Binuclear mercury(II) complexes of sulfonium ylides: Synthesis, structural characterization and anti-bacterial activity

Article abstract of DOI:10.1016/j.molstruc.2012.10.051

Reaction of α-keto stabilized sulfonium ylides (Me) ₂SCHC(O)C₆H₄R (R = p-Me (a); p-Cl (b)) with HgX₂ (X = Cl, Br and I) in equimolar ratios using methanol as solvent leads to binuclear products of the type [HgX₂(ylide)]₂ (X = Cl (1), Br (2) and I (3)). Single crystal X-ray diffraction analysis reveals the presence of unexpected asymmetric halide-bridged dinuclear structures for 1a and 2b. Characterization of the compounds by IR, ¹H- and ¹³C NMR spectroscopy confirmed coordination of the ylide to the metal through the carbon atom. In addition, the antibacterial effects of DMSO-solutions of the complexes were investigated by the disc diffusion method against three Gram positive and three negative bacteria. All complexes represent antibacterial activity against these bacteria with high levels of inhibitory potency exhibited against the Gram-positive species.

Full text of DOI:10.1016/j.molstruc.2012.10.051

Journal of Molecular Structure 1034 (2013) 265–270
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Binuclear mercury(II) complexes of sulfonium ylides: Synthesis, structural
characterization and anti-bacterial activity
a,
⇑
a
b
b
Seyyed Javad Sabounchei , Fateme Akhlaghi Bagherjeri , Colette Boskovic , Robert W. Gable ,
c
c
Roya Karamian , Mostafa Asadbegy
a
Faculty of Chemistry, Bu-Ali Sina University, Hamedan 65174, Iran
School of Chemistry, University of Melbourne, Victoria 3010, Australia
Department of Biology, Faculty of Science, Bu-Ali Sina University, Hamedan 65174, Iran
b
c
h i g h l i g h t s
"
"
"
"
"
The binuclear mercury complexes of sulfonium ylides are structurally characterized for the first time.
1
13
IR, H- and C NMR spectroscopy demonstrates C-coordination of the ylide to the metal.
There is an asymmetric halide-bridge structure similar to binuclear phosphonium analogs.
The HgAC bond length in mercury(II) complexes sulfonium ylides is less than phosphonium analogs.
All complexes display antibacterial activity against the bacteria tested especially on Gram positive ones.
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 30 June 2012
Received in revised form 21 October 2012
Accepted 22 October 2012
Available online 2 November 2012
2 6 4 2
Reaction of a-keto stabilized sulfonium ylides (Me) SCHC(O)C H R (R = p-Me (a); p-Cl (b)) with HgX
(X = Cl, Br and I) in equimolar ratios using methanol as solvent leads to binuclear products of the type
[
HgX (ylide)] (X = Cl (1), Br (2) and I (3)). Single crystal X-ray diffraction analysis reveals the presence
2
2
of unexpected asymmetric halide-bridged dinuclear structures for 1a and 2b. Characterization of the
compounds by IR, 1H- and C NMR spectroscopy confirmed coordination of the ylide to the metal
through the carbon atom. In addition, the antibacterial effects of DMSO-solutions of the complexes were
investigated by the disc diffusion method against three Gram positive and three negative bacteria. All
complexes represent antibacterial activity against these bacteria with high levels of inhibitory potency
exhibited against the Gram-positive species.
13
Keywords:
Sulfonium ylide
Mercury(II) halide complex
X-ray crystal structure
Antibacterial effect
Ó 2012 Elsevier B.V. All rights reserved.
1
. Introduction
The synthesis of complexes derived from sulfonium ylides and
mercury(II) halides was first reported in 1975 by Weleski et al.
[11], with a symmetric halide-bridge binuclear structure proposed.
In 1984, Tewari and Awasthi [12] reported the synthesis of a series
of transition metal halide complexes with various sulfonium ylides
without further characterization.
Antibacterial agents are often co-administered with an inhibitor
that deactivates the bacteria’s resistance mechanism and increases
the effectiveness of the antibacterial agents. The development of
compounds with the ability to inhibit bacterial growth have been
of great interest in recent years due to their potential use both in
hospital equipment and in everyday items such as soaps, deter-
gents, health and skincare products and household cleaners. Inor-
ganic antibacterial materials have several advantages over
traditionally used organic compounds, including chemical stability,
thermal resistance, safety to the user, long lasting action period,
etc. [13]. Bacterial resistance is a major drawback in chemotherapy
of infectious disease [14]. The emergence, and observed increase,
0
00
Sulfur ylides R
2
S@C(R )(R ) are very reactive species with inter-
esting applications in organic synthesis [1–4]. In addition they can
behave as ligands, since the carbanion located at the C of the ylide
is able to donate electron density to a transition metal [5,6]. In the
a
0
00
case of
a
-keto stabilized ylides, R
2
S@C(R )CO(R ), various binding
modes have been reported due to their ambidentate character
(Scheme 1) [7,8].
