From ∞1[(UO2)2O(MoO 4)4]6- to ∞ 1[(UO2)2(MoO4)3(MoO 5)]6- infinite chains in A6U2Mo 4O21 (A=Na, K, Rb, Cs) compounds: Synthesis and crystal structure

Article abstract of DOI:10.1016/j.jssc.2011.01.010

A new caesium uranyl molybdate belonging to the M₆U ₂Mo₄O₂₁ family has been synthesized by solid-state reaction and its structure determined from single-crystal X-ray diffraction data. Contrary to the other alkali uranyl molybdates of this family (A=Na, K, Rb) where molybdenum atoms adopt only tetrahedral coordination and which can be formulated A₆[(UO₂)₂O(MoO ₄)₄], the caesium compound Cs₆U ₂Mo₄O₂₁ should be written Cs ₆[(UO₂)₂(MoO₄)₃(MoO ₅)] with molybdenum atoms in tetrahedral and square pyramidal environments. Cs₆[(UO₂)₂(MoO₄) ₃(MoO₅)] crystallizes in the triclinic symmetry with space group P1 and a=10.4275(14) A, b=15.075(2) A, c=17.806(2) A, α=70.72(1)°, β=80.38(1)° and γ=86.39(1)°, V=2604.7(6) A³, Z=4, ρ_mes=5.02(2) g/cm ³ and ρ_cal=5.08(3) g/cm³. A full-matrix least-squares refinement on the basis of F² yielded R ₁=0.0464 and wR₂=0.0950 for 596 parameters with 6964 independent reflections with I≥2σ(I) collected on a BRUKER AXS diffractometer with Mo(Kα) radiation and a CCD detector. The crystal structure of Cs compound is characterized by _∞ ¹[(UO₂)₂(MoO₄)₃(MoO ₅)]^6- parallels chains built from U₂O ₁₃ dimeric units, MoO₄ tetrahedra and MoO₅ square pyramids, whereas, Na, K and Rb compounds are characterized by _∞¹[(UO₂)₂O(MoO ₄)₄]^6- parallel chains formulated simply of U₂O₁₃ units and MoO₄ tetrahedra. Infrared spectroscopy measurements using powdered samples synthesized by solid-state reaction, confirm the structural results. The thermal stability and the electrical conductivity are also studied. The four compounds decompose at low temperature (between 540 and 610 °C).

Full text of DOI:10.1016/j.jssc.2011.01.010

Journal of Solid State Chemistry 184 (2011) 971–981
Contents lists available at ScienceDirect
Journal of Solid State Chemistry
journal homepage: www.elsevier.com/locate/jssc
1
N
6ꢀ
1
N
6ꢀ
5
From [(UO ) O(MoO ) ] to [(UO ) (MoO ) (MoO )] infinite chains in
2 2
4 4
2 2
4 3
A U Mo O (A¼Na, K, Rb, Cs) compounds: Synthesis and crystal structure of
6
2
4 21
Cs [(UO ) (MoO ) (MoO )]
6
2 2
4 3
5
a,b
c,n
a
a
S. Yagoubi , S. Obbade , S. Saad , F. Abraham
a
Unit e´ de Catalyse et de Chimie du Solide, UCCS UMR CNRS 8181, USTL, ENSCL-B.P. 90108, 59652 Villeneuve d’Ascq Cedex, France
b
c
Groupe de Radiochimie, Institut de Physique Nucl e´ aire d’Orsay, Universit e´ Paris-Sud XI, 91406 Orsay Cedex, France
Laboratoire d’ E´ lectrochimie et de Physicochimie des Mat e´ riaux et des Interfaces, LEPMI, UMR 5279, CNRS-Grenoble INP-UdS-UJF,
1
130 Rue de la Piscine, BP 75, 38402 Saint-Martin d’H eꢀ res, France
a r t i c l e i n f o
a b s t r a c t
Article history:
A new caesium uranyl molybdate belonging to the M U Mo O family has been synthesized by solid-
6
2
4 21
Received 27 July 2010
Received in revised form
state reaction and its structure determined from single-crystal X-ray diffraction data. Contrary to the
other alkali uranyl molybdates of this family (A¼Na, K, Rb) where molybdenum atoms adopt only
2
3 December 2010
6 2 2 4 4
tetrahedral coordination and which can be formulated A [(UO ) O(MoO ) ], the caesium compound
Accepted 10 January 2011
Available online 2 March 2011
6 2 4 6 2 2 4 3 5
Cs U Mo O21 should be written Cs [(UO ) (MoO ) (MoO )] with molybdenum atoms in tetrahedral
and square pyramidal environments. Cs
¯
6
[(UO
˚
2
)
2
(MoO
4
)
3
(MoO
˚
5
)] crystallizes in the triclinic symmetry
˚
Keywords:
with space group P1 and a¼10.4275(14) A, b¼15.075(2) A, c¼17.806(2) A,
a¼70.72(1)1, b¼80.38(1)1
3
Uranyl molybdates
Crystal structure refinement
Compound with chains solid-state
synthesis
˚
3
3
and
g
¼86.39(1)1, V¼2604.7(6) A , Z¼4,
r
mes¼5.02(2) g/cm and
r
cal¼5.08(3) g/cm . A full-matrix
¼0.0950 for 596 parameters
2
least-squares refinement on the basis of F yielded R
1
¼0.0464 and wR
2
with 6964 independent reflections with IZ2
s(I) collected on a BRUKER AXS diffractometer with
Mo(K ) radiation and a CCD detector. The crystal structure of Cs compound is characterized by
a
Electrical conductivity
Infrared spectroscopy
1
6ꢀ
parallels chains built from U
N
[
(UO
2
)
2
(MoO
square pyramids, whereas, Na, K and Rb compounds are characterized by
parallel chains formulated simply of U 13 units and MoO tetrahedra.
4
)
3
(MoO
5
)]
2
O
13 dimeric units, MoO
4
tetrahedra and
1
N
6ꢀ
MoO
5
2 2 4 4
[(UO ) O(MoO ) ]
2
O
4
Infrared spectroscopy measurements using powdered samples synthesized by solid-state reaction,
confirm the structural results. The thermal stability and the electrical conductivity are also studied. The
four compounds decompose at low temperature (between 540 and 610 1C).
&
2011 Elsevier Inc. All rights reserved.
1
. Introduction
formation of the new compounds in the contaminated grounds
and the evolution of the obtained products after the nuclear
waste deterioration, but also by cationic exchanges, ionic con-
ductivity and fluorescence properties, that these materials can
generate [3–17]. From a solid-state chemistry point view, the
uranyl ion association to different oxoanions is particularly
interesting because it frequently generates original structures:
two-dimensional structures (2D) by the formation of infinite
layers, or more scarcely three-dimensional (3D) frameworks
presenting infinite tunnels [18]. These structures favour the
mobility of the cations localized in the tunnels or between layers,
as well as the possibility of intercalation/desintercalation of these
cations.
Since the first oil crisis, uranium, the only natural element
having a fissile isotope (U235), plays an important part in the field
of the energy production in the world, particularly in France.
Thus, any progress in physical and chemical knowledge of this
element, can present in the short or medium term an interest for
the control of different problems of the manufacture, the storage
and the reprocessing of nuclear fuel. So, the materials resulting
2
2
þ
pꢀ
from the association of ions uranyl UO
and oxoanions X
m n
O
,
with X¼C, N, P, S, Si, As, I, transition metals etc., have had a very
intense research activity in these last decades [1,2]. This research
is motivated not only by the environmental aspects, like the
possible oxidation of the uranium during the storage, the
Considering the presence of the long-living radioactive fission
1
37
93
isotopes
Cs and Mo in consequent quantities in radioactive
waste and spent nuclear fuel, and the possibility of the chemical
interaction, in normal or accidental conditions, of both fission
products ( Cs and Mo) between them as well as with uranium
oxide to form different caesium uranyl molybdate compounds,
n
Corresponding author.
1
37
93
E-mail addresses: said.obbade@phelma.grenoble-inp.fr,
said.obbade@lepmi.grenoble-inp.fr (S. Obbade).
0022-4596/$ - see front matter & 2011 Elsevier Inc. All rights reserved.
doi:10.1016/j.jssc.2011.01.010

9
72
S. Yagoubi et al. / Journal of Solid State Chemistry 184 (2011) 971–981
the identification of such compounds likely to form is necessary.
