Synthesis, x-ray structural characterization, and catalytic property of binuclear oxidovanadium(V) complex with 2,4-dibromo-6-(5-methylamino-[1,3,4]thiadiazol-2-yl) phenol

Article abstract of DOI:10.1080/15533174.2016.1186078

A novel binuclear oxidovanadium(V) complex [V₂O₂(μ-O)L₂(OEt)₂], where L is the deprotonated form of 2,4-dibromo-6-(5-methylamino-[1,3,4]thiadiazol-2-yl)phenol (HL), was prepared by the reaction of 2-(3,5-dibromo-2-hydroxybenzylidene)-N-methylhydrazinecarbothioamide (HL’) and VO(acac)₂ in ethanol. The ligand L’ underwent a cyclization during the coordination, to form a new ligand L. Structure of the complex was characterized by physicochemical methods and single-crystal X-ray determination. Crystal of the complex crystallizes in hexagonal space group R-3, with a = b = 33.302(3) ?, c = 15.308(2) ?, α = β = 90°, γ = 120°, V = 14702(3) ?3, Z = 18, R₁ = 0.0823, wR₂ = 0.2064, S = 1.011. X-ray analysis indicates that the V atom in the complex is in an octahedral coordination environment, constructed by the phenolate O and thiadiazol N atoms of L, one oxido O atom, one bridging O atom, and one deprotonated ethanol O atom. The distance between the two V atoms is 3.365(1) ?. The complex has an effective catalytic property for the oxidation of several olefins.

Full text of DOI:10.1080/15533174.2016.1186078

Inorganic and Nano-Metal Chemistry
ISSN: 2470-1556 (Print) 2470-1564 (Online) Journal homepage: http://www.tandfonline.com/loi/lsrt21
Synthesis, X-ray structural characterization, and
catalytic property of binuclear oxidovanadium(V)
complex with 2,4-dibromo-6-(5-methylamino-
[1,3,4]thiadiazol-2-yl)phenol
Yan Lei & Qiwen Yang
To cite this article: Yan Lei & Qiwen Yang (2017) Synthesis, X-ray structural characterization,
and catalytic property of binuclear oxidovanadium(V) complex with 2,4-dibromo-6-(5-
methylamino-[1,3,4]thiadiazol-2-yl)phenol, Inorganic and Nano-Metal Chemistry, 47:4, 526-530,
DOI: 10.1080/15533174.2016.1186078
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Date: 07 January 2017, At: 19:01

