Synthesis and X-ray structural studies of Cd(II) and Ni(II) complexes of 5-(4-methoxy phenyl), 5-(2-pyridyl) and 5-(2-methoxy phenyl)-1,3,4-oxadiazole-2- thione

Article abstract of DOI:10.1016/j.molstruc.2011.12.015

Three new mixed ligand complexes [Cd(en)₂(4-mpot)₂] (1) [Ni(2-pytone)₂(en)₂] (2) and [Ni(2-mpot) ₂(en)₂] (3) {4-mpot = 5-(4-methoxy-phenyl)-1,3,4- oxadiazole-2-thione, 2-pytone = 5-(2-pyrid

Full text of DOI:10.1016/j.molstruc.2011.12.015

Journal of Molecular Structure 1011 (2012) 34–41
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Synthesis and X-ray structural studies of Cd(II) and Ni(II) complexes
of 5-(4-methoxy phenyl), 5-(2-pyridyl) and 5-(2-methoxy phenyl)-
1,3,4-oxadiazole-2-thione
⇑
⇑
M.K. Bharty , A. Bharti, R.K. Dani, R. Dulare, P. Bharati, N.K. Singh
Department of Chemistry, Banaras Hindu University, Varanasi 221005, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Three new mixed ligand complexes [Cd(en)2(4-mpot)2] (1) [Ni(2-pytone)2(en)2] (2) and [Ni(2-mpo-
t)2(en)2] (3) {4-mpot = 5-(4-methoxy-phenyl)-1,3,4-oxadiazole-2-thione, 2-pytone = 5-(2-pyridyl)-1,3,4-
oxadiazole-2-thione, 2-mpot = 5-(2-methoxy-phenyl)-1,3,4-oxadiazole-2-thione} have been prepared
containing en as co-ligand. Potassium N-(4-methoxy benzoyl)-hydrazinecarbodithioate cyclized to 5-
(4-methoxy-phenyl)-1,3,4-oxadiazole-2-thiol on addition of tetrabutylammonium bromide which then
reacted with Cd(OAc)2ꢀ2H2O and ethylenediamine to form complex 1, whereas potassium N-(2-methoxy
benzoyl/pyridine-2-carbonyl)-hydrazinecarbodithioates (RCONHNHCSSK) underwent cyclization during
complexation in the presence of en to give the complexes of the corresponding 5-aryl-1,3,4-oxadiaz-
ole-2-thiones. The complexes have been characterized by physicochemical techniques and single crystal
X-ray structure determination. In the complexes the metal center has a six coordinate octahedral
arrangement coordinated by 4N atoms of two en and two covalently bonded N atoms of the oxadiaz-
ole-2-thione anions. All the complexes contain extended hydrogen bonding providing supramolecular
framework.
Received 6 September 2011
Received in revised form 7 December 2011
Accepted 8 December 2011
Available online 21 December 2011
Keywords:
5-Aryl-1,3,4-oxadiazole-2-thiones
Mixed ligand complexes
Cd(II) and Ni(II) complexes
Supramolecular architecture
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
investigate the bonding mode of the ligand in the complexes. In
view of this, we have prepared and characterized the Cd(II) complex
The coordination chemistry of nitrogen–sulfur chelating ligands
is an emerging and rapidly developing area of research [1–3]. The
multifaceted chemistry of metal sulfur bonds are apparent in the
application of these compounds as catalyst in biological and non-
biological processes [4,5]. A class of nitrogen sulfur ligand such as
N-aroyl dithiocarbazates and their salts could be converted to
1,3,4-oxadiazole-2-thione, which are biologically important mole-
cules [6–8]. The oxadiazole molecules act as spacer via coordination,
hydrogen bonding and show intermolecular cooperative interaction
[9]. 1,3,4-oxadiazole derivatives, which belong to an important
group of heterocyclic compounds is the subject of extensive study
in the recent years [7,8]. They show diverse biological activities,
such as anti-tuberculostatic, anti-inflammatory, anti-fungal, anal-
gesic, and anti-convulsant [10–12]. Although some work has been
reported on the binary complexes of 5-phenyl-1,3,4-oxadiazole-2-
thione [13], 5-(4-pyridyl)-1,3,4-oxadiazole-2-thione [14–19] and
5-(2-pyridyl)-1,3,4-oxadiazole-2-thione [20], but scanty of infor-
mation is available on the mixed ligand complexes of these ligands.
Since 1,3,4-oxadiazole-2-thiones may exist in both thione and
thiol forms in solution [21,22], it will therefore be of interest to
of 5-(4-methoxy-phenyl)-1,3,4-oxadiazole-2-thione and Ni(II)
complexes of 5-(2-pyridyl)-1,3,4-oxadiazole-2-thione and 5-(2-
methoxy-phenyl)-1,3,4-oxadiazole-2-thione in the presence of
ethylenediamine which act as a co-ligand.
2. Experimental
2.1. Chemical and starting materials
Commercial reagents were used without further purification
and all experiments were carried out in open atmosphere. Picolinic
acid hydrazide (Sigma–Aldrich), CS2 (S D Fine Chemicals, India) and
KOH (Qualigens) were used as received. 2-Methoxy benzoic acid
hydrazide and [Ni(en)2(SCN)2] were prepared by reported methods
[23,24]. All the solvents were purchased from Merck and used after
purification. The yield calculation is based on the weight of the li-
gand or the initial starting material where intermediate were not
isolated.