Thus, the Cs O–MoO –UO ternary system has been extensively
The present work is dedicated to the crystal structure deter-
mination of a new Cs-uranyl molybdate Cs [(UO (MoO (-
MoO )] synthesized by solid-state reaction. Its crystal structure
was determined from single crystal X-ray diffraction data and
compared to those of the other compounds A [(UO O(MoO )]
(A¼Na, K and Rb) previously reported [45,46]. The thermal,
electrical and spectroscopic results of this alkaline uranyl molyb-
date family are also reported
2
3
3
6
2
)
2
4 3
)
studied these three last decades, and several new caesium uranyl
molybdates have been identified and their crystal structures deter-
mined [19–29]. The reaction between the three metals Cs–U–Mo in
alteration products of spent nuclear fuel, to form caesium uranyl
molybdate compounds, under the similar conditions with those
expected in the nuclear waste repository at Yucca Mountain site in
Nevada, has been already shown by Buck et al. [10]. This study
revealed the presence of orthorhombic mixed Cs/Ba uranyl molybdate
5
6
2
)
2
4 4
)
2
. Experimental
(
Cs0.8Ba0.6)[(UO
2
)
5
(MoO
4
)O
4
(OH)
6
](ꢁ6H
2
O), characterized by Analy-
tical Transmission Electron Microscopy, after corrosion of commercial
oxide spent nuclear fuel. Thus, additional investigations of this
ternary system are very important for the understanding of evolution
and alteration of spent nuclear fuel and radioactive waste.
2.1. Synthesis of single crystals and powder samples
Yellow-orange transparent single crystals were obtained by
solid-state reactions from mixtures of U
MoO (Prolabo, 3 mol) and an excess of Cs
The mixture was slowly heated in platinum crucibles up to
50 1C, maintained at this temperature during 12 h and then
3
O
8
(Prolabo, 1 mol) and
So, if one considers the ternary system A
2
O–MoO
3
þ
–UO
3
þ
where
þ
þ
þ
3
2
CO (Aldrich, 10 mol).
3
A corresponds to monovalent cations (Li , Na , K , Rb , Cs
Ag , Tl and NH ), several uranyl molybdates families have been
,
þ
þ
þ
4
9
evidenced and their crystal structures determined from X-ray
diffraction data [10,19–46]. Concerning caesium uranyl molyb-
dates, only eight compounds have been reported and their crystal
structures were determined using single crystal X-ray diffraction
data. According to their composition the uranyl molybdate
entities adopt various dimensionalities in agreement with the
cooled at 5 1C/h to room temperature. The molten mixture was
washed with hot water and ethanol to dissolve alkaline salt
excess and separate yellow-orange single crystals of Cs
Mo 21. Presence and proportions of the metal elements, Cs, U
and Mo, in different obtained crystals were confirmed by Energy
Dispersive Spectroscopy analysis performed using a JEOL JSM-
5300 Scanning Microscope equipped with IMIX system of Prince-
ton Gamma Technology (PGT).
6 2-
U
4
O
diagram proposed by Alekseev et al. [29]: Cs
6
[(UO
[(UO )O(MoO
polyhedra (1D) [29], the
] [25], Cs [(UO )(MoO ] and its
](H O) [22,26] are layered com-
pounds (2D), the layers being built of UO and MoO entities, in
Cs [(UO O(MoO (MoO )] the layers are built from both MoO
and MoO5 polyhedra [24], finally the -form of Cs [(UO
MoO ] [25] and the dihydrate Cs [(UO (MoO (H O)
2
4 4
)(MoO ) ]
4
ꢀ
contains [UO
based upon chains of UO
-form of Cs [(UO (MoO
monohydrate Cs [(UO )(MoO
2
(MoO
4
)
4
]
units (0D) [24], Cs
2
2
4
) is
6
and MoO
4
Pure polycrystalline samples of A
were prepared by conventional solid-state reactions, using pure
initial materials U , MoO and A CO taken in molar ratio of
:12:9 according to the following reaction:
6
U
2
Mo
4
O
21 (A¼Na, K, Rb, Cs)
b
2
2
)
2
4
)
3
2
2
4 2
)
2
2
4
)
2
2
3
O
8
3
2
3
6
4
2
4
2
)
3
4
)
2
5
4
2
a
2
2
)
2/3U O þ4MoO þ3A CO þ1/3O (air)-A U Mo O21þ3CO2
3
8
3
2
3
2
6
2
4
(
4
)
3
2
2
)
6
4
)
7
2
2
] [23,34]
are framework-based structures (3D). Some of these compounds have
been also evidenced and characterized with other A monovalent
cations.
The homogeneous mixtures were slowly heated up to 500 1C
in a platinum crucible and maintained at this temperature during
10 days, with intermediate grindings, and finally slowly cooled to
þ
Fig. 1. Observed (dots), calculated (solid line) powder X-ray diffraction profiles of Cs
6
[(UO
2
)
2 4
(MoO )
3 5
(MoO )]. Difference (YobsꢀYcal) appears at the bottom of the plot and
allowed reflections are indicated by vertical lines.

S. Yagoubi et al. / Journal of Solid State Chemistry 184 (2011) 971–981
973
3
3
room temperature. For each sample, the reaction progress is
controlled by powder X-ray diffraction. Unit cell parameters of
formula per unit cell (
for Cs Mo
r
mes¼5.02(2) g/cm ,
r
cal¼5.08(3) g/cm )
6
U
2
4 21
O .
Cs
6
U
2
Mo
4
O
21were refined by using powder X-ray diffraction data
diffractometer equipped by CuKa
collected with a Bruker D8
y/
y
radiation, using Bragg–Brentano geometry, with steps of 0.031
and a counting time of 20 s per step, within an angular range of
2.2. Thermal analyses, electrical conductivity and infrared
spectroscopy measurements
1
0–801 in 2
method [47,48]. The refinement was carried out using the
’pattern matching’’ option of Fullprof program [49], where only
y. The unit cell parameters were refined using Rietveld
To determine the thermal stability of the studied compounds,
Differential Thermal Analyses (DTA) were performed in air, using
SETARAM 92-1600 thermal analyzer in the temperature range of
20–900 1C with heating and cooling rate 1.5 1C/min using plati-
num crucibles.
’
the profile parameters (cell dimensions, peak shapes, background,
zero point correction and symmetry) have been refined. The peak
shape was described by a pseudo-Voigt function with an asym-
metry correction at low angles. In order to describe the
angular dependence of the peak full-width at half-maxi-
mum (H), the formulation of Caglioti et al. [50] was used:
To evidence alkaline cations mobility in the four compounds
A
6
U
2
Mo
4
O
21 (A¼Na, K, Rb and Cs), electrical conductivity measure-
ments were carried out on cylindrical pellets (diameter, 5 mm;
thickness, 3.5 mm), obtained using a conventional cold press and
sintered at 500 1C for 2 days, followed by slow cooling, (5 1C/h), down
to room temperature. Gold electrodes were vacuum-deposited on
both flat surfaces of the pellets. Conductivity measurements were
2
2
H ¼U tan
yþV tan yþW where U, V and W parameters were
refined in the process. For Cs
6
U
2
Mo
4
O
21, the cell parameters
˚
refinement led to the following values a¼10.4216(3) A,
˚
˚
b¼15.0702(4) A, c¼17.7967(5) A,
a
¼70.73(1)1,
b
¼80.39(2)1 and
¼0.035,
¼1.05. The good agreement between observed
6
g
R
¼86.39(2) with the following profile factors:
R
p
performed by ac impedance spectroscopy over the range of 1–10 Hz
2
wp¼0.046 and
w
with a Solartron 1170 frequency-response analyzer. Measurements
were performed with 20 1C intervals between 200 and 500 1C on both
heating and cooling. Each set of values was recorded after a 1 h
stabilization time at a given temperature.
and calculated powder X-ray diffraction diagrams is shown in
Fig. 1 and the indexed powder pattern is reported in the Table 1.
The reliability of the unit cell refinement and indexing reflections
is indicated by the conventional figures of merit F20, defined by
Smith and Snyder [51], F20¼48 (0.0032, 130). The density
measured with an automated Micromeritics Accupy 1330 helium
For each compound infrared spectrum was recorded using the
KBr dispersion technique (1 mg of sample dispersed in 125 mg of
KBr and pressed at the pressure of 150 bars) with a Bruker Vector
22 Fourier Transform Infrared Spectrometer, which covers the
3
pycnometer using a 1-cm cell, indicates a good agreement
ꢀ
1
ꢀ1
between the calculated and measured densities, with four
range of 400–4000 cm
with a resolution of 0.1 cm
.
