Ni3(Mo2O8)(XO3) (X = Se, Te): The first nickel selenite- and tellurite-containing Mo4 clusters

Article abstract of DOI:10.1021/ic700500q

Two new nickel(II) molybdenum(VI) selenium(IV) and tellurium(IV) oxides generally formulated as Ni₃(Mo₂O₈)(XO ₃) (X = Se, Te) have been synthesized by solid-state reactions of NiO, MoO₃, and SeO₂

Full text of DOI:10.1021/ic700500q

Inorg. Chem. 2007, 46, 6495−6501
Ni3(Mo2O8)(XO3) (X
) Se, Te): The First Nickel Selenite- and
Tellurite-Containing Mo4 Clusters
Hai-Long Jiang,†,‡ Zhi Xie,†,‡ and Jiang-Gao Mao*,†
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of
Matter, Chinese Academy of Sciences, Fuzhou 350002, P. R. China, and Graduate School of the
Chinese Academy of Sciences, Beijing 100039, P. R. China
Received March 14, 2007
Two new nickel(II) molybdenum(VI) selenium(IV) and tellurium(IV) oxides generally formulated as Ni3(Mo2O8)(XO3)
(X Se, Te) have been synthesized by solid-state reactions of NiO, MoO3, and SeO2 (or TeO2). Both compounds
feature 3D network structures built of [Mo4O16
)
8-
]
tetranuclear cluster units and 2D nickel(II) selenite or tellurite
layers. The nickel(II) selenite layer in Ni3(Mo2O8)(SeO3) is formed by [Ni6O22]32- hexanuclear clusters interconnected
by selenite groups whereas the thick nickel(II) tellurite layer in Ni3(Mo2O8)(TeO3) is constructed by corrugated
nickel(II) oxide chains bridged by the tellurite groups. The results of magnetic property measurements indicate that
there are considerable ferromagnetic interactions between nickel(II) centers in both compounds. Their optical properties
and band structures have been also studied.
Introduction
to enhance the SHG properties.3-5 Recent studies also
indicate that the activation of both selenite or tellurite anions
and molybdate (or tungstate) for lanthanide ions can also
afford new luminescent materials in the near-IR region.6 We
deem that the combination of the lone-pair electrons of SeIV
or TeIV with the distorted MoO6 octahedron may lead to new
compounds in Ni-MoVI-SeIV/TeIV-O systems with novel
structures and unusual physical properties, such as magnetic
or optical properties. So far, only a Ni-MoVI-TeVI-O phase,
[Ni(H2O)6]3[TeMo6O24], has been reported,7 and no nickel
molybdenum(VI) selenite or tellurite has been structurally
characterized. Our exploration of new phases in nickel
molybdenum(VI) selenite or tellurite systems led to two
novel compounds, namely, Ni3(Mo2O8)(XO3) (X ) Se, Te).
Despite their similar chemical formulas, they display two
different types of 3D structures containing [Mo4O16]8-
tetranuclear cluster units and [Ni6O22]32- hexanuclear clusters
or 1D nickel oxide chains. Herein, we report their syntheses,
band and crystal structures, and magnetic properties.
Metal selenites or tellurites can adopt many unusual
structures due to the presence of the stereochemically active
lone-pair electrons.1 The asymmetric coordination polyhedron
adopted by the SeIV or TeIV atom may result in noncen-
trosymmetric structures with consequent interesting physical
properties, such as nonlinear optical second-harmonic gen-
eration (SHG).2-5 Transition-metal ions with d0 electronic
configuration such as Ti4+, Nb5+, Mo6+, W6+, etc, which
are susceptible to second-order Jahn-Teller distortions, have
been introduced into the metal selenite or tellurite systems
* To whom correspondence should be addressed. E-mail: mjg@
fjirsm.ac.cn.
† Fujian Institute of Research on the Structure of Matter, Chinese
Academy of Sciences.
‡ Graduate School of the Chinese Academy of Sciences.
(1) (a) Wickleder, M. S. Chem. ReV. 2002, 102, 2011 and references
therein. (b) Verma, V. P. Thermochim. Acta 1999, 327, 63 and
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10.1021/ic700500q CCC: $37.00
Published on Web 06/30/2007
© 2007 American Chemical Society
Inorganic Chemistry, Vol. 46, No. 16, 2007 6495

Jiang et al.
