Polyhedron 53 (2013) 1–7

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Polyhedron

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Reactivity of mercury(II) halides with the a-ketostabilized sulfonium ylides: Crystalstructures of two new polymer and binuclear complexes and in vitroantibacterial study

Seyyed Javad Sabounchei a,⇑, Fateme Akhlaghi Bagherjeri a, Colette Boskovic b, Robert W. Gable b,Roya Karamian c, Mostafa Asadbegy c

a Faculty of Chemistry, Bu-Ali Sina University, Hamedan 65174, Iranb School of Chemistry, University of Melbourne, Victoria 3010, Australiac Department of Biology, Faculty of Science, Bu-Ali Sina University, Hamedan 65174, Iran

a r t i c l e i n f o

Article history:Received 26 July 2012Accepted 26 October 2012Available online 8 February 2013

Keywords:Sulfonium ylideMercury(II) halide complexPolymeric chainX-ray crystal structureAntibacterial effect

0277-5387/$ - see front matter � 2013 Elsevier Ltd. Ahttp://dx.doi.org/10.1016/j.poly.2012.10.054

⇑ Corresponding author. Tel.: +98 811828280; fax:E-mail address: jsabounchei@yahoo.co.uk (S.J. Sab

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

(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 theylide to the metal through the carbon atom. Analytical data indicate a 1:1 stoichiometry between theylide and Hg(II) halide in all of products. The Hg(II) complexes with different ligands evaluated for theirantibacterial activity using disc diffusion method. The results show that all complexes represent antibac-terial activity against bacteria tested especially on Gram positive ones.

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1. Introduction

Sulfur ylides R2S = C (R0) (R00) (R, R0, R00 = alkyl or aryl groups) arevery reactive species with interesting applications in organic syn-thesis [1–4]. Juxtaposition of the keto group and carbanion in thea-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 thepotential to act as an ambidentate ligand and thus bond to a metalcenter through the carbanion (b), the enolate oxygen (c). The eno-late form (c) may assume either a cis or trans arrangement, thegeometry 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 extensivelystudied [5,6]. However the configuration of the analogous sulfo-nium ylide complexes is to date unknown as such species are yetto be crystallographically characterized.

The synthesis of complexes derived from sulfonium ylides andmercury(II) halides was first reported in 1975 by Weleski et al.[7], with a symmetric halide-bridged binuclear structure proposed.

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+98 8118257408.ounchei).

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.

The development of metal complexes with the ability to inhibitbacterial growth have been of great interest in recent years due totheir 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 observedthat 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 novelprokaryotic targets as well as new molecules which inhibit theiractivity [16]. Among these novel metal complexes derivativeswhich show considerable biological activity may represent aninteresting approach for designing new antibacterial drugs. Thismay be due to the dual possibility of both ligands plus metal ioninteracting 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.

This includes the first instance of polymeric structure of oneambidentate 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.

RO

(Me)2S

RO

(Me)2S

RO

(Me)2S

a b c

Scheme 1. The canonical forms of (Me)2SCHC(O)C6H4R (R = p-NO2 (Y) and p-Br)(Y0).

Table 1Crystal data and refinement details for complexes 3 and 6.

3 6

Identification code fa-Isng fa-Iso2gFormula C20H22Hg2I4N2O6S2 C10H11HgI2BrOSFormula weight 1359.30 713.55T (K) 130(2) 130(2)

k (ÅA0

) 0.71073 0.71073

Crystal system triclinic monoclinicSpace group P�1 P21/cUnit cell dimensions

7.8479(4) 7.72521(17)9.3780(4) 28.6099(6)10.7439(6) 7.49433(16)100.370(4)98.161(4) 110.017(3)95.413(4)

V (Å3) 764.08(6) 1556.32(6)Z 1 4Dcalc (mg/m3) 2.954 3.045Absorption coefficient

(mm�1)14.286 16.538

F(000) 608 1264Crystal size(mm) 0.24 � 0.15 � 0.14 0.32 � 0.12 � 0.06h Range for data collection