Table 1
6 2 2 4 3 5
Observed and calculated X-ray powder diffraction pattern for Cs [(UO ) (MoO ) (MoO )].
h
k
l
2h
obs
2h
cal
I (%)
h
k
l
2
h
obs
2h
cal
I (%)
0
0
1
1
0
1
2
2
1
0
1
0
1
1
0
1
2
2
3
1
1
3
3
4
3
2
3
4
3
0
4
2
5
1
1
2
2
3
4
1
2
0
3
5
2
5.3350
6.2250
6.7570
9.4140
5.3279
6.2149
6.7459
9.3962
4
3
ꢀ2
1
ꢀ3
ꢀ2
3
3
6
1
4
5
1
5
6
3
1
4
7
2
1
7
3
1
0
2
7
9
1
5
7
7
1
5
2
4
7
6
1
6
6
34.7204
38.4082
38.4595
38.5783
38.7943
39.4020
39.9124
41.3052
41.3770
41.7373
42.8292
43.2340
43.5627
44.2157
44.4690
44.8286
45.2730
45.3890
45.7460
46.6232
47.0841
47.6247
48.3970
48.5962
49.3220
49.9657
50.2649
51.2848
52.0370
52.5282
52.8865
53.1574
53.4591
54.3262
34.7214
38.4096
38.4607
38.5784
38.7943
39.4022
39.9121
41.3044
41.3753
41.7375
42.8277
43.2334
43.5606
44.2127
44.4688
44.8276
45.2718
45.3863
45.7444
46.6247
47.0853
47.6217
48.3951
48.5939
49.3213
49.9643
50.2652
51.2814
52.0364
52.5270
52.8851
53.1553
53.4553
54.3259
5
8
0
0
2
4
9
1
1
0
5
1
ꢀ4
6
2
10.5710
11.8312
13.5034
14.5966
16.9980
18.9850
19.3507
20.0590
21.0315
21.4030
21.6960
23.3390
24.0459
24.5841
24.9152
25.6604
26.2162
26.4193
26.8427
27.2808
27.7513
28.1570
28.3838
28.7931
29.4370
30.0540
30.3699
31.4225
32.0610
32.7124
33.6010
10.5768
11.8359
13.5080
14.6011
16.9800
18.9890
19.3542
20.0624
21.0256
21.4067
21.7000
23.3408
24.0496
24.5878
24.9179
25.6623
26.2184
26.4228
26.8461
27.2824
27.7534
28.1595
28.3862
28.7966
29.4387
30.0766
30.3710
31.4229
32.0610
32.7149
33.6022
22
2
1
2
3
5
7
0
24
10
4
ꢀ3
0
2
3
ꢀ
1
2
ꢀ
ꢀ
1
0
1
6
8
ꢀ4
ꢀ4
1
2
10
5
ꢀ1
1
8
ꢀ3
7
2
1
3
12
6
2
7
ꢀ2
1
3
3
2
ꢀ6
7
8
0
4
ꢀ1
ꢀ2
ꢀ3
ꢀ5
1
4
2
ꢀ
2
1
ꢀ
2
ꢀ
3
0
0
33
3
0
5
2
2
ꢀ4
0
7
ꢀ1
ꢀ1
1
7
9
4
7
4
2
1
10
100
24
7
4
ꢀ4
1
9
ꢀ3
3
4
4
2
3
7
1
ꢀ4
0
5
3
0
6
ꢀ5
7
5
0
ꢀ4
1
3
0
10
6
ꢀ
3
2
3
ꢀ
0
3
2
4
2
ꢀ3
ꢀ3
4
ꢀ1
4
5
ꢀ5
5
9
48
14
41
11
5
6
2
2
8
5
2
5
5
4
5
3
7
9
0
ꢀ4
5
4
ꢀ3
ꢀ4
4
5
0
17
4
ꢀ5
ꢀ4
5
3
ꢀ
2
ꢀ
2
3
4
3
4
3
5
4
ꢀ2
4

9
74
S. Yagoubi et al. / Journal of Solid State Chemistry 184 (2011) 971–981
2
.3. Single crystal X-ray diffraction and structure determination of
Table 3
A˚ 2
6 2 2
) for Cs (UO )
Cs
6
U
2
Mo
4
O
21
Atomic coordinates and equivalent displacement parameters (
4 3 5
(MoO ) (MoO ).
For structure determination, a well-shaped yellow-orange
single crystal of Cs Mo 21 phase was selected, mounted on
Atom
Site
x
y
z
U
eq
6
U
2
4
O
fibreglass and aligned on a Bruker AXS X-ray diffractometer
U1
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
0.39897(6)
0.81701(6)
ꢀ0.31502(6)
0.10827(6)
0.46569(11)
0.01619(12)
0.04102(11)
0.09439(5)
ꢀ0.29846(5)
0.78861(5)
0.41416(5)
ꢀ0.13847(9)
0.20235(8)
0.63218(9)
0.60956(9)
ꢀ0.11934(9)
ꢀ0.47557(9)
0.29636(8)
0.17648(4)
0.02682(4)
0.47221(4)
0.32271(4)
0.07678(8)
0.22275(7)
0.42322(8)
0.33049(8)
0.18420(8)
0.04663(8)
0.26608(7)
0.19485(8)
0.55717(8)
0.31000(8)
0.0150(2)
0.0156(2)
0.0145(2)
0.0153(2)
0.0258(3)
0.0254(3)
0.0251(3)
0.0275(3)
0.0313(3)
0.0318(3)
0.0242(3)
0.0344(3)
0.0284(3)
0.0315(3)
0.0351(4)
0.0340(3)
0.0182(4)
0.0185(4)
0.0163(4)
0.0157(3)
0.0175(4)
0.0174(4)
0.0166(4)
0.0175(4)
0.027(3)
0.023(2)
0.026(3)
0.027(3)
0.030(3)
0.018(2)
0.022(3)
0.026(3)
0.027(3)
0.027(3)
0.028(3)
0.019(3)
0.031(3)
0.028(3)
0.021(3)
0.028(3)
0.034(4)
0.038(4)
0.024(3)
0.028(3)
0.032(3)
0.029(3)
0.022(3)
0.035(4)
0.032(3)
0.029(3)
0.037(4)
0.036(4)
0.040(4)
0.032(3)
0.037(4)
0.033(4)
0.033(3)
0.041(4)
0.049(4)
0.031(3)
0.032(3)
0.033(4)
0.036(4)
0.036(4)
0.032(4)
0.023(3)
U2
equipped with a 1K SMART CCD. Intensities were collected at
˚
U3
room temperature using MoKa (l¼0.71073 A) radiation selected
U4
by a graphite monochromator. The individual frames were mea-
sured using a -scan technique with an omega rotation of 0.31
Cs1
Cs2
Cs3
Cs4
Cs5
Cs6
Cs7
Cs8
Cs9
Cs10
Cs11
Cs12
Mo1
Mo2
Mo3
Mo4
Mo5
Mo6
Mo7
Mo8
O1
o
and an acquisition time of 30 s per frame. A total of 1800 frames
were collected covering the full sphere. After data collection, the
intensity data were integrated and corrected for Lorentz-polar-
ization and background effects using the Bruker program
SAINT [52]. Once the data processing was performed, the absorp-
tion corrections were computed using a semi-empirical method
based on redundancy with the SADABS program [53]. Details
of the data collection and refinement are given in Table 2.
ꢀ0.28975(12)
0.76763(12)
1.19262(13)
0.50538(11)
0.44331(13)
ꢀ0.69057(11)
0.05619(12)
0.20803(12)
0.33759(13)
0.14704(15)
ꢀ0.01324(15)
0.41713(14)
ꢀ0.32771(14)
0.45587(14)
ꢀ0.30693(15)
0.07522(14)
0.83050(15)
0.9222(12)
0.2873(11)
ꢀ0.1749(11)
ꢀ0.0291(12)
ꢀ0.2022(12)
0.5149(10)
ꢀ0.2322(11)
0.5127(12)
0.2397(11)
ꢀ0.4302(12)
0.2783(12)
0.3441(11)
0.7182(11)
0.3723(11)
ꢀ0.2229(11)
ꢀ0.2800(11)
0.2207(12)
ꢀ0.0299(12)
0.5984(11)
0.0098(12)
ꢀ0.4480(12)
ꢀ0.3311(13)
ꢀ0.3967(11)
0.2224(12)
0.8679(12)
ꢀ0.0228(12)
0.0905(12)
0.6994(13)
ꢀ0.4768(13)
0.5122(12)
0.0184(12)
0.1282(11)
0.1053(14)
0.5094(12)
0.2568(14)
ꢀ0.1498(12)
0.4509(13)
0.9672(13)
ꢀ0.2644(13)
ꢀ0.0120(13)
0.7909(12)
0.3266(11)
ꢀ0.42008(10)
0.67709(9)
ꢀ0.09147(9)
ꢀ0.17653(10)
ꢀ0.00814(10)
0.03107(11)
0.85061(11)
ꢀ0.18384(11)
0.55176(11)
0.32033(11)
0.05541(11)
0.68746(11)
ꢀ0.56170(11)
ꢀ0.3273(8)
0.1333(8)
ꢀ0.05987(8)
0.43866(9)
0.06651(10)
0.55222(10)
0.32005(10)
0.56648(9)
0.04850(9)
0.31619(10)
0.17702(10)
0.18417(10)
ꢀ0.0534(7)
0.2484(7)
0.2490(8)
0.3864(7)
0.3876(7)
0.1340(7)
0.6506(7)
0.1109(7)
0.2568(8)
0.5531(7)
0.3647(8)
ꢀ0.0240(7)
0.1088(8)
0.2688(7)
0.5658(7)
0.3398(8)
0.1526(8)
0.2469(8)
ꢀ0.0204(7)
0.0871(7)
0.2694(8)
0.4057(7)
0.4874(7)
0.1499(8)
0.1042(8)
0.6284(8)
0.0295(8)
0.2520(8)
0.6227(8)
0.2539(7)
0.0988(8)
0.4837(8)
0.2179(8)
0.3943(9)
ꢀ0.0057(9)
0.5045(8)
0.0955(8)
0.2337(8)
0.5035(8)
0.5955(8)
0.1474(8)
0.0654(7)
The triclinic unit-cell parameters of Cs
˚
6
U
2
Mo
4
O
˚
21 single crystal
˚
were refined to a¼10.4275(14) A, b¼15.075(2) A, c¼17.806(2) A,
a
¼70.72(1)1,
b¼80.38(1)1 and g¼86.39(1)1.
