Syntheses and structures of n'-(5-bromo-2-hydroxybenzylidene)-4- methoxybenzohydrazide and its dioxomolybdenum(vi) complex with catalytic epoxidation property

Article abstract of DOI:10.1080/00958972.2013.805213

A new Schiff base N'-(5-bromo-2-hydroxybenzylidene)-4-methoxybenzohydrazide (H2BMH) and its dioxomolybdenum(VI) complex [MoO2(BMH)(EtOH)] have been synthesized and characterized by elemental analysis, IR spectra, and single crystal X-ray determination. The Schiff base crystallized in the orthorhombic space group P212121 and the complex crystallized in the triclinic space group P-1. The Schiff base coordinates to Mo through the phenolate O, imine N, and enolic O. The asymmetric unit of the complex contains two mononuclear dioxomolybdenum molecules. Each Mo is six-coordinate octahedral. The only significant difference between the complex and the ligand is the geometry involving donors. The coordination of the ligand to Mo is also reflected in the IR spectra. The complex shows high catalytic property and selectivity in epoxidation of cyclohexene with t-butylhydroperoxide as oxidant.

Full text of DOI:10.1080/00958972.2013.805213

This article was downloaded by: [Universite Laval]
On: 11 July 2014, At: 08:57
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered
office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Journal of Coordination Chemistry
Publication details, including instructions for authors and
subscription information:
http://www.tandfonline.com/loi/gcoo20
Syntheses and structures of N’-(5-
bromo-2-hydroxybenzylidene)-4-
methoxybenzohydrazide and its
dioxomolybdenum(VI) complex with
catalytic epoxidation property
Yong-Ming Cui a , Yan Wang a , Ying-Jie Cai a , Xue-Jun Long a & Wu
Chen a
a Ministry of Education, Engineering Research Center for Clean
Production of Textile Printing , Wuhan Textile University , Wuhan ,
P.R. China
Accepted author version posted online: 16 May 2013.Published
online: 11 Jun 2013.
To cite this article: Yong-Ming Cui , Yan Wang , Ying-Jie Cai , Xue-Jun Long & Wu Chen (2013)
Syntheses and structures of N’-(5-bromo-2-hydroxybenzylidene)-4-methoxybenzohydrazide and
its dioxomolybdenum(VI) complex with catalytic epoxidation property, Journal of Coordination
Chemistry, 66:13, 2325-2334, DOI: 10.1080/00958972.2013.805213
To link to this article: http://dx.doi.org/10.1080/00958972.2013.805213
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the
“Content”) contained in the publications on our platform. However, Taylor & Francis,
our agents, and our licensors make no representations or warranties whatsoever as to
the accuracy, completeness, or suitability for any purpose of the Content. Any opinions
and views expressed in this publication are the opinions and views of the authors,
and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content
should not be relied upon and should be independently verified with primary sources
of information. Taylor and Francis shall not be liable for any losses, actions, claims,
proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or
howsoever caused arising directly or indirectly in connection with, in relation to or arising
out of the use of the Content.
This article may be used for research, teaching, and private study purposes. Any
substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing,
systematic supply, or distribution in any form to anyone is expressly forbidden. Terms &

Conditions of access and use can be found at http://www.tandfonline.com/page/terms-
and-conditions

