Synthesis and crystal structures of dioxomolybdenum(VI) complexes with similar benzohydrazone ligands

Article abstract of DOI:10.1080/15533174.2012.751419

Two new dioxomolybdenum(VI) complexes, [MoO₂L¹(EtOH)] (1) and [MoO₂L²(H₂O)] (2), where L¹ and L² are the dianionic forms of N′-(3-ethoxy-2- hydroxybenzylidene)-4-hydroxybenzoh- ydrazide and N′-(3-ethoxy-2- hydroxybenzylidene)-2-methylbenz- ohydrazide, respectively, have been synthesized and characterized by elemental analysis, FT-IR spectra, and single-crystal X-ray determination. The crystal of (1) is triclinic: space group P-1, a = 7.806(2), b = 9.947(2), c = 12.225(3) A, α = 82.915(2), β = 89.845(2), γ = 78.063(2)°, V = 921.4(4) A³, Z = 2, R ₁ = 0.0374, wR₂ = 0.1041. The crystal of (2) is monoclinic: space group P2₁/c, a = 8.120(2), b = 25.848(2), c = 8.590(2) A, β = 95.247(2)°, V = 1795.3(6) A³, Z = 4, R ₁ = 0.0473, wR₂ = 0.0734. Mo atoms in the complexes are coordinated by phenolic O, imino N, and enolic O atoms of the benzohydrazone ligand, oxo O atoms, and solvate O atom, forming octahedral coordination. In the crystal structure of (1), adjacent two molecules are linked through intermolecular O-H···N hydrogen bonds, forming dimers. The dimers are further linked through intermolecular O-H···O hydrogen bonds, forming 1D chains. In the crystal structure of (2), adjacent two molecules are linked through intermolecular O-H···N and O-H···O hydrogen bonds, forming dimers. The complexes have effective catalytic properties for sulfoxidation. Supplemental materials are available for this article. Go to the publisher's online edition of Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry to view the supplemental file. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/15533174.2012.751419

This article was downloaded by: [University of Maastricht]
On: 08 June 2014, At: 10:54
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
Synthesis and Reactivity in Inorganic, Metal-Organic,
and Nano-Metal Chemistry
Publication details, including instructions for authors and subscription information:
http://www.tandfonline.com/loi/lsrt20
Synthesis and Crystal Structures of
Dioxomolybdenum(VI) Complexes With Similar
Benzohydrazone Ligands
Ling-Wei Xue a b , Qing-Bin Li a , Song-Tian Li a & Yan-Hui Zhang a
a College of Chemistry and Chemical Engineering , Pingdingshan University , Pingdingshan
Henan , P. R. China
b School of Chemistry and Biological Engineering , University of Science and Technology
Beijing , Beijing , P. R. China
Published online: 25 Aug 2013.
To cite this article: Ling-Wei Xue , Qing-Bin Li , Song-Tian Li & Yan-Hui Zhang (2013) Synthesis and Crystal Structures of
Dioxomolybdenum(VI) Complexes With Similar Benzohydrazone Ligands, Synthesis and Reactivity in Inorganic, Metal-Organic,
and Nano-Metal Chemistry, 43:10, 1338-1343, DOI: 10.1080/15533174.2012.751419
To link to this article: http://dx.doi.org/10.1080/15533174.2012.751419
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

Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 43:1338–1343, 2013
Copyright ꢀ Taylor & Francis Group, LLC
C
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2012.751419
Synthesis and Crystal Structures of Dioxomolybdenum(VI)
Complexes With Similar Benzohydrazone Ligands
Ling-Wei Xue,1,2 Qing-Bin Li,1 Song-Tian Li,1 and Yan-Hui Zhang1
1College of Chemistry and Chemical Engineering, Pingdingshan University, Pingdingshan Henan,
P. R. China
2School of Chemistry and Biological Engineering, University of Science and Technology Beijing, Beijing,
P. R. China
in recent years for their catalytic properties[1–4] and versatile
structures.[5–7] Benzohydrazone derivatives are a kind of special
Schiff bases which have been used as interesting ligands in
coordination chemistry.[8–10] Hundreds of complexes of copper,
iron, vanadium, manganese, and molybdenum derived from
benzohydrazone derivatives have so far been reported. However,
due to the best of our knowledge, dioxomolybdenum complexes
with such ligands have seldom been reported. Some of these
dioxomolybdenum complexes have been shown to possess
oxygen atom transfer properties as they were found to oxidize
thiols, hydrazine, polyketones, and tertiary phosphines.[11–13]
As an extension of work on the structures and catalytic proper-
ties of such complexes, we report in this article the synthesis,
structures, and properties of two new dioxomolybdenum(VI)
complexes, [MoO2L1(EtOH)] (1) and [MoO2L2(H2O)] (2),
where L1 and L2 are the dianionic forms of Nꢁ-(3-ethoxy-2-
hydroxybenzylidene)-4-hydroxybenzohydrazide (H2L1) and
Nꢁ-(3-ethoxy-2-hydroxybenzylidene)-2-methylbenzohydrazide
(H2L2), respectively (Scheme 1).