Crystal structure was determined in the centrosymmetric P-1
space group, by direct methods using SHELXS program [54] which
readily localize the more heavy atoms U and Cs. The positions of
molybdenum and oxygen atoms were deduced from subsequent
refinements and difference Fourier maps, using the SHELXL
option of the SHELXTL software [55]. The atomic scattering
factors for neutral atoms were taken from ‘‘International Tables
for X-ray Crystallography’’ [56]. The last cycle of refinement
including atomic positions and anisotropic displacement para-
meters for all atoms, yielded to the final refinement factor
R1¼0.046 for 6964 independent reflections. Refinement results
O2
O3
0.0393(8)
O4
0.4454(9)
O5
0.7788(9)
O6
0.2218(8)
O7
0.4913(8)
O8
0.0470(9)
O9
0.3825(9)
O10
O11
O12
O13
O14
O15
O16
O17
O18
O19
O20
O21
O22
O23
O24
O25
O26
O27
O28
O29
O30
O31
O32
O33
O34
O35
O36
O37
O38
O39
O40
O41
O42
0.8081(9)
ꢀ0.2488(8)
0.3837(8)
Table 2
ꢀ0.2681(9)
ꢀ0.0671(9)
0.6595(8)
Crystal data, intensity collection and structure refinement parameters for Cs
6 2 2
(UO )
(
MoO (MoO ).
4
)
3
5
0.1553(9)
Compound
6
Cs (UO
2
)
2 4
(MoO )
3
5
(MoO )
0.745(1)
0.7263(10)
0.3271(8)
Crystal data
Crystal symmetry
Space group
Unit cell
Triclinic
-1
P
¯
0.7052(9)
0.0707(9)
a¼10.4275(14) A
b¼15.075(2) A˚
˚
ꢀ0.0414(8)
0.6529(8)
c¼17.806(2) A˚
0.0229(9)
a
b
g
¼70.72(1)1
¼80.38(1)1
¼86.39(1)1
ꢀ0.4558(9)
0.7408(8)
0.1485(9)
V¼2604.7(6) A˚
3
ꢀ0.5463(10)
0.5124(10)
ꢀ0.2334(10)
ꢀ0.0443(9)
0.8525(9)
Z
4
3
3
Calculated density
Measured density
r
cal¼5.08(3) g/cm
rmes¼5.02(2) g/cm
Data collection
0.5635(9)
Temperature (K)
293(2)
.71073 A
ꢀ0.181(1)
0.0033(11)
0.8618(9)
Radiation Mo(K
a
)
˚
0
Scan mode
o
Recording angular range (deg.)
Recording reciprocal space
3.24/29.27
0.4052(9)
ꢀ14rhr14
ꢀ0.5978(8)
0.4878(9)
ꢀ
ꢀ
19rkr20
23rhr23
0.9378(9)
Number of reflections measured/independent
12,635/6964
225.98
ꢀ0.649(1)
0.2154(8)
ꢀ
1
Absorption
Colour
m
(cm
)
Yellow
Refinement
Refined parameters/restraints
596/0
2
Goodness of fit on F
1.012
R1 [I42
wR2 [I42
Largest diff peak and hole (e A˚
s
(I)]
0.046
of the atomic coordinates with equivalent isotropic thermal
factors are reported in Table 3 and anisotropic displacement
parameters are listed in Table 4. Table 5 provides the most
s
(I)]
0.095
ꢀ
3
2.457/ꢀ3.290
)

S. Yagoubi et al. / Journal of Solid State Chemistry 184 (2011) 971–981
975
Table 4
Anisotropic displacement parameters ( A˚ 2) for Cs
6
(UO
2 2 4 3 5
) (MoO ) (MoO ).
Atom
U11
U22
U33
U12
0.0005(3)
U13
U23
U1
0.0145(3)
0.0172(3)
0.0153(3)
0.0154(3)
0.0270(6)
0.0300(6)
0.0240(6)
0.0302(6)
0.0294(7)
0.0378(7)
0.0272(6)
0.0305(7)
0.0272(7)
0.0265(6)
0.0229(6)
0.0367(7)
0.0164(7)
0.0190(8)
0.0164(7)
0.0154(7)
0.0179(8)
0.0179(8)
0.0160(7)
0.0201(8)
0.035(7)
0.027(7)
0.026(7)
0.029(7)
0.040(8)
0.018(6)
0.026(7)
0.031(7)
0.020(6)
0.036(7)
0.039(8)
0.023(6)
0.024(7)
0.025(7)
0.026(7)
0.024(7)
0.025(7)
0.030(8)
0.023(7)
0.037(8)
0.035(8)
0.047(8)
0.020(6)
0.029(7)
0.032(7)
0.043(8)
0.035(8)
0.045(8)
0.034(8)
0.037(8)
0.035(8)
0.014(6)
0.061(10)
0.026(7)
0.039(9)
0.031(7)
0.056(9)
0.042(8)
0.043(8)
0.051(9)
0.035(8)
0.026(7)
0.0154(4)
0.0154(4)
0.0143(3)
0.0154(4)
0.0254(7)
0.0240(6)
0.0233(7)
0.0271(7)
0.0316(7)
0.0276(7)
0.0238(6)
0.0364(8)
0.0290(7)
0.0302(7)
0.0394(8)
0.0342(8)
0.0176(8)
0.0187(8)
0.0162(8)
0.0154(8)
0.0179(8)
0.0158(8)
0.0164(8)
0.0152(8)
0.020(7)
0.033(8)
0.023(7)
0.031(8)
0.040(9)
0.020(7)
0.011(6)
0.031(8)
0.030(8)
0.033(8)
0.014(7)
0.021(7)
0.033(8)
0.029(8)
0.018(7)
0.022(7)
0.037(9)
0.05(1)
0.0149(4)
0.0146(4)
0.0130(4)
0.0149(4)
0.0245(7)
0.0215(7)
0.0267(7)
0.0268(7)
0.0352(8)
0.0362(8)
0.0231(7)
0.0275(8)