Journal of Coordination Chemistry, 2013
Vol. 66, No. 13, 2325–2334, http://dx.doi.org/10.1080/00958972.2013.805213
Syntheses and structures of N'-(5-bromo-2-
hydroxybenzylidene)-4-methoxybenzohydrazide and its
dioxomolybdenum(VI) complex with catalytic epoxidation
property
YONG-MING CUI, YAN WANG, YING-JIE CAI, XUE-JUN LONG and WU CHEN*
Ministry of Education, Engineering Research Center for Clean Production of Textile
Printing, Wuhan Textile University, Wuhan, P.R. China
(Received 12 January 2013; in final form 2 April 2013)
A new Schiff base N′-(5-bromo-2-hydroxybenzylidene)-4-methoxybenzohydrazide (H2BMH) and
its dioxomolybdenum(VI) complex [MoO2(BMH)(EtOH)] have been synthesized and characterized
by elemental analysis, IR spectra, and single crystal X-ray determination. The Schiff base crystal-
lized in the orthorhombic space group P212121 and the complex crystallized in the triclinic space
ꢀ
group P1. The Schiff base coordinates to Mo through the phenolate O, imine N, and enolic O. The
asymmetric unit of the complex contains two mononuclear dioxomolybdenum molecules. Each Mo
is six-coordinate octahedral. The only significant difference between the complex and the ligand is
the geometry involving donors. The coordination of the ligand to Mo is also reflected in the IR
spectra. The complex shows high catalytic property and selectivity in epoxidation of cyclohexene
with t-butylhydroperoxide as oxidant.
Keywords: Schiff base; Dioxomolybdenum(VI) complex; Crystal structure; Coordination compound;
Epoxidation
1. Introduction
Molybdenum complexes have been investigated as oxidation catalysts for a variety of
organic substrates [1–4], particularly for sulfoxidation and epoxidation of olefins [5–8].
Schiff bases, especially those of hydrazone type, have attracted interest in coordination
chemistry [9, 10]. Dioxomolybdenum complexes derived from such hydrazone type Schiff
bases have been reported to possess effective catalytic properties [11–13]. However, the
number of such complexes is small. Recently, we reported some complexes derived from
hydrazone type Schiff bases [14, 15]. As a further study of the coordination of such
ligands to molybdenum, in the present work, a new Schiff base N′-(5-bromo-2-hydroxyb-
enzylidene)-4-methoxybenzohydrazide (H2BMH) and its dioxomolybdenum(VI) complex
[MoO2(BMH)(EtOH)] (scheme 1) have been synthesized and characterized. The particular
interest is to compare the various properties related to the uncoordinated and coordinated
molecule.
*Corresponding author. Email: cym@smail.hust.edu.cn
Ó 2013 Taylor & Francis

2326
Y.-M. Cui et al.
OMe
OMe
Br
N
N
H
N
Br
O
O
N
O
Mo
O
O
OEt
OH
H2O
H
Scheme 1. H2BMH and [MoO2(BMH)(EtOH)].
2. Experimental
2.1. Materials and methods
5-Bromosalicylaldehyde and 4-methoxybenzohydrazide were purchased from Alfa Aesar.
[MoO2(acac)2] was prepared according to the literature method [16]. All chemicals and
solvents were of analytical grade and used as obtained. Microanalyses of the Schiff
bases and dioxomolybdenum(VI) complex were performed with a Vario EL III CHNOS
elemental analyzer. Infrared spectra were recorded as KBr pellets with an FTS-40
spectrophotometer.
2.2. Synthesis of N′-(5-bromo-2-hydroxybenzylidene)-4-methoxybenzohydrazide
(H2BMH)
A mixture of 5-bromosalicylaldehyde (2.01 g, 10 mM) and 4-methoxybenzohydrazide
(1.66 g, 10 mM) in 50 mL ethanol was refluxed for 2 h and cooled to room temperature.
The colorless solution was left in air for a week until most of the solvent was evaporated,
yielding block-shaped single crystals of H2BMH, isolated by filtration, and dried in air.
Yield 2.82 g (77%). Anal. Calcd for C15H15BrN2O4 (%): C, 49.1; H, 4.1; N, 7.6. Found:
C, 48.9; H, 4.1; N, 7.7. IR (KBr, νmax/cmÀ1): 3417 (OH), 3228 (NH), 1651 (C=O), 1615
(C=N).
2.3. Synthesis of [MoO2(BMH)(EtOH)]
A stirred solution of H2BMH·H2O (0.367 g, 1 mM) in ethanol (20 mL) was mixed with
[MoO2(acac)2] (0.326 g, 1 mM) and the resulting reaction mixture was refluxed on a water
bath for 1 h, and then cooled to room temperature, yielding a yellow solution. The solution
was left at ambient temperature to slowly evaporate solvent for a week, yielding orange
block-shaped single crystals of the complex. Yield 0.313 g (60%). Anal. Calcd for
C17H17BrMoN2O6 (%): C, 39.2; H, 3.3; N, 5.4. Found: C, 39.0; H, 3.4; N, 5.2. IR (KBr,
ν
max/cm–1): 3410 (OH), 1609 (C=N), 1359 (C–O, enolic), 1259 (C–O, phenolate), 1031
(N–N), 915 (Mo=O), 642, 567, 466 (Mo–O, Mo–N).
2.4. X-ray structure determination
Data were collected on a Bruker SMART 1000 CCD area diffractometer using
graphite-monochromated Mo Kα radiation (λ = 0.71073 Å) at 298(2) K and corrected with
SADABS [17]. The structures were solved by direct methods [18] and refined on F2 by

