
discussed below. FePO4·2H2O, phosphosiderite, is formed with
higher water content (see reation F); this was also a common
product of reactions using the degraded FeCl3 that had been dried
in an oven. Where the ratio of FeCl3 was reduced, increasing the
water ratio resulted instead in the formation of FeC2O4·2H2O
(see reactions G-J). Reactions based on the ratios in reaction
E were also used to examine the effect of time; after 1 day a
very small quantity of lilac crystals were formed, reactions after
2, 5 and 6 days showed that the crystal size first increased and
later the yield improved. I and II were not observed at any
temperature other than 110 ◦C: other reaction temperatures of
80, 100, 120, 140 and 200 ◦C were investigated. At 200 ◦C iron
ammonium phosphates or iron phosphates were formed and the
products of the other reactions were soluble in water and dissolved
upon washing. Experiments varying the ratios of phosphoric
and oxalic acid led to the formation of iron phosphate or iron
oxalate.
The iron co-ordination environments in [Fe2(HPO4)2(C2O4)-
(H2O)2]·2H2O, I, and [Fe2(HPO4)2(C2O4)(H2O)2], II, are shown in
Fig. 1. For further comparison, the equivalent view of the related
material that was reported by Choudhury et al.7 is also shown.
I and the material reported by Choudhury et al. have identical
chemical compositions and hence are polymorphs; they also
show very similar Fe3+ co-ordination, with each iron connected
to three hydrophosphate tetrahedra, one oxalate unit (bidentate)
and one water molecule. The O-Fe-O angles vary between 79.2◦
(O(5)-Fe-O(6)) and 99.8◦ (O(3)-Fe-O(7)), the smallest angle is part
of the bidentate oxalate co-ordination where a five-membered
ring is formed. There is an important difference between the
two materials, however; in I the phosphate groups are in a mer
configuration about the Fe(III) centre, whereas in the previously
described material they are oriented in a fac configuration. Both
materials contain a free water molecule, and one oxygen on the
phosphate groups (O(1) and O(7) respectively) is protonated, i.e.
it is a hydrophosphate group. Each hydrophosphate tetrahedra
is co-ordinated to three irons, and each oxalate to two. In both
materials this leads to the formation of iron phosphate layers.
Considering only the iron and phosphorus atoms (analogous to
the way T atoms are represented in a zeolite structure10) these
layers are constructed from four and eight membered rings, as
shown in Fig. 2. Bisbidentate oxalate anions bridge the layers in
both materials resulting in three-dimensional connectivity, Fig. 3.
According to the structural classification proposed by Cheetham
et al. for hybrid inorganic-organic materials,11 both I and the
material reported by Choudhury et al. have I2O1 connectivity;
that is, the inorganic structure extends in two dimensions and
the organic in one dimension, overall giving a three-dimensional
structure.
Results and discussion
Table 2 shows some typical reaction conditions used in the
synthesis of Fe(III) oxalate phosphates. Two experiments labelled
D and C were found to form reproducibly I and II, respectively,
as phase-pure samples. Cyclohexylamine is required under the
conditions used here to form the new materials: presumably it
is controlling pH as there is no evidence of it in the products,
as template, for example. Attempts were also made to synthe-
sise the material [Fe2(HPO4)2(C2O4)(H2O)2]·2H2O reported by
Choudhury et al.7 This material was reported to be formed using
polypropylene bottles as reaction vessels, however these were
found to be unsatisfactory, since some degree evaporation of
water during the hydrothermal reaction often occurred, making
synthesis difficult to reproduce. Interestingly, Reaction J (Table 2)
Table 1 Details of single crystal structure solution and refinement for I