0.0276(8)
0.0316(8)
0.0345(9)
0.0371(8)
0.0186(9)
0.0180(9)
0.0155(9)
0.0158(8)
0.0156(9)
0.0182(9)
0.0163(9)
0.0178(9)
0.019(7)
0.003(6)
0.027(8)
0.024(8)
0.012(7)
0.014(7)
0.028(8)
0.021(8)
0.035(8)
0.011(7)
0.028(8)
0.015(7)
0.032(9)
0.024(8)
0.027(8)
0.045(9)
0.044(10)
0.034(9)
0.024(8)
0.021(8)
0.022(8)
0.020(8)
0.027(8)
0.036(9)
0.025(8)
0.035(8)
0.041(10)
0.029(9)
0.032(9)
0.016(8)
0.040(9)
0.043(9)
0.018(8)
0.066(11)
0.031(9)
0.042(9)
0.025(8)
0.049(10)
0.034(9)
0.041(9)
0.033(9)
0.019(7)
ꢀ0.0027(3)
ꢀ0.0031(3)
ꢀ0.0027(3)
ꢀ0.0029(3)
ꢀ0.0043(5)
ꢀ0.0056(5)
ꢀ0.0041(5)
ꢀ0.0031(5)
ꢀ0.0048(6)
ꢀ0.0052(6)
ꢀ0.0072(5)
ꢀ0.0063(6)
ꢀ0.0060(5)
ꢀ0.0062(5)
ꢀ0.0039(6)
ꢀ0.0013(6)
ꢀ0.0031(6)
ꢀ0.0063(6)
ꢀ0.0039(6)
ꢀ0.0027(6)
ꢀ0.0033(6)
ꢀ0.0052(6)
ꢀ0.0039(6)
ꢀ0.0047(6)
0.000(6)
ꢀ0.0045(3)
ꢀ0.0049(3)
ꢀ0.0032(3)
ꢀ0.0042(3)
ꢀ0.0072(5)
ꢀ0.0060(5)
ꢀ0.0068(5)
ꢀ0.0105(6)
ꢀ0.0126(6)
ꢀ0.0190(6)
ꢀ0.0085(5)
0.0022(6)
ꢀ0.0061(6)
ꢀ0.0008(6)
ꢀ0.0011(7)
ꢀ0.0214(6)
ꢀ0.0032(7)
ꢀ0.0045(7)
ꢀ0.0031(6)
ꢀ0.0041(6)
ꢀ0.0035(6)
ꢀ0.0036(7)
ꢀ0.0032(7)
ꢀ0.0051(7)
ꢀ0.003(6)
ꢀ0.001(5)
ꢀ0.008(6)
ꢀ0.015(6)
ꢀ0.014(6)
ꢀ0.006(5)
0.000(5)
U2
0.0000(3)
ꢀ0.0001(3)
0.0000(3)
ꢀ0.0012(5)
0.0009(5)
0.0031(5)
ꢀ0.0056(5)
ꢀ0.0069(6)
0.0004(6)
0.0033(5)
ꢀ0.0008(6)
ꢀ0.0014(6)
0.0000(6)
0.0000(6)
ꢀ0.0020(6)
0.0002(6)
ꢀ0.0008(7)
ꢀ0.0009(6)
ꢀ0.0010(6)
ꢀ0.0006(6)
ꢀ0.0015(6)
ꢀ0.0005(6)
ꢀ0.0018(6)
0.012(6)
U3
U4
Cs1
Cs2
Cs3
Cs4
Cs5
Cs6
Cs7
Cs8
Cs9
Cs10
Cs11
Cs12
Mo1
Mo2
Mo3
Mo4
Mo5
Mo6
Mo7
Mo8
O1
O2
0.009(6)
0.002(5)
O3
ꢀ0.001(6)
0.004(6)
0.003(6)
O4
ꢀ0.001(6)
0.005(6)
O5
ꢀ0.011(7)
ꢀ0.006(5)
ꢀ0.011(5)
0.006(6)
O6
0.004(5)
O7
ꢀ0.009(6)
ꢀ0.005(6)
ꢀ0.005(6)
0.006(6)
O8
ꢀ0.018(6)
ꢀ0.018(6)
ꢀ0.012(6)
ꢀ0.004(6)
ꢀ0.003(5)
ꢀ0.010(7)
0.007(6)
O9
0.017(6)
O10
O11
O12
O13
O14
O15
O16
O17
O18
O19
O20
O21
O22
O23
O24
O25
O26
O27
O28
O29
O30
O31
O32
O33
O34
O35
O36
O37
O38
O39
O40
O41
O42
0.002(6)
ꢀ0.013(6)
ꢀ0.002(5)
ꢀ0.010(6)
0.001(6)
ꢀ0.002(6)
ꢀ0.012(5)
0.012(6)
ꢀ0.015(6)
ꢀ0.011(6)
ꢀ0.013(6)
ꢀ0.011(6)
0.007(6)
ꢀ0.012(5)
0.006(6)
ꢀ0.012(6)
ꢀ0.016(7)
ꢀ0.018(7)
ꢀ0.021(7)
ꢀ0.006(6)
ꢀ0.005(6)
0.006(6)
0.002(6)
0.005(7)
0.022(7)
0.024(7)
0.030(8)
0.019(7)
0.019(7)
0.037(9)
0.028(8)
0.009(6)
0.024(8)
0.040(9)
0.049(10)
0.045(9)
0.028(8)
0.040(9)
0.020(7)
0.038(9)
0.079(13)
0.024(8)
0.016(7)
0.010(7)
0.035(9)
0.024(8)
0.038(9)
0.023(7)
0.003(5)
ꢀ0.005(5)
ꢀ0.008(6)
ꢀ0.007(6)
ꢀ0.021(6)
ꢀ0.012(5)
ꢀ0.009(6)
0.001(6)
ꢀ0.002(6)
ꢀ0.006(6)
0.013(6)
ꢀ0.001(6)
ꢀ0.003(6)
0.001(7)
ꢀ0.001(5)
ꢀ0.020(6)
0.004(6)
0.002(6)
ꢀ0.005(6)
ꢀ0.001(6)
ꢀ0.002(7)
ꢀ0.015(7)
0.003(7)
ꢀ0.019(6)
ꢀ0.018(7)
0.008(7)
ꢀ0.002(6)
0.011(7)
ꢀ0.027(7)
ꢀ0.002(7)
ꢀ0.020(7)
0.003(7)
ꢀ0.009(7)
0.006(6)
ꢀ0.012(6)
0.006(6)
ꢀ0.014(7)
ꢀ0.001(6)
ꢀ0.015(7)
ꢀ0.029(7)
ꢀ0.008(7)
ꢀ0.015(6)
ꢀ0.014(7)
ꢀ0.035(7)
ꢀ0.022(7)
ꢀ0.016(7)
ꢀ0.015(6)
ꢀ0.005(5)
ꢀ0.013(7)
ꢀ0.001(6)
ꢀ0.013(8)
ꢀ0.026(9)
ꢀ0.010(7)
ꢀ0.005(6)
ꢀ0.001(6)
ꢀ0.013(7)
ꢀ0.017((7)
ꢀ0.015(7)
ꢀ0.005(6)
ꢀ0.002(7)
ꢀ0.008(7)
0.032(8)
ꢀ0.007(6)
0.001(6)
0.006(6)
0.018(7)
0.001(7)
ꢀ0.017(7)
0.005(6)
significant interatomic metal-oxygen distances, uranyl angles and
valence bonds calculated using Brese and O’Keeffe data [57] with
3. Crystal structure description of Cs
and discussion
6 2 2 4 3 5
[(UO ) (MoO ) (MoO )]
˚
b¼0.37 A except for U–O bonds where the coordination indepen-
˚
˚
dent parameters (Rij¼2.051 A, b¼0.519 A) were taken from Burns
The structure of Cs
symmetrically independent U
6
[(UO
2
)
2
(MoO
4
)
3
(MoO
5
)] contains four
6
þ
et al. [58].
cations. Each uranium atom is

9
76
S. Yagoubi et al. / Journal of Solid State Chemistry 184 (2011) 971–981
Table 5
Interatomic distances ( A˚ ), valence bond and uranyl angles (deg.) in Cs
6
2 2 4 3 5
(UO ) (MoO ) (MoO ).