Table 1. Crystal Data and Structural Refinements for
Ni3(Mo2O8)(XO3) (X ) Se, Te)
Experimental Section
Materials and Instrumentation. All of the chemicals except
NiO were analytically pure from commercial sources and used
without further purification. Neodymium(III) oxide, transition-metal
oxides, and halides were purchased from the Shanghai Reagent
Factory, and TeO2 (99+%) and SeO2 (99+%) were purchased from
Acros Organics. NiO was synthesized by heating Ni2O3 in air at
610 °C for 12 h, and its purity was checked by X-ray powder
diffraction (XRD) (see the Supporting Information).8a XRD patterns
were collected on a XPERT-MPD θ-2θ diffractometer. The
chemical compositions of the two compounds were analyzed by a
field-emission scanning-electron microscope (FESEM, JSM6700F)
equipped with an energy dispersive X-ray spectroscope (EDS,
Oxford INCA). The absorption spectra were recorded on a PE
Lambda 900 UV-vis spectrophotometer in the wavelength range
of 200-2200 nm. The absorption spectra were determined by the
diffuse-reflectance technique.8b F(R) and R are linked by F(R) )
(1 - R)2/2R, where R is the reflectance and F(R) is the Kubelka-
Munk remission function. The minima in the second-derivative
curves of the Kubelka-Munk function are taken as the position of
the absorption bands. IR spectra were recorded on a Magna 750
Ni3(Mo2O8)(SeO3)
Ni3(Mo2O8)(TeO3)
fw
622.97
671.61
space group
a, Å
b, Å
P1h (No. 2)
6.4630(7)
6.4654(4)
10.0262(5)
73.949(10)
86.288(17)
84.856(16)
400.65(5)
2
5.164
14.565
0.984
0.0357, 0.0847
0.0412, 0.0878
C2/m (No. 12)
9.562(3)
8.756(3)
10.082(3)
90
103.228(7)
90
821.7(4)
4
5.429
13.254
1.106
0.0175, 0.0413
0.0186, 0.0418
c, Å
R, deg
â, deg
γ, deg
V, Å3
Z
D
calcd, g‚cm-3
µ, mm-1
GOF on F2
R1, wR2 [I>2σ(I)]a
R1, wR2 (all data)
a R1 ) ∑||Fo| - |Fc||/∑|Fo|, wR2 ) {∑w[(Fo)2 - (Fc)2]2/∑w[(Fo)2]2}1/2
.
Ni3(Mo2O8)(TeO3) was obtained quantitatively by the reaction of
a mixture of NiO/MoO3/TeO2 in a molar ratio of 3:2:1 at 720 °C
for 6 days (see the Supporting Information). IR data (KBr, cm-1):
990 (vw), 928 (vs), 895 (vs), 770 (s), 748 (s), 670 (vs), 652 (s),
636 (vs), 478 (m), 456 (s), 417 (w).
FT-IR spectrometer as KBr pellets in the range of 4000-400 cm-1
.
Thermogravimetric analyses (TGA) were carried out with a
NETZSCH STA 449C unit, at a heating rate of 10 °C/min under a
static air atmosphere. Magnetic susceptibility measurements on
polycrystalline samples were performed with a PPMS-9T magne-
tometer in the temperature range 2-300 K.
Single-Crystal Structure Determination. Data collections for
the two compounds were performed on a Rigaku Mercury CCD
diffractometer equipped with a graphite-monochromated Mo KR
radiation source (λ ) 0.71073 Å) at 293 K. Both data sets were
corrected for Lorentz and polarization factors as well as for
absorption by the multiscan method.9a Both structures were solved
by direct methods and refined by full-matrix least-squares fitting
on F2 by SHELX-97.9b All of the atoms were refined with
anisotropic thermal parameters. Crystallographic data and structural
refinements for the two compounds are summarized in Table 1.
Important bond distances are listed in Table 2. More details on the
crystallographic studies as well as atomic displacement parameters
are given as Supporting Information.
Computational Descriptions. The crystallographic data of the
two compounds were used for the band-structure calculations. The
ab initio band-structure calculations were performed by using the
computer code CASTEP.10 This code employs density functional
theory (DFT) using a plane-wave basis set with Vanderbilt ultrasoft
pseudopotentials to approximate the interactions between core and
valence electrons.11 The exchange-correlation energy was calculated
using the Perdew-Burke-Ernzerhof modification to the generalized
gradient approximation.12 A kinetic-energy cutoff of 300 eV was
used throughout our work. Pseudoatomic calculations were per-
formed for O 2s22p4, Se 4s24p4, Te 5s25p4, Mo 4s24p64d55s1, and
Ni 3d84s2. The parameters used in the calculations and convergence
criteria were set by the default values of the CASTEP code.10
Preparation of Ni3(Mo2O8)(SeO3). Green brick-shaped crystals
of Ni3(Mo2O8)(SeO3) were initially prepared by the solid-state
reaction of a mixture of Nd2O3 (0.118 g, 0.35 mmol), MoO3 (0.050
g, 0.35 mmol), NiCl2 (0.045 g, 0.35 mmol), and SeO2 (0.155 g,
1.4 mmol) in our attempt to prepare a Nd-Mo-Ni-Se-O-Cl
phase. The reaction mixture was thoroughly ground and pressed
into a pellet, which was then sealed into an evacuated quartz tube.