2.2. Physical measurements
Carbon, hydrogen and nitrogen contents were estimated on a
Carlo Erba 1108 model microanalyser. Magnetic susceptibility
measurements were performed at room temperature on a Cahn
⇑
Corresponding authors. Tel.: +91 5426702452; fax: +91 5422368127.
E-mail addresses: mkbharty@bhu.ac.in (M.K. Bharty), singhnk_bhu@yahoo.com
(N.K. Singh).
0022-2860/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2011.12.015

M.K. Bharty et al. / Journal of Molecular Structure 1011 (2012) 34–41
35
Faraday balance using Hg[Co(NCS)4] as the calibrant. Electronic
spectra were recorded on a Shimadzu 1700 UV–Vis spectropho-
tometer as Nujol mulls. IR spectra were recorded in the 4000–
400 cmꢁ1 region as KBr pellets on a Varian Excalibur 3100-FT IR
spectrophotometer. 1H and 13C NMR spectra were recorded in
DMSO-d6 and CDCl3 on a JEOL AL 300 FT NMR spectrometer using
TMS as internal reference.
diagrams were generated by use of the ORTEP-3 for windows pro-
gram [28].
2.4. Synthesis
2.4.1. Synthesis of tetrabutylammonium 5-(4-methoxy phenyl)-1,3,4-
oxadiazole-2-thiol
Tetrabutylammonium 5-(4-methoxy-phenyl)-1,3,4-oxadiazole-
2-thiol was synthesized by adding CS2 (1.5 mL, 20 mmol) dropwise
to a suspension of 4-methoxy benzoic acid hydrazide (3.32 g,
20 mmol) in methanol (30 mL) in the presence of potassium
hydroxide (1.2 g, 20 mmol) and stirring the reaction mixture for
30 min at room temperature. The yellow solid product obtained
in the above reaction was dissolved in water and an aq. solution
of tetrabutylammonium bromide (3.22 g, 10 mmol) was added.
The resulting yellow solid was obtained which was filtered off
and dried. Yield (1.625 g, 60 %). Anal. Found: C, 66.72; H, 9.55; N,
9.30; S, 7.05 %. Calc. for C25H43N3O2S (449.69): C, 66.77; H, 9.63;
2.3. X-ray crystallography
Crystals suitable for X-ray analyses of the complexes 1, 2 and 3
were grown at room temperature. Data for complexes 1, 2 and 3
were recorded at 293(2) and 296(2) on an Oxford Diffraction Gem-
ini [25] and a Bruker three-circle diffractometer, respectively
equipped with a CrysAlis Pro./SMART 6000 CCD software using a
graphite mono-chromated MoKa (k = 0.71073 Å) radiation source.
The structures were solved by direct methods and refined (SHELX-
08) against all data by full matrix least-square on F2 using aniso-
tropic displacement parameters for all non-hydrogen atoms. All
hydrogen atoms were included in the refinement at geometrically
ideal position and refined with a riding model [26]. The MERCURY
package was used for molecular graphics [27]. Molecular structure
N, 9.34; S, 7.13 %. M.p.105 °C; IR (KBr,
m m(C@N),
, cmꢁ1): 1602s
1066s (NAN), 988s
m
m
(C@S). 1H NMR (CDCl3, TMS; d, ppm): 10.8
(s, 1H, NH), 3.80 (s, 3H, OCH3), 7.0–7.7 (m, 4H, C6H5), 1.0 (t, 3H,
CH3), 1.4 (sext, 2H, CH2), 1.6 (quint., 2H, CH2) 3.3 (t, 2H, NACH2).
13C NMR (CDCl3; d, ppm): 197.15 (CAS), 160.38 (C@N), 113.92
O
H
O
S-K+
N
NH2
N
H
CS2
MeOH
KOH
N
H
S
H3CO
O
H3CO
Tetrabutyl ammonium bromide
n-Bu
S
1
4
5
3
8
n-Bu
N
2
N
N
H3CO
n-Bu
6
9
7
n-Bu
.
Cd(OAc)2 2H2O
H2N
NH2
S
OCH3
O
N
N
O
N
en
Cd
Light yellow ppt
N
H3CO
NH2
H2N
S
Scheme 1. Synthesis of tetrabutylammonium 5-(4-methoxy phenyl)-1,3,4-oxadiazole-2-thiol and Cd(II) complex.
O
H
N
4
S-K+
O
3
1
5
6
N
H
2
NH2
+ CS2 + KOH
N
S
N
H
[K+(H2L)-]
N
7
Ni(OAc)2.4H2O
N
S
H2N
NH2
N
en
Brown ppt
N
O
MeOH
Ni
N
O
N
H2N
NH2
S
N
Scheme 2. Preparation of [Ni(2-pytone)2(en)2] (1).

36
M.K. Bharty et al. / Journal of Molecular Structure 1011 (2012) 34–41
O
O
H
N
4
3
S-K+
1
NH2
5
6
2
N
H
MeOH
CS2
KOH
N
H
8
S
OCH3
OCH3
7
9
[K+(H2L')-]
[Ni(en)2(NCS)2]
MeOH
H2N
NH2
S
O
N
H3CO
N
N
N
Ni
OCH3
O
S
H2N
NH2
Scheme 3. Preparation of [Ni(2-mpot)2(en)2] (2).