(�)3.02–29.95 2.98–29.02

Limiting indices �11 6 h 6 10 �10 6 h 6 9�12 6 k 6 12 �38 6 k 6 38�10 6 l 6 14 �9 6 l 6 10

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2. Experimental

2.1. Physical measurements and materials

All solvents were reagent grade and used without further puri-fications. NMR spectra were obtained on 400 MHz Varian MR400and 90 MHz Jeol spectrometers in DMSO-d6 and CDCl3 as the sol-vent. Chemical shifts (d) are reported relative to internal TMS (1Hand 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 spectrawere recorded on a Shimadzu 435-U-04 spectrophotometer andsamples were prepared as KBr pellets.

Reflections collected 3933 3912Unique Rint 3549 (0.0267) 3558 (0.0267)Completeness 99.69% 99.81%Absorption correction Gaussian GaussianRefinement method Full-matrix least-

squares on F2Full-matrix least-squares on F2

Data/restraints/parameters 3933/0/163 3912/0/147Goodness-of-fit on F2 0.712 1.130Final R indices [I > 2r(I)] R1 = 0.0282,

wR2 = 0.0873R1 = 0.0275,wR2 = 0.0589

R indices (all data) R1 = 0.0339,wR2 = 0.0972

R1 = 0.0326,wR2 = 0.0610

Largest differences peak andhole (e Å3)

1.311 and �1.657 1.865 and �1.011

2.2. X-ray crystallography

Data collection from suitable crystals of 3 and 6 was performedon an Oxford Diffraction single-crystal X-ray diffractometer usingmirror monochromated Mo Ka radiation (0.71073 Å) at 130 K (Ta-ble 1). Gaussian absorption corrections were carried out using amultifaceted crystal model, using CrysAlisPro [18]. All two struc-tures were solved by direct methods and refined by the full-matrixleast-squares method on F2 using the SHELXTL-97 crystallographicpackage [19,20]. All non-hydrogen atoms were refined anisotropi-cally. Hydrogen atoms were inserted at calculated positions using ariding model, with isotropic displacement parameters.

2.3. Antibacterial activity

The potential antibacterial effects of the Hg(II) complexes wereinvestigated by disc diffusion method against three Gram positivebacteria, 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 (PTCC1079), and Serratia marcescens (PTCC 1111) [21]. The complexeswere dissolved in DMSO to a final concentration of 1 mg ml�1

and then sterilized by filtration using 0.45 lm Millipore. All testswere carried using 10 ml of suspension containing 1.5 � 108 bacte-ria/ml and spread on nutrient agar medium. Negative controlswere prepared by using DMSO. Gentamycin, Penicillin, Neomycinand Nitrofurantion were used as positive reference standards.The diameters of inhibition zones generated by the complexeswere measured.

2.4. Statistical analysis

All data, for both antibacterial tests, are the average of triplicateanalyses. Analysis of variance was performed by Excel and SPSSprocedures Statistical analysis was performed using Student’s t-test, and p value < 0.05 was regarded as significant.

2.5. Sample preparation

2.5.1. SynthesisThe room temperature reactions of HgX2 (X = Cl, Br and I) with

sulfonium ylides Y and Y0 (prepared by reacting dimethylsulfidewith an acetone solution of 2-bromo-40-nitroacetophenone and2-bromo-40-bromoacetophenon and treatment with aqueousNaOH solution) for 4 h (1:1 M ratio) in CH3OH gave the binuclearcomplexes 1–5 and polymeric complex 6. The aims of our presentwork are to describe the NMR spectroscopy and X-ray diffractionanalysis, allowing determination of the structures. X-ray qualitycrystals of the complexes 3 and 6 were grown by the direct diffu-sion of methanol in the dimethylsulfoxide solution over severaldays.