INORGANIC AND NANO-METAL CHEMISTRY
2017, VOL. 47, NO. 4, 526–530
http://dx.doi.org/10.1080/15533174.2016.1186078
Synthesis, X-ray structural characterization, and catalytic property of binuclear
oxidovanadium(V) complex with 2,4-dibromo-6-(5-methylamino-[1,3,4]thiadiazol-2-yl)
phenol
,
Yan Leia b and Qiwen Yangc
aSchool of Chemistry and Environmental Engineering, Chongqing Three Gorges University, Chongqing, P. R. China; bKey Laboratory of Water
Environment Evolution and Pollution Control in Three Gorges Reservoir, Chongqing Three Gorges University, Chongqing, P. R. China; cChina Huaxi
Engineering Design and Construction Co., Ltd., Sichuan, P. R. China
ABSTRACT
ARTICLE HISTORY
Received 19 June 2015
Accepted 1 May 2016
A novel binuclear oxidovanadium(V) complex [V2O2(m-O)L2(OEt)2], where L is the deprotonated form
of 2,4-dibromo-6-(5-methylamino-[1,3,4]thiadiazol-2-yl)phenol (HL), was prepared by the reaction of
2-(3,5-dibromo-2-hydroxybenzylidene)-N-methylhydrazinecarbothioamide (HL’) and VO(acac)2 in
ethanol. The ligand L’ underwent a cyclization during the coordination, to form a new ligand L.
Structure of the complex was characterized by physicochemical methods and single-crystal X-ray
determination. Crystal of tꢀhe complex crystallizes in hexagonal space group R-3, with a D b D
KEYWORDS
Vanadium complex;
thiadiazol ligand; synthesis;
crystal structure; catalytic
oxidation
ꢀ
ꢀ
33.302(3) A, c D 15.308(2) A, a D b D 90ꢀ, g D 120ꢀ, V D 14702(3) A3, Z D 18, R1 D 0.0823, wR2
D
0.2064, S D 1.011. X-ray analysis indicates that the V atom in the complex is in an octahedral
coordination environment, constructed by the phenolate O and thiadiazol N atoms of L, one oxido
O atom, one bridging O atom, and one deprotonated ethanol O atom. The distance between the
ꢀ
two V atoms is 3.365(1) A. The complex has an effective catalytic property for the oxidation of
several olefins.
Introduction
Physical measurements
The coordination chemistry of vanadium has attracted con- Infrared spectra (4000–400 cm¡1) were recorded as KBr discs
[1–3]
siderable attention due to its biological importance
and with an FTS-40 Bio-Rad FT-IR spectrophotometer. Microanal-
their application as catalysts in various oxidations reac- yses (C, H, N) of the ligands and the complexes were carried
tions.[4–6] Recent reports indicated that vanadium complexes out on a Carlo-Erba 1106 elemental analyzer. Solution electrical
with hydrazone ligands possess efficient catalytic properties conductivity was measured at 298 K using a DDS-11 conduc-
in various organic syntheses.[7,8] In addition, vanadium tivity meter. GC analyses were performed on a Shimadzu GC-
complexes show interesting insulin-like activities.[9,10] In 2010 gas chromatograph.
this study, we report the synthesis, X-ray crystal structures,
and catalytic oxidation property of a novel oxidovanadium
(V) complex, [V2O2(m-O)L2(OEt)2], where L is the deproto-
nated form of 2,4-dibromo-6-(5-methylamino-[1,3,4]thiadia-
X-ray crystallography
zol-2-yl)phenol (HL; Scheme 1). It is interesting that HL Crystallographic data of the complex were collected on a
was formed during the coordination process of 2-(3,5- Bruker SMART CCD area diffractometer with graphite
ꢀ
dibromo-2-hydroxybenzylidene)-N-methylhydrazinecarbo-
thioamide (HL’; Scheme 2) with VO(acac)2 in ethanol.
monochromated Mo-Ka radiation (λ D 0.71073 A) at 298(2)
K. Absorption corrections were applied using the multi-scan
program.[11] The structure was solved by direct methods and
successive Fourier difference syntheses (SHELXS-97), and
anisotropic thermal parameters for all non-hydrogen atoms
were refined by full-matrix least-squares procedure against
F2 (SHELXL-97).[12] All non-hydrogen atoms were refined
Experimental
Materials
VO(acac)2, 3,5-dibromosalicylaldehyde, and N-methylhydra- anisotropically. Hydrogen atoms were set in calculated
zinecarbothioamide were purchased from Aldrich. All other positions and refined by a riding mode, with a common
reagents were used as received without further purification.
thermal parameter. The ethanolate group (C20-C19-O6) is
CONTACT Yan Lei
leiyan222@126.com
School of Chemistry and Environmental Engineering, Chongqing Three Gorges University, Chongqing 404000, P. R.
China
Supplementary data are available from the Cambridge Crystallographic Data Center (CCDC), 12 Union Road, Cambridge CB2 1EZ, UK (fax: C44-1223-336-033; e-mail:
deposit@ccdc.cam.ac.uk; or via www.ccdc.cam.ac.uk/conts/retrieving.html) on request, quoting the deposition numbers: CCDC 1404116.
© 2017 Taylor & Francis Group, LLC