Far more widely studied than sulfonium ylides, are their phos-
phorus analogs, with the configuration of mercury(II) halides com-
plexes with phosphonium ylides well-known and extensively
studied [9,10]. However the configuration of the analogous sulfo-
nium ylide complexes is to date unknown as such species are yet
to be structurally characterized.
⇑
Corresponding author. Tel.: +98 811828280; fax: +98 8118257408.
E-mail address: jsabounchei@yahoo.co.uk (S.J. Sabounchei).
0
022-2860/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molstruc.2012.10.051

2
66
S.J. Sabounchei et al. / Journal of Molecular Structure 1034 (2013) 265–270
Table 1
(
Me)2S
O
(Me)2S
O
Crystal data and refinement details for complexes 1a and 2b.
(
Me)2S
O
1
a
2b
Identification code
Formula
Fa-lsmg
28 Cl
Fa-rslg
C H22 Br Cl Hg O
20 4 2 2 2
R
R
R
C
22
H
4
Hg
2
O
2
S
2
S
2
a
b
c
Formula weight
931.54
130(2)
0.71073
1150.22
130(2)
0.71073
Temperature (K)
0
Scheme 1. The canonical forms of (Me)
2
SCHC(O)C
6
H
4
R (R = p-Me (a); p-Cl (b)).
Wavelength ( AÅ )
Crystal system space
group
Triclinic P ꢀ 1
Triclinic P ꢀ 1
of bacterial resistance to antibiotics has become a serious health
problem worldwide, resulting in the diminution of the effective-
ness of a number of important drugs. As a result there has been
increasing interest in the use of inhibitors of antibiotic resistance
for combination therapy [15–18].
Here we present the preparation, spectroscopic and structural
characterization of binuclear mercury(II) complexes with sulfo-
nium ylides, together with an in vitro determination of their anti-
bacterial activity. This includes the first instance of sulfur ylide
complexes of mercury(II) halides being structurally characterized,
the complexes having an unexpected asymmetric halide-bridged
dinuclear structure. The structures are compared with those of
the analogous phosphorus ylides.
Unit cell dimensions
a = 8.0210(4)
b = 8.3249(4)
c = 10.8031(5)
8.4703(5)
8.6912(4)
10.5054(5)
97.513(4)
112.188(5)
90.483(4)
708.55(6)
1, 2.696
a
= 99.745(4)
b = 103.853(4)
= 104.519(4)
c
Volume (Å3)
657.53(5)
1, 2.353
Z, Calculated density
3
(
Mg/m )
Absorption coefficient
12.245
16.813
(mmꢀ1
)
F(000)
436
524.0
Crystal size (mm)
h Range for data
collection (°)
0.51 ꢁ 0.26 ꢁ 0.19
0.23 ꢁ 0.20 ꢁ 0.06
2.87–29.99
2.93–29.99
Limiting indices
ꢀ11 6 h 6 11
ꢀ11 6 h 6 11
ꢀ9 6 k 6 12
ꢀ14 6 l 6 13
3657
3190 [R(int) = 0.0347]
99.88%
ꢀ
ꢀ
11 6 k 6 11
11 6 l 6 15
2
. Experimental
Reflections collected/
unique
Completeness
Absorption correction
Refinement method
3398
3172 [R(int) = 0.0394]
99.90%
Gaussian
2.1. Physical measurements and materials
Gaussian
Full-matrix least-
Full-matrix least-
All solvents were reagent grade and used without further puri-
squares on F2
squares on F2
fications. NMR spectra were obtained on 400 MHz Varian MR400
and 90 MHz Jeol spectrometers in DMSO-d and CDCl as the sol-
vent. Chemical shifts (d) are reported relative to internal TMS ( H
Data/restraints/
parameters
3398/0/145
3657/0/145
6
3
1
Goodness-of-fit on F2
0.913
0.784
1
3
Final R indices [I > 2
I)]
r
R
1
= 0.0449,
wR = 0.1170
= 0.0492,
R
1
= 0.0378,
wR = 0.1037
1
R = 0.0470,
and C). Melting points were measured on a Stuart SMPI appara-
tus. Elemental analysis for C, H and N were performed using a
Perkin–Elmer 2400 series analyzer. Fourier transform infrared
spectra were recorded on a Shimadzu 435-U-04 spectrophotome-
ter and samples were prepared as KBr pellets.
(
2
2
R indices (all data)
R
1
wR2 = 0.1216
4.704 and ꢀ5.509
wR2 = 0.1140
2.21 and ꢀ2.00
Largest diff. peak and
3
hole (eÅ )
2 2 6 4 2 2 2 6 4 2
1a: [HgCl (Me SCHC(O)C H -p-Me)] and 2b: [HgBr (Me SCHC(O)C H -p-Cl)]
2
.2. X-ray crystallography
The diameters of inhibition zones generated by the complexes
were measured.