Atom
Distance
s
ij
Atom
Distance
s
ij
U1–O2
1.803(12)
1.806(13)
2.179(12)
2.378(15)
2.398(11)
2.415(15)
2.449(12)
1.613
1.603
0.781
0.534
0.512
0.497
0.464
6.004
U2–O1
1.805(13)
1.811(14)
2.195(13)
2.345(13)
2.395(12)
2.394(12)
2.443(14)
1.606
1.588
0.756
0.566
0.515
0.516
0.470
6.017
U1–O8
U2–O13
U2–O12
U2–O27
U2–O42
U2–O25
U2–O20
ii
ii
ii
U1–O6
U1–O24
U1–O42
U1–O21
U1–O14
i
iii
R
s
ij
Rs
ij
U3–O5
1.791(12)
1.806(13)
2.182(13)
2.346(15)
2.376(11)
2.410(15)
2.451(11)
1.650
1.600
0.777
0.566
0.535
0.501
0.464
6.093
U4–O9
1.798(13)
1.812(13)
2.194(14)
2.381(12)
2.389(16)
2.403(12)
2.406(12)
1.628
1.585
0.761
0.528
0.520
0.508
0.505
6.035
U3–O10
U3–O23
U3–O36
U3–O15
U3–O34
U3–O22
U4–O4
vi
U4–O7
vi
iv
vi
U4–O26
U4–O38
U4–O15
U4–O33
iv
v
R
s
ij
Rs
ij
Mo1–O31
Mo1–O35
Mo1–O24
Mo1–O27
1.710(13)
1.715(16)
1.759(15)
1.773(13)
1.703
1.676
1.488
1.436
6.303
Mo2–O40
Mo2–O32
Mo2–O36
Mo2–O26
1.731(16)
1.745(12)
1.749(14)
1.756(11)
1.609
1.549
1.533
1.504
6.195
R
s
ij
Rs
ij
Mo3–O11
Mo3–O30
Mo3–O14
Mo3–O34
1.722(12)
1.740(14)
1.768(12)
1.773(17)
1.644
1.575
1.456
1.436
6.111
Mo4–O29
Mo4–O39
Mo4–O7
1.725(13)
1.735(15)
1.884(12)
1.899(11)
2.010(13)
1.635
1.592
1.064
1.022
0.757
6.07
Mo4–O23
Mo4–O15
Rs
ij
Rs
ij
Mo5–O37
Mo5–O19
Mo5–O12
Mo5–O6
1.739(16)
1.747(11)
1.867(12)
1.899(11)
2.056(13)
1.579
1.537
1.114
1.019
0.669
5.918
Mo6–O3
1.728(12)
1.742(16)
1.763(10)
1.775(14)
1.627
1.562
1.472
1.425
6.086
Mo6–O16
Mo6–O22
Mo6–O21
Mo5–O42
Rs
ij
Rs
ij
Mo7–O17
Mo7–O18
Mo7–O20
Mo7–O33
1.714(13)
1.743(15)
1.778(14)
1.796(13)
1.685
1.562
1.421
1.35
Mo8–O28
Mo8–O41
Mo8–O38
Mo8–O25
1.725(14)
1.749(17)
1.764(14)
1.766(12)
1.635
1.533
1.476
1.464
6.108
R
s
ij
6.018
Rs
ij
vii
ii
Cs1–O17
Cs1–O30
Cs1–O8
3.047(13)
3.110(12)
3.134(15)
3.141(12)
3.143(15)
3.193(12)
3.448(14)
3.456(15)
3.498(13)
0.182
0.154
0.144
0.141
0.141
0.123
0.062
0.060
0.054
1.061
Cs2–O1
Cs2–O2
2.968(11)
3.005(12)
3.055(16)
3.088(13)
3.127(13)
3.223(13)
3.278(13)
3.396(12)
0.226
0.204
0.179
0.163
0.147
0.113
0.098
0.071
1.201
vi
iv
Cs2–O26
Cs2–O38
Cs2–O3
ii
Cs1–O8
Cs1–O35
Cs1–O13
Cs1–O19
Cs1–O35
Cs1–O42
vi
Cs2–O40
Cs2–O41
Cs2–O16
ii
ii
ii
iv
Rs
ij
Rs
ij
v
viii
Cs3–O11
Cs3–O39
2.982(13)
3.054(14)
3.072(13)
3.183(12)
3.181(14)
3.245(15)
3.260(13)
0.218
0.179
0.170
0.126
0.126
0.106
0.102
1.027
Cs4–O29
Cs4–O39
Cs4–O23
Cs4–O28
Cs4–O30
Cs4–O18
Cs4–O5
2.979(14)
3.067(13)
3.090(13)
3.121(17)
3.150(13)
3.190(13)
3.270(15)
0.219
0.173
0.162
0.149
0.138
0.123
0.099
1.063
vi
vi
Cs3–O7
Cs3–O4
vi
iv
iv
Cs3–O18
Cs3–O4
Cs3–O5
R
s
ij
Rs
ij
i
iii
ix
iii
Cs5–O31
Cs5–O13
Cs5–O18
2.888(12)
3.076(16)
3.094(13)
3.105(15)
3.107(13)
3.126(15)
3.496(12)
0.281
0.168
0.161
0.156
0.154
0.148
0.054
1.122
Cs6–O12
Cs6–O19
Cs6–O37
3.042(13)
3.092(13)
3.222(14)
3.232(13)
3.266(15)
3.324(13)
3.341(16)
3.394(12)
3.430(14)
0.185
0.161
0.114
0.111
0.101
0.086
0.082
0.071
0.065
0.976
iii
i
x
Cs5–O3
Cs6–O1
iii
x
Cs5–O30
Cs5–O35
Cs6–O33
Cs6–O41
Cs6–O25
Cs6–O25
Cs6–O20
ii
iii
x
Cs5–O5
Rs
ij
iii
Rs
ij
ii
Cs7–O6
Cs7–O9
2.908(14)
2.991(12)
3.067(14)
3.070(11)
0.265
0.212
0.172
0.172
Cs8–O19
3.050(12)
3.145(11)
3.154(14)
3.281(14)
0.181
0.139
0.136
0.097
xi
Cs8–O7
xi
Cs7–O37
Cs7–O10
Cs8–O29
Cs8–O17
vi
vii

S. Yagoubi et al. / Journal of Solid State Chemistry 184 (2011) 971–981
977
Table 5 (continued )
Atom
Distance
s
ij
Atom
Distance
s
ij
i
Cs7–O16
3.129(12)
3.134(16)
3.326(12)
3.388(14)
0.146
0.144
0.085
0.072
1.268
Cs8–O28
Cs8–O12
Cs8–O30
Cs8–O33
3.283(14)
3.357(12)
3.465(17)
3.495(15)
3.525(13)
3.585(13)
0.096
0.079
0.059
0.054
0.050
0.043
0.934
v
ii
Cs7–O28
v
Cs7––O41
i
vii
Cs7–O21
vii
R
s
ij
Cs8–O9
Cs8–O13
Rs
ij
viii
xii
Cs9–O39
Cs9–O23
Cs9–O32
Cs9–O29
Cs9–O11
Cs9–O28
3.107(16)
3.155(11)
3.192(13)
3.279(14)
3.301(14)
3.307(13)
3.382(13)
3.432(13)
3.434(14)
3.552(16)
3.667(13)
0.155
0.136
0.123
0.097
0.091
0.090
0.074
0.064
0.064
0.047
0.034
0.975
Cs10–O24
Cs10–O3
3.096(12)
3.120(12)
3.133(14)
3.236(12)
3.254(16)
3.260(13)
3.272(11)
3.507(17)
3.633(13)
3.674(15)
0.160
0.150
0.144
0.109
0.104
0.102
0.099
0.052
0.037
0.034
0.991
vii
Cs10–O32
Cs10–O11
Cs10–O40
iv
xi
vi
vii
Cs10–O5
viii
Cs9–O4
Cs10–O14
Cs10–O18
Cs10–O36
Cs10–O31
iv
vii
vii
Cs9–O34
Cs9–O10
Cs9–O16
Cs9–O26
viii
xii
Rs
ij
Rs
ij
ii
vii
xi
vi
vi
Cs11–O19
Cs11–O27
3.084(12)
3.096(12)
3.103(11)
3.143(12)
3.256(19)
3.382(13)
3.432(13)
3.471(17)
3.595(14)
0.165
0.160
0.157
0.141
0.104
0.074
0.064
0.058
0.042
0.965
Cs12–O32
Cs12–O22
Cs12–O36
Cs12–O10
Cs12–O34
Cs12–O21
Cs12–O14
Cs12–O22
Cs12–O2
2.950(13)
3.089(14)
3.161(14)
3.279(15)
3.305(16)
3.348(13)
3.382(14)
3.439(13)
3.461(12)
3.582(14)
0.237
0.163
0.134
0.097
0.090
0.081
0.073
0.063
0.060
0.043
1.041
xiii
ii
Cs11–O6
vii
Cs11–O20
Cs11–O35
xiii
i
Cs11–O3
Cs11–O8
ii
xiv
vii
i
Cs11–O41
Cs11–O17
vi
R
s
ij
Cs12–O40
Rs
ij
Uranyl angles (deg.)
O2–U1–O8
175.5(6)
175.5(6)
O1–U2–O13
O9–U4–O4
177.3(6)
177.5(6)
O5–U3–O10
Symmetry codes: (i) 1þx, y, z; (ii) 1ꢀx, ꢀy, ꢀz; (iii) 1þx, ꢀ1þy, z; (iv) ꢀ1þx, 1þy, z; (v) x, 1þy, z; (vi) ꢀx, 1ꢀy, 1ꢀz; (vii) x, ꢀ1þy, z; (viii) ꢀ1ꢀx, 1ꢀy, 1ꢀz;
ix) 2ꢀx, ꢀy, ꢀz; (x) 2ꢀx, ꢀ1ꢀy, ꢀz; (xi) ꢀx, ꢀy, 1ꢀz; (xii) ꢀ1þx, y, z; (xiii) ꢀx, ꢀy, ꢀz; (xiv) 1ꢀx, ꢀ1ꢀy, ꢀz.
(
strongly bonded to two oxygen atoms, forming an approximately
atoms are surrounded by five oxygen atoms to form a strongly
distorted MoO environment. Each distorted MoO polyhedron
2
þ
linear uranyl ion [O¼U¼O] , with average bond-lengths /U¼OS
5
5
˚
˚
of 1.804(12), 1.808(13), 1.794(12) and 1.805(13) A with uranyl ang-
consists of four Mo–O distances in the range of 1.72(1)–1.90(1) A
˚
les [O(2)¼U(1)¼O(8)]¼175.5(5)1; [O(1)¼U(2)¼O(13)]¼177.3(6)1;
and one Mo–O bond length of 2.01(1) and 2.06(1) A for Mo(4)
[
O(5)]¼U(3)¼O(10)]¼175.5(5)1; [O(9)¼U(4)¼O(4)]¼177.5(6)1, for
and Mo(5), respectively. In this coordination, bond valence sums
calculation provide 6.07 and 5.92 v.u. values for Mo(4) and Mo(5),
respectively. The long Mo–O distances of 2.01(1) and 2.06(1) A
U(1), U(2), U(3) and U(4), respectively. Each uranyl ion is coordinated
by five additional oxygen atoms in his equatorial plane, to form a
˚
pentagonal bipyramid (UO
2
)O
5
, with mean /U–OeqS equatorial
correspond to 0.757 and 0.669 v.u. for Mo(4)–O(15) and Mo(5)–
O(42), respectively, exclusion of these bonds would result in serious
deficiencies in the bond valence sums for Mo(4), Mo(5), O(15) and
O(42) atoms, (see Table 5). Similar coordination of Mo cation has
been already observed in the structure of two other compounds
˚
bond-lengths of 2.364(12), 2.354(12), 2.353(13) and 2.355(13) A, for
U(1), U(2), U(3) and U(4), respectively. The calculated average values
of uranium–oxygen distances are in excellent agreement with the
6
þ
˚
average bond lengths of /U¼OS¼1.79(4) and /U–OeqS¼2.37(9) A
determined from numerous well refined structures by Burns
et al. [58] for uranyl ions in pentagonal bipyramidal coordination.