Dioxomolybdenum(VI)
2327
Table 1. Crystallographical and experimental data for H2BMH and [MoO2(BMH)(EtOH)].
Compound
H2BMH
[MoO2(BMH)(EtOH)]
Formula
Mr
C15H15BrN2O4
367.2
C17H17BrMoN2O6
521.2
T (K)
298(2)
298(2)
Crystal shape/color
Crystal size/mm3
Crystal system
Space group
Block/colorless
0.18 Â 0.17 Â 0.15
Orthorhombic
P212121
Block/orange
0.23 Â 0.20 Â 0.20
Triclinic
ꢀ
P1
a/Å
b/Å
c/Å
α/°
β/°
4.485(1)
6.682(1)
51.149(2)
90
90
90
1533.0(1)
4
1.591
3.841
744
7.825(1)
11.090(1)
22.471(2)
88.312(2)
87.747(2)
75.371(2)
1885.0(2)
4
γ/°
V/Å3
Z
Dc/(g/cmÀ3
)
1.836
2.852
1032
β (MoKα) (cmÀ1
F(000)
)
Rint
0.0534
2841
0.0359
7152
Unique reflections
Observed reflections I P 2σ(I)
Min. and max. transmission
Parameters
2627
0.5448/0.5965
210
5188
0.5600/0.5993
491
Restraints
3
0
Goodness-of-fit on F2
R1, wR2 [I P 2σ(I)]a
R1, wR2 (all data)a
1.064
1.217
0.0333, 0.0800
0.0375, 0.0824
0.376/À0.571
0.0651, 0.1459
0.0949, 0.1552
1.207/À0.860
Large diff. peak and hole/(e.ÅÀ3
)
aR1 = ∑||Fo|-|Fc||/∑|Fo|; wR2 = [∑w (Fo2 À Fc2)2/∑w(Fo2)2]1/2
.
full-matrix least-squares using SHELXL [19]. All non-hydrogen atoms were refined
anisotropically. H2 attached to N2 and the water hydrogens in H2BMH were located
from difference Fourier maps and refined isotropically, with N–H, O–H, and H···H
distances restrained to 0.90(1), 0.85(1), and 1.37(2) Å, respectively. The other hydrogens
were placed in calculated positions and included in the last cycle of refinement. Crystal
data and details of the data collection and refinement are listed in table 1. Selected
bond lengths and angles are listed in table 2. Hydrogen bonding parameters are given in
table 3.
2.5. Catalytic epoxidation test
Epoxidation of cyclohexene by dioxomolybdenum(VI) complex with tert-butyl hydroper-
oxide (TBHP) was carried out according to the following procedure. A mixture of catalyst
(0.003 mM), cyclohexene (6.56 g, 0.08 M), and 1,2-dichloroethane (5 mL) was placed in a
three-necked round-bottomed flask equipped with a condenser and a magnetic stirrer. The
mixture was stirred for 5 min at 353(2) K and then 2 mL (0.02 M) anhydrous TBHP was
added. The reaction was monitored at certain time intervals to determine the concentrations
of TBHP and 1,2-epoxycyclohexene by GC and was left to proceed until near complete
conversion of TBHP.