Two new dioxomolybdenum(VI) complexes, [MoO2L1(EtOH)]
(1) and [MoO2L2(H2O)] (2), where L1 and L2 are the dianionic
forms of Nꢀ-(3-ethoxy-2-hydroxybenzylidene)-4-hydroxybenzoh-
ydrazide and Nꢀ-(3-ethoxy-2-hydroxybenzylidene)-2-methylbenz-
ohydrazide, respectively, have been synthesized and characterized
by elemental analysis, FT-IR spectra, and single-crystal X-ray de-
termination. The crystal of (1) is triclinic: space group P–1, a =
7.806(2), b = 9.947(2), c = 12.225(3) Å, α = 82.915(2), β = 89.845(2),
γ = 78.063(2)◦, V = 921.4(4) Å3, Z = 2, R1 = 0.0374, wR2 = 0.1041.
The crystal of (2) is monoclinic: space group P21/c, a = 8.120(2),
b = 25.848(2), c = 8.590(2) Å, β = 95.247(2)◦, V = 1795.3(6) Å3,
Z = 4, R1 = 0.0473, wR2 = 0.0734. Mo atoms in the complexes are
coordinated by phenolic O, imino N, and enolic O atoms of the ben-
zohydrazone ligand, oxo O atoms, and solvate O atom, forming oc-
tahedral coordination. In the crystal structure of (1), adjacent two
molecules are linked through intermolecular O−H···N hydrogen
bonds, forming dimers. The dimers are further linked through in-
termolecular O−H···O hydrogen bonds, forming 1D chains. In the
crystal structure of (2), adjacent two molecules are linked through
intermolecular O−H···N and O−H···O hydrogen bonds, form-
ing dimers. The complexes have effective catalytic properties for
sulfoxidation.
Supplemental materials are available for this article. Go to the
publisher’s online edition of Synthesis and Reactivity in Inorganic,
Metal-Organic, and Nano-Metal Chemistry to view the supplemen-
tal file.
Keywords benzohydrazone, catalytic property, crystal structure,
dioxomolybdenum, hydrogen bonds
INTRODUCTION
SCH. 1. The benzohydrazone ligands.
Coordination chemistry of dioxomolybdenum complexes
with multidentate ligands has received considerable attention
EXPERIMENTAL
Materials and Methods
Received 16 October 2012; accepted 16 November 2012.
This research was supported by the National Sciences Foundation
of China (Nos. 20676057 and 20877036) and Top-Class Foundation of
Pingdingshan University (No. 2008010).
Address correspondence to Ling-Wei Xue, College of Chemistry
and Chemical Engineering, Pingdingshan University, Pingdingshan
Henan 467000, P. R. China. E-mail: pdsuchemistry@163.com
3-Ethoxysalicylaldehyde, 4-hydroxybenzohydrazide, and 2-
methylbenzohydrazide were purchased from Fluka (Switzer-
land). Other reagents and solvents were analytical grade and
used without further purification. Elemental (C, H, and N) anal-
yses were made on a Perkin-Elmer Model 240B automatic ana-
lyzer (USA). IR spectra were recorded on an IR-408 Shimadzu
1338

DIOXOMOLYBDENUM(VI) COMPLEXES
1339
568 spectrophotometer (Japan). 1H NMR spectra were recorded
on Bruker Avance 300 MHz spectrometer (Germany).