The valence bond sums are in the range of 6.004–6.093 v.u., in
agreement with the expected (þVI) valence of uranium.
4 2 3 4 2 5
containing uranyl ion : in Cs (UO ) O(MoO ) (MoO ), where there
˚
are four Mo–O distances in the range of 1.71(2)–1.87(2) A, and one
˚
at 2.27(2) A [24], and in the structure of deloryite Cu
(Mo )(OH) with four short Mo–O distances ranged from
1.77(2) to 1.88(2) A and a large bond length of 2.58(2) A [59]. This
4 2
(UO )
O
2 8
6
6
þ
˚
˚
There are eight symmetrically independent Mo
cations in
6
þ
the structure. The six molybdenum cations Mo(1), Mo(2), Mo(3),
Mo(6), Mo(7) and Mo(8) are coordinated by four oxygen atoms
located at the vertices of tetrahedra, with Mo–O bond lengths
distorted coordination was also found for W
Rb [(UO (WO ], where two tungsten atoms are surrounded by
five oxygen atoms to form distorted trigonal bipyramids, with a
in the structure of
6
)
2 2
4 4
)
˚
˚
in the range of 1.71(1)–1.79(1) A. Each MoO
4
tetrahedron
fifth W–O distance of 2.03 (2) and 2.45(3) A [60].
þ
contains two slightly shorter Mo–O distances concerning
non-linked oxygen atoms and two longer Mo–O bond-lengths
The structure contains also 12 symmetrically independent Cs
cations surrounded by seven to nine oxygen atoms in the range of
˚
relative to the oxygen atoms shared with (UO
2
)O
5
pentagonal
2.89(1)–3.67(1) A, to form complex polyhedra and giving valence
bipyramids. The /Mo–OS distances of these tetrahedra range
bond sums between 0.934 and 1.268 v.u.
˚
between 1.74(1) and 1.76(1) A, in good agreement with values in
MoO tetrahedra-containing uranyl molybdates [23,38,39,44].
By sharing equatorial oxygen atoms O(42) and O(15), both
4
bipyramid couples [U(1)O
two similar dimers [U(1)O
respectively. Inside each dimer [U
7
U(2)O
OU(2)O
7
] and [U(3)O
7
U(4)O
and [U(4)O
7
] generate
1
4ꢀ
14ꢀ
The valence bond sums for these molybdenum atoms are in the
range of 6.018–6.303. The Mo(4) and Mo(5) molybdenum
6
6
]
6
OU(3)O
6
]
,
1
4ꢀ
2
O
13
]
, the link between the

9
78
S. Yagoubi et al. / Journal of Solid State Chemistry 184 (2011) 971–981
1
N
6ꢀ
infinite uranyl molybdate ribbons in the structure of Cs
Fig. 2. The
[(UO
)
2 2
4
(MoO )
3 5
(MoO )]
6 2 2 4 3 5
[(UO ) (MoO ) (MoO )], (a) ball-and-stick representation and
(b) polyhedral representation.
two UO
7
polyhedra is reinforced on one side by a MoO
4
tetra-
hedron and on another side by a MoO
5
square pyramid, to form an
10ꢀ
10ꢀ
4
uranomolybdate entity [U
2
O
13Mo
2
O
4
]
2 2
. These [U O13Mo O ]
units are connected by sharing vertices with two MoO
4
tetrahedra,
parallel to the
1
N 2 2 4 3 5
6ꢀ
to form infinite ribbon
[(UO ) (MoO ) (MoO )]
[
1 1¯ 2] direction, Fig. 2. The infinite ribbons are associated in pseudo-
þ
layers, linked to each other by alkaline cations Cs , which insure the
crystal structure cohesion, Fig. 3.
6
þ
In the A
cations are in tetrahedral MoO
4 4
developed formula A [(UO O(MoO )
6
U
2
Mo
4
O
21 compounds with A¼Na, K and Rb, all Mo
environment to give the following
]. For caesium compound, two
4
6
2
)
2
of the eight molybdenum sites, Mo(4) and Mo(5), are coordinated
with a fifth oxygen atom (Osh), which is common to both uranium
atoms of each U
a square pyramidal MoO
formulae Cs [(UO (MoO
2
O
13 dimer ,U(3)U(4)O13 and U(1)U(2)O13. They adopt
coordination to give a different developed
(MoO )], Fig. 2. The fivefold coordination
5
6
2
)
2
4
)
3
5
of the Mo atoms is realized by the formation of long Mo–O bonds
with the Osh atoms bridging between two U centres in the
6 2 2 4 3 5
Fig. 3. Polyhedral representation of the structure of Cs [(UO ) (MoO ) (MoO )],
showing the stacking of infinite uranyl molybdate ribbons to form pseudo-layers,
þ
with interleaved Cs ions.
4 2 2 4
[O (UO )Osh(UO )O ] dimmers. It is noteworthy that the arrangement
of the longer Mo–Osh bonds is asymmetrical relative to the chain
extension.
Table 6
Evolution of average distances /Mo–Osh
S
and /U–Osh
S
( A˚ ) in the
While the Mo–Osh and U–Osh distances slightly and regularly
decrease and increase respectively from Na to Rb compounds, the
formation of square pyramidal environments for Mo(4) and
Mo(5) atoms in the Cs compound is accompanied by a large
variation of these distances. As a consequence, the intradimer
U–U largely increases (Table 6). As can be seen from Fig. 2
the direction of the Mo(5)–O(42) bond is antiparallel to the
direction of the Mo(4)–O(15) bond, i.e. the fivefold coordinated
Mo atoms are located on different sides of the dimers relative
to the chain extension. The identity period of the chain in the
Cs compound is doubled compared to the chain in the Rb
compound, and quadrupled compared to Na and K crystal
structures.
A
6
(UO
2
)
2
(MoO
4
)
3
(MoO
5
) structures (A¼Na, K, Rb, Cs).
Na
K
Rb
Cs
Mo–Osh ( A˚ )
Mo–Osh ( A˚ )
U–Osh ( A˚ )
3.08(1)
3.08(1)
2.12(1)
2.99(3)
2.99(3)
2.16(3)
2.73(1)
3.40(1)
2.19(7)
2.06(1)
3.44(1)
2.38(1)
2.01(1)
3.65(1)
2.40(1)
2.17(7)
2.40(1)
2.40(1)
a
˚
4.232(3)
180
4.312(6)
4.267(7)
4.664(6)
4.705(6)
U –U (A)
U–Osh–U (1)
U–U ( A˚ )
180
156.4(4)
154.9(5)
6.661(9)
158.0(5)
6.735(9)
b
6.512(4)
6.711(6)
6.679(10)
a
Intradimer U–U distance.
interdimer U–U distance.
b
The uranyl molybdate chains differ also by the relative
orientation of molybdenum polyhedra. In the four compounds
the molybdenum polyhedra on one side of a chain all point in the
same direction, while in the compounds with the smallest ions
4
(Na and K), the MoO tetrahedra on both sides of a chain point in
opposite directions, in Rb and Cs compounds they point in the
same direction but in opposite direction for two adjacent chains

S. Yagoubi et al. / Journal of Solid State Chemistry 184 (2011) 971–981
979
1
N
6ꢀ
Fig. 4. Comparison of
[U
2
Mo
4
O
21
]
infinite ribbons observed in the structures of A
6
U
2
Mo
4
O
21 (A¼Na, K, Rb, Cs).
(
Fig. 4) leading to corrugated and linear chains, respectively, and
Fig. 6 shows the temperature dependence of the conductivity for
the four compounds. The observed linear variation of log versus 1/T
þ
for all compounds to pseudo-layers, linked together by A alka-
line cations, Fig. 5. These differences explain the unexpected unit
cell volume variation, while the unit cell volume decrease from
Na to K and from Rb to Cs, the unit cell volumes of K and Rb
compounds are almost equal.
s
shows that the ionic conductivity obeys to the Arrhenius law over the
investigated temperature range, with high activation energy values of
þ
þ
þ
þ
about 0.87; 0.88, 0.97 and 1.08 eV for Na , K , Rb and Cs ,
respectively. The low conductivity and high activation energy
observed in these compounds may be explained by the rigidity of
their environment in the spaces located between chains and by their
coordination by oxygen atoms not involved in the chain formation. As
expected from the ionic radius increase, the conductivity decreases
from Na to Cs.