and II
I
II
Empirical formula
T/K
FePO8CH5
120
Mo Ka
0.20 ¥ 0.10 ¥ 0.04
Block
Monoclinic
P21/n
8.1041(3)
6.6254(2)
12.0431(4)
90
108.423(2)
90
613.49(4)
4
2.722
6105/1402
1322
FePO7CH3
293
Mo Ka
0.20 ¥ 0.10 ¥ 0.10
Block
Triclinic
P-1
5.0365(3)
7.6400(5)
7.6678(6)
97.292(6)
101.847(6)
106.380(6)
271.62(3)
2
l
Crystal size/mm3
Crystal form
Crystal system
Space group
˚
a/A
˚
b/A
˚
c/A
a/◦
b/◦
g /◦
3
˚
V/A
Z
m/mm-1
3.049
2581/1277
1193
0.0205, 0.0527
1.107
Reflections collected/unique
Reflections I > 2s(I)
Rint, Rw (I > 2s(I))
GOF
0.0261, 0.0635
1.056
Table 2 Examples of reacting ratios in the synthesis of I and II. All
reactions were carried out at 110 ◦C for 7 days
Experiment FeCl3 H3PO4 H2C2O4 C6H11NH2 H2O Product
A
B
C
D
E
F
2
2
2
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
—
1
1
1
2
2
4
8
16
32
II
II + impurity
II
I
I
1
FePO4·2H2O
phosphosiderite
(JCPDS 33-0666)
I
G
H
I
1
1
1
2
2
2
1
1
1
1
1
1
4
8
16
I
I + FeC2O4·2H2O
(JCPDS 23-0293)
Ja
1
2
1
1
122 FeC2O4·2H2O
(JCPDS 23-0293)
In contrast, II is a two-dimensional material. The co-ordination
environment around the Fe3+ (Fig. 1c) is analogous to that
of Choudhury’s material, where three phosphate tetrahedra are
a Reactant ratios from the reported synthesis of Fe2(HPO4)2-
(C2O4)(H2O)2]·2H2O.7
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Fig. 2 Layers in (a) I and (b) [Fe2(HPO4)2(C2O4)(H2O)2]·2H2O7 showing
Fe (green) and phosphorus (pink) only.
Fig. 1 Co-ordination environment of Fe3+ for (a) I, (b) II, and
(c) [Fe2(HPO4)2(C2O4)(H2O)2]·2H2O.7 Fe green, P pink, O red, C black, H
white.
is due to the oxalate co-ordination, while the largest angle is found
between the oxygen atoms opposite. II also has one protonated
oxygen per phosphate (O(6)), but no free water molecules were
located in the single crystal structure. Phosphate tetrahedra and
iron octahedra form ladders along the a axis, Fig. 4a, which are
connected into layers in the [01-1] plane by oxalate anions, Fig. 4b.
Using the classification of Cheetham et al.,11 II has I1O1 structural
connectivity. The layers in II are stacked in an ABA sequence.
There is evidence for hydrogen bonding interactions between
found in a fac configuration. The octahedral co-ordination is
completed by one water molecule and one bidentate oxalate unit
as before. The iron is found in a distorted octahedron as in I,
with minimum and maximum angles of 78.3◦ (O(1)-Fe-O(2)) and
103.1◦ (O(4)-Fe-O(5)). As in I, the smallest intra-octahedral angle
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◦
◦
small step similar to I around 500 C. By 700 C a further 4.2%
is lost, corresponding to a total loss of 29.5%. The absence of an
initial loss from II below 200 ◦C is consistent with the lack of
free water in the structure; this water in I accounts for 7.8% by
weight which is close to the loss observed (8.4%), bearing in mind
the likely presence of surface water. Both materials show a mass
at 700 ◦C consistent with the loss of all the remaining water and
oxalate to form FePO4 (calculated total loss of 35.0% for I, 29.5%
for II).
Variabletemperaturepowder X-raydiffractionofbothmaterials
is shown in Fig. 6 upon heating the samples in air and recording
patterns at intervals of between 25 and 50 ◦C as shown. The sample
was heated at 0.5 ◦C s-1 and then held for 20 minutes equilibration
followed by data collection at the desired temperature. Patterns
calculated from the single crystal structures show excellent agree-
ment with the measured room temperature patterns (as shown on
Fig. 6) confirming the phase purity of the samples. Bragg peaks
of I can be seen up to 175 ◦C, which would correspond to the loss
of water, based on the TGA results. (Note that the heating rate
is not directly comparable with the TGA.) Patterns collected at
◦
200 and 250 C show the appearance of a new crystalline phase.