(C3) 132.77 (C4, C8), 153.10 (C5, C7), 119.36 (C6), 59.04 (OCH3),
29.12, 24.13, 19.78, 13.68 (n-butyl carbons) (Scheme 1).
tered off, washed with 10% (v/v) mixture of ethanol ether and
dried.
2.4.2. Synthesis of potassium N-aroylhydrazine carbodithioate
2.4.2.1. Potassium N-(pyridine-2-carbonyl)-hydrazine carbodithioate
[K+(H2L)ꢁ]. Yield (1.287 g, 85 %). Anal. Found: C, 33.50; H, 2.30; N,
16.75; S, 25.40%. Calc. for C7H6N3OS2K (251.36): C, 33.41; H, 2.38;
Potasꢁsium N-(pyridine-2-carbonyl)-hydrazine carbodithioate
[K+(H2L) ] and potassium N0-(2-methoxybenzoyl)]-hydrazine car-
bodithioate [K+(H2L0)ꢁ] were prepared by adding CS2 (1.5 mL,
25 mmol) dropwise to a suspension of picolinic acid hydrazide
(2.7 g, 20 mmol) or 2-methoxy benzoic acid hydrazide (3.32 g,
20 mmol) in methanol (30 mL) in the presence of potassium
hydroxide (1.2 g, 20 mmol). The reaction mixtures were stirred
continuously for 30 min and the solids which separated were fil-
N, 16.70; S, 25.46%. M.p. 190 °C; IR (KBr,
m
, cmꢁ1): 3211 m, 3073 m
(C@S). 1H NMR
m
(NH), 1673s (C@O), 1091s (NAN), 993s m
m
m
(DMSO-d6, d, ppm): 11.45, 10.07 (s, 2H, NH), 8.64, 8.01, 7.60 (m,
4H, pyridine ring). 13C NMR (DMSO-d6, d, ppm): d 207.65 (>C@S),
162.96 (>C@O), 137.95 (C4), 155.92 (C7), 148.81 (C3), 127.00
(C5), 121.84 (C6) (Scheme 2).
Table 1
Crystallographic data and structure refinement for complexes 1, 2 and 3.
Compound
1
C
2
3
Empirical formula
Formula weight
T (K)
22H30N8CdO4S2
C18H24N10NiO2S2
535.30
293(2)
C22H30N8NiO4S2
593.37
296(2)
647.09
293(2)
K
(MoKa
) (Å)
0.71073
0.71073
0.71073
Crystal system
Space group
a (Å)
b (Å)
c (Å)
Monoclinic
P 21/n
10.0246(6)
12.4246(6)
11.6853(6)
90.00
110.996(6)
90.00
1358.79(13)
2
Monoclinic
P 21/n
10.941(3)
10.230(2)
11.977(2)
90.00
114.06(3)
90.00
1224.1(5)
2
Triclinic
P-1
7.793(5)
13.592(8)
13.937(9)
70.360(100)
84.271(10)
83.620(10)
1378.87(15)
2
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalc(mg mꢁ3
)
1.582
1.001
1.452
0.999
1.429
0.898
l
(mmꢁ1
)
F (000)
660
556
620
Crystal size (mm3)
h range (°)
0.30 ꢂ 0.27 ꢂ 0.25
3.28–29.07
ꢁ10 ꢃ h ꢃ 13
ꢁ11 ꢃ k ꢃ 16
ꢁ14 ꢃ l ꢃ 15
6178
3631
3631/0/170
1.007
0.27x0.25x0.23
3.73–29.00
ꢁ14 ꢃ h ꢃ 14
ꢁ10 ꢃ k ꢃ 13
ꢁ16 ꢃ l ꢃ 14
4739
3246
3246/0/152
1.066
0.49 ꢂ 0.12 ꢂ 0.11
2.57– 29.58
ꢁ8 ꢃ h ꢃ 10
ꢁ18 ꢃ k ꢃ 19
ꢁ19 ꢃ l ꢃ 19
14,888
7740
7740/0/337
1.064
Index ranges
Reflections collected
Independent reflections
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices
0.0273
0.0536
0.0363
wR2 [I > 2
r
(I)](Rint
)
0.0629
0.1543
0.0944
Final R indices (all data)
R1 = 0.0379
wR2 = 0.0684
0.317, ꢁ0.311
R1 = 0.0991
wR2 = 0.2367
0.863, ꢁ1.035
R1 = 0.0511
wR2 = 0.0995
0.785, ꢁ0.422
Largest diff. peak/hole (e Åꢁ3
)
P
P
aR1
=
||Fo| ꢁ |Fc|| |Fo|.
P
P
2
2 1=2
bR2 ¼ ½ wðjFo2j ꢁ jFc2jÞ = wjFo2j ꢄ
.

M.K. Bharty et al. / Journal of Molecular Structure 1011 (2012) 34–41
37
Fig. 1. Ortep diagram of [Cd(en)2(4-mpot)2] with the atomic labeling scheme. Hydrogen atoms are omitted for clarity.
2.4.2.2. Pꢁotassium N0-(2-methoxybenzoyl)]-hydrazine carbodithioate
[K+(H2L0) ]. Yield (1.013 g, 60 %). Anal. Found: C, 38.60; H, 3.15; N,
10.00; S, 22.90%. Calc. for C9H9O2N2S2K (280.40): C, 38.51; H, 3.20;
v/v) (10 mL) of potassium N0-(4-methoxy-benzoyl)-dithiocarbazate
[K+(H2L0)ꢁ] (0.560 g, 2 mmol) and the reaction mixture was filtered.