4
. Thermal analysis, electrical conductivity and infrared
spectroscopy results
The infrared spectra of A
Cs), given in Fig. 7, are characterized by the vibrations of uranyl
6
U
2
Mo
4
O
21 family (A¼Na, K, Rb, and
Differential Thermal Analysis study of each sample showed an
endothermic peak due to a non-congruent melting point, with
decomposition temperatures ranging between 540 and 610 1C from
Cs to Na containing compound. The powder X-ray diffraction analysis
of residue, after each DTA measurement, confirmed the product as a
2
þ
UO
onment and MoO
and n¼5 square pyramids only for Cs). For all compounds, the
2
, equatorial (secondary) U–Oeq bonds in pentagonal envir-
n
polyhedra (n¼4 tetrahedra for Na, K, Rb, Cs
ꢀ
1
vibration modes in the frequency domain of 933–903 cm , may
mixture of, (UO
decomposition sequence of A
2
)MoO
4
, A
2
MoO
4
and A
2
O (A¼Na, K, Rb, Cs). The
be assigned to the asymmetric stretching vibration
n
3
of uranyl
6
U
2
Mo 21 is shown below
4
O
2
þ
ions UO
2
. Two vibrations were observed for Na compound (933,
ꢀ
1
A
6
U
2
Mo
4
O
21-2(UO
2
)MoO
4
þ2A
2
MoO
4
þA
2
O
903 cm ), and only one vibration in the case of the last three

9
80
S. Yagoubi et al. / Journal of Solid State Chemistry 184 (2011) 971–981
Fig. 5. Comparison of the crystal structure arrangements in the A
6
U
2 4
Mo O
21 (A¼Na, K, Rb, Cs) compounds.
Fig. 6. Temperature dependence of ionic conductivity for A
6
U
2
Mo
4
O
21 (A¼Na, K,
Rb, Cs) compounds.
ꢀ
1
other compounds, with bands at about 920, 918 and 925 cm for
K, Rb and Cs, respectively. The localized bands at 868 (Na), 847
(
K), 872 (Rb), 872–848 (Cs) are assigned to the symmetric
2
þ
stretching vibration
n
1
ꢀ
UO
1
2
. The lower bands observed in the
may be assigned to U–Oeq vibrations
between uranium and equatorial oxygen atoms. The assignment
the frequency vibrations molybdenum MoO
polyhedra (n¼4
tetrahedra or 5 square pyramids), are also given in Table 7.
For Cs [(UO (MoO (MoO )] compound, the spectrum
shows two strong bands at about 925 and 848 cm , which have
range of 518–582 cm
n
6
2
)
2
4
)
3
5
ꢀ
1
2
2
þ
been attributed to asymmetrical and symmetrical UO
stretching vibrations and , respectively. These two vibrations
are in good agreement with the mathematical model suggested
by Bagnall and Wakerley [61]to determine the value of from
uranyl
n
3
n
1
n
1
Fig. 7. Infrared absorption spectra of A
6
U
2
4
Mo O
21 compounds (A¼Na, K, Rb, Cs).

S. Yagoubi et al. / Journal of Solid State Chemistry 184 (2011) 971–981
981
Table 7
Infrared spectrum of A
6
U
2
Mo
4
O
21 compounds (A¼Na, K, Rb and Cs).
ꢀ
1
Vibrational mode
m
(cm
)
2
þ
2þ
2
(UO )
m
3
(UO
2
)
m
1
m
U–Oeq
4 5
m MoO and m MoO
Na
6
U
2
Mo
Mo
Mo
Mo
4
O
21
21
21
21
933–903
920
868
847
872
540
833–891–714–771–802
822–883–741–768
K
6
U
2
4
O
534
Rb
Cs
6
U
2
4
O
918
521
829–895–725–744–775
825–885–676–776
6
U
2
4
O
925
872–848
518–548–582
the one of
¼ 0:912
n
3
, given by the following expression:
[18] P.C. Burns, Can. Mineral. 43 (2005) 1839.
[19] M. Ross, H.T. Evans, J. Inorg. Nucl. Chem. 15 (1960) 338.
ꢀ1:04ðcmꢀ Þ:
1
n
1
n
3
[20] T.I. Krasovskaya, Yu.A. Polyakov, I.A. Rozanov, Izv. Akad. Nauk SSSR, Neorg.
Mater 16 (1980) 1824.
Thus, the application of Veal et al.’s [62] empirical equation
relating bond length (dU–O) to the asymmetric stretching vibra-
[
21] V.N. Serezhkin, E.E. Tatarinova, L.B. Serezhkina, Zh. Neorg. Khim. 32 (1987) 227.
[22] R.K. Rastsvetaeva, A.V. Barinova, A.M. Fedoseev, N.A. Budantseva,
Yu.V. Nikolaev, Dokl. Chem. 365 (1999) 52.
ꢀ
1
tion
3
n (925 cm ) for uranyl groups
[
[
[
23] S.V. Krivovichev, P.C. Burns, Can. Mineral. 39 (2001) 207.
24] S.V. Krivovichev, P.C. Burns, Can. Mineral. 40 (2002) 201.
25] S.V. Krivovichev, C.L. Cahill, P.C. Burns, Inorg. Chem. 41 (2002) 34.
ꢀ
2=3
d
U2O ¼ 81:2
n
þ0:895
3
˚
[26] S.V. Krivovichev, P.C. Burns, Can. Mineral. 43 (2005) 713.
27] E.V. Nazarchuk, S.V. Krivovichev, S.K. Filatov, Radiochemistry 46-5 (2004)
38 Translated from Radiokhimiya 46 (2004) 405.
[28] E.V. Nazarchuk, S.V. Krivovichev, P.C. Burns, Radiochemistry 47-5 (2005) 447
Translated from Radiokhimiya 47 (2005) 408.
leads to the predicted uranyl bond length of 1.1.801 A, in good
agreement with the average value obtained from X-ray structure
results, /U–OS¼1.804(6) A˚ .
[
4
[
29] E.V. Alekseev, S.V. Krivovichev, T. Armbruster, W. Depmeier, E.V. Suleimanov,
E.V. Chuprunov, A.V. Golubev, Z. Anorg. Allg. Chem. (2007) 1979.
30] C. Dion, A. No e¨ l, Bull. Soc. Chim. Fr. 9-10 (1981) 371.
5
. Conclusion
[
[
31] C. Dion, A. No e¨ l, Bull. Soc. Chim. Fr. 11–12 (1983) 257.
A new compound of the A
6
U
2
Mo
4
O
21 series has been prepared
[32] G.G. Tabachenko, L.M. Kovba, V.P. Serzhkin, Koord. Khim. 10 (1983) 558.
[33] G.G. Sadikov, T.I. Krasovskaya, Yu.A. Polyakov, V.P. Nikolaev, Izv. Akad Nauk
SSSR, Neorg. Mater 24 (1988) 109.
for A¼Cs. Its structure is, as the other compounds previously
reported for A¼Na, K, Rb, characterized by infinite uranyl molyb-
date chains. However some differences appear within the chains
and in the chains arrangement illustrating the key role of the ionic
radius of the monovalent cation, in particular with the formation,
of penta-coordinated molybdenum atoms with Cs. Study of such
compounds involving two monovalent cations and divalent
cations are planned with the aim to precise this role and to
obtain other geometric isomers of the uranyl molybdate chains.
[
34] I. Duribreux, Ph.D. Thesis, Universit e´ des Sciences et Technologies de Lille,
1997.
[35] N.L. Misra, K.L. Chawla, V. Venugopal, N.C. Jayadevan, D.D. Sood, J. Nucl.
Mater. 226 (1997) 120.
[36] R.K. Rastsvetaeva, A.V. barinova, A.M. Fedoseev, N.A. Budantseva,
Yu.P. Nekrasov, Dokl. Akad. Nauk. 365 (1999) 68.
[37] V.N. Krustalev, G.B. Andreev, M. Yu., A.M. Antipin, N.A. Fedosev, Bbudantseva,
I.B. Shirokova, Zh. Neorg. Khim 45 (2000) 1996.
[
[
[
38] S.V. Krivovichev, P.C. Burns, Can. Mineral. 39 (2001) 197.
39] S.V. Krivovichev, P.C. Burns, J. Solid State Chem. 168 (2002) 245.
40] S.V. Krivovichev, P.C. Burns, Inorg. Chem. 41 (2002) 4108.
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