From 300 to 600 ◦C the mat◦erial is largely amorphous but the
final pattern collected at 700 C shows the appearance of peaks
similar to the tridymite form of quartz. This form of FePO4 has
been reported previously as a result of heating iron phosphate
materials.12 The experiment was repeated with heating up to 250 ◦C
where the new crystalline phase was formed, followed by cooling to
room temperature. The phase remains stable throughout cooling,
however could not be identified by a search of the JCPDS database.
Various iron (III) phosphate phases have been reported by Reale
et al.12 and Song et al.13 were also considered as candidates
for the unknown phase, but none of these match the pattern
obtained. Diffraction patterns from II (Fig. 6b) show similar
behaviour, with a (different) new phase observed at 300 and 350 ◦C,
and the appearance of the tridymite structure at 700 ◦C. Again
the experiment was repeated, heating to the appearance of the
new phase (350 ◦C) followed by cooling to room temperature.
In contrast to I, this intermediate phase was not stable during
the cooling process, at which point peaks from a further phase
appeared.
Plots of magnetic susceptibility per Fe vs temperature are
shown in Fig. 7 where parameters derived from analysis of
these traces are shown. (There is possibly evidence of a very
small amount of a paramagnetic impurity in II but this does
not affect the analysis.) Both materials show antiferromagnetic
behaviour, with Ne´el temperatures of ~29 K, rather similar to
other reported iron phosphate oxalates.7 In both I and II oxalate
is co-ordinated in a bis-bidentate mode to iron; the remaining
connectivity provided by corner-sharing phosphate tetrahedra.
The same mode of coordination is seen in the four materials
reported by Choudhury et al., all of which order antiferro-
magnetically between 25 and 40 K.7 The iron (III) arsenate
oxalate [NH3(CH2)CH(NH3)CH3]3[Fe6(AsO4)2(HAsO4)6(C2O4)3]
also shows antiferromagnetic ordering below 31 K.14 Al-
though this structure is quite different in appearance to
those described here, the local connectivity is similar, i.e. bis-
bidentate oxalate and corner-sharing polyhedra. The Fe(II)-
containing (N2C4H12)[Fe4(C2O4)3(HPO4)2(H2O)2] includes oxalate
co-ordinating in two different modes (mono- and bidentate) and
Fig. 3 Three-dimensional structure of (a) I and (b) [Fe2(HPO4)2(C2O4)-
(H2O)2]·2H2O.7 FeO6 octahedra pale green, PO4 tetrahedra dark blue,
O red, C black, H white.
neighbouring layers: the distance between O6 (the P-OH oxygen)
and O7 (an oxygen bridging Fe and P in a neighbouring layer) is
˚
2.703 A, and the distance between O3 (of the water coordinated
to Fe) and O5 (another bridging oxygen in a neighbouring layer)
˚
is 2.912 A.
Thermogravimetric analysis of I (shown in Fig◦. 5) shows an
◦
initial mass loss of 8.4% between 100 C and 220 C. There is a
further rapid loss of 29.7% to 295 ◦C, followed by a small loss
◦
between 515 and 700 C, bringing the total mass loss to◦34.8%.
In contrast, II shows no weight change until nearly 200 C (see
Fig. 6). A rapid loss of 25.3% occurs to 350 ◦C, followed by a
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Fig. 4 The structure of II (a) ladders showing Fe and P only (b) view of a single layer and (c) showing the stacking of the layers. Colours as for Fig. 1
and 2.