The filtrate was kept for crystallization; where upon orange crystals
of the complex 3 were obtained after 10 days. Yield (0.582 g, 55%).
Anal. Found: C, 44.53; H, 5.09; N, 18.80; S, 10.84. Calc for
N, 9.98; S, 22.82%. M.p. 245 °C; IR (KBr,
m
, cmꢁ1): 3246 m, 3169 m
m
(NH), 1637s (C@O), 1000 m (NAN), 886m
m
m
(C@S). 1H NMR
(DMSO-d6 d, ppm): 3.80 (s, 3H, OCH3), 7.0–7.7 (d, 4H, C6H5), 9.65
(m, 2H, NH). 13C NMR (DMSO-d6, d, ppm): d 178.90 (C@S), 160.38
(C@O), 117.87 (C1), 113.67 (C2), 126.64 (C3), 128.95 (C4), 55.28
(OCH3) (Scheme 3).
C
22H30N8O4S2Ni (593.37): C, 44.69; H, 5.05; N, 18.75; S, 10.95.
M.p. 210 °C; IR (KBr, (NH), 1608s (C@N), 1255s
cmꢁ1): 3234s
(CAOAC), 1072s; (NAN), 977; (C@S), 471s (NiAN).
m
m
m
m
m
m
m
3. Results and discussion
2.4.3. Synthesis of [Cd(en)2(4-mpot)2] (1)
Cd(OAc)2ꢀ2H2O (0.266 g, 1 mmol) and freshly prepared
tetrabutylammonium 5-(4-methoxy-phenyl)-1,3,4-oxadiazole-2-
thiol (0.900 g, 2 mmol) were dissolved separately in 15–20 mL
methanol, mixed together and stirred for 20 min. The white precip-
itate was separated by filtration, washed successively with metha-
nol–water mixture (50:50) and finally with methanol. A methanol
solution (10 mL) of ethylenediamine (0.30 mL, 4 mmol) was added
to the methanol suspension of the above compound and stirred for
1 h. A colorless solution was obtained which was filtered and kept
for crystallization. White needle shaped crystals of 1 suitable for an
X-ray analyses were obtained by slow evaporation of the above
solution over a period of 10 days. Yield: (0.323 g, 50 %). Anal.
Found: C, 40.72; H, 4.58; N, 17.25; S, 9.80 %. Calc. For
It has been observed that the potassium salt of N-acylhydrazin-
ecarbodithioates reacted with metal salt and then with ethylenedi-
amine to form the complexes of 1,3,4-oxadiazole-2-thione
containing en as the coligand yielding complexes 2 and 3 whereas
the potassium N-(4-methoxy benzoyl)-hydrazinecarbodithioate
cyclized to 5-(4-methoxy-phenyl)-1,3,4-oxadiazole-2-thiol on
addition of tetrabutylammonium bromide which then reacted with
Cd(OAc)2ꢀ2H2O and ethylenediamine to form complex 1. The ele-
mental analyses and physical measurements of complexes 1, 2
and 3 indicate that both hydrazinic hydrogens from acylhydrazine
carbodithioate [AC(O)NHNHC(S)SꢁA] moiety and one sulfur atom
were missing from the resulting complexes. Thus, complex 2 was
obtained by shaking [Ni(H2L)2] with a methanol solution of
ethylenediamine taken in 1:4 molar ratio whereas complex 3
was obtained by the reaction of potassꢁium N0-(2-methoxyben-
zoyl)]-hydrazine carbodithioate [K+(H2L0) ] with [Ni(en)2(NCS)2].
C
22H30N8CdO4S2 (647.09): C, 40.79; H, 4.63; N,17.30; S,9.89 %.
M.p. 218 °C; IR (KBr, (NH) 1609s (C@N) 1245s
cmꢁ1): 3232s
(CAOAC) 1066s (NAN), 983 (C@S), 479s (CdAN).
m
m
m
m
m
m
m
2.4.4. Synthesis of [Ni(2-pytone)2(en)2] (2)
Freshly prepared potassium N-(pyridine-2-carbonyl)-hydrazine
carbodithioate [(K+(H2L)ꢁ] (0.500 g, 2 mmol) was dissolved in
water (20 mL) and an aqueous solution of Ni(OAc)2ꢀ4H2O
(0.250 g, 1 mmol) was added to the above solution and stirred
for 15 min. The brown solid which separated was filtered, washed
with methanol–water mixture (50:50) and dried. A methanol solu-
tion (10 mL) of ethylenediamine (0.30 mL, 4 mmol) was added to
the methanol suspension of the above compound and after shaking
for a few minutes the resulting clear brown solution was filtered
and kept for crystallization. Brown crystals of 2 suitable for an
X-ray analysis were obtained by slow evaporation of the solution
over a period of 10 days. Yield (0.664 g, 62 %). Anal. Found: C,
44.90; H, 4.90; N, 20.80; S, 12.00. Calc. for C20H26NiN8O2S2
(535.30): C, 44.83; H, 4.85; N, 20.92; S, 11.95. M.p. 225 °C; IR
Table 2
Selected bond lengths (Å) and bond angles (°) for [Cd(en)2(4-mpot)2].