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 mixturewas stirred for 12 h. The solid product (sulfonium salt) was iso-lated by filtration, washed with ether and dried under reducedpressure. Further treatment with aqueous 10% NaOH solution ledto elimination of HBr, giving the free ligand Y [22]. IR (KBr disk):m (cm�1) 1551 (C = O) and 875 (S–C). 1H NMR (CDCl3): d (ppm)2.9 (s, 6H, S(CH3)2); 4.2 (1H, CH); 7.8 (d, 3JHH = 8.1 Hz, 2H, Ph);8.1 (d, 3JHH = 8.5 Hz, 2H, Ph). 13C NMR (CDCl3, ppm): d 28.3 (s,

S.J. Sabounchei et al. / Polyhedron 53 (2013) 1–7 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).

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 ligandY0. IR (KBr disk): m (cm�1) 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).

2.5.3. Synthesis of complex [HgCl2(Y)]2 (1)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 solidwas filtered and washed with diethyl ether. Yield 0.243 g, 98%.Anal. Calc. for Hg2Cl4O6S2N2C20H22: C, 24.18; H, 2.23. Found: C,23.92; H, 2.18%. M.p. 197–198 �C. IR (KBr disk): m (cm�1) 1641(CO) and 818 (S+–C�). 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).

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:C, 20.73; H, 1.94%. M.p. 200–201 �C. IR (KBr disk): m (cm�1) 1658(CO) and 807 (S+–C�). 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).

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 (cm�1) 1650(CO) and 803 (S+–C�). 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 (cm�1) 1647(CO) and 822 (S+–C�). 1H NMR (DMSO-d6, ppm): d 2.9 (s, 6H,S(CH3)2); 5.4 (s, 1H, CH); 7.7 (d, 3JHH = 8.1 Hz, 2H, Ph); 7.8 (d,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).

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): m (cm�1) 1646(CO) and 820 (S+–C�). 1H NMR (DMSO-d6, ppm): d 2.9 (s, 6H,

S(CH3)2); 5.4 (s, 1H, CH); 7.6 (d, 3JHH = 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).

2.5.8. 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,16.66; H, 1.62%. M.p. 181–183 �C. IR (KBr disk): m (cm�1) 1630(CO) and 814 (S+–C�). 1H NMR (DMSO-d6, ppm): d 2.8 (s, 6H,S(CH3)2); 5.2 (s, 1H, CH); 7.6 (d, 3JHH = 8.1 Hz, 2H, Ph); 7.7 (d,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).

2.6. Results and discussion

2.6.1. SpectroscopyIn the infrared spectra the m (CO) that is sensitive to complexa-

tion, occurs at 1551 and 1578 cm�1 for Y and Y0 ylides, as in thecase of other resonance stabilized ylides [8]. Coordination of theylide through carbon causes an increase in m (CO), while for O-coor-dination a decrease of m (CO) is expected. The infrared absorptionbands observed for all our complexes at about 1630–1658 cm�1

suggest coordination of the ylide through carbon atom. The m(S+–C�) which is also diagnostic of the coordination mode occursat around 848 cm�1 in Me2S+–CH2 and at about 865 cm�1 in ylides.In the present study, the m (S+–C�) values for all complexes wereshifted to lower frequencies around 814 cm�1, suggesting partialremoval of electron density from the S�C bond due to coordination[8].

The 1H NMR signals for the SCH group of all complexes areshifted 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 ambienttemperature indicates the presence of only one geometrical isomerfor all complexes as expected for C-coordination. It must be notedthat O-coordination of the ylide leads to the formation of cis andtrans 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 alower shielding was observed in [5,6,24], and is due to the changein hybridization of the ylidic carbon atom from sp2 to sp3. The 13Cchemical shifts of the CO group in the complexes are around190 ppm, relative to �181 ppm noted for the same carbon in theparent ylides, indicating decreased shielding of this carbon atomin mercury complexes. No coupling to (199Hg, 16.8% abundance,I = 1/2) was observed at room temperature in 1H and 13C NMRspectra. 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].

