Reactivity of mercury(II) halides with the α-keto stabilized sulfonium ylides: Crystal structures of two new polymer and binuclear complexes and in vitro antibacterial study

Article abstract of DOI:10.1016/j.poly.2012.10.054

Reaction of α-keto stabilized sulfonium ylides (Me) ₂SCHC(O)C₆H₄R (R = p-NO₂ (Y) and p-Br(Y′)) with HgX₂ (X = Cl, Br and I) in equimolar ratios using methanol as solvent leads to two types of products. Single crystal X-ray diffraction analysis reveals (i) binuclear complex of [HgI₂(Y)] ₂ (3) with an asymmetric halide-bridged structure and (ii) one-dimensional polymer of [HgI₂(Y′)]_n (6) that the monomeric -Hg-I-Hg- bridging leads to a zig-zag polymeric chain in which mercury assumes a distorted tetrahedral geometry. Characterization of the compounds by IR, ¹H and ¹³C NMR spectroscopy confirmed coordination of the ylide to the metal through the carbon atom. Analytical data indicate a 1:1 stoichiometry between the ylide and Hg(II) halide in all of products. The Hg(II) complexes with different ligands evaluated for their antibacterial activity using disc diffusion method. The results show that all complexes represent antibacterial activity against bacteria tested especially on Gram positive ones.

Full text of DOI:10.1016/j.poly.2012.10.054

Polyhedron 53 (2013) 1–7
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Reactivity of mercury(II) halides with the -ketostabilized sulfonium ylides: Crystal
a
structures of two new polymer and binuclear complexes and in vitro
antibacterial study
a
b
b
Seyyed Javad Sabounchei a, , Fateme Akhlaghi Bagherjeri , Colette Boskovic , Robert W. Gable ,
⇑
Roya Karamian c, Mostafa Asadbegy c
a Faculty of Chemistry, Bu-Ali Sina University, Hamedan 65174, Iran
b School of Chemistry, University of Melbourne, Victoria 3010, Australia
c Department of Biology, Faculty of Science, Bu-Ali Sina University, Hamedan 65174, Iran
a r t i c l e i n f o
a b s t r a c t
Reaction of a
-keto stabilized sulfonium ylides (Me)2SCHC(O)C6H4R (R = p-NO2 (Y) and p-Br(Y0)) with HgX2
Article history:
Received 26 July 2012
Accepted 26 October 2012
Available online 8 February 2013
(X = Cl, Br and I) in equimolar ratios using methanol as solvent leads to two types of products. Single crys-
tal X-ray diffraction analysis reveals (i) binuclear complex of [HgI2(Y)]2 (3) with an asymmetric halide-
bridged structure and (ii) one-dimensional polymer of [HgI2(Y0)]n (6) that the monomeric –Hg–I–Hg–
bridging leads to a zig-zag polymeric chain in which mercury assumes a distorted tetrahedral geometry.
Characterization of the compounds by IR, 1H and 13C NMR spectroscopy confirmed coordination of the
ylide to the metal through the carbon atom. Analytical data indicate a 1:1 stoichiometry between the
ylide and Hg(II) halide in all of products. The Hg(II) complexes with different ligands evaluated for their
antibacterial activity using disc diffusion method. The results show that all complexes represent antibac-
terial activity against bacteria tested especially on Gram positive ones.
Keywords:
Sulfonium ylide
Mercury(II) halide complex
Polymeric chain
X-ray crystal structure
Antibacterial effect
Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction
In 1984, Tewari et al. [8] reported the synthesis of a series of tran-
sition metal halide complexes with various sulfonium ylides with-
out further characterization.
Sulfur ylides R2S = C (R0) (R00) (R, R0, R00 = alkyl or aryl groups) are
very reactive species with interesting applications in organic syn-
thesis [1–4]. Juxtaposition of the keto group and carbanion in the
The development of metal complexes with the ability to inhibit
bacterial growth have been of great interest in recent years due to
their potential use in everyday products like paints, kitchenware,
school and hospital utensils, etc. Metal complexes play an impor-
tant role in many biological systems [9–11]. It has been observed
that metal ions have considerable effect on the antimicrobial activ-
ity of antibiotics [12–15]. Emerging bacterial resistance to the cur-
rently available antibiotics has driven the search for novel
prokaryotic targets as well as new molecules which inhibit their
activity [16]. Among these novel metal complexes derivatives
which show considerable biological activity may represent an
interesting approach for designing new antibacterial drugs. This
may be due to the dual possibility of both ligands plus metal ion
interacting with different steps of the pathogen life cycle [17].
The aims of our present work are to describe the preparation,
spectroscopic and structural characterization and in vitro assess-
ment antibacterial activity of mercury(II) complexes with two sul-
fonium ylides.
a-keto stabilized sulfonium ylides allow for the resonance delocal-
ization of the ylidic electron density providing additional stabiliza-
tion to the ylide species (Scheme 1). This provides them with the
potential to act as an ambidentate ligand and thus bond to a metal
center through the carbanion (b), the enolate oxygen (c). The eno-
late form (c) may assume either a cis or trans arrangement, the
geometry of which will be retained upon bonding to metal.