2328
Y.-M. Cui et al.
Table 2. Selected bond lengths/Å and angles/° for H2BMH and [MoO2(BMH)(EtOH)].
H2BMH
N1–C7
N2–C8
C2–O1
1.284(4)
1.354(4)
1.350(4)
N1–N2
C8–O2
1.377(3)
1.228(4)
[MoO2(BMH)(EtOH)]
Mo1–O1
Mo1–N1
Mo1–O5
Mo2–O7
Mo2–N3
Mo2–O11
N1–C7
N2–C8
1.929(6)
2.243(7)
1.688(6)
1.928(6)
2.252(7)
1.697(6)
1.29(1)
Mo1–O2
Mo1–O4
Mo1–O6
Mo2–O8
Mo2–O10
Mo2–O12
N1–N2
C8–O2
2.016(6)
2.321(6)
1.690(7)
2.003(5)
2.368(7)
1.709(7)
1.397(9)
1.31(1)
1.32(1)
C2–O1
1.34(1)
N3–C24
1.29(1)
N3–N4
C25–O8
1.398(9)
1.32(1)
N4–C25
C19–O7
1.30(1)
1.35(1)
O5–Mo1–O6
O6–Mo1–O1
O6–Mo1–O2
O5–Mo1–N1
O1–Mo1–N1
O5–Mo1–O4
O1–Mo1–O4
N1–Mo1–O4
O11–Mo2–O7
O11–Mo2–O8
O7–Mo2–O8
O12–Mo2–N3
O8–Mo2–N3
O12–Mo2–O10
O8–Mo2–O10
103.8(3)
O5–Mo1–O1
O5–Mo1–O2
O1–Mo1–O2
O6–Mo1–N1
O2–Mo1–N1
O6–Mo1–O4
O2–Mo1–O4
O11–Mo2–O12
O12–Mo2–O7
O12–Mo2–O8
O11–Mo2–N3
O7–Mo2–N3
O11–Mo2–O10
O7–Mo2–O10
N3–Mo2–O10
103.3(3)
99.6(3)
96.2(3)
158.6(3)
81.3(2)
83.9(3)
81.5(3)
76.1(2)
102.0(3)
98.4(3)
150.9(3)
97.8(3)
71.5(2)
171.8(3)
79.0(2)
97.5(3)
149.8(3)
95.8(3)
71.7(2)
171.6(3)
79.3(2)
105.4(3)
98.7(3)
95.8(3)
155.7(3)
81.5(2)
81.7(3)
83.5(3)
74.7(2)
Table 3. Hydrogen bonding for the ligand and the complex.
D–H∙∙∙A
d(D–H) (Å)
d(H∙∙∙A) (Å)
d(D∙∙∙A) (Å)
\(D–H∙∙∙A) (°)
H2BMH
O1–H1Á Á ÁN1
0.82
0.82
0.90(1)
0.85(1)
1.97
2.58
2.00(2)
2.05(2)
2.678(3)
3.062(3)
2.886(3)
2.880(4)
144
119
169(4)
167(5)
O1–H1Á Á ÁO4i
N2–H2Á Á ÁO4ii
O4–H4BÁ Á ÁO1
[MoO2(BMH)(EtOH)]
O4–H4AÁ Á ÁN2iii
0.93
0.93
1.93
1.94
2.814(9)
2.819(9)
159(3)
157(3)
O10–H10AÁ Á ÁN4iv
Symmetry codes: (i) À1 + x, y, z; (ii) À1 + x, À1 + y, z; (iii) 1Àx, Ày, Àz; (iv) Àx, Ày, 1Àz.
3. Results and discussion
Reaction between equimolar quantities of [MoO2(acac)2] with H2BMH in ethanol afforded
[MoO2(BMH)(EtOH)]. BMH adopts an enolic tautomeric form on complexation. The
Schiff base crystallizes as colorless crystals and the dioxomolybdenum(VI) complex
crystallizes as orange crystals. Both the ligand and the complex are stable in air at room
temperature and soluble in common polar organic solvents, such as DMSO, DMF, MeOH,
EtOH, and MeCN, but insoluble in water.