2.6.2. Crystal structures analysisThe molecular structures of 3 and 6 were determined through

single crystal X-ray diffraction methods. The molecular drawingof complexes 3 and 6 are shown in Figs. 1 and 2. Crystallographicdata and parameters concerning data collection and structure solu-tion and refinement are summarized in Table 1 and selected bonddistances and angles are presented in Table 2.

The binuclear structure adopted by complex 3 is in contrast tothe trinuclear structure exhibited by O-coordinated of the phos-phorus ylide (Ph3PCHC(O)Ph) complex of mercury(II) [26], but issimilar to the structure of C-coordinated dinuclear mercury(II) ha-lide complexes of the phosphorus ylides Ph3PCHC(O)OEt (EPPY)

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.

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.

4 S.J. Sabounchei et al. / Polyhedron 53 (2013) 1–7

[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–Cbond 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 thanthose of phosphorus in a phosphonium group [27,28]. However incomparison with the analogous mercury complexes with phospho-rus ylides derived from triphenylphosphonium (Table 2), the p–doverlap of the phosphonium group appears to be more pronouncedthan that with the dimethyl sulfonium groups incorporated intoylides Y and Y0. This inversion is quite likely due to the differencein functional groups (alkyl vs. aryl) attached to the positive atom.So the dimethyl sulfonium ylides are more basic than the triphenylphosphonium ylides, which is evident from the shorter Hg–C bondlengths in sulfonium ylides complexes compared with the equiva-lent distances in the phosphorus analogs (Table 2). The terminalHg–I bond length is very similar to that of found in phosphorusanalog. The two bridging Hg–I bonds are very similar, in contrastto 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 varyfrom 90.692(11)� to 128.91(13)�, indicating very distorted tetrahe-dral coordination geometry. The widening of the I–Hg–C anglefrom the tetrahedral angle must be due to the higher s characterof the sp3 hybrid mercury orbitals involved in the above bondsand the formation of a strong halide-bridged between Hg atomswhich requires the internal I–Hg–I angle 90.692(11)� to be consid-erably smaller. The two mercury atoms and two bridging halidesare perfectly coplanar. The internuclear distance between mercuryatoms at the distance of 4.159 Å is less than in the phosphoniumanalog (Table 2), but these distances are much longer than thesum of Van der Waals radii (3 Å) of the two mercury atoms [29]indicating the absence of significant bonding interactions betweenthe mercury atoms in the molecular structures.

In complex 3, the nitro group is almost coplanar with the phenylring, 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 aboveC5 (and C5i lies above C7), while C6i is positioned above the centerof the phenyl ring and N1i lies vertically above C3 (Table 3). Thenitrogen and one of the oxygen atoms of the nitro group, N1 andO2, are involved in a dipole–dipole interaction with the correspond-ing atoms of the nitro group from a third molecule; the separationbeing similar to that found for p-nitrophenyl isocyanide [30]. Theseinteractions link the molecules along the [�21 �1] direction.

Table 3Short intermolecular contacts for complexes 3 and 6.

3 6

C5� � �C7a 3.385(6) H1� � �I1a 3.165C3� � �N1a 3.241(5) C1–H1 1.00C6� � �C5� � �C7a 91.3(3) C1� � �I1a 4.110(5)C2� � �C3� � �N1a 85.3(2) C1–H1...I1a 158.1O2–N1b 2.867(5) H10B� � �I1a 3.104N1–O2b 2.867(5) C10–H10B 0.98N1� � �O2� � �N1b 92.0(3) C10� � �I1a 4.047(6)O2� � �N1� � �O2b 88.0(3) C10–H10B� � �I1a 161.9H9B� � �I1c 3.129 H5� � �O1b 2.362C9–H9B 0.98 C5–H5 0.95C9–H9B� � �I1c 144.3 C5� � �O1b 3.209(6)C9� � �I1c 3.966(5) C5–H5� � �O1b 148.3H7� � �I1d 3.138 I1� � �S1c 3.7675(13)C7–H7 0.95 Hg1–I1 2.7215(4)C7–H7� � �I1d 143.8 Hg1–I1� � �S1c 125.03(2)C7� � �I1d 3.945(4) I2� � �S1d 3.6538(13)H1 � � �I2d 3.027 Hg1–I2 2.7749(4)C1–H1 1.00 Hg1–I2� � �S1d 124.52(2)C1–H1� � �I2d 152.8 Br1...Br1e 3.3751(11)C1� � �I2d 3.943(4) Br1–C6 1.897(5)