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 [5,6]. However the configuration of the analogous sulfo-
nium ylide complexes is to date unknown as such species are yet
to be crystallographically characterized.
The synthesis of complexes derived from sulfonium ylides and
mercury(II) halides was first reported in 1975 by Weleski et al.
[7], with a symmetric halide-bridged binuclear structure proposed.
This includes the first instance of polymeric structure of one
ambidentate sulfonium ylide with mercury(II) halide, 6, character-
ized by single X-ray diffraction. The structure of complex 3 is com-
pared with the analogous phosphorus ylide.
⇑
Corresponding author. Tel.: +98 811828280; fax: +98 8118257408.
E-mail address: jsabounchei@yahoo.co.uk (S.J. Sabounchei).
0277-5387/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.10.054

2
S.J. Sabounchei et al. / Polyhedron 53 (2013) 1–7
Table 1
Crystal data and refinement details for complexes 3 and 6.
(Me)2S
O
(Me)2S
O
(Me)2S
O
3
6
Identification code
Formula
fa-Isng
fa-Iso2g
C10H11HgI2BrOS
713.55
130(2)
0.71073
C
20H22Hg2I4N2O6S2
R
R
R
Formula weight
1359.30
130(2)
0.71073
T (K)
a
b
c
0
k (AÅ)
Scheme 1. The canonical forms of (Me)2SCHC(O)C6H4R (R = p-NO2 (Y) and p-Br)
(Y0).
Crystal system
Space group
triclinic
monoclinic
P21/c
ꢀ
P1
Unit cell dimensions
7.8479(4)
9.3780(4)
10.7439(6)
100.370(4)
98.161(4)
95.413(4)
764.08(6)
1
7.72521(17)
28.6099(6)
7.49433(16)
2. Experimental
110.017(3)
2.1. Physical measurements and materials
V (Å3)
1556.32(6)
4
3.045
All solvents were reagent grade and used without further puri-
fications. NMR spectra were obtained on 400 MHz Varian MR400
and 90 MHz Jeol spectrometers in DMSO-d6 and CDCl3 as the sol-
vent. Chemical shifts (d) are reported relative to internal TMS (1H
and 13C). Melting points were measured on a Stuart SMPI appara-
tus. Elemental analysis for C, H and N were performed using a Per-
kin-Elmer 2400 series analyzer. Fourier transform infrared spectra
were recorded on a Shimadzu 435-U-04 spectrophotometer and
samples were prepared as KBr pellets.
Z
Dcalc (mg/m3)
2.954
14.286
Absorption coefficient
16.538
(mmꢀ1
)
F(000)
608
1264
Crystal size(mm)
h Range for data collection
(°)
0.24 ꢁ 0.15 ꢁ 0.14
0.32 ꢁ 0.12 ꢁ 0.06
3.02–29.95
2.98–29.02
Limiting indices
ꢀ11 6 h 6 10
ꢀ12 6 k 6 12
ꢀ10 6 l 6 14
3933
3549 (0.0267)
99.69%
ꢀ10 6 h 6 9
ꢀ38 6 k 6 38
ꢀ9 6 l 6 10
3912
3558 (0.0267)
99.81%
Reflections collected
Unique Rint
Completeness
Absorption correction
Refinement method
2.2. X-ray crystallography
Gaussian
Gaussian
Full-matrix least-
squares on F2
3933/0/163
0.712
R1 = 0.0282,
wR2 = 0.0873
R1 = 0.0339,
wR2 = 0.0972
Full-matrix least-
squares on F2
3912/0/147
1.130
R1 = 0.0275,
wR2 = 0.0589
R1 = 0.0326,
wR2 = 0.0610
1.865 and ꢀ1.011
Data collection from suitable crystals of 3 and 6 was performed
on an Oxford Diffraction single-crystal X-ray diffractometer using
mirror monochromated Mo Ka radiation (0.71073 Å) at 130 K (Ta-
ble 1). Gaussian absorption corrections were carried out using a
multifaceted crystal model, using CrysAlisPro [18]. All two struc-
tures were solved by direct methods and refined by the full-matrix
least-squares method on F2 using the SHELXTL-97 crystallographic
package [19,20]. All non-hydrogen atoms were refined anisotropi-
cally. Hydrogen atoms were inserted at calculated positions using a
riding model, with isotropic displacement parameters.