Bond lengths (Å)
Bond angles (°)
Cd(1)AN(4)
Cd(1)AN3)
Cd(1)AN(1)
S(1)AC(1)
2.299(18)
2.345(19)
2.445(17)
1.688(2)
1.410(3)
N(4)ACd(1)AN(3)
N(4)ACd(1)AN(3)#
N(4)ACd(1)AN(1)
N(4)ACd(1)AN(1)#
N(3)ACd(1)AN(1)
77.08(7)
102.92(7)
92.76(7)
87.24(7)
85.31(7)
N(1)AN(2)
Table 3
Selected molecular dimensions (Å and °) in [Ni(2-pytone)2(en)2].
Bond lengths (Å)
Bond angles (°)
NiAN(4)
NiAN(5)
NiAN(3)
S(1)AC(1)
O(1)AC(2)
O(1)AC(1)
N(3)AN(2)
2.101(4)
2.105(4)
2.122(3)
1.695(5)
1.353(6)
1.392(5)
1.413(5)
N(4)ANiAN(5)
N(4)ANiAN(5)
N(4)ANiAN(3)
N(4)ANiAN(3)
N(5)ANiAN(3)
N(5)ANiAN(3)
N(2)AN(3)ANi
82.61(16)
97.39(16)
89.87(14)
90.13(14)
89.79(15)
90.21(15)
118.2(3)
(KBr,
m
, cmꢁ1): 3231 m
(C@N) 1287w
(NAN), 999 m (C@S), 517 w m(NiAN).
m(NH), 1588
m
m(CAOAC),
1093
m
m
2.4.5. Synthesis of [Ni(2-mpot)2(en)2] (3)
methanolic solution (10 mL) of [Ni(en)2(NCS)2] (0.23 g,
1 mmol) was mixed with an aqueous methanolic solution (50:50
A

38
M.K. Bharty et al. / Journal of Molecular Structure 1011 (2012) 34–41
Table 4
after loss of H2S and formation of oxadiazole moiety. A negative
shift in (NH) of ethylenediamine and appearance of a new band
near 520 cmꢁ1 due to
(MAN) suggests formation of a chelate.
Selected molecular dimensions (Å and °) in [Ni(2-mpot)2(en)2].
m
m
Ni(1)
Ni(2)
The IR spectra of complexes 1, 2 and 3 show bands in the region
of 3256–3232 cmꢁ1 due to the NAH stretching vibrations of en
which are shifted to lower frequencies than those encountered in
Bond lengths (Å)
Ni(1)AN(1A)
Ni(1)AN(2A)
Ni(1)AN(3A)
S(1A)AC(3A)
O(1A)AC(3A)
N(3A)AN(4A)
2.101(18)
2.087(17)
2.111(15)
1.687(2)
1.386(2)
1.400(2)
Ni(2)AN(1B)
Ni(2)AN(2B)
Ni(2)AN(3B)
S(1B)AC(3B)
O(1B)AC(3B)
N(3B)AN(4B)
2.088(16)
2.098(17)
2.153(15)
1.689(2)
1.384(2)
1.406(2)
free en [29]. Absence of
m
ꢁ (NH) band due to hydrazinic moiety of
[K+(H2L)ꢁ] and [K+(H2L0) ] suggests loss of hydrazinic protons in
the complexes. Appearance of two new bands near 530 cmꢁ1 due
to m(MAN) suggests formation of a chelate with en and bonding
Bond angles (°)
of the oxadiazole nitrogen with the metal ion. The IR data are thus
consistent with the presence of a 1,3,4-oxadiazole moiety in com-
plexes 1, 2 and 3 [30]. Complexes 1, 2 and 3 show a very small neg-
N(2A)ANi(1)AN(1A)
N(2A)ANi(1)AN(1A)
N(2A)ANi(1)AN(3A)
N(1A)ANi(1)AN(3A)
N(4A)AN(3A)ANi(1)
82.95(8)
87.05(8)
90.72(6)
90.55(7)
116.87(12)
N(2B)ANi(2)AN(1B)
N(2B)ANi(2)AN(1B)
N(2B)ANi(2)AN(3B)
N(1B)ANi(2)AN(3B)
N(4B)AN(3B)ANi(2)
97.26(7)
82.74(7)
87.08(6)
89.45(6)
118.41(12)
ative shift in
m(C@S) showing that the exocyclic sulfur is not
participating in bonding; rather, this small shift can be attributed
to the involvement of sulfur in hydrogen bonding with the NH2
hydrogens of ethylenediamine.
Schemes 1–3 depict the synthesis of ligands and their Cd(II) and
Ni(II) complexes. The complexes are stable towards air and mois-
ture for several days. The complexes 1, 2 and 3 are insoluble in eth-
anol, methanol and chloroform but are soluble in DMF, and melt at
218, 225 and 210 °C, respectively. The complexes were fully char-
acterized by magnetic susceptibility measurements, IR, UV–Vis and
single crystal X-ray. The analytical data for the complexes corrob-
orated well with their respective formulations.
3.2. Magnetic moment and electronic spectra
[Cd(en)2(4-mpot)2] complex is diamagnetic and show absorp-
tion in the high energy region due to intraligand/charge transfer
transition. Complexes [Ni(2-pytone)2(en)2] and [Ni(2-mpot)2(en)2]
show magnetic moment values of 3.0 and 2.91 BM, respectively and
each of these exhibit two d–d bands at 11,430, 20,000, and 12,605,
18,985 cmꢁ1 assigned to the 3A2g ? 3T2g(F) ( 1) and 3T1g(F) (m2
m )
transitions, which suggest a distorted octahedral geometry for the
complexes 2 and 3 [31].