Found: C, 68.6; H, 6.0; N, 9.3. C17H18N2O3 Anal. Calcd. (%):
C, 68.4; H, 6.1; N, 9.4.
Synthesis of [MoO2L1(EtOH)] (1)
Synthesis of H2L1
MoO2(acac)2 (0.1 mmol, 33 mg) in ethanol (10 mL) was
added with stirring to H2L1 (0.1 mmol, 30.0 mg) in methanol
(10 mL). The mixture was stirred at refluxed for 30 min to give
an orange solution. The solution was left still at room temper-
ature in air to give orange block-shaped single crystals, which
were collected by filtration and dried in vacuum containing an-
hydrous CaCl2. The yield is 21 mg (44%). Found (%): C, 45.6;
H, 4.3; N, 6.1. C18H20MoN2O7 Anal. Calcd. (%): C, 45.8; H, 4.3;
N, 5.9.
3-Ethoxysalicylaldehyde (1.66 g, 0.01 mol) and 4-hyd-
roxybenzohydrazide (1.52 g, 0.01 mol) were mixed in methanol
(30 mL). The mixture was stirred at reflux for 30 min and three
quarter of the solvent was evaporated, to give colorless solid
product of H2L1, which was collected by filtration and dried in
vacuum containing anhydrous CaCl2. The yield is 2.5 g (83%).
Found (%): C, 63.8; H, 5.4; N, 9.4. C16H16N2O4 Anal. Calcd.
(%): C, 64.0; H, 5.4; N, 9.3.
Synthesis of H2L2
3-Ethoxysalicylaldehyde (1.66 g, 0.01 mol) and 2-meth-
ylbenzohydrazide (1.50 g, 0.01 mol) were mixed in methanol
Synthesis of [MoO2L2(H2O)] (2)
MoO2(acac)2 (0.1 mmol, 33 mg) in ethanol (10 mL) was
(30 mL). The mixture was stirred at reflux for 30 min and three- added with stirring to H2L2 (0.1 mmol, 29.8 mg) in methanol
quarters of the solvent was evaporated, to give colorless solid (10 mL). The mixture was stirred at refluxed for 30 min to
product of H2L2, which was collected by filtration and dried in give an orange solution. The solution was left still at room
vacuum containing anhydrous CaCl2. The yield is 2.3 g (77%). temperature in air to give red block-shaped single crystals, which
TABLE 1
Crystal and structure refinement data for the complexes
(1)
(2)
Molecular formula
Molecular weight
C18H20MoN2O7
472.3
C17H18MoN2O6
442.3
Crystal system
Space group
a /Å
Triclinic
P–1
Monoclinic
P21/c
8.120(2)
25.848(2)
8.590(2)
90
95.247(2)
90
1795.3(6)
4
7.806(2)
9.947(2)
12.225(3)
82.915(2)
89.845(2)
78.063(2)
921.4(4)
2
b /Å
c /Å
α /◦
β /◦
γ /◦
V /Å
3
´
Z
Dcalc (g cm−3
)
1.702
1.636
Crystal dimensions (mm)
0.20 × 0.18 × 0.17
0.20 × 0.20 × 0.18
μ (mm−1
)
0.757
0.767
´
´
Radiation λ
Mo Kα (0.71073 Å)
Mo Kα (0.71073 Å)
Tmin/Tmax
0.8634/0.8821
7524
−9, 9; −12, 12; −15, 14
2.53–27.00
3924 [Rint = 0.0205]
3483
0.8618/0.8743
Reflections measured
Range/indices (h, k, l)
θ limit (◦)
Unique reflections
Observed reflections (I > 2σ(I))
Parameters
10053
−7, 10; −33, 28; −10, 10
2.51–27.00
3882 [Rint = 0.0457]
2869
258
243
Restraints
15
1.046
0.0374, 0.1041
0.0434, 0.1089
3
Goodness of fit on F2
R1, wR2 [I ≥ 2σ(I)]a
R1, wR2 (all data)a
1.031
0.0473, 0.0733
0.0744, 0.0805
ꢀ
ꢀ
ꢀ
ꢀ
2
2 2
2 2 1/2
aR1 = ||Fo|-|Fc||/ |Fo|, wR2 = [ w(Fo -Fc ) / w(Fo ) ]
.

1340
L.-W. XUE ET AL.