The quartz tube was heated at 300 °C for 1 day and at 700 °C for
5 days, then slowly cooled to 295 °C at 4.5 °C/hr. It was finally
cooled to room temperature in 16 h. Results of the EDS elemental
analyses gave a molar ratio of Ni/Mo/Se equal to 3.2/1.9/1.0, which
is in good agreement with the one determined from single-crystal
X-ray structural analysis. Though Nd(III) is not present in
Ni3(Mo2O8)(SeO3), the addition of Nd2O3 helps the crystallization
of Ni3(Mo2O8)(SeO3), and the quality of the crystals is very poor
when the synthesis is carried out in the absence of Nd2O3. The
pure powder product of Ni3(Mo2O8)(SeO3) was obtained quanti-
tatively by the reaction of a mixture of NiO/MoO3/SeO2 in a molar
ratio of 3:2:1 at 710 °C for 6 days in a similar procedure described
above (see the Supporting Information). IR data (KBr, cm-1): 961
(vs), 928 (vs), 858 (s), 764 (m), 710 (m), 656 (s), 624 (s), 524 (m),
462 (m), 442 (w), 410 (w).
Preparation of Ni3(Mo2O8)(TeO3). Green brick-shaped crystals
of Ni3(Mo2O8)(TeO3) were prepared by the solid-state reaction of
a mixture containing NiO (37.3 mg, 0.5 mmol), MoO3 (72.0 mg,
0.5 mmol), and TeO2 (239.4 g, 1.5 mmol). The reaction mixture
was thoroughly ground and pressed into a pellet, which was then
sealed into an evacuated quartz tube. The quartz tube was heated
at 720 °C for 6 days and then cooled to 270 °C at 4.5 °C/hr before
switching off the furnace. The EDS elemental analyses gave a molar
ratio of Ni/Mo/Te equal to 3.1/2.2/1.0, which is in good agreement
with the one determined from single-crystal X-ray structural
analysis. After proper structural analysis, a pure sample of
Results and Discussion
Solid-state reactions of nickel(II) oxide, molybdenum(VI)
oxide, and SeO2 or TeO2 afforded two new nickel(II)
(9) (a) CrystalClear, version 1.3.5; Rigaku Corp.: Woodlands, TX, 1999.
(b) Sheldrick, G. M. SHELXTL, Crystallographic Software Package,
version 5.1; Bruker-AXS: Madison, WI, 1998.
(10) (a) Segall, M. D.; Lindan, P. L. D.; Probert, M. J.; Pickard, C. J.;
Hasnip, P. J.; Clark, S. J.; Payne, M. C. J. Phys.: Condens. Matter
2002, 14, 2717. (b) Segall, M.; Lindan, P.; Probert, M.; Pickard, C.;
Hasnip, P.; Clark, S.; Payne, M. Materials Studio CASTEP, version
2.2; Accelerys, Inc.: San Diego, CA, 2002.
(11) Vanderbilt, D. Phys. ReV. B: Condens. Matter Mater. Phys. 1990,
41, 7892.
(8) (a) Barrett, C. A.; Evans, E. B. J. Am. Ceram. Soc. 1964, 47, 533. (b)
Kubelka, P.; Munk, F. Z. Tech. Phys. 1931, 12, 593.
(12) Perdew, J. P.; Burke, K.; Ernzerhof, M. Phys. ReV. Lett. 1996, 77,
3865.
6496 Inorganic Chemistry, Vol. 46, No. 16, 2007

First Compounds in the Ni-Mo-X-O (X ) Se, Te) Systems
Table 2. Important Bond Lengths (Å) and Bond Angles (deg) for
Ni3(Mo2O8)(XO3) (X ) Se, Te)a
Ni3(Mo2O8)(SeO3)
Ni(1)-O(11)
Ni(1)-O(9)#2
Ni(1)-O(8)
Ni(2)-O(10)#3
Ni(2)-O(1)
Ni(2)-O(9)
Ni(3)-O(5)#6
Ni(3)-O(6)
Ni(3)-O(8)#4
Mo(1)-O(4)
Mo(1)-O(8)
Mo(1)-O(6)#4
Mo(2)-O(11)
Mo(2)-O(9)
Mo(2)-O(7)#4
Se(1)-O(1)
1.988(4) Ni(1)-O(9)#1
2.082(5) Ni(1)-O(3)
2.108(5) Ni(1)-O(2)
1.983(4) Ni(2)-O(3)#2
2.039(4) Ni(2)-O(7)#4
2.091(4) Ni(2)-O(2)#5
2.013(4) Ni(3)-O(4)
2.021(5) Ni(3)-O(2)#4
2.084(4) Ni(3)-O(7)#5
1.721(4) Mo(1)-O(5)
1.914(4) Mo(1)-O(7)
2.271(4) Mo(1)-O(6)#1
1.719(4) Mo(2)-O(10)
1.893(4) Mo(2)-O(6)
2.284(5) Mo(2)-O(8)#5
1.659(5) Se(1)-O(3)#3
1.780(5)
2.081(4)
2.090(4)
2.132(5)
2.014(5)
2.084(5)
2.160(4)
2.016(4)
2.042(5)
2.091(4)
1.722(4)
1.926(5)
2.283(4)
1.723(4)
1.965(4)
2.304(4)
1.708(4)
Se(1)-O(2)
O(8)-Mo(1)-O(7)
O(4)-Mo(1)-O(6)#1
O(10)-Mo(2)-O(7)#4 161.8(2)
148.0(2)
163.5(2)
O(5)-Mo(1)-O(6)#4
O(9)-Mo(2)-O(6)
O(11)-Mo(2)-O(8)#5 163.9(2)
162.8(2)
145.6(2)
Figure 1. View of the structure of Ni3(Mo2O8)(SeO3) down the b axis.