3.1. IR spectra
The IR spectrum of tetrabutylammonium 5-(4-methoxy-
phenyl)-1,3,4-oxadiazole-2-thiol shows no band due to
cating loss of both hydrazinic protons on formation of the salt.
Absorption (
cmꢁ1) due to the stretching modes of C@N (1602),
CAS (988) and NAN (1066) indicate the cyclization of dithiolate
m
(NH) indi-
3.3. Crystal structure description of complexes 1, 2 and 3
m
The molecular structures of complexes 1, 2 and 3 were deter-
mined by single crystal X-ray diffraction. The details of data
Fig. 2. Regular arrangement of molecules of Cd(II) complex forming a supramolecular architecture by NAHꢀ ꢀ ꢀS and CAHꢀ ꢀ ꢀS hydrogen bonding.
Fig. 3.
p–p Stacking and NAHꢀ ꢀ ꢀO hydrogen bonding in complex 1.

M.K. Bharty et al. / Journal of Molecular Structure 1011 (2012) 34–41
39
Fig. 4. ORTEP diagram of [Ni(2-pytone)2(en)2] showing atomic numbering scheme with ellipsoids of 30% probability. H atoms are omitted for clarity.
Fig. 5. CAHꢀ ꢀ ꢀO and CAHꢀ ꢀ ꢀN hydrogen bonding in complex 1.
collection, structure solution and refinement are listed in Table 1.
Ortep diagrams of complexes 1, 2 and 3 with atom numbering
schemes are shown in Figs. 1, 4 and 6 respectively. Selected bond
lengths and angles are given in Tables 2–4. The single crystal
X-ray diffraction studies indicate that the ligands adopt the thione
form in complexes 1, 2 and 3.
The molecular structure of 1 shows that in the monomeric unit
[Cd(en)2(4-mpot)2] possesses a centrosymmetry cadmium at the
inversion center. The elements of the structure are joint to each
other in the crystal packing by means of an extended system of
H-bonds where hydrogen belonging to the en are participating in
the structure. Its coordination environment is fulfilled by two axial
(4-mpot) anions at trans position to each other, each bonded
through oxadiazole nitrogen atom and the four equatorial sites
are occupied by the two bidentate N,N0-ethylenediamine. The
bonding of two en designated as, CdAN(4) has a distance of
2.299(9)° and that of CdAN(3) at a distance of 2.345(2) Å, (Table
2) the complex involves two five membered chelate rings C2N2Cd
with bite angle of 77.08(7)°, and represent a major deviation from
the octahedral geometry. The geometry and bonding parameters
Fig. 6. ORTEP diagram of [Ni(2-mpot)2(en)2] showing atomic numbering scheme with ellipsoids of 30% probability. H atoms are omitted for clarity.

40
M.K. Bharty et al. / Journal of Molecular Structure 1011 (2012) 34–41
Fig. 7. Perspective view of the crystal packing of [Ni(2-mpot)2(en)2] along the a axis.
The molecular structure of 2 shows that in the centrosymmetric
unit of [Ni(2-pytone)2(en)2] the metal ion is six coordinate, bond-
ing through four nitrogens of en and two oxadiazole nitrogens.
The complex consists of two ethylenediamine ligands which che-
late nickel in the equatorial positions and two 1,3,4-oxadiazole-
2-thione ligands in the apical positions, in a trans manner. The
NiAN distances are in the range of 2.101–2.105 Å (Table 3) which
is normal for NiAN amine coordination. The bite angle for the
NiC2N4 five membered rings is 82.61°(16) indicating a minor dis-
tortion from an octahedral geometry in the molecule. The geome-
try and bonding parameters within the en molecule agree with
those of other en complexes [33–35]. The nickel in D4h symmetry
is bonded to four nitrogen atoms of two en ligands which offer
interesting hydrogen bonding. The elements of the structure are
linked together in the crystal packing via intramolecular CAHꢀ ꢀ ꢀN
interactions between the pyridine carbon atoms and NH2 hydrogen
atoms of the en. The CAHꢀ ꢀ ꢀO intramolecular interactions occur be-
tween the oxadiazole oxygen and NH2 hydrogen atoms of en mol-
ecule leading to the formation a supramolecular network (Fig. 5).
The single crystal X-ray diffraction studies of complex 3 indicate
that the ligand (2-mpotꢁ) adopts the thione form with two inde-
pendent complexes in the asymmetric unit; in each unit Ni atom
is on a center of inversion. The arrangement of the monomeric units
of [Ni(2-mpot)2(en)2] (3) in two dimensional arrangement along
Table 5
Hydrogen bond parameters in [Ni(2-mpot)2(en)2] (Å and °).