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2
r
(I)]
R indices (all data)
Largest differences peak and 1.311 and ꢀ1.657
hole (e Å3)
2.5. Sample preparation
2.5.1. Synthesis
2.3. Antibacterial activity
The room temperature reactions of HgX2 (X = Cl, Br and I) with
sulfonium ylides Y and Y0 (prepared by reacting dimethylsulfide
with an acetone solution of 2-bromo-40-nitroacetophenone and
2-bromo-40-bromoacetophenon and treatment with aqueous
NaOH solution) for 4 h (1:1 M ratio) in CH3OH gave the binuclear
complexes 1–5 and polymeric complex 6. The aims of our present
work are to describe the NMR spectroscopy and X-ray diffraction
analysis, allowing determination of the structures. X-ray quality
crystals of the complexes 3 and 6 were grown by the direct diffu-
sion of methanol in the dimethylsulfoxide solution over several
days.
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
(Wild) and Bacillus megaterium (PTCC 1017), and three Gram neg-
ative bacteria, namely Escherichia coli (Wild), Proteus vulgaris (PTCC
1079), and Serratia marcescens (PTCC 1111) [21]. The complexes
were dissolved in DMSO to a final concentration of 1 mg mlꢀ1
and then sterilized by filtration using 0.45 lm Millipore. All tests
were carried using 10 ml of suspension containing 1.5 ꢁ 108 bacte-
ria/ml and spread on nutrient agar medium. Negative controls
were prepared by using DMSO. Gentamycin, Penicillin, Neomycin
and Nitrofurantion were used as positive reference standards.
The diameters of inhibition zones generated by the complexes
were measured.
2.5.2. Synthesis of ylides [(Me)2SCHC(O)C6H4R] (R = p-NO2 (Y) and p-
Br (Y0))
2.5.2.1. (Me)2SCHC(O)C6H4(p-NO2) (Y). To an acetone solution
(10 ml) of dimethylsulfide (0.062 g, 1.0 mmol) was added 2-bro-
mo-40-nitroacetophenone (0.244 g, 1.00 mmol) and the mixture
was stirred for 12 h. The solid product (sulfonium salt) was iso-
lated by filtration, washed with ether and dried under reduced
pressure. Further treatment with aqueous 10% NaOH solution led
to elimination of HBr, giving the free ligand Y [22]. IR (KBr disk):
2.4. Statistical analysis
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.
m
(cmꢀ1) 1551 (C = O) and 875 (S–C). 1H NMR (CDCl3): d (ppm)
3
2.9 (s, 6H, S(CH3)2); 4.2 (1H, CH); 7.8 (d, JHH = 8.1 Hz, 2H, Ph);
8.1 (d, JHH = 8.5 Hz, 2H, Ph). 13C NMR (CDCl3, ppm): d 28.3 (s,
3

S.J. Sabounchei et al. / Polyhedron 53 (2013) 1–7
3
3
S(CH3)2); 54.26 (s, CH); 123.1 (s, Ph(m)); 127.2 (s, Ph(o)); 128.4 (s,
Ph(i)); 146.8 (s, Ph(p)); 180.1 (s, CO).
S(CH3)2); 5.4 (s, 1H, CH); 7.6 (d, JHH = 8.1 Hz, 2H, Ph); 7.8 (d,
3JHH = 8.5 Hz, 2H, Ph). 13C NMR (DMSO-d6, ppm): d 27.1 (s,
S(CH3)2); 64.9 (s, CH); 127.6 (s, Ph(i)); 130.0 (s, Ph(o)); 131.9 (s,
Ph(m)); 134.4 (s, Ph(p)); 191.4 (s, CO).
2.5.2.2. (Me)2SCHC(O)C6H4-p-Br (Y0). Ylide Y0 was prepared follow-
ing the same synthetic method as that reported for ligand Y. Thus,
dimethylsulfide (0.062 g, 1.00 mmol) was reacted with 2-bromo-
40-bromoacetophenone (0.260 g, 1.00 mmol) giving the free ligand
2.5.8. Synthesis of complex [HgI2(Y0)]n (6)
Complex 6 was prepared following the same synthetic method
as that reported for 1. Thus, HgI2 (0.227 g, 0.500 mmol) was re-
acted with ylide Y0 (0.129 g, 0.50 mmol) giving 6. Yield 0.306 g,
86%. Anal. Calc. for HgI2BrOSC10H11: C, 16.83; H, 1.55. Found: C,
Y0. IR (KBr disk):
m
(cmꢀ1) 1578 (C = O) and 855 (S–C). 1H NMR
(CDCl3): d (ppm) 2.9 (s, 6H, S(CH3)2); 4.2 (1H, CH); 7.4 (d,
3JHH = 8.1 Hz, 2H, Ph); 7.6 (d, 3JHH = 8.1 Hz, 2H, Ph). 13C NMR (CDCl3,
ppm): d 28.1 (s, S(CH3)2); 52.3 (s, CH); 123.0 (s, Ph(i)); 127.6 (s,
Ph(o)); 130.4 (s, Ph(m)); 139.7 (s, Ph(p)); 180.5 (s, CO).