INORGANIC AND NANO-METAL CHEMISTRY
527
Table 1. Crystallographic data for the single crystal of the complex.
Parameters
Value
Empirical formula
Formula weight
Temperature (K)
Crystal system
C22H22Br4N6O7S2V2
968.1
298(2)
Hexagonal
R–3
Space group
ꢀ
a (A)
b (ꢀA)
33.302(3)
33.302(3)
15.308(2)
90
90
120
ꢀ
c (A)
a (ꢀ)
b (ꢀ)
g (ꢀꢀ )
V (A3)
14702(3)
18
Z
F(000)
8460
5698/43/412
1.011
R1 D 0.0823
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2s(I)]
wR2 D 0.2064
Scheme 1. HL.
disordered over two sites with occupancies of 0.436(3) and
0.564(3). The crystallographic data and experimental details
for the structure analysis are summarized in Table 1, and the 1530w, 1496w, 1450m, 1427s, 1393s, 1349w, 1304m, 1286s,
selected bond lengths and angles are listed in Table 2.
1239s, 1190m, 1172w, 1132w, 1087m, 1042s, 959s, 907m,
862m, 750m, 703m, and 686m.
Preparation of HL’
Hot methanol solutions of 3,5-dibromosalicylaldehyde and N-
methylhydrazinecarbothioamide (1:1) were stirred under reflux
for 1 h and cooled to room temperature. The colorless precipi-
tate was then filtered, washed with methanol, and dried in
vacuo. Yield: 87%. Anal. calcd. for C9H9Br2N3OS (%): C, 29.4;
H, 2.5; N, 11.4. Found (%): C, 29.6; H, 2.5; N, 11.3. IR data
(KBr, cm¡1): 3420m, 3151w, 1616s, 1540s, 1440m, 1397m,
1327w, 1258s, 1170m, 1113w, 1037m, 930w, 855w, 741w,
Results and discussion
Synthesis
HL0 was prepared by condensation reaction of 3,5-dibromo-
salicylaldehyde with N-methylhydrazinecarbothioamide in
methanol. The stoichiometric reaction of HL0 with VO
(acac)2 in refluxing ethanol yielded the binuclear oxidovana-
dium(V) complex with a ligand change from L0 to L. We
have attempted to prepare and cultivate diffraction quality
crystals of the complex from various solvents; yet, only etha-
nol is suitable. The molar conductance value of the complex
1
691m, 578w, 471w. H NMR (300 MHz, DMSO) d 11.59 (s,
1H, NH), 10.04 (s, 1H, NH), 8.64 (s, 1H, CH D N), 8.30 (s, 1H,
OH), 8.10 (d, 1H, ArH), 7.76 (d, 1H, ArH), and 3.02 (s, 3H,
CH3).
measured in absolute ethanol at the concentration of 10¡3
M
is 25 V¡1 cm2 mol¡1, indicating the non-electrolytic nature
of the complex in solution.[13] The VO(IV) in VO(acac)2 was
oxidized to VO(V) in the complex, which was due to the
Preparation of the complex
To a stirred solution of H2L0 (0.37 g, 1 mmol), 30-mL ethanol
was added VO(acac)2 (0.26 g, 1 mmol). The resulting mixture
was refluxed for 1 h. The deep brown reaction solution was fil-
tered and the solvent removed under reduced pressure, yield-
ing brown solid of the complex. Yield: 63%. Brown single
crystals suitable for X-ray diffraction were obtained by recrys-
tallization of the solid from ethanol. Anal. calcd. for
C22H22Br4N6O7S2V2 (%): C, 27.3; H, 2.3; N, 8.7. Found (%):
C, 27.1; H, 2.4; N, 8.6. IR data (KBr, cm¡1): 3265m, 1575s,
ꢀ
Table 2. Selected bond distances (A) and bond angles (ꢀ) for the complex.
V(1)-O(1)
V(1)-O(4)
V(1)-N(1)
V(2)-O(2)
V(2)-O(5)
V(2)-N(2)
O(4)-V(1)-O(6)
O(6)-V(1)-O(3)
O(6)-V(1)-O(1)
O(4)-V(1)-N(1)
O(3)-V(1)-N(1)
O(4)-V(1)-N(5)
O(3)-V(1)-N(5)
N(1)-V(1)-N(5)
O(5)-V(2)-O(3)
O(5)-V(2)-O(2)
O(3)-V(2)-O(2)
O(7)-V(2)-N(4)
O(2)-V(2)-N(4)
O(7)-V(2)-N(2)
O(2)-V(2)-N(2)
1.968(9)
1.621(10)
2.169(11)
1.951(8)
1.583(8)
2.374(11)
102.5(6)
101.0(5)
92.8(5)
V(1)-O(3)
V(1)-O(6)
V(1)-N(5)
V(2)-O(3)
V(2)-O(7)
V(2)-N(4)
O(4)-V(1)-O(3)
O(4)-V(1)-O(1)
O(3)-V(1)-O(1)
O(6)-V(1)-N(1)
O(1)-V(1)-N(1)
O(6)-V(1)-N(5)
O(1)-V(1)-N(5)
O(5)-V(2)-O(7)
O(7)-V(2)-O(3)
O(7)-V(2)-O(2)
O(5)-V(2)-N(4)
O(3)-V(2)-N(4)
O(5)-V(2)-N(2)
O(3)-V(2)-N(2)
N(4)-V(2)-N(2)
1.822(8)
1.714(12)
2.387(10)
1.787(9)
1.767(8)
2.185(9)
102.9(5)
95.9(5)
153.6(4)
163.5(5)
78.4(4)
87.4(5)
81.6(4)
92.4(5)
82.4(4)
169.9(5)
76.7(4)
77.6(3)
101.8(4)
96.5(4)
102.4(4)
101.9(4)
92.0(4)
153.9(3)
160.7(4)
77.9(4)
95.1(4)
82.0(4)
172.0(4)
79.5(4)
84.9(4)
79.8(4)
77.2(3)
Scheme 2. HL’.