The NiO6 and MoO6 octahedra are shaded in cyan and olive, respectively.
Se and O atoms are drawn as pink and green circles, respectively.
Ni3(Mo2O8)(TeO3)
2.021(2) Ni(1)-O(2)#2
Ni(1)-O(7)#1
Ni(1)-O(6)#3
Ni(1)-O(1)
2.027(2)
2.052(2)
2.142(2)
2.011(2)
2.064(3)
2.099(2)
1.737(2)
1.911(2)
2.274(2)
1.732(2)
1.980(3)
2.319(2)
1.863(2)
2.045(2) Ni(1)-O(2)#4
2.087(2) Ni(1)-O(3)#5
2.011(2) Ni(2)-O(5)
2.015(3) Ni(2)-O(1)
2.099(2) Ni(2)-O(3)#7
1.737(2) Mo(1)-O(5)
1.911(2) Mo(1)-O(3)#8
2.274(2) Mo(1)-O(4)#9
1.732(2) Mo(2)-O(7)#1
1.812(3) Mo(2)-O(4)
2.319(2) Mo(2)-O(3)#9
1.863(2) Te(1)-O(2)
1.923(3)
Ni(2)-O(5)#6
Ni(2)-O(4)#5
Ni(2)-O(3)#5
Mo(1)-O(5)#8
Mo(1)-O(3)
Mo(1)-O(4)
Mo(2)-O(7)
Mo(2)-O(6)
Mo(2)-O(3)#8
Te(1)-O(2)#6
Te(1)-O(1)
and 1.719(4)-2.304(4) Å, respectively, for Mo(1) and Mo(2)
atoms (Table 2). Hence, both MoO6 octahedra are severely
distorted. The Mo(1) atom is distorted toward an edge
(O(4)‚‚‚O(5) (local C2 direction) with two “short” (1.721(4)
and 1.722(4) Å), two “normal” (1.914(4) and 1.926(5) Å),
and two “long” (2.271(4) and 2.283(4) Å) Mo6+-O bonds
(Figure 2a, Table 2).3d The Mo(2) atom adopts a similar
distortion to that of Mo(1) (Figure 2a, Table 2). Taking into
account the six Mo-O bond lengths as well as the deviations
of the three trans O-Mo-O bond angels from 180°, the
magnitudes of the distortions (∆d) were calculated to be 1.18
and 1.29 Å, respectively for Mo(1) and Mo(2), both of which
are very strong (∆d > 0.8 Å).3d The SeIV atom is in a ψ-SeO3
trigonal-pyramidal geometry with the lone pair of SeIV
occupying the pyramidal site. The Se-O distances range
from 1.659(5) to 1.780(5) Å (Table 2). Bond-valence
calculations indicate that the Ni atom is in an oxidation state
of +2 and that the Mo and Se atoms are in the states of +6
and +4, respectively. The calculated total bond valences for
the Ni(1), Ni(2), Ni(3), Mo(1), Mo(2), and Se(1) atoms are
1.91, 2.02, 2.10, 5.97, 5.90, and 3.92, respectively.14
O(3)-Mo(1)-O(3)#8 149.1(1)
O(5)-Mo(1)-O(4)#9 163.4(1)
O(7)-Mo(2)-O(3)#8 162.8(1)
O(5)#8-Mo(1)-O(4)
O(6)-Mo(2)-O(4)
O(7)#1-Mo(2)-O(3)#9 162.8(1)
163.4(1)
143.6(1)
a Symmetry transformations used to generate equivalent atoms. For
Ni3(Mo2O8)(SeO3): #1, x, y - 1, z; #2, -x + 1, -y + 1, -z + 2; #3, x +
1, y, z; #4, -x + 1, -y + 1, -z + 1; #5, x, y + 1, z; #6, - x, -y + 1, -z
+ 1. For Ni3(Mo2O8)(TeO3): #1, x, -y + 1, z; #2, -x + 1, y, -z; #3, x +
1/2, y - 1/2, z; #4, x + 1/2, -y + 1/2, z; #5, -x + 3/2, -y + 1/2, -z + 1; #6,
x, -y, z; #7, -x + 3/2, y - 1/2, -z + 1; #8, -x + 1, y, -z + 1; #9, -x +
1, -y + 1, -z + 1.
molybdenum(VI) selenite and tellurite compounds, namely,
Ni3(Mo2O8)(XO3) (X ) Se, Te). The syntheses of Ni3-
(Mo2O8)(XO3) (X ) Se, Te) can be expressed by the
following reactions at 710 or 720 °C: 3NiO + 2MoO3 +
XO2 f Ni3(Mo2O8)(XO3) (X ) Se, Te). They display two
different types of 3D structures containing [Mo4O16]8-
clusters and [Ni6O22]32- clusters or 1D nickel oxide chains.