16.66; H, 1.62%. M.p. 181–183 °C. IR (KBr disk):
m
(cmꢀ1) 1630
(CO) and 814 (S+–Cꢀ). 1H NMR (DMSO-d6, ppm): d 2.8 (s, 6H,
3
S(CH3)2); 5.2 (s, 1H, CH); 7.6 (d, JHH = 8.1 Hz, 2H, Ph); 7.7 (d,
2.5.3. Synthesis of complex [HgCl2(Y)]2 (1)
3JHH = 8.5 Hz, 2H, Ph). 13C NMR (DMSO-d6, ppm): d 26.6 (s,
S(CH3)2); 63.2 (s, CH); 126.4 (s, Ph(i)); 129.3 (s, Ph(o)); 131.2 (s,
Ph(m)); 134.9 (s, Ph(p)); 189.1 (s, CO).
To a methanolic solution (15 ml) of HgCl2 (0.135 g, 0.500 mmol)
was added a methanolic solution (10 ml) of ylide Y (0.112 g,
0.50 mmol). The mixture was stirred for 4 h. The separated solid
was filtered and washed with diethyl ether. Yield 0.243 g, 98%.
Anal. Calc. for Hg2Cl4O6S2N2C20H22: C, 24.18; H, 2.23. Found: C,
2.6. Results and discussion
23.92; H, 2.18%. M.p. 197–198 °C. IR (KBr disk):
m
(cmꢀ1) 1641
2.6.1. Spectroscopy
(CO) and 818 (S+–Cꢀ). 1H NMR (DMSO-d6, ppm): d 2.9 (s, 6H,
S(CH3)2); 5.6 (s, 1H, CH); 8.2 (m, 4H, Ph). 13C NMR (DMSO-d6,
ppm): d 27.1 (s, S(CH3)2); 65.2 (s, CH); 124.1 (s, Ph(m)); 129.6 (s,
Ph(o)); 140.3 (s, Ph(i)); 150.1 (s, Ph(p)); 191.1 (s, CO).
In the infrared spectra the m (CO) that is sensitive to complexa-
tion, occurs at 1551 and 1578 cmꢀ1 for Y and Y0 ylides, as in the
case of other resonance stabilized ylides [8]. Coordination of the
ylide through carbon causes an increase in
dination a decrease of (CO) is expected. The infrared absorption
bands observed for all our complexes at about 1630–1658 cmꢀ1
m (CO), while for O-coor-
m
2.5.4. Synthesis of complex [HgBr2(Y)]2 (2)
Complex 2 was prepared following the same synthetic method
as that reported for 1. Thus, HgBr2 (0.180 g, 0.500 mmol) was re-
acted with ylide Y (0.112 g, 0.50 mmol) giving 2. Yield 0.263 g,
90%. Anal. Calc. for Hg2Br4O6S2N2C20H22: C, 20.51; H, 1.89. Found:
suggest coordination of the ylide through carbon atom. The m
(S+–Cꢀ) which is also diagnostic of the coordination mode occurs
at around 848 cmꢀ1 in Me2S+–CH2 and at about 865 cmꢀ1 in ylides.
In the present study, the
m
(S+–Cꢀ) values for all complexes were
C, 20.73; H, 1.94%. M.p. 200–201 °C. IR (KBr disk):
m
(cmꢀ1) 1658
shifted to lower frequencies around 814 cmꢀ1, suggesting partial
removal of electron density from the SꢀC bond due to coordination
[8].
(CO) and 807 (S+–Cꢀ). 1H NMR (DMSO-d6, ppm): d 2.9 (s, 6H,
S(CH3)2); 5.5 (s, 1H, CH); 8.1 (m, 4H, Ph). 13C NMR (DMSO-d6,
ppm): d 26.8 (s, S(CH3)2); 64.2 (s, CH); 123.4 (s, Ph(m)); 128.8 (s,
Ph(o)); 140.8 (s, Ph(i)); 149.3 (s, Ph(p)); 188.5 (s, CO).
The 1H NMR signals for the SCH group of all complexes are
shifted downfield compared to those of the free ylides, as a conse-
quence of the inductive effect of the metal center [6]. The appear-
ance of single signals for the SCH group in 1H NMR at ambient
temperature indicates the presence of only one geometrical 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 and
trans isomers giving rise to two different signals in 1H NMR [23].
The most interesting aspect of the 13C NMR spectra of the com-
plexes is the lower shielding of the ylidic carbon atoms. Such a
lower shielding was observed in [5,6,24], and is due to the change
in hybridization of the ylidic carbon atom from sp2 to sp3. The 13C
chemical shifts of the CO group in the complexes are around
190 ppm, relative to ꢂ181 ppm noted for the same carbon in the
parent ylides, indicating decreased shielding of this carbon atom
in mercury complexes. No coupling to (199Hg, 16.8% abundance,
I = 1/2) was observed at room temperature in 1H and 13C NMR
spectra. Failure to observe satellites in the above spectra was pre-
viously noted in the ylide complexes of Hg(II) which has been ex-
plained by fast exchange of the ylide with the metal [25].