Data collection from suitable crystals of 1a and 2b was per-
formed on an Oxford Diffraction single-crystal X-ray diffractometer
using mirror monochromated Mo K radiation (0.71073 Å) at 130 K
Table 1). Gaussian absorption corrections were carried out using a
a
2.4. Statistical analysis
(
multifaceted crystal model, using CrysAlisPro [19]. All three struc-
tures were solved by direct methods and refined by the full-matrix
least-squares method on F using the SHELXTL-97 crystallographic
package [20,21]. All non-hydrogen atoms were refined anisotropi-
cally. Hydrogen atoms were inserted at calculated positions using
a riding model, with isotropic displacement parameters.
All data, for both antibacterial tests, are the average of triplicate
analyses. Analysis of variance was performed by Excel and SPSS
procedures Statistical analysis was performed using Student’s t-
test, and P value < 0.05 was regarded as significant.
2
2.5. Sample preparation
2.3. Antibacterial activity
2.5.1. Synthesis of ylides(Me) SCHC(O)C H R (R = p-Me (a); p-Cl (b))
2 6 4
(
Me)
2
SCHC(O)C
6
H
4
-p-Me (a): To an acetone solution (10 ml) of
0
The potential antibacterial effects of the Hg(II) complexes were
investigated by disc diffusion method against three Gram positive
bacteria, namely Bacillus cereus (PTCC 1247), Staphylococcus aureus
dimethylsulfide (0.062 g, 1.0 mmol) was added 2-bromo-4 -meth-
ylacetophenone (0.213 g, 1.00 mmol) and the mixture was stirred
for 12 h. The solid product (sulfonium salt) was isolated by filtra-
tion, washed with ether and dried under reduced pressure. Further
treatment with aqueous 10% NaOH solution led to elimination of
(
Wild) and Bacillus megaterium (PTCC 1017), and three Gram neg-
ative bacteria, namely Escherichia coli (Wild), Proteus vulgaris (PTCC
ꢀ
1
1
079), and Serratia marcescens (PTCC 1111) [22]. The complexes
HBr, giving the free ligand a [23]. IR (KBr disk):
(C@O) and 879 (SAC). H NMR (CDCl
m
(cm ) 1564
ꢀ1
1
were dissolved in DMSO to a final concentration of 1 mg ml
3
): d (ppm) 2.32 (s, 3H,
3
and then sterilized by filtration using 0.45
l
m Millipore. All tests
CH ); 2.93 (s, 6H, S(CH ); 4.28 (1H, CH); 7.10 (d,
3
3
)
2
J
HH = 8.1 Hz,
HH = 8.1 Hz, 2H, arom.). C NMR (CDCl
); 28.33 (s, S(CH ); 50.33 (s, CH); 125.98
8
3
13
were carried using 10 ml of suspension containing 1.5 ꢁ 10 bacte-
ria/ml and spread on nutrient agar medium. Negative controls
were prepared by using DMSO. Gentamicin, Penicillin, Neomycin
and Nitrofurantoin were used as positive reference standards.
2H, arom.); 7.65 (d,
ppm): d 20.80 (s, CH
J
3
,
3
3 2
)
(s, Ph(p)); 128.13 (s, Ph(m)); 138.08 (s, Ph(o)); 138.96 (s, Ph(i));
182.32 (s, CO).

S.J. Sabounchei et al. / Journal of Molecular Structure 1034 (2013) 265–270
267
(
Me)
2
SCHC(O)C
6
H
4
-p-Cl (b): ylide b was prepared following the
Br
4 2 2 2 20
Cl O S C H22: C, 20.88; H, 1.93; Found: C, 20.55; H, 1.98.
ꢀ
1
same synthetic method as that reported for ligand a. Thus, dimeth-
ylsulfide (0.062 g, 1.00 mmol) was reacted with 2-bromo-4 -
chloroacetophenon (0.233 g, 1.00 mmol) giving the free ligand b.
IR (KBr disk):
M.p. 196–198 °C. IR (KBr disk):
m
(cm ) 1646 (CO) and 822
, ppm): d 2.90 (s, 6H, S(CH ); 5.41
(s, 1H, CH); 7.49 (d, JHH = 8.1 Hz, 2H, arom.); 7.86 (d, JHH = 9.0 Hz,
0
+
ꢀ
1
(S AC ). H-NMR (DMSO-d
6
3 2
)
3
3
ꢀ1
1
13
m
(cm ) 1578 (C@O) and 856 (SAC). H NMR
); 4.20 (1H, CH); 7.22 (d,
6 3 2
2H, arom.). C NMR (DMSO-d , ppm): d 27.07 (s, S(CH ) ); 65.17 (s,
CH); 128.98 (s, Ph(m)); 129.94 (s, Ph(p)); 134.01 (s, Ph(i)); 138.49
(s, Ph(o)); 191.39 (s, CO).