TABLE 2
were collected by filtration and dried in vacuum containing
anhydrous CaCl2. The yield is 17 mg (38%). Found (%): C,
46.1; H, 4.2; N, 6.4. C17H18MoN2O6 Anal. Calcd. (%): C, 46.2;
H, 4.1; N, 6.3.
Selected bond lengths (Å) and angles (◦) for the complexes
(1)
Bond lengths
Mo1-O1
Mo1-O4
X-Ray Diffraction
1.908 (2)
2.373 (3)
1.710 (2)
Mo1-O3
Mo1-O5
Mo1-N1
1.999 (2)
1.693 (3)
2.240 (3)
Data were collected from selected crystals mounted on
glass fibers. The data for the complexes were processed with
SAINT[14] and corrected for absorption using SADABS.[15]
Multi-scan absorption corrections were applied with ψ scans.[16]
The structures of the complexes were solved by direct method
using the SHELXS-97 program and refined by full-matrix least-
squares techniques on F2 using anisotropic displacement param-
eters.[17] All non-hydrogen atoms were refined anisotropically.
Water and ethanol hydrogen atoms were located from difference
Fourier maps and refined isotropically, with O−H and H···H
distances restrained to 0.85(1) and 1.37(2) Å, respectively. The
remaining hydrogen atoms were placed at the calculated po-
sitions. Crystallographic data for the complexes are listed in
Table 1. Selected bond lengths and angles are given in Table 2.
Hydrogen bonds are listed in Table 3.
Mo1-O6
Bond angles
O5-Mo1-O6
O6-Mo1-O1
O6-Mo1-O3
O5-Mo1-N1
O1-Mo1-N1
O5-Mo1-O4
O1-Mo1-O4
N1-Mo1-O4
106.2 (1)
102.4 (1)
98.1 (1)
97.2 (1)
81.2 (1)
172.1 (1)
83.4 (1)
75.3 (1)
O5-Mo1-O1
O5-Mo1-O3
O1-Mo1-O3
O6-Mo1-N1
O3-Mo1-N1
O6-Mo1-O4
O3-Mo1-O4
98.2 (1)
96.5 (1)
150.2 (1)
155.4 (1)
71.4 (1)
80.9 (1)
78.8 (1)
(2)
Bond lengths
Mo1-O2
Mo1-O4
1.918 (2)
1.692 (3)
2.303 (3)
Mo1-O3
Mo1-O6
Mo1-N1
2.019 (2)
1.713 (2)
2.215 (3)
Catalytic Oxidation
Mo1-O5
The dioxomolybdenum complexes (0.001 M) and phenyl Bond angles
methyl sulfide (0.1 M) were dissolved at room temperature in
a mixture of CH2Cl2 and CH3OH (6:4) together with 1,3,5-
trimethoxybenzene (0.1 M) as internal standard. The resulting
solution was cooled to 283 K and H2O2 (35% w/w) added drop-
wise (0.125 M). An aliquot of the reaction solution (2.0 mL)
was quenched with 5 mL of a stock solution of Na2SO3 (0.1 M)
and extracted with dichloromethane (three times 4 mL). From
the collected organic phases the solvent was removed under re-
duced pressure to complete dryness and the residue redissolved
O4-Mo1-O6
O6-Mo1-O2
O6-Mo1-O3
O4-Mo1-N1
O2-Mo1-N1
O4-Mo1-O5
O2-Mo1-O5
N1-Mo1-O5
106.0 (1)
106.0 (1)
95.1 (1)
94.2 (1)
81.1 (1)
170.9 (1)
79.5 (1)
76.8 (1)
O4-Mo1-O2
O4-Mo1-O3
O2-Mo1-O3
O6-Mo1-N1
O3-Mo1-N1
O6-Mo1-O5
O3-Mo1-O5
98.3 (1)
97.8 (1)
148.7 (1)
157.1 (1)
71.0 (1)
83.0 (1)
80.4 (1)
1
in deuterated chloroform (0.6 mL) and analyzed by H NMR
to determine the yield with reference to the internal standard
1,3,5-trimethoxybenzene.