2.5.5. Synthesis of complex [HgI2(Y)]2 (3)
Complex 3 was prepared following the same synthetic method
as that reported for 1. Thus, HgI2 (0.227 g, 0.500 mmol) was re-
acted with ylide Y (0.112 g, 0.50 mmol) giving 3. Yield 0.298 g,
88%. Anal. Calc. for Hg2I4O6S2N2C20H22: C, 17.67; H, 1.63. Found:
C, 17.44; H, 1.58%. M.p. 187–188 °C. IR (KBr disk):
m
(cmꢀ1) 1650
(CO) and 803 (S+–Cꢀ). 1H NMR (DMSO-d6, ppm): d 2.9 (s, 6H,
S(CH3)2); 5.4 (s, 1H, CH), 8.2 (m, 4H, Ph). 13C NMR (DMSO-d6,
ppm): d 26.9 (s, S(CH3)2); 63.8 (s, CH); 123.3(s, Ph(m)); 128.6 (s,
Ph(o)); 141.7 (s, Ph(i)); 149.1 (s, Ph(p)); 186.9 (s, CO).
2.5.6. Synthesis of complex [HgCl2(Y0)]2 (4)
Complex 4 was prepared following the same synthetic method
as that reported for 1. Thus, HgCl2 (0.135 g, 0.500 mmol) was re-
acted with ylide Y0 (0.129 g, 0.50 mmol) giving 4. Yield 0.254 g,
96%. Anal. Calc. for Hg2Cl4Br2O2S2C20H22: C, 22.63; H, 2.09. Found:
C, 22.43; H, 2.12%. M.p. 200–202 °C. IR (KBr disk):
m
(cmꢀ1) 1647
(CO) and 822 (S+–Cꢀ). 1H NMR (DMSO-d6, ppm): d 2.9 (s, 6H,
3
S(CH3)2); 5.4 (s, 1H, CH); 7.7 (d, JHH = 8.1 Hz, 2H, Ph); 7.8 (d,
2.6.2. Crystal structures analysis
3JHH = 8.5 Hz, 2H, Ph). 13C NMR (DMSO-d6, ppm): d 27.2 (s,
S(CH3)2); 64.2 (s, CH); 127.7 (s, Ph(i)); 130.0 (s, Ph(o)); 131.9 (s,
Ph(m)); 134.3 (s, Ph(p)); 190.6 (s, CO).
The molecular structures of 3 and 6 were determined through
single crystal X-ray diffraction methods. The molecular drawing
of complexes 3 and 6 are shown in Figs. 1 and 2. Crystallographic
data and parameters concerning data collection and structure solu-
tion and refinement are summarized in Table 1 and selected bond
distances and angles are presented in Table 2.
The binuclear structure adopted by complex 3 is in contrast to
the trinuclear structure exhibited by O-coordinated of the phos-
phorus ylide (Ph3PCHC(O)Ph) complex of mercury(II) [26], but is
similar to the structure of C-coordinated dinuclear mercury(II) ha-
lide complexes of the phosphorus ylides Ph3PCHC(O)OEt (EPPY)
2.5.7. Synthesis of complex [HgBr2(Y0)]2 (5)
Complex 5 was prepared following the same synthetic method
as that reported for 1. Thus, HgBr2 (0.180 g, 0.500 mmol) was re-
acted with ylide Y0 (0.129 g, 0.50 mmol) giving 5. Yield 0.284 g,
92%. Anal. Calc. for Hg2Br6O2S2C20H22: C, 19.39; H, 1.79; Found:
C, 19.55; H, 1.84%. M.p. 195–196 °C. IR (KBr disk):
(CO) and 820 (S+–Cꢀ). 1H NMR (DMSO-d6, ppm): d 2.9 (s, 6H,
m
(cmꢀ1) 1646

4
S.J. Sabounchei et al. / Polyhedron 53 (2013) 1–7
Fig. 1. ORTEP view of the X-ray crystal structure of 3. H atoms are omitted for clarity. Symmetry code; a: 1 ꢀ x, 1 ꢀ y, 2 ꢀ z.
[24], and (P-tolyl)3PCHC(O)OCH2Ph (BTPY) [5], Ph3PCHC(O)C5H4-p-
NO2 [6]. The Hg(II) center is four-coordinate with sp3 hybridization.
This environment involves one short terminal Hg–I bond, one Hg–C
bond and two asymmetric bridging Hg–I 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 [27,28]. However in
comparison with the analogous mercury complexes with phospho-
rus ylides derived from triphenylphosphonium (Table 2), the p–d
overlap of the phosphonium group appears to be more pronounced
than that with the dimethyl sulfonium groups incorporated into
ylides Y and Y0. 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 triphenyl
phosphonium ylides, which is evident from the shorter Hg–C bond
lengths in sulfonium ylides complexes compared with the equiva-
lent distances in the phosphorus analogs (Table 2). The terminal
Hg–I bond length is very similar to that of found in phosphorus
analog. The two bridging Hg–I bonds are very similar, in contrast
to the phosphorus analog, nevertheless they are clearly asymmet-
ric as well as the phosphorus complex.