(
CDCl ): d (ppm) 2.88 (s, 6H, S(CH
3
3
)
2
3
3
13
J
HH = 8.1 Hz, 2H, arom.); 7.63 (d,
NMR (CDCl , ppm): d 28.09 (s, S(CH
Ph(p)); 127.35 (s, Ph(m)); 134.46 (s, Ph(o)); 139.24 (s, Ph(i));
80.27 (s, CO).
JHH = 8.1 Hz, 2H, arom.).
C
3
3
)
2
); 52.46 (s, CH); 124.81 (s,
[HgI
following the same synthetic method as that reported for 1a. Thus,
HgI (0.227 g, 0.500 mmol) was reacted with ylide b (0.107 g,
.50 mmol) giving 3b. Yield 0.287 g, 86%. Anal. Calc. for Hg Cl
2 20
S C H22: C, 17.95; H, 1.66; Found: C, 17.66; H, 1.62. M.p. 186–
2 2 6 4 2
(Me SCHC(O)C H -p-Cl)] (3b): Complex 3b was prepared
1
2
0
2
I
4
2 2
O
2
(
.5.2. Synthesis of complexes [HgX
1a), Br (2a), I (3a))
HgCl (Me SCHC(O)C
15 ml) of HgCl
2
(Me
2
6
SCHC(O)C H
4
-p-Me)]
2
(X = Cl
ꢀ1
+
ꢀ
1
188 °C. IR (KBr disk):
m
(cm ) 1630 (CO) and 816 (S AC ). H-
); 5.27 (s, 1H, CH);
7.49 (d, JHH = 8.1 Hz, 2H, arom.); 7.84 (d, JHH = 9.0 Hz, 2H, arom.).
[
2
2
6
H
4
-p-Me)]
2
(1a): To a methanolic solution
NMR (DMSO-d , ppm): d 2.87 (s, 6H, S(CH )
6
3 2
3
3
(
2
(0.135 g, 0.500 mmol) was added a methanolic
1
3
solution (10 ml) of ylide a (0.097 g, 0.50 mmol). The mixture was
6 3 2
C NMR (DMSO-d , ppm): d 27.17 (s, S(CH ) ); 64.10 (s, CH);
stirred for 4 h. The separated solid was filtered and washed with
128.94 (s, Ph(m)); 129.92 (s, Ph(p)); 134.20 (s, Ph(i)); 138.07 (s,
Ph(o)); 190.07 (s, CO).
diethyl ether [12]. Yield 0.228 g, 98%. Anal. Calc. for Hg
2 4 2 2 22
Cl O S C
H
28: C, 28.36; H, 3.03; Found: C, 28.02; H, 2.97. M.p. 192–193 °C. IR
ꢀ1
+
ꢀ
1
(
KBr disk):
m
(cm ) 1646 (CO) and 844 (S AC ). H-NMR (DMSO-
, ppm): d 2.35 (s, 3H, CH ); 2.92 (s, 6H, S(CH ); 5.49 (s, 1H, CH);
.22 (d, JHH = 8.1 Hz, 2H, arom.); 7.79 (d, JHH = 8.1 Hz, 2H, arom.).
2.6. Results and discussion
2.6.1. Synthesis
d
6
3
3 2
)
3
3
7
1
3
C NMR (DMSO-d
6
, ppm): d 21.66 (s, CH
3
); 26.98 (s, S(CH
3
)
2
);
The room temperature reactions of HgX (X = Cl, Br and I) with
2
5
2.50 (s, CH); 128.20 (s, Ph(p)); 129.52 (s, Ph(m)); 132.45 (s,
sulfonium ylides a and b (prepared by reacting dimethylsulfide
0
Ph(o)); 144.20 (s, Ph(i)); 192.97 (s, CO).
HgBr (Me SCHC(O)C -p-Me)] (2a): Complex 2a was pre-
pared following the same synthetic method as that reported for
a. Thus, HgBr (0.180 g, 0.500 mmol) was reacted with ylide a
0.097 g, 0.50 mmol) giving 2a [12]. Yield 0.263 g, 95%. Anal. Calc.
for Hg Br 28: C, 23.82; H, 2.54; Found: C, 23.71; H, 2.49.
M.p. 199–200 °C. IR (KBr disk):
with an acetone solution of 2-bromo-4 -methylacetophenone and
0
[
2
2
6
H
4
2
2-bromo-4 -chloroacetophenon and treatment with aqueous NaOH
solution) for 4 h (1:1 M ratio) in CH OH gave the binuclear com-
3
1
(
2
plexes 1–3 (a and b) (Scheme 2). Some of these complexes have
been previously reported by Tewari and Awasthi [12], however
only elemental analysis and infrared spectra were given, whereas
herein we report comprehensive characterizations utilizing NMR
spectroscopy and X-ray structural analysis. X-ray quality crystals
of the complexes 1a and 2b were grown by the direct diffusion
of methanol in the dimethylsulfoxide solution over several days.