DAHꢀ ꢀ ꢀA
d(DAH)
d(Hꢀ ꢀ ꢀA)
d(Dꢀ ꢀ ꢀA)
3.596(2)
3.3879(17)
3.4113(18)
3.3564(17)
3.4278(18)
3.4618(18)
3.4430(19)
<(DHA)
N(1A)AH(1AD)ꢀ ꢀ ꢀS(1A)
N(2A)AH(2AC)ꢀ ꢀ ꢀS(1A)#3
N(2A)AH(2AD)ꢀ ꢀ ꢀS(1A)#1
N(1B)AH(1BC)ꢀ ꢀ ꢀS(1B)#4
N(1B)AH(1BD)ꢀ ꢀ ꢀS(1B)#2
N(2B)AH(2BC)ꢀ ꢀ ꢀS(1A)#3
N(2B)AH(2BD)ꢀ ꢀ ꢀS(1B)
0.90
0.90
0.90
0.90
0.90
0.90
0.90
2.86
2.83
2.62
2.86
2.64
2.72
2.68
139.8
121.1
147.2
116.1
146.9
140.0
142.9
#1 ꢁx + 1, ꢁy + 2, ꢁz.
#2 ꢁx, ꢁy + 1, ꢁz.
#3 x ꢁ 1, y, z.
#4 x + 1, y, z.
within the en molecule agree with [Cd(en)3](ClO4)2 [32]. Weak
intermolecular NAHꢀ ꢀ ꢀS interaction between thione sulfur and
NH2 hydrogen atoms and CAHꢀ ꢀ ꢀS interaction between thione sul-
fur and CH3 hydrogen atoms provide a supramolecular network
which stabilize the structure of Cd(II) complex (Fig. 2). In addition,
the complex 1 is stabilized by weak
between phenyl (Cgph) and 1,3,4-oxadiazole (Cgoxa) rings from a
nearby molecule with a distance of 3.979 Å (Fig. 3).
pꢀ ꢀ ꢀp interactions occurring
Fig. 8. Intermolecular NAHꢀ ꢀ ꢀS and intramolecular CAHꢀ ꢀ ꢀN hydrogen bonding in complex 2.

M.K. Bharty et al. / Journal of Molecular Structure 1011 (2012) 34–41
41
the a axis provides a supramolecular network by means of various
types of H-bonds (Fig. 7). The two 2-mpotꢁ ligands are covalently
bonded to nickel in a distorted octahedral geometry with axial bond
angles of 90.73(6) and 92.92(6)° but equatorial bond angles of
82.95(8) and 82.74(7)°, respectively in units containing Ni(1) and
Ni(2). The two 2-mpot anions occupy the trans positions, bonded
through oxadiazole nitrogens at the distances of 2.111 Å Ni(1)
and 2.153 Å Ni(2). The four equatorial sites in complex 3 are occu-
pied by the two bidentate N,N0-ethylenediamine co-ligands. The
bond length for Ni(1)AN(3A) (Noxa) is shorter than the correspond-
ing bond length in Ni(2), showing stronger bonds in Ni(1) as com-
pared to Ni(2). The two NiAN(en) distances in both the units are
different. The Ni(1)AN(1A) bond length is longer than Ni(2)AN(1B)
while Ni(1)AN(2A) is shorter than Ni(2)AN(2B). The binding of
nickel with en involves the formation of two five membered chelate
rings with bite angles of 82.95(8)° and 82.74(7)° in Ni(1) and Ni(2),
respectively, again showing a slight distortion from an ideal octahe-
dral geometry. Weak intermolecular NAHꢀ ꢀ ꢀS interactions (Table 5)
between thione sulfur of oxadiazole and CH2 and NH2 hydrogens of
en stabilize the crystal structure of 3 (Fig. 8). In addition, there are
intramolecular CAHꢀ ꢀ ꢀN interactions between hydrogen of phenyl
ring and nitrogen atoms of oxadiazole ring which lead to the forma-
tion of a supramolecular architecture (Fig. 8).
or e-mail: deposit@ccdc.cam.ac.uk. Supplementary data associated
with this article can be found, in the online version, at doi:10.1016/
j.molstruc.2011.12.015.
References
[1] B.J. McCormick, R. Bereman, D.M. Baird, Coord. Chem. Rev. 54 (1984)
99–130.
[2] R.P. Burns, F.P. McCullough, C.A. McAuliffe, Adv. Inorg. Radiochem. 23 (1980)
211–280.
[3] T.N. Lockyer, R.L. Martin, Prog. Inorg. Chem. 27 (1980) 223–324.
[4] R. Beckett, B.F. Hoskins, Chem. Commun. (1967) 909–910.
[5] R. Beckett, B.F. Hoskins, J. Chem. Soc., Dalton Trans. (1974) 622–625.
[6] P. Tripathi, A. Pal, V. Jancik, A.K. Pandey, J. Singh, N.K. Singh, Polyhedron 26
(2007) 2597–2602.
[7] V. Jakubkiene, M.M. Burbuliene, G. Mekuskiene, E. Udrenaite, P. Gaidelis, P.
Vainilavicius, IL Farmaco 58 (2003) 323–328.
[8] M.M. Dutta, B.N. Goswami, J.C.S. Kataky, J. Heterocyclic Chem. 23 (1986) 793–
795.
[9] M. Du, X.-J. Zhao, J. Mol. Struct. 694 (2004) 235–240.
[10] I. Mir, M.T. Siddiqui, A.M. Comrie, J. Chem. Soc. 16 (1971) 2798–2799.
[11] A. Omar, M.E. Mohsen, O.M. Aboulwafa, J. Heterocyclic Chem. 21 (1984) 1415–
1418.
[12] G.L. Hassert, J.W. Poutsiava, D. Papadrianos, J.C. Burke, B.V. Carver, Toxicol.