Crystal Structure Description of the Complexes
The molecular structures of the complexes are shown in
Figures 1 and 2. The coordination geometry around Mo atom
in each of the complexes is octahedrally distorted. The ben-
zohydrazone ligand coordinates through phenolic O, imino N,
and enolic O atoms to the MoO2 moiety, forming a five- and
a six-membered chelate rings with Mo atom. The sixth coor-
dination is weakly coordinated by a solvate O atom. For the
Mo1 coordination of complex (1), atoms O1, O3, N1, and O6
located at the equatorial plane show a high degree of planarity,
with mean deviation from the plane of 0.061(3) Å. The Mo1
atom deviates from the least-squares plane defined by the four
RESULTS AND DISCUSSION
Reaction of the benzohydrazone ligands with MoO2(acac)2
affords the orange products of complexes (1) and (2) (Scheme 2).
The complexes are soluble in DMF, DMSO, methanol, ethanol,
and acetonitrile. We have attempted to grow diffraction qual-
ity crystals from various solvents. However, well-shaped single
crystals suitable for X-ray diffraction were finally obtained from
the mixture solvent of ethanol and methanol containing the com-
plexes.
SCH. 2. The preparation of the complexes. X = OH, Y = H for (1); X = H, Y = Me for (2).

DIOXOMOLYBDENUM(VI) COMPLEXES
1341
TABLE 3
Hydrogen geometries for the complexes
d(D–H) d(H···A) d(D···A)
Angle
(D–H···A) (◦)
D–H···A
(Å)
(Å)
(Å)
(1)
O4–H4A···N2i 0.85(1) 1.93(2) 2.764(3)
167(5)
176
O7–H7···O6ii
0.82
1.95
2.773(3)
(2)
O5–H5B···N2iii 0.85(1) 1.95(2) 2.769(4)
162(5)
171(5)
O5–H5A···O6iv 0.85(1) 1.96(2) 2.792(4)
FIG. 2. Molecular structure of complex (2) at 30% probability displacement.
Symmetry codes: i) 2 – x, – y, 1 – z; ii) 2 – x, 1 – y, 1 – z; iii) 1 – x,
1 – y, 1 – z; iv) – x, 1 – y, 1 – z.
Infrared Spectra
In the infrared spectra of the free benzohydrazone ligands,
there showed stretching bands attributed to C O, C N, C-OH,
and NH at about 1660, 1635, 1180, and 3255 cm−1, respectively.
In addition, strong bands indicative of the C N N C
groups are observed at about 1625 cm−1. In the spectra of the
complexes, there showed two prominent bands at about 952 and
893 cm−1 for complex (1), and 940 and 888 cm−1 for com-
plex (2), which attributed to cis-dioxomolybdenum groups. The
equatorial donor atoms by 0.334(2) Å in the direction of the
axial atom O5. For the Mo1 coordination of complex (2), atoms
O2, O3, N1, and O6 located at the equatorial plane show a
high degree of planarity, with mean deviation from the plane
of 0.014(3) Å. The Mo1 atom deviates from the least-squares
plane defined by the four equatorial donor atoms by 0.325(2)
Å in the direction of the axial atom O4. The Mo-Ooxo bonds
in each of the complexes are almost equal. The remaining co-
ordinate bond lengths in both complexes are similar to each
other, and also comparable to those observed in dioxomolyb-
denum(VI) complexes with benzohydrazone ligands.[18,19] The
angular distortion in the octahedral coordination comes from the
bites O3-Mo1-N1 taken by the benzohydrazone ligands. The di-
hedral angles between the benzene rings are 1.9(4)◦ in complex
(1), and 10.3(4)◦ in complex (2). In the crystal of complex (1),
adjacent two [MoO2L1] moieties are linked through intermolec-
ular O–H···N hydrogen bonds, to form dimers. The dimers are
further linked through intermolecular O–H···O hydrogen bonds,
to form 1D chains (Figure 3). In the crystal of complex (2),
adjacent two [MoO2L2] moieties are linked through intermolec-
ular O–H···N and O–H···O hydrogen bonds, to form dimers
(Figure 4).
bands due to νC and νNH are absent in the complexes, and
O
FIG. 1. Molecular structure of complex (1) at 30% probability displacement.
FIG. 3. The hydrogen bonds linked 1D chain structure of complex (1).