These two compounds represent the first examples of nickel-
(II) selenite and tellurite decorated by polyoxomolybdate
clusters.
The four MoVIO6 octahedra are interconnected by edge-
sharing (O(6)‚‚‚O(7) and O(6)‚‚‚O(8)) bonds to form a cyclic
[Mo4O16]8- tetranuclear cluster unit. The Mo‚‚‚Mo separa-
tions for a pair of edge-sharing MoO6 octahedra are in the
range of 3.297(1)-3.722(1) Å. O(6) is a µ3 metal linker and
bridges with three MoVI centers (2 Mo1 and 1 Mo2). It should
be noted that such cyclic Mo4 clusters have been observed
in many molybdenum(VI) coordination compounds.15
The structure of Ni3(Mo2O8)(SeO3) features a 3D network
in which [Ni6O22]32- cluster units are interconnected by
[Mo4O16]8- clusters and SeO32- anions (Figure 1). All three
Ni(II) ions in the asymmetric unit are octahedrally coordi-
nated by six oxygen atoms with Ni-O distances ranging
from 1.983(4) to 2.160(4) Å (Table 2), which are comparable
to those reported in other nickel(II) selenites.13 Both Mo
atoms are octahedrally coordinated by six oxygen atoms. The
Mo-O bond distances are in the range of 1.721(4)-2.283(4)
(13) (a) Johnsson, M.; To¨rnroos, K. W.; Lemmens, P.; Millet, P. Chem.
Mater. 2003, 15, 68. (b) Shen, Y. L.; Mao, J.-G.; Jiang, H. L. J. Solid
State Chem. 2005, 178, 2949. (c) Johnsson, M.; Lidin, S.; To¨rnroos,
K. W.; Bu¨rgi, H. B.; Millet, P. Angew. Chem., Int. Ed. 2004, 43, 4292.
(d) Jiang, H. L.; Mao, J. G. Inorg. Chem. 2006, 45, 7593.
(14) (a) Brown, I. D.; Altermatt, D. Acta Crystallogr. 1985, B41, 244. (b)
Brese, N. E.; O’Keeffe, M. Acta Crystallogr. 1991, B47, 192.
Inorganic Chemistry, Vol. 46, No. 16, 2007 6497

Jiang et al.
Figure 2. (a) A [Mo4O16]8- tetranuclear cluster unit in Ni3(Mo2O8)(SeO3). (b) A [Ni6O22]32- hexanuclear cluster unit in Ni3(Mo2O8)(SeO3). (c) A nickel(II)
selenium(IV) oxide layer in Ni3(Mo2O8)(SeO3).
Six NiO6 octahedra are interconnected into a hexanuclear
[Ni6O22]32- cluster unit through edge-sharing bonds (O(2)‚‚‚
O(7), O(2)‚‚‚O(8), O(2)‚‚‚O(9) and O(3)‚‚‚O(9)). Both O(2)
and O(9) act as µ3 metal linkers (Figure 2b). The intracluster
Ni‚‚‚Ni separations between a pair of edge-sharing NiO6
octahedra are in the range of 3.034(1)-3.245(1) Å (Figure
2b). To the best of our knowledge, this type of Ni6 cluster
has not been reported.
into a 3D network structure. The lone-pair electrons of the
selenium(IV) atoms are orientated to the cavities of the
structure (Figure 1).
The structure of Ni3(Mo2O8)(TeO3) features a 3D structure
in which the corrugated nickel oxide anionic chains are
2-
bridged by [Mo4O16]8- cluster units and TeO3 anions
(Figure 3). There are two unique Ni atoms, two Mo atoms,
and one Te atom in the asymmetric unit. All the Ni and Mo
atoms are octahedrally coordinated by six oxygens. The
Ni-O distances range from 2.011(2) to 2.142(2) Å (Table
2), which are comparable to those in Ni3(Mo2O8)(SeO3) and
other nickel(II) tellurites reported.13 Similar to that in Ni3-
(Mo2O8)(SeO3), the MoVI atoms are in a severely distorted
octahedral-coordinated environment with Mo-O bond lengths
ranging from 1.732(2) to 2.319(2) Å (Table 2). Likewise, in
Ni3(Mo2O8)(SeO3), the Mo(1)O6 octahedron in Ni3(Mo2O8)-
(TeO3) is distorted toward an edge (O(5)‚‚‚O(5)) (local C2
direction distortion) (Figure 4a, Table 2).3d The Mo(2)O6
octahedron is also distorted toward an edge (O(7)‚‚‚O(7))
(Figure 4a, Table 2). The magnitudes of the distortion (∆d)
were calculated to be 1.12 and 1.44 Å, respectively, for
Mo(1) and Mo(2),3d which are very strong and comparable
The [Ni6O22]32- cluster units are bridged by SeO32- groups
to form a 2D nickel selenite layer parallel to the ab plane
2-
(Figure 2c). Each SeO3 anion is bridged to three clusters
by its three oxygen atoms. O(1) is monodentate and connects
with a nickel(II) ion of a cluster unit, O(2) connects with
two nickel(II) ions from another cluster unit, and O(3) is
bridged to three nickel(II) ions from the third cluster (Figure
2c). Neighboring nickel selenite layers are further intercon-
nected by the [Mo4O16]8- clusters via Mo-O-Ni bridges
(15) (a) Chisholm, M. H.; Huffman, J. C.; Kirkpatrick, C. C.; Leonelli, J.;