Dioxomolybdenum(VI)
2329
3.1. IR spectra
IR spectra of the Schiff base and the dioxomolybdenum(VI) complex provide information
about metal-ligand bonding. Assignments are based on typical group frequencies. The
medium and broad band at 3380–3450 cmÀ1 is assigned to ν(O–H). The ν(C=O) at
1651 cmÀ1 and the sharp ν(NH) of 3228 cmÀ1 for H2BMH are absent in the complex,
indicating enolization of the amide functionality and subsequent proton replacement by
molybdenum, in accord with the results obtained by X-ray determination. The ν(C–O)
(enolic) of the complex is at 1359 cmÀ1. The strong band at 1615 cmÀ1 of the Schiff base
is assigned to azomethine and observed at 1609 cmÀ1 in the complex, indicating coordina-
tion of the azomethine N to Mo [20]. The medium band observed at 915 cmÀ1 for the
complex is assigned to Mo=O stretch [21]. Bands indicative of Mo–O and Mo–N
vibrations are at 450–650 cmÀ1 [11, 22].
3.2. Structures of the Schiff base ligand and the dioxomolybdenum(VI) complex
Figures 1 and 2 give perspective views of the mono-hydrated Schiff base and the
dioxomolybdenum(VI) complex together with atomic labeling systems. There is an intra-
molecular O1–H1Á Á ÁN1 hydrogen bond in the Schiff base and the dihedral angle between
the two benzene rings is 21.1(3)°. All the bond lengths in the Schiff base are comparable
to those observed in similar Schiff base compounds [23, 24].
The complex, derived from the Schiff base ligand, is a mononuclear dioxomolybdenum
(VI) compound. There are two independent molecules, A and B (figure 2), in the asym-
metric unit of the complex. BMH forms one five-membered and one six-membered che-
late rings with bite angles of 71.7(2) and 81.3(2)° for molecule A, and of 71.5(2) and
81.5(2)° for molecule B. The Mo ions are in distorted octahedral O5N coordination
spheres. The phenolate O, imine N, and enolic O of BMH and one methoxy O constitute
the equatorial planes, with mean deviations (the maximum deviation of the atoms consti-
tuting the mean plane) of 0.020(3) Å for molecule A and 0.064(3) Å for molecule B. The
two axial positions are occupied by one oxo and one ethanol. Displacements of Mo from
the equatorial planes toward the axial oxo are 0.312(2) Å for molecule A and 0.327(2) Å
for molecule B. The cis bond angles are 71.5(2)–105.4(3)° and the trans bond angles are
Figure 1. ORTEP plots (30% probability level) and atom labeling scheme for H2BMH. Hydrogen bonds are
shown as dashed lines.

2330
Y.-M. Cui et al.
Figure 2. ORTEP plots (30% probability level) and atom labeling scheme for [MoO2(BMH)(EtOH)].
149.8(3)–171.8(3)°. The Mo–O and Mo–N bond lengths are comparable with those
reported for dioxomolybdenum(VI) complexes with similar ligands [25, 26]. As com-
monly observed in analogous species, the elongated Mo1–O4 and Mo2–O10 bonds trans
to the oxo groups in the complex indicate weak coordination of ethanol at the axial posi-
tions. The dihedral angles between the two benzene rings in the complex are 5.7(2)° for
molecule A and 5.5(2)° for molecule B. The relatively large deviations from linearity in
the O1–Mo1–O2 and O7–Mo2–O8 angles (150°) are caused by the strain created by the
five- and six-membered chelate rings. From the above analysis, it can be seen that mole-
cules A and B are very similar.
The Schiff base coordinates to Mo through the phenolate O, imine N, and enolic O. The
bond lengths of C7=N1 and C24=N3 [1.29(1) Å], and N1–N2 and N3–N4 [1.40(1) Å] in
Figure 3. Molecular packing diagram for H2BMH, viewed along the b axis. Hydrogen bonds are shown as
dashed lines.

Dioxomolybdenum(VI)
2331
the complex are similar to those [1.28(1) and 1.38(1) Å] in the Schiff base. Bond lengths
of C2–O1 [1.34(1) Å] and C19–O7 [1.35(1) Å] in the complex are comparable to that
[1.35(1) Å] in the Schiff base, which might be associated with the presence of the intramo-
lecular O1–H1Á Á ÁN1 hydrogen bond. Distances between C8 and N2 [1.32(1) Å] and C25
and N4 [1.30(1) Å] in the complex are shorter than between C8 and N2 [1.35(1) Å] in the
ligand, and the distances between C8 and O2 [1.31(1) Å] and C25 and O8 [1.32(1) Å] in
the complex are longer than between C8 and O2 [1.23(1) Å] in the ligand, indicating enoli-
zation of N2–C8–O2 and N4–C25–O8 in the complex.
In the crystal structure of the Schiff base, molecules are linked via intermolecular
N–HÁ Á ÁO and O–HÁ Á ÁO hydrogen bonds, forming a 3-D network, as shown in figure 3. In
the crystal structure of the complex, adjacent two molecules are linked via intermolecular
O–HÁ Á ÁN hydrogen bonds, forming a dimer, as shown in figure 4.
3.3. Catalytic epoxidation of cyclohexene
According to Sobczak’s idea [27], the probable mechanism of the catalytic epoxidation
is shown in scheme 2. First, formation of the intermediate complex [MoO2(BMH)
(t-BuOOH)] and activation of TBHP. Second, interaction between cyclohexene and
TBHP molecule activated in the coordination sphere of the molybdenum complex. Third,
formation of epoxide and conversion of TBHP into t-BuOH. Finally, substitution of
t-BuOH by TBHP and reproduction of the intermediate complex [MoO2(BMH)
(t-BuOOH)].
The catalytic activity of dioxomolybdenum(VI) complex was determined from the yield
for epoxidation of cyclohexene using TBHP as oxidant. The yields in the reaction are
Figure 4. Molecular packing diagram for [MoO2(BMH)(EtOH)], viewed along the c axis. Hydrogen bonds are
shown as dashed lines.