1342
L.-W. XUE ET AL.
of the sulfoxides with 1,3,5-trimethoxybenzene (TMB) as inter-
nal standard to determine the yields. The reaction was started
by the addition of hydrogen peroxide. A control reaction under
the same condition without any complex present leads to less
than 1% sulfide conversion within 4 h. In the presence of the
complexes conversions of about 72% for (1) and 86% for (2) of
sulfide to the corresponding sulfoxide within 60 min reaction
time were observed. After about 2 h in all cases the conversions
of total amount of sulfide were complete. Under the given con-
ditions no over oxidation to the sulfone could be detected. Both
complexes show catalytic properties for the sulfoxidation.
CONCLUSION
In summary, two new dioxomolybdenum(VI) complexes
with similar benzohydrazone ligands have been synthesized
and characterized. The benzohydrazone ligands coordinate to
the Mo atom through enolic forms by using phenolic O, imino
N, and enolic O atoms. Both complexes have effective catalytic
properties for the sulfoxidation of sulfides.
FIG. 4. The hydrogen bonds linked dimeric structure of complex (2).
SUPPLEMENTARY MATERIALS
CCDC-892776 (1) and 892777 (2) contain the supplementary
crystallographicdatafor this paper. The data canbe obtainedfree
of charge at http://www.ccdc.cam.ac.uk/const/retrieving.html or
from the Cambridge Crystallographic Data Centre (CCDC),
12 Union Road, Cambridge CB2 1EZ, UK; fax: +44(0)1223-
336033 or e-mail: deposit@ccdc.cam.ac.uk.
the formation of new C O absorption at about 1253 cm−1 for
complex (1) and 1264 cm−1 for complex (2). This suggests oc-
currence of keto-imino tautomerization of the ligands during
complexation.[18] The C N N C absorptions observed in
the free ligands are shifted to lower wave numbers in the com-
plexes, 1611 cm−1 for complex (1) and 1608 cm−1 for complex
(2). The weak and broad bands centered at 3439 cm−1 for com-
plex (1) and 3357 cm−1 for complex (2) were attributed to the
O H vibrations. The weak bands in the low wave numbers
are assigned to the Mo O and Mo N vibrations. The simi-
lar absorptions in the spectra indicate similar structures of the
complexes.
REFERENCES
1. Gamelas, C.A.; Gomes, A.C.; Bruno, S.M.; Paz, F.A.A.; Valente, A.A.;
Pillinger, M.; Romao, C.C.; Goncalves, I.S. Molybdenum(VI) catalysts ob-
tained from eta(3)-allyl dicarbonyl precursors: Synthesis, characterization
and catalytic performance in cyclooctene epoxidation. Dalton Trans. 2012,
41, 3474–3484.
2. Feng, L.S.; Maass, J.S.; Luck, R.L. Synthesis and characterization of four
cubical molybdenum(V) tetramers and their catalytic properties for the
epoxidation of cis-cyclooctene using H2O2. Inorg. Chim. Acta 2011, 373,
85–92.
Catalytic Sulfoxidation
Catalytic oxidation test of the complexes on the oxidation of
sulfides under homogeneous conditions in solution using methyl
phenyl sulfide (thioanisol) as substrate was shown as Scheme 3.
As oxidant hydrogen peroxide was used in a slight excess of 1.25
equivalents based on the sulfide substrate. Reactions were run
with 1 mol% of catalyst based on the substrate at a temperature
of 10◦C. NMR technique has been used to monitor the formation
3. Bagherzadeh, M.; Amini, M.; Ellern, A.; Woo, L.K. Catalytic efficiency of
a novel complex of oxoperoxo molybdenum(VI): synthesis, X-ray structure
and alkane oxidation. Inorg. Chem. Commun. 2012, 15, 52–55.
4. Rayati, S.; Rafiee, N.; Wojtczak, A. cis-Dioxo-molybdenum(VI) Schiff
base complexes: Synthesis, crystal structure and catalytic performance for
homogeneous oxidation of olefins. Inorg. Chim. Acta 2012, 386, 27–35.
5. Ceylan, B.I.; Kurt, Y.D.; Ulkuseven, B. Synthesis and characterization
of new dioxomolybdenum(VI) complexes derived from benzophenone-
thiosemicarbazone (H2L). Crystal structure of [MoO2L(PrOH)]. J. Coord.
Chem. 2009, 62, 757–766.