The angles subtended by the ligands at the Hg(II) center vary
from 90.692(11)° to 128.91(13)°, indicating very distorted tetrahe-
dral coordination geometry. The widening of the I–Hg–C angle
from the tetrahedral angle must be due to the higher s character
of the sp3 hybrid mercury orbitals involved in the above bonds
and the formation of a strong halide-bridged between Hg atoms
which requires the internal I–Hg–I angle 90.692(11)° to be consid-
erably smaller. The two mercury atoms and two bridging halides
are perfectly coplanar. The internuclear distance between mercury
atoms at the distance of 4.159 Å is less than in the phosphonium
analog (Table 2), but these distances are much longer than the
sum of Van der Waals radii (3 Å) of the two mercury atoms [29]
indicating the absence of significant bonding interactions between
the mercury atoms in the molecular structures.
In complex 3, the nitro group is almost coplanar with the phenyl
ring, the dihedral angle being 5.2(7)°. Two nitro-phenyl groups,
from two different molecules, are linked together via p–p stacking.
The nitro-phenyl groups are arranged in an anti parallel fashion,
with a separation of 3.37 Å, C7i (i: 1 ꢀ x, 2 ꢀ y, ꢀz) is situated above
C5 (and C5i lies above C7), while C6i is positioned above the center
of the phenyl ring and N1i lies vertically above C3 (Table 3). The
nitrogen and one of the oxygen atoms of the nitro group, N1 and
O2, are involved in a dipole–dipole interaction with the correspond-
ing atoms of the nitro group from a third molecule; the separation
being similar to that found for p-nitrophenyl isocyanide [30]. These
Fig. 2. ORTEP view of the X-ray crystal structure of 6. (a) Asymmetric unit and (b)
polymeric chain. H atoms have been omitted for clarity. Symmetry code; a: x, 1/
2 ꢀ y, 1/2 + z.
ꢀ
interactions link the molecules along the [ꢀ211] direction.

S.J. Sabounchei et al. / Polyhedron 53 (2013) 1–7
5
Table 2
Selected bond lengths (Å) and bond angles (°) for complexes 3 and 6 and comparison of selected internuclear separations with triphenylphosphonium analogs.
Bond distances
3
[6]
6
Bond angles
3
6
Hg1–C1
Hg1–I1
Hg1–I1a
Hg1–I2
C1–C2
2.234(6)
2.8817(4)
3.0336(4)
2.6775(4)
1.496(8)
1.766(5)
1.221(7)
2.292(5)
2.229(5)
2.7749(4)
3.2390(4)
2.7215(4)
1.483(7)
1.775(5)
1.223(6)
I1–Hg1–I1a
S1–C1–Hg1
I2–Hg1–I1a
C2–C1–Hg1
I2–Hg1–I1
C1–Hg1–I2
C1–Hg1–I1
C1–Hg1–I1a
90.692(11)
110.0(3)
103.729(13)
107.3(3)
109.779(14)
128.91(13)
111.69(13)
104.27(14)
92.726(9)
110.8(2)
102.088(11)
106.3(3)
110.588(12)
123.07(13)
122.25(13)
95.40(12)
2.6846(7)
3.1924(6)
2.7900(6)
C1–S1
C2–O1
See Figs. 1 and 2 for the atom numbering.
Symmetry code; a: 1 ꢀ x, 1 ꢀ y, 2 ꢀ z (3), x, 1/2ꢀy, 1/2 + z (6).
Table 3
Short intermolecular contacts for complexes 3 and 6.
Additional C–Hꢃ ꢃ ꢃI interactions link the molecules into a 3D
arrangement.
The X-ray analysis for complex 6 reveals the coordination of the
ligand through the carbon atom. The Hg(II) atom is located in a dis-
torted tetrahedral environment with one C, one terminal I and two
bridging I atoms, resulting in a one-dimensional polymeric chain.