2332
Y.-M. Cui et al.
Scheme 2. Probable mechanism of cyclohexene epoxidation with the complex as catalyst and TBHP as oxidant.
expressed as Y= (Cepox/CTBHP) Â 100%, where Cepox and CTBHP (M LÀ1) are the concentra-
tion of epoxide formed and initial concentration of TBHP, respectively. The selectivity
with respect to TBHP reacted was calculated by the ratio S = (Cepox/(CTBHP À C)) Â 100,
where C is the final TBHP concentration. The yields are shown in figure 5. After 20 min
of reaction, the yield is nearly 100% with selectivity at 100%. This is comparable to the
catalytic property of a multiwall carbon nanotube supported tungsten hexacarbonyl [28],
which can convert the cyclohexene to its epoxide with 100% yield and conversion within
2 h. When compared to the multiwall carbon nanotube supported manganese(III) tetraphen-
ylporphyrin (97% conversion and 97% epoxide yield within 150 min) [29], the complex in
the present work has more efficient catalysis. Maurya and coworkers reported oxidation of
cyclohexane with TBHP catalyzed by a Schiff base copper(II) complex [30]. Bagherzadeh
and Zare reported oxidation of olefins with a Schiff base manganese(III) complex [31].
However, the conversion and selectivity of the copper(II) and manganese(III) complexes are
low. In addition, there are many other species including vanadium [32, 33] having efficient

Dioxomolybdenum(VI)
2333
100
80
60
40
20
0
0
10
20
30
40
50
60
Time (min)
Figure 5. Yield and time curve of the catalytic epoxidation reaction.
catalytic epoxidation properties. In general, vanadium and molybdenum complexes are
more efficient for catalytic epoxidation with higher selectivity than other metal complexes.
4. Conclusion
Using new tridentate Schiff base ligand prepared from 5-bromosalicylaldehyde with
4-methoxybenzohydrazide in ethanol, a new dioxomolybdenum(VI) complex has been
synthesized. The structures of the Schiff base and the complex were characterized and
compared. The dianionic Schiff base ligand coordinates to Mo through phenolate-O,
imine-N, and enolic-O. The complex shows high catalytic activity and selectivity in
epoxidation of cyclohexene with TBHP as oxidant. Further work needs to be done to
explore its application in various organic syntheses.
Supplementary material
CCDC 919060 and 919061 contain the supplementary crystallographic data for this article.
These data can be obtained free of charge from The Cambridge Crystallographic Data
Center via www.ccdc.cam.ac.uk/data_request/cif.
Acknowledgment
This work was financed by the Education Office of Hubei Province (Q20101610).
References
[1] C.A. Gamelas, A.C. Gomes, S.M. Bruno, F.A.A. Paz, A.A. Valente, M. Pillinger, C.C. Romao, I.S. Goncalves.
Dalton Trans., 41, 3474 (2012).
[2] T. Szymanska-Buzar. Curr. Org. Chem., 16, 3 (2012).
[3] M.R. Reithofer, R.R. Schrock, P. Muller. J. Am. Chem. Soc., 132, 8349 (2010).