Folting, K. J. Am. Chem. Soc. 1981, 103, 6093. (b) Liu, S. C.; Shaikh,
S. N.; Zubieta, J. Inorg. Chem. 1987, 26, 4303. (c) Kang, H.; Liu, S.
C.; Shaikh, S. N.; Nicholson, T.; Zubieta, J. Inorg. Chem. 1989, 28,
920. (d) Limberg, C.; Buchner, M.; Heinze, K.; Walter, O. Inorg.
Chem. 1997, 36, 872.
6498 Inorganic Chemistry, Vol. 46, No. 16, 2007

First Compounds in the Ni-Mo-X-O (X ) Se, Te) Systems
nickel(II) oxide architectures may result from the different
coordination modes of the selenite and tellurite groups as
well as the different ionic radii of SeIV and TeIV.
Neighboring corrugated nickel(II) oxide chains are bridged
2-
by TeO3 anions to form a thick nickel(II) tellurite layer
parallel to the ab plane. Different from the SeO32- group in
Ni3(Mo2O8)(SeO3), each TeO3 group bridges with seven
nickel(II) ions: O(1) connects with three nickel(II) ions from
one nickel(II) oxide chain whereas two O(2) atoms bridge
with four nickel(II) ions from another nickel(II) oxide chain.
The thickness of the layer is about 12.1 Å. Such layers are
further interconnected by the [Mo4O16]8- clusters via Mo-
O-Ni bridges into a 3D network structure. The lone-pair
electrons of the tellurium(IV) atoms are orientated to the
tunnels of the structure (Figure 3). The effective volume of
the lone-pair electrons is approximately the same as the
volume of an O2- anion, according to Galy et al.17
Figure 3. View of the structure of Ni3(Mo2O8)(TeO3) down the c axis.
The NiO6 and MoO6 octahedra are shaded in cyan and olive, respectively.
Te atoms are drawn as pink circles.
Magnetic Properties. Ni3(Mo2O8)(SeO3) obeys the Curie-
Weiss law in the temperature range of 50-300 K; below 50
K, a slight deviation was observed (Figure 5a). At 300 K,
the øMT value is 3.99 emu‚mol-1‚K, which corresponds to
an effective magnetic moment (µeff) of 5.65 µB for three
isolated Ni2+ (S ) 1, g ) 2.4957) ions. The øMT value
increases upon cooling and reaches a maximum of 5.52
emu‚mol-1‚K at 28 K. Below 28 K, it decreases continuously
upon cooling and a value of 0.51 emu‚mol-1‚K is reached
at 2.0 K. The linear fit of the magnetic data in the range of
50-300 K gave a Weiss constant (θ) of 15.4(2) K, indicating
significant ferromagnetic interactions between magnetic
centers. It is expected that the magnetic interactions should
be dominated by the magnetic interactions between nickel(II)
ions within the hexanuclear [Ni6O22]32- cluster. As mentioned
before, the intracluster Ni‚‚‚Ni separations are in the range
of 3.034(1)-3.245(1) Å. The shortest intercluster Ni‚‚‚Ni
contact is 4.666(1) Å. Ni3(Mo2O8)(TeO3) obeys the Curie-
Weiss law in the temperature range of 50-300 K; below
about 50 K, a significant deviation was observed (Figure
5b). At 300 K, the øMT value is 3.92 emu‚mol-1‚K, which
corresponds to an effective magnetic moment (µeff) of 5.62
µB for three isolated Ni2+ (S ) 1, g ) 2.28) ions. The øMT
value increases upon cooling and reaches a maximum of at
4.28 emu‚mol-1‚K at 56 K. Below 56 K, it decreases
continuously upon cooling and a value of 0.32 emu‚mol-1‚K
is reached at 2.0 K. The linear fit of the magnetic data in
the range of 50-300 K gave a Weiss constant (θ) of 5.5(1)
K, indicating weak ferromagnetic interactions between Ni2+
ions. It is expected that such magnetic interactions are
dominated by the magnetic interactions between the Ni(II)
ions within the 1D [Ni3O11]16- anionic chain. As mentioned
earlier, the Ni‚‚‚Ni separations between pairs of edge-sharing
NiO6 octahedra are in the range of 3.016(2)-3.072(1) Å.