2
4 2 2 22
O S C H
ꢀ1
+
m
(cm ) 1637 (CO) and 825 (S -
, ppm): d 2.36 (s, 3H, CH ); 2.89 (s, 6H,
HH = 8.1 Hz, 2H, arom.); 7.76
HH = 8.1 Hz, 2H, arom.). C NMR (DMSO-d , ppm): d 21.72
s, CH ); 26.89 (s, S(CH ); 65.46 (s, CH); 128.18 (s, Ph(p));
29.46 (s, Ph(m)); 132.62 (s, Ph(o)); 144.09 (s, Ph(i)); 192.41 (s,
CO).
HgI
following the same synthetic method as that reported for 1a. Thus,
HgI (0.227 g, 0.500 mmol) was reacted with ylide a (0.097 g,
.50 mmol) giving 3a. Yield 0.291 g, 90%. Anal. Calc. for Hg
28: C, 20.37; H, 2.18; Found: C, 20.12; H, 2.11. M.p. 187–
-
1
C ). H-NMR (DMSO-d
6
3
3
S(CH ); 5.41 (s, 1H, CH); 7.22 (d, J
3
)
2
3
13
(
(
d,
J
6
3
3 2
)
1
2
.6.2. Spectroscopy
In the infrared spectra the
tion, occurs at 1564 and 1578 cm for a and b ylides, as in the case
m
(CO) that is sensitive to complexa-
[
2 2 6
(Me SCHC(O)C H
4
-p-Me)]
2
(3a): Complex 3a was prepared
ꢀ1
of other resonance stabilized ylides [12]. Coordination of the ylide
2
through carbon causes an increase in
m (CO), while for O-coordina-
0
2 4 2 2
I O S
tion a decrease of
m
(CO) is expected. The infrared absorption bands
C
1
22
H
ꢀ1
observed for all our complexes are in the range 1629–1647 cm
suggesting coordination of the ylide through carbon atom. The
ꢀ
1
+
-
1
88 °C. IR (KBr disk):
m
(cm ) 1629 (CO) and 824 (S -C ). H-
); 2.86 (s, 6H, S(CH );
HH = 8.1 Hz, 2H, arom.); 7.74 (d,
HH = 8.1 Hz, 2H, arom.). C NMR (DMSO-d , ppm): d 21.91 (s,
CH ); 27.04 (s, S(CH ), 65.65 (s, CH), 128.31 (s, Ph(p)); 129.56
s, Ph(m)); 132.86 (s, Ph(o)); 144.189 (s, Ph(i)); 192.21 (s, CO).
m
NMR (DMSO-d
6
, ppm): d 2.35 (s, 3H, CH
3
3
)
2
+
ꢀ
(
S AC ) which is also diagnostic of the coordination mode occurs
3
5
.27 (s, 1H, CH); 7.21 (d,
J
ꢀ1
+
ꢀ1
at around 850 cm in Me
In the present study, the
shifted to lower frequencies around 820 cm , suggesting partial
2
S ACH
m
2
and at about 867 cm in ylides.
3
13
J
6
+
ꢀ
(S AC ) values for all complexes were
3
3
)
2
–1
(
removal of electron density from the SAC bond due to coordination
[
12].
2
.5.3. Synthesis of complexes [HgX
2
(Me
2 6 4 2
SCHC(O)C H -p-Cl)] (X = Cl
The 1H NMR signals for the SCH group of all complexes are
(1b), Br (2b), I (3b))
shifted downfield compared to those of the free ylides, as a conse-
quence of the inductive effect of the metal center [9,10]. The
appearance of single signals for the SCH group in H NMR at ambi-
[
HgCl (Me SCHC(O)C
2
2
6
H
4
-p-Cl)]
2
(1b): Complex 1b was prepared
following the same synthetic method as that reported for 1a. Thus,
HgCl (0.135 g, 0.500 mmol) was reacted with ylide b (0.107 g,
.50 mmol) giving 1b [12]. Yield 0.235 g, 97%. Anal. Calc. for Hg
Cl 22: C, 24.70; H, 2.28; Found: C, 24.56; H, 2.23. M.p.
06–208 °C. IR (KBr disk):
1
2
ent temperature indicates the presence of only one geometrical
0
2
6 2 2 20
O S C H
ꢀ1
+
ꢀ
2
m
(cm ) 1647 (CO) and 824 (S AC ).
R
1
C
O
H-NMR (DMSO-d
6
, ppm): d 2.94 (s, 6H, S(CH ); 5.53 (s, 1H,
3 2
)
3
3
O
CH); 7.50 (d,
J
HH = 8.1 Hz, 2H, arom.); 7.91 (d,
arom.). C NMR (DMSO-d , ppm): d 27.03 (s, S(CH
CH); 129.01 (s, Ph(m)); 129.94 (s, Ph(p)); 133.82 (s, Ph(i)); 138.55
s, Ph(o)); 191.69 (s, CO).