edge-sharing FeO6 octahedra; this material also shows antiferro-
magnetism at low temperatures (23 K).9
Fisher), H2C2O4·2H2O (BDH, 99%) and cyclohexylamine (Acros,
99%). Reactants were added directly to PTFE autoclave liners with
stirring. The stainless steel autoclaves, approximate volume 15 ml,
were sealed and placed in an oven at 110 ◦C for 1 week. After
cooling to room temperature the contents of the autoclaves were
filtered and washed with deionised water. Anhydrous FeCl3 was
kept in a vacuum desiccator to avoid water uptake. Keeping FeCl3
at ~70 ◦C was found to be unsatisfactory as the material degraded
Experimental
Synthesis
Materials were synthesised hydrothermally in deionised water
from FeCl3 (anhydrous, Alfa Aesar, 98%), H3PO4 (85% in water
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Crystal structure analysis
For I, [Fe2(HPO4)2(C2O4)(H2O)2]·2H2O, single crystal data were
collected at the EPSRC Crystallography Service at the University
of Southampton. For II, [Fe2(HPO4)2(C2O4)(H2O)2], data were
collected on an Oxford Diffraction Gemini four-circle system
with a Gemini CCD area detector. Details of structure solution
and refinement are given in Table 1. Both structures were
solved by direct methods using SHELXS15 and light atoms were
located by Fourier methods. Hydrogen atoms were located in a
difference map and given isotropic displacement parameters equal
to 1.5 times the displacement parameter of the oxygen atoms
to which they are attached. All other atoms were refined with
anisotropic thermal parameters. Semi-empirical absorption cor-
rections were applied based on symmetry-equivalent and repeated
reflections.
Fig. 5 Thermogravimetric analysis plots of I (solid line) and II (dashed
line).
Laboratory characterisation
Powder X-ray diffraction patterns were collected on a Bruker
D5000 diffractometer with Cu Ka radiation, using alu-
minium sample holders in Bragg-Brentano geometry for phase
and gave irreproducible synthesis results. Specific details of the
synthesis are described below.
Fig. 6 Powder XRD recorded on heating to 700 ◦C for (a) I and (b) II. The simulated powder patterns of I and II were generated from the single crystal
structures reported in the text and the Miller indices of the strong peaks of the tridymite form of FePO412 are indicated on the pattern of the final product.
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Acknowledgements
We thank the EPSRC for funding ZADL (EP/C516591), the
EPSRC crystallography service for recording one of the single
crystal datasets and Dave Hammond, Department of Physics,
University of Warwick for measuring TGA data. We are grateful
to Martin Lees, Department of Physics, University of Warwick,
for access to the SQUID magnetometer. The TGA apparatus and
single-crystal X-ray diffractometer used in this research at the
University of Warwick was obtained through the Science City
Advanced Materials project “Creating and Characterising Next
Generation Advanced Materials” with support from Advantage
West Midlands (AWM) and part funded by the European Regional
Development Fund (ERDF).
References
Fig. 7 Magnetic susceptibility vs temperature plots of I (closed spheres)
and II (open spheres) with the extracted parameters shown in the inset
table.
1 A. K. Cheetham, G. Fe´rey and T. Loiseau, Angew. Chem., Int. Ed., 1999,
38, 3268; G. Fe´rey, Chem. Soc. Rev., 2008, 37, 191; R. Murugavel, A.
Choudhury, M. G. Walawalkar, R. Pothiraja and C. N. R. Rao, Chem.
Rev., 2008, 108, 3549.
2 J. R. Long and O. M. Yaghi, Chem. Soc. Rev., 2009, 38, 1213.
3 A. U. Czaja, N. Trukhan and U. Mu¨ller, Chem. Soc. Rev., 2009, 38,
1284.
4 G. Fe´rey and C. Serre, Chem. Soc. Rev., 2009, 38, 1380.
5 C. N. R. Rao, S. Natarajan and R. Vaidhyanathan, Angew. Chem., Int.
Ed., 2004, 43, 1466.
6 C. Mathoniere, C. J. Nuttall, S. G. Carling and P. Day, Inorg. Chem.,
1996, 35, 1201; C. J. Nuttall and P. Day, Chem. Mater., 1998, 10,
3050; C. J. Nuttall and P. Day, J. Solid State Chem., 1999, 147, 3; E.