6. Sokolov, M.N.; Mikhailov, M.A.; Abramov, P.A.; Fedin, V.P. Crystal
structures of two solvates of molybdenum octahedral clusters: (Bu4N)2
[Mo6Cl8(O3SC6H4CH3)6]·2CH3CN and (Bu4N)2[Mo6Cl8(O3SC6H4
CH3)6]·2CH2Cl2. J. Struct. Chem. 2012, 53, 197–201.
7. Gao, S.-P. Synthesis and crystal structures of Nꢁ-(3-ethoxy-2-
hydroxybenzylidene)-3-methylbenzohydrazide and its dioxomolybdenum
(VI) complex. J. Coord. Chem. 2011, 64, 2869–2877.
SCH. 3. The sulfoxidation process.

DIOXOMOLYBDENUM(VI) COMPLEXES
1343
8. Vrdoljak, V.; Prugovecki, B.; Matkovic-Calogovic, D.; Pisk, J.; Dreos,
R.; Siega, P. Supramolecular hexagon and chain coordination polymer
containing the MoO2 core: structural transformation in the solid state.
13. Dinda, R.; Ghosh, S.; Falvello, L.R.; Tomas, M.; Mak, T.C.S. Synthe-
sis, structure, and reactivity of some new dipyridyl and diamine-bridged
dinuclear oxomolybdenum(VI) complexes. Polyhedron 2006, 25, 2375–
2382.
2+
Cryst. Growth Des. 2011, 11, 1244–1252.
9. Chakraborty, J.; Thakurta, S.; Pilet, G.; Luneau, D.; Mitra, S. A novel
tetra(μ3-phenoxo) bridged copper(II) Schiff base complex containing a
Cu4O4 cubane core: synthesis, structural aspects and magneto-structural
correlations. Polyhedron 2009, 28, 819–825.
14. Bruker, SMART, and SAINT. Area Detector Control and Integration Soft-
ware; Bruker Analytical X-ray Instruments Inc., Madison, WI, 1997.
15. Sheldrick, G.M. SADABS. Program for Empirical Absorption Correction of
Area Detector Data; University of Go¨ttingen, Go¨ttingen, Germany, 1997.
16. North, A.C.T.; Phillips, D.C.; Mathews, F.S. A semi-empirical method of
absorption correction. Acta Crystallogr. 1968, A24, 351–359.
10. Monfared, H.H.; Sanchiz, J.; Kalantari, Z.; Janiak, C. Structure and mag-
netic properties of a tetranuclear Cu4O4 open-cubane in [Cu(L)]4center dot
4H2O with L2− = (E)-Nꢁ-(2-oxy-3-methoxybenzylidene)benzohydrazide. 17. Sheldrick, G.M. SHELXL-97. Program for the Refinement of Crystal Struc-
Inorg. Chim. Acta 2009, 362, 3791–3795.
tures; University of Go¨ttingen, Go¨ttingen, Germany, 1997.
18. Rao, S.N.; Munshi, K.N.; Rao, N.N.; Bhadbhade, M.M.; Suresh, E. Synthe-
sis, spectral and X-ray structural characterization of [cis-MoO2(L)(solv)]
(L = salicylidene salicyloyl hydrazine) and its use as catalytic oxidant.
Polyhedron 1999, 18, 2491–2497.
11. Mancka, M.; Plass, W. Dioxomolybdenum(VI) complexes with amino acid
functionalized N-salicylidene hydrazides: synthesis, structure and catalytic
activity. Inorg. Chem. Commun. 2007, 10, 677–680.
12. Rao, S.N.; Kathale, N.; Rao, N.N.; Munshi, K.N. Catalytic air oxidation
of olefins using molybdenum dioxo complexes with dissymmetric triden- 19. Xu, W.-X.; Li, W.-H. Synthesis, crystal structure and catalytic prop-
tate O,N,S-donor Schiff base ligands derived from o-hydroxyacetophenone
and S-benzyldithiocarbazate or S-methyldithiocarbazate. Inorg. Chim. Acta
2007, 360, 4010–4016.
erty of a dioxomolybdenum(VI) complex derived from Nꢁ-[1-(2-hyd-
roxynaphthyl)ethylidene]-3-methylbenzohydrazide. Synth. React. Inorg.
Met.-Org. Nano-Met. Chem. 2012, 42, 160–164.