The shortest interchain Ni‚‚‚Ni separation is 4.715(1) Å.
to those of Ni3(Mo2O8)(SeO3). The TeIV atom is coordinated
by three oxygen atoms in a distorted ψ-TeO3 tetrahedral
geometry, with the fourth site occupied by the lone-pair
electrons with Te-O distances ranging from 1.863(2) to
1.923(3) Å. The oxidation states of the Ni, Mo, and Te atoms
are +2, +6, and +4, respectively, according to the results
of bond-valence calculations.14 The calculated total bond
valences for the Ni(1), Ni(2), Mo(1), Mo(2), and Te(1) atoms
are 2.00, 2.07, 5.89, 5.98, and 3.88, respectively.
Similar to that in Ni3(Mo2O8)(SeO3), the four MoVIO6
octahedra in Ni3(Mo2O8)(TeO3) are interconnected via edge-
sharing to form a [Mo4O16]8- tetranuclear cluster unit (Figure
4a).
Two Ni(1)O6 and one Ni(2)O6 octahedra are intercon-
nected via edge-sharing (O(1)‚‚‚O(3) and O(1)‚‚‚O(6)) into
a [Ni3O13]20- trinuclear unit. Neighbors of such trinuclear
units are further interconnected through edge-sharing
(O(2)‚‚‚O(2)) into a corrugated [Ni3O11]16- anionic chain
along the b axis with the Ni(1)-O(2)-Ni(1) bond angle of
84.65(9)° (Figure 4b). The intercluster Ni‚‚‚Ni separation is
3.016(2) Å, whereas the intracluster Ni(1)‚‚‚Ni(1) and
Ni(1)‚‚‚Ni(2) distances are 3.072(1) and 3.021(1) Å, respec-
tively. This nickel oxide chain can also be viewed as Ni(2)O6
octahedra being grafted onto the corrugated chain of Ni(1)O6
through edge-sharing (O(3)‚‚‚O(1) and O(2)‚‚‚O(2)). Such
a corrugated nickel(II) oxide chain has not been reported,
and only simple 1D nickel oxide single chains were
characterized in Ni(SeO4)(H2O) and NiTe2O5.16 It is interest-
ing to note that [Ni6O22]32- clusters are formed in Ni3-
(Mo2O8)(SeO3), whereas corrugated [Ni3O11]16- anionic
chains are observed in Ni3(Mo2O8)(TeO3). Both nickel oxide
building units are based on Ni3O triangles. The Ni3O triangles
in [Ni6O22]32- clusters are condensed via sharing Ni-Ni
edges whereas those in [Ni3O11]16- anionic chains are
interconnected through Ni-O-Ni bridges. These different
Thermogravimetric Analysis. TGA analyses under an air
atmosphere indicate that Ni3(Mo2O8)(SeO3) and Ni3(Mo2O8)-
(TeO3) are stable up to 570 and 850 °C, respectively (Figure
(16) (a) Giester, G.; Wildner, M. Neues Jahrb. Mineral. Monatsh. 1992,
1992, 135. (b) Platte, C.; Troemel, M. Acta Crystallogr. 1981, B37,
1276.
(17) Galy, J.; Meunier, G.; Andersson, S.; Åstro¨m, A. J. Solid State Chem.
1975, 13, 142.
Inorganic Chemistry, Vol. 46, No. 16, 2007 6499

Jiang et al.
Figure 4. (a) A [Mo2O14]16- cluster unit in Ni3(Mo2O8)(TeO3). (b) A 1D [Ni3O11]16- corrugated chain along the b axis in Ni3(Mo2O8)(TeO3).
6). Both compounds exhibit two main steps of weight loss.
The first steps of weight loss occurred in the temperature
ranges of 570-895 and 850-1100 °C, respectively, for
Ni3(Mo2O8)(SeO3) and Ni3(Mo2O8)(TeO3), which corre-
sponds to the release of 1 mol of SeO2 or TeO2 per formula
unit. The observed weight losses of 17.8% for Ni3(Mo2O8)-
(SeO3) and 22.3% for Ni3(Mo2O8)(TeO3) are close to the
calculated ones (17.8 and 23.8%, respectively). Ni3(Mo2O8)-
(SeO3) exhibits a plateau in the wide range of 895-1100
°C. Above 1100 °C, both compounds are further decom-
posed. The total weight losses at 1300 °C are 36.0 and 31.0%,
respectively, for the Se and Te compounds, and the final
residuals are not characterized due to the fact that the
residuals had been melted by the TGA buckets (made of
Al2O3) under such high temperatures.
Band Structure and Density of States. Spin-polarized
band-structure calculations for Ni3(Mo2O8)(XO3) (X ) Se,
Te) based on the DFT method have been made. On the basis
of the calculations, the integrated spin density (12.0 e) and
integrated absolute spin density (12.5628 and 12.4764 e,
respectively, for Se and Te compounds) per unit cell are
almost identical, indicating possible ferromagnetic interac-
tions between nickel(II) centers in both compounds, which
is in good agreement with the results from magnetic
measurements.