Appl. Pharmacol. 3 (1961) 726–741.
[13] O.H. Amin, L.J. Al-Hayaly, S.A. Al-Jibori, T.A.K. Al-Allaf, Polyhedron 23 (2004)
2013–2020.
[14] H.X. Xu, J.P. Ma, R.Q. Huang, Y.B. Dong, Acta Cryst.
m2462–2463.
E 61 (2005)
[15] Y.T. Wang, G.M. Tang, Inorg. Chem. Commun. 10 (2007) 53–56.
[16] M. Du, Z.H. Zhang, X.J. Zhao, Q. Xu, Inorg. Chem. 45 (2006) 5785–5792.
[17] Y.T. Wang, G.M. Tang, W.Y. Ma, W.Z. Wan, Polyhedron 26 (2007)
782–790.
[18] Z.H. Zhang, C.P. Li, Y.L. Tian, Y.M. Guo, Inorg. Chem. Commun. 11 (2008) 326–
329.
[19] Z.H. Zhang, Y.L. Tian, Y.M. Guo, Inorg. Chim. Acta 360 (2007) 2783–2788.
[20] Y.T. Wang, G.M. Tang, Z.W. Qiang, Polyhedron 26 (2007) 4542–4550.
[21] K. Obi, A. Kojima, H. Fukuda, K. Hirai, Bioorg. Med. Chem. Lett. 5 (1995) 2777–
2782.
[22] L. Mishra, M.K. Said, H. Itokawa, K. Takeya, Bioorg. Med. Chem. 3 (1995) 1241–
1245.
[23] K.M. Khan, M. Rasheed, Z. Ullah, S. Hayat, F. Kaukab, M.I. Choudhary, A.
Rahman, S. Perveen, Bioorg. Med. Chem. 11 (2003) 1381–1387.
[24] B.W. Brown, E.C. Lingafelter, Acta Cryst. 16 (1963) 753–758.
[25] Oxford Diffraction, (2007) CrysAlis RED and CrysAlis CCD Versions 1.171.31.8.
Oxford Diffraction Ltd Abingdon, Oxafordshire, England.
[26] G.M. Sheldrick, Acta Cryst. A 64 (2008) 112–122.
[27] I.J. Bruno, J.C. Cole, P.R. Edgington, M. Kessler, C.F. Macrae, P. McCabe, J.
Pearson, R. Taylor, Acta Cryst. Sect. B 58 (2002) 389–397.
[28] L.J.J. Farrugia, Appl. Cryst. 30 (1997) 565.
4. Conclusion
This paper reports on the syntheses and crystal structures of
three new Cd(II) and Ni(II) complexes of 5-(4-methoxy-phenyl)-
1,3,4-oxadiazole-2-thione, 5-(2-pyridyl)-1,3,4-oxadiazole-2-thione
and 5-(2-methoxy-phenyl)-1,3,4-oxadiazole-2-thione containing
ethylenediamine as the coligand. In [Cd(4-mpot)2(en)2] (1), [Ni(2-
pytone)2(en)2] (2) and [Ni(2-mpot)2(en)2] (3) the metal ion has a
six coordinate octahedral arrangement involving 4N atoms of
two en ligands and two covalently bonded N atoms of oxadiaz-
ole-2-thione anions. There are two independent complexes in the
asymmetric unit of complex 3 and in each unit the nickel atom is
on the center of inversion. The crystal structures of the complexes
are stabilized by intermolecular and intramolecular hydrogen
bonding. Complex 1 is also stabilized by weak
occurring between phenyl (Cgph) and 1,3,4-oxadiazole (Cgoxa
rings.
p p interactions
ꢀ ꢀ ꢀ
)
[29] P. Molina, A. Tarraga, A. Espinosa, Synthesis 9 (1988) 690–693.
[30] G.S. Patricia, G.T. Javier, A.M. Miguel, J.A. Francisco, R. Teofilo, Inorg. Chem. 41
(2002) 1345–1347.
[31] A.B.P. Lever, Inorganic Electronic Spectroscopy, second ed., Elsevier,
Amsterdam, 1984.
[32] G. Ma, A. Fischer, R. Nieuwendaal, K. Ramaswamy, S.E. Hayes, Inorg. Chim. Acta
358 (2005) 3165–3173.
Appendix A. Supplementary material
CCDC 840588, 813076 and 813077 contain the supplementary
crystallographic data for [Cd(4-mpot)2(en)2] (1), [Ni(2-pytone)2
(en)2] (2) and [Ni(2-mpot)2(en)2] (3), respectively. These data can
be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/
retrieving.html, or from the Cambridge Crystallographic Data cen-
ter, 12 Union Road, Cambridge CB2 IEZ, UK; fax: +44 1223 336 033;
[33] A. Terron, A.G. Rosa, J.J. Fiol, S. Amengual, M.B. Oliver, R.M. Totaro, M.C. Apella,
E. Molins, I. Mata, J. Inorg. Biochem. 98 (2004) 632–638.
[34] P.J. Squattrito, T. Iwamoto, S. Nishikiori, Chem. Commun. 23 (1996) 2665–
2666.
[35] H. Icbudak, H. Olmez, O.Z. Yesilel, F. Arslan, P. Naumov, G. Jovanovski, A.R.
Ibrahim, A. Usman, H.K. Fun, S. Chantrapromma, S.W. Ng, J. Mol. Struct. 657
(2003) 255–270.