The terminal Hg–I bond distance 2.7215(4) Å is comparable to
3
6
C5ꢃ ꢃ ꢃC7a
3.385(6)
3.241(5)
91.3(3)
85.3(2)
2.867(5)
2.867(5)
92.0(3)
88.0(3)
3.129
0.98
144.3
3.966(5)
3.138
0.95
H1ꢃ ꢃ ꢃI1a
3.165
1.00
4.110(5)
158.1
3.104
0.98
4.047(6)
161.9
2.362
0.95
C3ꢃ ꢃ ꢃN1a
C1–H1
C6ꢃ ꢃ ꢃC5ꢃ ꢃ ꢃC7a
C2ꢃ ꢃ ꢃC3ꢃ ꢃ ꢃN1a
O2–N1b
C1ꢃ ꢃ ꢃI1a
C1–H1...I1a
H10Bꢃ ꢃ ꢃI1a
C10–H10B
C10ꢃ ꢃ ꢃI1a
C10–H10Bꢃ ꢃ ꢃI1a
H5ꢃ ꢃ ꢃO1b
C5–H5
those of 2.706(1) Å found in
a [{HgI2[PPh2CH2CH2PPh2 = -
N1–O2b
N1ꢃ ꢃ ꢃO2ꢃ ꢃ ꢃN1b
O2ꢃ ꢃ ꢃN1ꢃ ꢃ ꢃO2b
H9Bꢃ ꢃ ꢃI1c
C9–H9B
C(H)C(O)Ph]}n [31]. The asymmetric bridging nature of the other
two iodo ligands is indicated by the two bridging different Hg–I
distances of 2.7749(4) and 3.2390(4) Å. The latter distance being
rather long, indicates a weak bridging Hg–I interaction. The bond
angles around Hg atom (Table 2) indicate a severe distortion from
ideal tetrahedral geometry. The deviation of atom Hg1 from the
best least-squares plane defined by atoms I1, I2 and C1, is only
0.297 Å. This is comparable to the previous observations in the
complexes and [31] and [HgX2{Ph2PCH2CH2P(O)-Ph2}]n (X = Br, I)
[32] where a weak coordination of the one of the ligands lead to
a flattened tetrahedral geometry as shown by the small deviations
(ranging from 0.244 to 0.406 A) of the Hg atom from the plane de-
fined by other three strongly bonded atoms.
The bridging Hg–I bonds link the Hg atoms into a one dimen-
sional chain, lying along the c-axis. Further interactions (Table 3)
involving C–Hꢃ ꢃ ꢃI and C–Hꢃ ꢃ ꢃO hydrogen bonds, Sꢃ ꢃ ꢃI interactions
(comparable to those found in sulfur iodoform [33]) and Brꢃ ꢃ ꢃBr
interactions (comparable to those observed in [34,35]) link these
chains into a 3D arrangement.
C9–H9Bꢃ ꢃ ꢃI1c
C5ꢃ ꢃ ꢃO1b
3.209(6)
148.3
C9ꢃ ꢃ ꢃI1c
C5–H5ꢃ ꢃ ꢃO1b
I1ꢃ ꢃ ꢃS1c
H7ꢃ ꢃ ꢃI1d
3.7675(13)
2.7215(4)
125.03(2)
3.6538(13)
2.7749(4)
124.52(2)
3.3751(11)
1.897(5)
148.71(15)
C7–H7
Hg1–I1
C7–H7ꢃ ꢃ ꢃI1d
C7ꢃ ꢃ ꢃI1d
143.8
3.945(4)
3.027
1.00
152.8
Hg1–I1ꢃ ꢃ ꢃS1c
I2ꢃ ꢃ ꢃS1d
H1 ꢃ ꢃ ꢃI2d
Hg1–I2
C1–H1
Hg1–I2ꢃ ꢃ ꢃS1d
Br1...Br1e
Br1–C6
C1–H1ꢃ ꢃ ꢃI2d
C1ꢃ ꢃ ꢃI2d
3.943(4)
C6–Br1ꢃ ꢃ ꢃBr1e
a
b
c
1 ꢀ x, 2ꢀy, ꢀz 1 + x, y, z.
2ꢀx, 2 ꢀ y – z x, y, ꢀ1 + z.
ꢀx, 1 – y, 1 – z ꢀ1 + x, y, ꢀ1 + z.
1 ꢀ x, 2 ꢀ y, 1 – z x, 1/2ꢀy, ꢀ1/2 + z.
ꢀx, 1 ꢀ y, ꢀ1 – z.
d
e
Since the halide-bridged bonds in the complexes containing
chloride and bromide are shorter and stronger than iodine species
[26], it seems the bridge splitting only occurs in the longer and
weaker iodo bonds of complex 6 and complexes 2–5 are binuclear
structures similar to complex 3.
The adaptation of these structures in Hg(II) ylide complexes
may be explained both by the preference of Hg(II) for four coordi-
nation and the stability of the 18 electron configuration around
Hg(II).
or percentage of mixture has to be considered [36–38]. Also, we
can consider that the coordination may facilitate the ability of a
complex to cross the lipid layer of the bacterial cell membrane
and in this way may be effected the mechanisms of growth and
development of bacteria [39,40]. The above results indicate that
the new complexes studied may be used in the treatment of dis-
eases caused by bacteria tested. Further studies are needed to eval-
uate the in vivo potential of these compounds in animal models.