The top of the valence bands (VBs) is nearly flat and close
to the Fermi level (0.0 eV), and the bottom of the conduction
bands (CBs) exhibits small dispersion. For Ni3(Mo2O8)-
(SeO3), both the lowest energy (0.75 eV) of the CBs and
the highest energy (-0.01 eV) of the VBs are located at the
G point (Table 3). Hence, it represents a semiconductor
character with a direct band gap of around 0.76 eV. As for
Ni3(Mo2O8)(TeO3), the lowest of the CBs with energy of
0.76 eV is located at the M point, and the highest of the
VBs is located at the V point with an energy of 0.00 eV
(Table 3). Therefore, it is reasonable to consider Ni3(Mo2O8)-
(TeO3) as a semiconductor with an indirect band gap of 0.76
eV. The absorption edges of both compounds are very close
to 1715 nm (0.72 eV), and both compounds exhibit strong
absorption peaks at 360 nm (3.45 eV), 770 nm (1.61 eV),
and 1270 nm (0.98 eV) (See the Supporting Information).
Hence, our calculated band gaps are close to those of the
experimental results.
For both compounds, the VBs lying near -62.6 and -36.9
eV are mainly the contributions of the Mo 4s and Mo 4p
states, respectively (see the Supporting Information). The O
2s and Se 4s (or Te 5s) states dominate the VBs between
-22.2 and -10.0 eV. The main contributions of the VBs,
ranging from -7.9 eV to the Fermi level, are the Ni 3d and
O 2p states, with a small mixing of Mo 4d and Se 4p (or Te
5p) states. The CBs are dominated by unoccupied Ni 3d,
Mo 4d, and O 2p states. The Ni 3d states are found to be
The band structures of both compounds are similar and
display a small band gap (see the Supporting Information).
6500 Inorganic Chemistry, Vol. 46, No. 16, 2007

First Compounds in the Ni-Mo-X-O (X ) Se, Te) Systems
Figure 6. TGA curves for Ni3(Mo2O8)(XO3) (X ) Se, Te).
Table 3. The State Energies (eV) of the Lowest Conduction Band
(L-CB) and the Highest Valence Band (H-VB) at Some k Points for
Ni3(Mo2O8)(XO3) (X ) Se, Te)
Ni3(Mo2O8)(SeO3)
k point
G
F
X
Z
L-CB
H-VB
0.75206
-0.00771
0.80638
-0.03240
0.85980
-0.04425
0.81896
-0.01634
Ni3(Mo2O8)(TeO3)
A
k point
L-CB
L
M
G
Z
V
0.92117 0.76385 0.82050 0.91676 0.92117 0.90344
H-VB -0.06470 -0.03491 -0.05261 -0.00592 -0.06470 0
Table 4. The Calculated Bond Orders of Ni3(Mo2O8)(XO3) (X ) Se,
Te)
Figure 5. ø versus T and øT versus T plots for Ni3(Mo2O8)(SeO3) (a)
and Ni3(Mo2O8)(TeO3) (b). The red line represents the linear fit of data
according to the Curie-Weiss law.
Ni3(Mo2O8)(SeO3)
Ni3(Mo2O8)(TeO3)
bond
bond length
bond order
bond length
bond order
Ni-O
Mo-O
Mo-O
Mo-O
X-O
1.983-2.159
1.719-1.724
1.895-1.965
2.269-2.303
1.661-1.780
0.16-0.32
0.78-0.79
0.41-0.48
0.15-0.16
0.18-0.52
2.011-2.142
1.732-1.737
1.812-1.980
2.274-2.319
1.864
0.17-0.31
0.80
0.38-0.53
0.15-0.17
0.18-0.37
spin-polarized, which is responsible for the ferromagnetism
of the two compounds. It is observed that the Ni 3d states
display two peaks, which correspond to the doubly degener-
ate eg states and threefold degenerate t2g states of the
octahedrally coordinated nickel(II) ions.
Acknowledgment. This work was supported by the
National Natural Science Foundation of China (Nos. 20573113
and 20521101) and the NSF of Fujian Province (No.
E0420003).
The chemical bonds for both compounds were studied by
population analyses. The calculated bond orders are 0.16-
0.32, 0.15-0.80, and 0.18-0.52 e for Ni-O, Mo-O, and
X-O bonds, respectively (Table 4). It is generally assumed
that a covalent single-bond order corresponds to 1.0 e. It is
observed that the elongated Mo-O bonds are much weaker
than those of the normal Mo-O bonds; the latter are also
significantly weaker than those of the short Mo-O bonds
(Table 4).
Supporting Information Available: X-ray crystallographic
files in CIF format, simulated and experimental XRD powder
patterns, and diagrams for band structures and density-of-
states for Ni3(Mo2O8)(SeO3) and Ni3(Mo2O8)(TeO3). This material
is available free of charge via the Internet at http://pubs.
acs.org.
IC700500Q
Inorganic Chemistry, Vol. 46, No. 16, 2007 6501