528
Y. LEI AND Q. YANG
Figure 1. ORTEP diagram of the complex with 30% thermal ellipsoid.
oxidation of the oxygen in air, because no other oxidant was by weak Br¢¢¢O and Br¢¢¢S interactions, to form a three-
added during the preparation.
dimensional network (Figure 2).
Description of the structure of the complex
IR spectral characterization
The perspective view of the complex is shown in Figure 1.
The weak bands centered at 3151 cm¡1 for HL0 and
3265 cm¡1 for the complex can be attributed to the nNH
vibrations. The hydrazone ligand shows stretching bands
The two V atoms are bridged by one O group, and two
ꢀ
thiadiazol groups of L, with a separation of 3.365(1) A. The
ligand L coordinates to the V atoms in its deprotonated
form, with the deprotonated phenolate oxygen and thiadia-
zol nitrogen donor atoms. The dihedral angles between the
benzene ring and the thiadiazol ring in L are 25.3(3)ꢀ and
30.0(3)ꢀ. The V atoms in the complex are in octahedral
geometry, with the phenolate oxygen and thiadiazol nitro-
gen of L, the deprotonated ethanol oxygen, and the bridging
oxygen group defining the equatorial plane, and with the
thiadiazol nitrogen of another L and the oxido oxygen
occupying the axial positions. The equatorial donor atoms
for V(1) and V(2) form high degree of planarity, with mean
attributed to CHN and CÀÀOH at 1616 and 1258 cm¡1
,
respectively.[16] The corresponding absorptions of the
complex are observed at 1575 and 1239 cm¡1, respectively.
The VHO stretching mode in the complex occurs as a
single and strong band at 959 cm¡1 [17]
.
deviations from the least-squares planes of 0.038(3) and
ꢀ
0.004(3) A, respectively. The V(1) and V(2) atoms are dis-
ꢀ
placed by 0.292(2) and 0.307(3) A, respectively, toward the
axial oxido oxygen from the least-squares planes defined by
the equatorial donor atoms. The V–O and V–N bonds in
the complex are comparable to those observed in other
vanadium complexes.[14,15] The rather long V(1)-O(6) and
V(2)-O(7) bonds and consequently weak bonding are due
to the trans influence of the oxido groups. The distortion of
the octahedral coordination of both structures can also be
observed from the bond angles related to the V atoms. The
N(5)–V(1)–O(3) and N(4)–V(2)–O(3) bond angles are
much less than the ideal value of 90ꢀ, as a result of the
strain created by the five-membered chelate ring V(1)–N
(5)–N(4)–V(2)–O(3). Molecules of the complex are linked Figure 2. Molecular packing diagram of the complex.