3. Concluding remarks
2.6.3. Antibacterial activity
The new complexes represent a moderate antibacterial activity
against all bacteria tested especially on Gram positive ones. In con-
trast, Serratia marcescens (ꢀ) was the most resistant bacterium (Ta-
bles 4 and 5). When comparing the antimicrobial activity of the
tested samples to those of reference antibiotics, the inhibitory po-
tency of the tested complexes were found to be remarkable (Table
6). The DMSO negative control showed no activity against any bac-
terial strain. Antibacterial activity of complexes is more with in-
crease of the concentration. The presence of Cl, Br and I groups
exerts a number of changes on antibacterial activity of the tested
complexes. Generally antibacterial activity of compounds is attrib-
uted mainly to its major components. However, today it is known
that the synergistic or antagonistic effect of one compound in min-
The present study describes the synthesis and characterization
of some mercury (II) complexes of ambidentate sulfonium ylides.
On the basis of the physico-chemical and spectroscopic data is
clear that the sulfonium ylide ligands exhibit monodentate C-coor-
dination to the metal centers. The single crystal X-ray analysis re-
veals the presence of an asymmetric halide-bridged binuclear
structure for complex 3 similar to that observed for phosphonium
analog and a zig-zag polymer chain for complex 6 that is quite
new. It seems the bridge splitting only occurs in the longer and
weaker iodo bridges of complex 6. The complex 6 is the first
one-dimensional polymer mercury complex of an a-keto stabilized
sulfonium ylide to be observed. A comparison of important bond
lengths reveals a significant difference between the Hg–C bond

6
S.J. Sabounchei et al. / Polyhedron 53 (2013) 1–7
Table 4
Antibacterial activities of [HgX2(Me2SCHC(O)C6H4-p-NO2)]2 (X = Cl (1), Br (2), I (3)).
Microorganism
Inhibition zone (mm)
Concentration (1 mg mlꢀ1
)
Concentration (0.1 mg mlꢀ1
)
Concentration (0.01 mg mlꢀ1
)
1
2
3
1
2
3
1
2
3
P. vulgaris (ꢀ)
E. coli (ꢀ)
17 0.28a
21 0.64a
22 0.58a
25 0.26a
20 0.22a
14 0.12a
16 0.22a
20 0.34a
22 0.45a
22 0.55a
15 0.18a
11 0.14a
12 0.18a
19 0.15a
20 0.33a
25 0.33a
19 0.38a
11 0.44a
15 0.36b
18 0.14b
13 0.11b
18 0.16b
16 0.24b
11 0.24b
10 0.24b
12 0.18b
10 0.18b
11 0.25b
8
9
10 0.32b
14 0.26b
13 0.14b
12 0.16b
7
9
10 0.28c
7
7
0.00c
0.16c
8
7
7
7
Na
Na
0.14c
0.00c
0.00c
0.11c
12 0.34c
B .cereus (+)
8
0.14c
7c 0.24c
S. aureus (+)
B. megaterium (+)
S. marcescens (ꢀ)
11 0.25c
0.00c
10 0.18c
Na
7
Na
0.00b
0.14b
0.11b
0.22b
7
0.00c
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 activities of [HgX2(Me2SCHC(O)C6H4-p-Br)]2 (X = Cl (4), Br (5)) and [HgI(Me2SCHC(O)C6H4-p-Br)]n (6).
Microorganism
Inhibition zone (mm)
Concentration (1 mg/ml)
Concentration (0.1 mg/ml)
Concentration (0.01 mg/ml)
4
5
6
4
5
6
4
5
6
P. vulgaris (ꢀ)
E. coli (ꢀ)
17 0.18a
21 0.34a
15 0.26a
25 0.66a
22 0.54a
14 0.15a
16 0.25a
20 0.33a
22 0.33a
22 0.43a
20 0.38a
14 0.22a
17 0.56a
20 0.44a
22 0.66a
25 0.48a
21 0.25a
12 016a
10 0.24b
15 0.46b
10 0.26b
10 0.15b
16 0.36b
10 0.22b
10 0.16b
10 0.14b
10 0.11b
10 0.22b
10 0.33b
10 0.14b
11 0.36b
10 0.28b
14 0.18b
13 0.15b
10 0.34b
Na
7
7
7
8
8
7
0.26c
0.14c
0.00c
0.00c
0.18c
0.14c
9
7
8
Na
7
0.12c
0.00c
0.22c
13 0.28c
Na
B. cereus (+)
S. aureus (+)
7
7
8
0.15c
0.00c
0.24c
B. megaterium (+)
S. marcescens (ꢀ)
0.14c
0.16c
9
0.15b
8
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 6
Antibacterial activity of antibiotics as positive controls and DMSO solve as negative control.
Microorganism
Inhibition zone (mm)
Positive controls
Gentamaicen
Negative controls
DMSO
Penicillin
Nitrofurantion
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.
lengths that is attributed to Lewis basicity of dialkylsulfonium
ylide ligands versus triarylphosphonium ylide ligands. Results
from the present study clearly demonstrate that the complexes ex-
hibit significant antibacterial activity, which may help to inform
the design of improved antibacterial agents.
Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223 336 033; or
e-mail: deposit@ccdc.cam.ac.uk. Supplementary data associated
with this article can be found, in the online version, at http://
dx.doi.org/10.1016/j.poly.2012.10.054.
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