Coronado, J. R. Galan-Mascaros, C. J. Gomez-Garcia and V. Laukhin,
Nature, 2000, 408, 447; D. J. Price, A. K. Powell and P. T. Wood, Dalton
Trans., 2003, 2478; M. Y. Zhang, Y. Ma, A. L. Cheng, Q. Yue, Q. Sun
and E. Q. Gao, Dalton Trans., 2008, 2061.
identification and to verify sample purity. For variable temperature
experiments, an MRI TC-Basic furnace was fitted and alumina
sample holders were used. The sample was heated to the de-
sired temperature and equilibrated for 20 minutes before data
was collected. Thermogravimetric analysis was performed on a
◦
Mettler Toledo TGA/DSC 1 from 30–900 ◦C at 10 C min-1
in flowing air. Variable temperature magnetisation measurements
were taken in an external field of 1000 G between 2 and
350 K using a Quantum Design MPMS-5 SQUID magne-
tometer. Powdered samples were held in gel-capsules within
plastic straws and the diamagnetic contributions from the sample
mount and sample (Pascals constants) were corrected for in all
calculations.
7 A. Choudhury, S. Natarajan and C. N. R. Rao, Chem. Eur. J, 2000, 6,
1168.
8 Z. A. D. Lethbridge, S. K. Tiwary, A. Harrison and P. Lightfoot,
J. Chem. Soc., Dalton Trans., 2001, 1904; N. Rajic, D. Stojakovic, D.
Hanzel, N. Z. Logar and V. Kaucic, Microporous Mesoporous Mater.,
2002, 55, 313; Z. A. D. Lethbridge, M. J. Smith, S. K. Tiwary, A.
Harrison and P. Lightfoot, Inorg. Chem., 2004, 43, 11; Y. C. Jiang, S. L.
Wang, K. H. Lii, N. Nguyen and A. Ducouret, Chem. Mater., 2003, 15,
1633; M. F. Tang and K. H. Lii, J. Solid State Chem., 2004, 177, 1912;
T. Huang, B. A. Vanchura, Y. K. Shan and S. D. Huang, J. Solid State
Chem., 2007, 180, 2110; X. Yang, J. Li, Y. Hou, S. Shi and Y. Shan,
Inorg. Chim. Acta, 2008, 361, 1510; J. Zheng, Y. X. Shen, T. Song and
A. Y. Zhang, Acta Crystallogr., Sect. E: Struct. Rep. Online, 2009, 65,
i32.
Conclusions
Small changes in reaction conditions lead to quite dramatic
changes in the structures of iron oxalate phosphates that crystallise
under hydrothermal conditions. The local coordination about Fe
can thus be adjusted in a subtle manner (fac/mer arrangements
of coordinating groups) and the resulting dimensionality of
structure can be affected by changing the relative ratios of
reagents, in particular the water content of the synthesis mixture.
Although the resulting materials have rather similar magnetic
behaviour their long-range crystal structures are clearly dictated
by the connectivity induced by the local arrangement about
Fe(III) and this would have implications in the “design” of
new hybrid organic-inorganic materials by control of reaction
conditions.
9 H. Meng, G. H. Li, Y. Xing, Y. L. Yang, Y. J. Cui, L. Liu, H. Ding and
W. Q. P a n g , Polyhedron, 2004, 23, 2357.
10 http://www.iza-online.org/databases/.
11 A. K. Cheetham, C. N. R. Rao and R. K. Feller, Chem. Commun.,
2006, 4780.
12 P. Reale, B. Scrosati, C. Delacourt, C. Wurm, M. Morcrette and C.
Masquelier, Chem. Mater., 2003, 15, 5051.
13 Y. N. Song, P. Y. Zavalij, M. Suzuki and M. S. Whittingham, Inorg.
Chem., 2002, 41, 5778.
14 V. K. Rao, K. C. Kam, A. K. Cheetham and S. Natarajan, Solid State
Sci., 2006, 8, 692.
15 G. M. Sheldrick, Acta Crystallogr., Sect. A: Found. Crystallogr., 2007,
64, 112.
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