HgBr (Me SCHC(O)C
following the same synthetic method as that reported for 1a. Thus,
HgBr (0.180 g, 0.500 mmol) was reacted with ylide b (0.107 g,
.50 mmol) giving 2b [12]. Yield 0.264 g, 92%. Anal. Calc. for Hg
J
HH = 9.0 Hz, 2H,
SMe2
(Me)2S CH
X
X
1
3
CH3OH
4 hr, r. t.
R
C
H
+ HgX2
6
3 2
)
); 64.65 (s,
M
M
X
X
HC
C
S(Me)2
(
R= Ph-p-Me (a) or Ph-p-Cl (b)
X = Cl (1), Br (2) or I (3)
[
2
2
6 4 2
H -p-Cl)] (2b): Complex 2b was prepared
O
R
2
0
2
Scheme 2. Synthesis and reactivity of mercury(II)-sulfur ylide complexes.

2
68
S.J. Sabounchei et al. / Journal of Molecular Structure 1034 (2013) 265–270
drawing of complexes 1a and 2b are shown in Figs. 1 and 2. Crys-
tallographic data and parameters pertaining to the data collection,
structure solution and refinement are summarized in Table 1. Se-
lected bond distances and angles, together with those of the phos-
phonium analogs are presented in Table 2.
The binuclear structure adopted by all complexes is in contrast
to the trinuclear structure exhibited by O-coordinated of the phos-
[
26]
phorus ylide (Ph
ilar to the structure of C-coordinated dinuclear mercury(II) halide
complexes of the phosphorus ylides Ph PCHC(O)OEt (EPPY) [27]
and Ph PCHC(O)Ph (BPPY) [28] and Ph PCHC(O)C OCH
MBPPY) [29]. The Hg(II) cenetr in complexes 1a and 2b is four-
3
PCHCOPh) complex of mercury(II),
but is sim-
3
3
3
H
6 4
3
(
3
coordinate with sp hybridization. This environment involves one
short terminal HgAX (X = Cl and Br) bond, one HgAC bond and
two asymmetric bridging HgAX bonds.
It is generally accepted that the d orbitals of sulfur in a sulfo-
nium group stabilize an adjacent carbanion to a greater extent
than those of phosphorus in a phosphonium group [30,31]. How-
ever by comparing the sulfonium dinuclear mercury complexes
with phosphorus analogs (Table 2) appears the p–d overlap of
the triphenylphosphonium group to be more pronounced than
that with the dimethylsulfonium groups incorporated into ylides
a and b. This inversion is quite likely due to the difference in
functional groups (alkyl vs. aryl) attached to the positive atom.
So the dimethyl sulfonium ylides are more basic than the tri-
phenyl phosphonium ylides, which is evident from the shorter
HgAC bond lengths in sulfonium ylides complexes compared with
the equivalent distances in the phosphorus analogs (Table 2). The
terminal HgABr bond length is very similar to that of found in
phosphorus analog, although this is less true for HgACl species.
In contrast to the phosphorus analogs, the two bridging HgAX
bonds in 1a are very similar. These bond lengths in 2b are clearly
asymmetric, but slightly less asymmetric than in the phosphorus
analogs.
Fig. 1. ORTEP view of the X-ray crystal structure of 1a. H atoms are omitted for
clarity. Symmetry code; a: 1 ꢀ x, 1 ꢀ y, 2 ꢀ z.
isomer for all complexes as expected for C-coordination. It must be
noted that O-coordination of the ylide leads to the formation of cis
1
and trans isomers giving rise to two different signals in H NMR
1
3
[
24]. The C chemical shifts of the CO group in the complexes
are around 191 ppm, relative to ꢂ182 ppm noted for the same car-
bon in the parent ylides, indicating decreased shielding of this car-
bon atom in mercury complexes. No coupling to (1 Hg, 16.8%
99
1
abundance, I = 1/2) was observed at room temperature in H and
1
3
C NMR spectra. Failure to observe satellites in the above spectra
was previously noted in the ylide complexes of Hg(II) which has
been explained by fast exchange of the ylide with the metal [25].
2.6.3. Crystal structures analysis
The molecular structures of 1a and 2b were determined
through single crystal X-ray structural analysis. The molecular
Fig. 2. ORTEP view of the X-ray crystal structure of 2b. H atoms are omitted for clarity. Symmetry code; a: 1 ꢀ x, ꢀy, 1 ꢀ z.
Table 2
Selected bond lengths (Å) and bond angles (°) for complexes 1a and 2b along with comparison of selected internuclear separations of them with phosphonium analogs.