2334
Y.-M. Cui et al.
[4] Y.-L. Wong, L.H. Tong, J.R. Dilworth, D.K.P. Ng, H.K. Lee. Dalton Trans., 39, 4602 (2010).
[5] S. Rayati, N. Rafiee, A. Wojtczak. Inorg. Chim. Acta, 386, 27 (2012).
[6] T.R. Amarante, P. Neves, C. Tome, M. Abrantes, A.A. Valente, F.A.A. Paz, M. Pillinger, I.S. Goncalves.
Inorg. Chem., 51, 3666 (2012).
[7] M. Bagherzadeh, M. Amini, A. Ellern, L.K. Woo. Inorg. Chem. Commun., 15, 52 (2012).
[8] L.S. Feng, J.S. Maass, R.L. Luck. Inorg. Chim. Acta, 373, 85 (2011).
[9] S.-P. Gao. J. Coord. Chem., 64, 2869 (2011).
[10] X. Wang, X.-M. Zhang, H.-X. Liu. J. Coord. Chem., 33, 223 (1994).
[11] S.N. Rao, K.N. Munshi, N.N. Rao, M.M. Bhadbhade, E. Suresh. Polyhedron, 18, 2491 (1999).
[12] M. Bagherzadeh, M. Amini, H. Parastar, M. Jalali-Heravi, A. Ellern, L.K. Woo. Inorg. Chem. Commun., 20,
86 (2012).
[13] Y. Sui, X. Zeng, X. Fang, X. Fu, Y. Xiao, L. Chen, M. Li, S. Cheng. J. Mol. Catal. A: Chem., 270, 61
(2007).
[14] Y.-M. Cui, Y.-J. Cai, W. Chen. J. Coord. Chem., 64, 1385 (2011).
[15] Y.-M. Cui, Y.-J. Cai, W. Chen. Russ. J. Coord. Chem., 37, 908 (2011).
[16] G.J.J. Chen, J.W. McDonald, W.E. Newton. Inorg. Chem., 15, 2612 (1976).
[17] G.M. Sheldrick. SADABS, Siemens Analytical X-ray Instrument Division, Bruker AXS Inc., Madison,
Wiskonsin, USA (1995).
[18] G.M. Sheldrick. SHELXS97 Program for Solution of Crystal Structures, University of Göttingen, Germany
(1997).
[19] G.M. Sheldrick. SHELXTL (Version 5.1), Bruker Analytical X-ray Instruments Inc., Madison, Wisconsin,
USA (1998).
[20] N.K. Ngan, K.M. Lo, C.S.R. Wong. Polyhedron, 30, 2922 (2011).
[21] V. Vrdoljak, B. Prugovecki, D. Matkovic-Calogovic, J. Pisk, R. Dreos, P. Siega. Cryst. Growth Des., 11,
1244 (2011).
[22] T. Glowiak, L. Jerzykiewicz, J.M. Sobczak, J.J. Ziolkowski. Inorg. Chim. Acta, 356, 387 (2003).
[23] Z.-P. Li, Y.-J. Li, Z.-X. Li, H. Li, Z.-P. Xiao. J. Chem. Crystallogr., 41, 1568 (2011).
[24] G. Dutkiewicz, B. Narayana, S. Samshuddin, H.S. Yathirajan, M. Kubicki. J. Chem. Crystallogr., 31, 1442
(2011).
[25] R. Dinda, P. Sengupta, S. Ghosh, H. Mayer-Figge, W.S. Sheldrick. J. Chem. Soc., Dalton Trans., 4434
(2002).
[26] S. Gupta, A.K. Barik, S. Pal, A. Hazra, S. Roy, R.J. Butcher, S.K. Kar. Polyhedron, 26, 133 (2007).
[27] J. Sobczak, J.J. Ziolkowski. J. Mol. Catal., 13, 11 (1981).
[28] M. Nooraeipour, M. Moghadam, S. Tangestaninejad, V. Mirkhani, I. Mohammadpoor-Baltork, N. Iravani.
J. Coord. Chem., 65, 226 (2012).
[29] M. Zakeri, M. Moghadam, I. Mohammadpoor-Baltork, S. Tangestaninejad, V. Mirkhani, A.R. Khosropour.
J. Coord. Chem., 65, 1144 (2012).
[30] M.R. Maurya, P. Saini, C. Haldar, A.K. Chandrakar, S. Chand. J. Coord. Chem., 65, 2903 (2012).
[31] M. Bagherzadeh, M. Zare. J. Coord. Chem., 65, 4054 (2012).
[32] A. Ghaffari, M. Behzad, G. Dutkiewicz, M. Kubicki, M. Salehi. J. Coord. Chem., 65, 840 (2012).
[33] N. Xing, H. Shan, H.-Y. Zhao, Y.-H. Xing. J. Coord. Chem., 65, 898 (2012).