INORGANIC AND NANO-METAL CHEMISTRY
529
Table 3. Catalytic oxidation resultsa.
Substrate
Product
Conversion (%)b
90
Selectivity (%)
100
89
100
85
100
100
100
100
100
100
100
aThe molar ratio of catalyst:substrate:TBHP is 1:300:1000. The reactions were performed in mixture of CH3OH/CH2Cl2 (V:V D 7:3; 1.5 mL).
bThe GC conversion (%) was measured relative to the starting substrate after 1 h.
Scheme 3. Proposed catalytic oxidation mechanism.

530
Y. LEI AND Q. YANG
Catalytic epoxidation results
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yields are less than 100%. Thus, it is obvious that the terminal
double bonds are less reactive than the conjugated double
bonds. This is in agreement with those reported in the litera-
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substrates is 100%. The proposed catalytic mechanism is
depicted in Scheme 3. At the first step, TBHP was activated by
coordination to the V atoms and formation of hepta-coordi-
nated vanadium intermediate. Then, olefin as a nucleophile
attacked the electrophile oxygen atom of the coordinated
TBHP. Finally, the epoxides were formed, and TBHP was
reduced as tert-butyl alcohol.
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Conclusion
A novel binuclear oxidovanadium(V) complex with 2,4-
dibromo-6-(5-methylamino-[1,3,4]thiadiazol-2-yl)phenol as
ligands was prepared by the reaction of 2-(3,5-dibromo-2-
hydroxybenzylidene)-N-methylhydrazinecarbothioamide and
VO(acac)2 in ethanol. The original hydrazone underwent a
cyclization during the coordination process, to form a new thia-
diazol ligand. The complexes show effective catalytic property
in the oxidation of olefins to their corresponding epoxides.
10. Pillai, S. I.; Subramanian, S. P.; Kandaswamy, M. A novel insulin
mimetic vanadium-flavonol complex: Synthesis, characterization and
in vivo evaluation in STZ-induced rats. Eur. J. Med. Chem. 2013, 63,
109–117.
11. Blessing, R. H. An empirical correction for absorption anisotropy.
Acta Crystallogr. A. 1995, 51, 33–38.
12. Sheldrick, G. M. SHELXTL97, Program for Refining Crystal Structure
Refinement; University of G€ottingen: G€ottingen, Germany, 1997.
13. Geary, W. J. Use of conductivity measurements in organic solvents for
characterisation of coordination compounds. Coord. Chem. Rev.
1971, 7, 81–122.
14. Ren, J.-Q.; Jiao, Q.-Z.; Wang, Y.-N.; Xu, F.-Y.; Cheng, X.-S.; You, Z.-L.
Synthesis, structures and Helicobacter pylori urease inhibition of Schiff
base vanadium complexes containing acetohydroxamate ligands. Chi-
nese J. Inorg. Chem. 2014, 30, 640–648.
15. Qu, D.; Niu, F.; Zhao, X. L.; Yan, K.-X.; Ye, Y.-T.; Wang, J.; Zhang, M.;
You, Z. Synthesis, crystal structures, and urease inhibition of an aceto-
hydroxamate-coordinated oxovanadium(V) complex derived from
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Funding
This project was supported by the Scientific and Technological Research
Program of Chongqing Municipal Education Commission (Grant No.
KJ1401025), the Science and Technology of Wanzhou Science Committee
(Grant No. 201403062), and the Youth Foundation of Three Georges Uni-
versity (Grant No. 13QN13).
16. El-Tabl, A. S.; Aly, F. A.; Shakdofa, M. M. E.; Shakdofa, A. M. E. Syn-
thesis, characterization, and biological activity of metal complexes of
azohydrazone ligand. J. Coord. Chem. 2010, 63, 700–712.
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