Bond distance
1a
[Hg(MBPPY)Cl
[29]
2
]
2
2b
(X = Br)
[Hg(MBPPY)Br
[29]
]
2 2
Bond angles
1a
(X = Cl)
2b
(X = Br)
(X = Cl)
Hg1AC1
Hg1AX1
Hg1AX1a
Hg1AX2
C1AC2
C1AS1
C2AO1
Hgꢃ ꢃ ꢃHg
2.162(6)
2.7223(16
2.7415(15)
2.3746(17)
1.494(9)
1.789(6)
1.231(8)
3.848
2.215(4)
2.418(14)
2.884(12)
2.504(11)
–
2.165(7)
2.6930(6
2.9596(6
2.5445(7)
1.501(8)
1.801(6)
1.215(8)
3.903
2.218(11)
2.559(2)
2.603(3)
3.022(2)
–
X1AHg1AX1a
S1AC1AHg1
X2AHg1AX
C2AC1AHg1
X2AHg1AX1
C1AHg1AX2
C1AHg1AX1
C1AHg1AX1a
90.45
92.787(17)
119.8(3)
94.76(2)
110.6(3)
93.39(6)
107.9(4)
98.60(5)
149.77(17)
110.08(17)
99.93(17)
108.8(4)
102.40(2)
130.83(16)
121.88(15)
102.70(16)
–
–
–
–
3.901
3.994
See Figs. 1 and 2 for the atom numbering. Symmetry code; a: 1 ꢀ x, 1 ꢀ y, 2 ꢀ z (1a), 1 ꢀ x, ꢀy, 1 ꢀ z (2b).
a: [HgCl (Me SCHC(O)C -p-Me)] ; 2b: [HgBr (Me SCHC(O)C -p-Cl)]
1
2
2
H
6 4
2
2
2
6
H
4
2
.

S.J. Sabounchei et al. / Journal of Molecular Structure 1034 (2013) 265–270
269
Table 3
2 2 6 4 2
Antibacterial activities of [HgX (Me SCHC(O)C H -p-Me)] (X = Cl (1a), Br (2a), I (3a)).
Inhibition zone (mm)
Concentration – 1 mg/ml
Concentration – 0.1 mg/ml
Concentration – 0.01 mg/ml
Microorganism
1a
2a
3a
1a
2a
3a
1a
2a
3a
a
a
a
a
a
a
a
a
a
a
a
a
17 ± 0.56a
10 ± 0.24b
10 ± 0.16b
11 ± 0.36b
c
c
9 ± 0.12c
P. vulgaris (ꢀ)
E. coli (ꢀ)
17 ± 0.18
21 ± 0.34
15 ± 0.26
25 ± 0.66
22 ± 0.54
14 ± 0.15
16 ± 0.25
20 ± 0.33
22 ± 0.33
22 ± 0.43
20 ± 0.38
14 ± 0.22
Na
13 ± 0.28
Na
7 ± 0.15
7 ± 0.00
7 ± 0.26
7 ± 0.14
7 ± 0.00
8 ± 0.00
8 ± 0.18
7 ± 0.14
a
b
b
b
c
c
20 ± 0.44
15 ± 0.46
10 ± 0.14
10 ± 0.28
7 ± 0.00
c
c
c
8 ± 0.22c
Na
B. cereus (+)
22 ± 0.66a
25 ± 0.48a
10 ± 0.26b
10 ± 0.15b
10 ± 0.11b
10 ± 0.22b
14 ± 0.18b
13 ± 0.15b
c
S. aureus (+)
B. megaterium (+)
S. marcescens (ꢀ)
a
b
b
b
c
c
21 ± 0.25
12 ± 016
16 ± 0.36
10 ± 0.33
10 ± 0.34
7 ± 0.14
a
10 ± 0.22b
10 ± 0.14b
9 ± 0.15b
c
c
8 ± 0.16c
8 ± 0.24
Experiment was performed in triplicate and expressed as mean ± SD. Values with different superscripts within each column (for any bacteria in different concentrations) are
significantly different (P < 0.05).
Na: No active.
Table 4
2 2 6 4 2
Antibacterial activities of [HgX (Me SCHC(O)C H -p-Cl)] (X = Cl (1b), Br (2b), I (3b)).
Inhibition zone (mm)
Concentration – 1 mg/ml
Concentration – 0.1 mg/ml
Concentration – 0.01 mg/ml
Microorganism
1b
2b
3b
1b
2b
3b
1b
2b
3b
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
12 ± 0.14b
14 ± 0.28b
10 ± 0.26b
9 ± 0.22b
10 ± 0.24b
20 ± 0.33b
11 ± 0.15b
Na
c
7 ± 0.00c
10 ± 0.14c
Na
P. vulgaris (ꢀ)
E. coli (ꢀ)
14 ± 0.18
17 ± 0.14
20 ± 0.35
22 ± 0.54
25 ± 0.64
10 ± 0.14
16 ± 0.34
16 ± 0.26
20 ± 0.18
14 ± 0.22
12 ± 0.18
14 ± 0.24
17 ± 0.16
32 ± 0.66
18 ± 0.24
17 ± 0.14
15 ± 0.14
12 ± 0.18
Na
Na
9 ± 0.33
12 ± 0.25
11 ± 0.17
Na
7 ± 0.15
7 ± 0.00
Na
c
b
b
c
c
c
B. cereus (+)
14 ± 0.33
8 ± 0.17
c
S. aureus (+)
18 ± 0.25b
10 ± 0.15b
Na
7 ± 0.14
Na
Na
b
b
7 ± 0.11c
Na
B. megaterium (+)
S. marcescens (ꢀ)
15 ± 0.12
11 ± 0.18
8 ± 0.00b
11 ± 0.18b
8 ± 0.00b
7 ± 0.00
c
Experiment was performed in triplicate and expressed as mean ± SD. Values with different superscripts within each column (for any bacteria in different concentrations) are
significantly different (P < 0.05).
Na: No active.
Table 5
Antibacterial activity of antibiotics as positive controls and DMSO solve as negative control.
Inhibition zone (mm)
Positive controls
Gentamicin
Negative controls
DMSO
Microorganism
Penicillin
Nitrofurantoin
Neomycin
P. vulgaris (ꢀ)
E. coli (ꢀ)
30 ± 0.14
Na
25 ± 0.18
35 ± 0.24
25 ± 0.33
27 ± 0.18
Na
Na
Na
Na
Na
Na
15 ± 0.22
25 ± 0.22
10 ± 0.12
30 ± 0.34
20 ± 0.28
18 ± 0.14
22 ± 0.16
20 ± 0.33
20 ± 0.36
25 ± 0.45
20 ± 0.55
22 ± 0.28
Na
Na
Na
Na
Na
Na
B. cereus (+)
S. aureus (+)
B. megaterium (+)
S. marcescens (ꢀ)
Experiment was performed in triplicate and expressed as mean ± SD.
Na: No active.
The angles subtended by the ligands at the Hg(II) center vary
2.6.4. Antibacterial activity
from 90.45(4)° to 149.77(17)° in 1a and 92.787(17)° to
Results from antibacterial assessments of the samples are pres-
ented in Tables 3 and 4. Positive controls and negative control are
in Table 5. All complexes display antibacterial activity against the
bacteria tested especially for the Gram positive ones. In contrast,
Serratia marcescens (ꢀ) was the most resistant bacterium. With
comparing their antibacterial activities with those of reference
antibiotics, it seems that the complexes have remarkable inhibi-
tory potencies against bacteria. Generally the antibacterial activity
of compounds is attributed mainly to its major components. How-
ever, today it is known that the synergistic or antagonistic effect of
one compound even when it is a minor component of mixture has
to be considered. The complexes reported herein showed more
activity against some bacteria, than others, under identical exper-
imental conditions. This would suggest that the structure of com-
plexes may reduce the polarity of the metal ion mainly. Also, we
can consider that the formation of a neutral coordination complex
may facilitate crossing of the lipid layer of the bacterial cell mem-
brane and in this way may be effected the mechanisms of growth
1
30.83(16)° in 2b, indicating very distorted tetrahedral coordina-
tion geometry. The widening of the XAHgAC angle from the tetra-
3
hedral angle must be due to the higher s character of the sp hybrid
mercury orbitals involved in the above bonds and the formation of
a strong halide-bridge between Hg atoms which requires the inter-
nal XAHgAX angles 90.45(4)° 1a and 92.787(17)° 2b to be consid-
erably smaller. The two mercury atoms and two bridging halides in
each case are perfectly coplanar. The internuclear distances be-
tween mercury atoms at the distances of 3.848 1a and 3.903 Å
2
b are less than in the phosphonium analogs (Table 2), but these
distances are much longer than the sum of Van der Waals radii
3.0 Å) of the two mercury atoms [32] indicating the absence of
(
significant bonding interactions between the mercury atoms in
the molecular structures. The adaptation of binuclear structures
in Hg(II) ylide complexes may be explained both by the preference
of Hg(II) for four coordination and the stability of the 18 electron
configuration around Hg(II).

2
70
S.J. Sabounchei et al. / Journal of Molecular Structure 1034 (2013) 265–270
and development of bacteria. Composition of the coordination site
and the geometry of the tested complexes seemed to be the prin-
cipal factor that influences the antibacterial activity. The presence
of H, Br, Cl and I groups exerts a number of changes on antibacte-
rial activity of the tested complexes (Tables 3 and 4). The above re-
sults indicate that the complexes studied may be used in the
treatment of diseases caused by the bacteria that were tested. Fur-
ther studies are needed to evaluate the in vivo potential of these
compounds in animal models.
ciated with this article can be found, in the online version, at
http://dx.doi.org/10.1016/j.molstruc.2012.10.051.
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0
33; or e-mail: deposit@ccdc.cam.ac.uk. Supplementary data asso-