C6–Br1� � �Br1e 148.71(15)

a 1 � x, 2�y, �z 1 + x, y, z.b 2�x, 2 � y – z x, y, �1 + z.c �x, 1 – y, 1 – z �1 + x, y, �1 + z.d 1 � x, 2 � y, 1 – z x, 1/2�y, �1/2 + z.e �x, 1 � y, �1 – z.

Table 2Selected 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 2.234(6) 2.292(5) 2.229(5) I1–Hg1–I1a 90.692(11) 92.726(9)Hg1–I1 2.8817(4) 2.6846(7) 2.7749(4) S1–C1–Hg1 110.0(3) 110.8(2)Hg1–I1a 3.0336(4) 3.1924(6) 3.2390(4) I2–Hg1–I1a 103.729(13) 102.088(11)Hg1–I2 2.6775(4) 2.7900(6) 2.7215(4) C2–C1–Hg1 107.3(3) 106.3(3)C1–C2 1.496(8) 1.483(7) I2–Hg1–I1 109.779(14) 110.588(12)C1–S1 1.766(5) 1.775(5) C1–Hg1–I2 128.91(13) 123.07(13)C2–O1 1.221(7) 1.223(6) C1–Hg1–I1 111.69(13) 122.25(13)

C1–Hg1–I1a 104.27(14) 95.40(12)

See Figs. 1 and 2 for the atom numbering.Symmetry code; a: 1 � x, 1 � y, 2 � z (3), x, 1/2�y, 1/2 + z (6).

S.J. Sabounchei et al. / Polyhedron 53 (2013) 1–7 5

Additional C–H� � �I interactions link the molecules into a 3Darrangement.

The X-ray analysis for complex 6 reveals the coordination of theligand through the carbon atom. The Hg(II) atom is located in a dis-torted tetrahedral environment with one C, one terminal I and twobridging I atoms, resulting in a one-dimensional polymeric chain.The terminal Hg–I bond distance 2.7215(4) Å is comparable tothose of 2.706(1) Å found in a [{HgI2[PPh2CH2CH2PPh2 = -C(H)C(O)Ph]}n [31]. The asymmetric bridging nature of the othertwo iodo ligands is indicated by the two bridging different Hg–Idistances of 2.7749(4) and 3.2390(4) Å. The latter distance beingrather long, indicates a weak bridging Hg–I interaction. The bondangles around Hg atom (Table 2) indicate a severe distortion fromideal tetrahedral geometry. The deviation of atom Hg1 from thebest least-squares plane defined by atoms I1, I2 and C1, is only0.297 Å. This is comparable to the previous observations in thecomplexes and [31] and [HgX2{Ph2PCH2CH2P(O)-Ph2}]n (X = Br, I)[32] where a weak coordination of the one of the ligands lead toa 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–H� � �I and C–H� � �O hydrogen bonds, S� � �I interactions(comparable to those found in sulfur iodoform [33]) and Br� � �Brinteractions (comparable to those observed in [34,35]) link thesechains into a 3D arrangement.

Since the halide-bridged bonds in the complexes containingchloride and bromide are shorter and stronger than iodine species[26], it seems the bridge splitting only occurs in the longer andweaker iodo bonds of complex 6 and complexes 2–5 are binuclearstructures similar to complex 3.

The adaptation of these structures in Hg(II) ylide complexesmay be explained both by the preference of Hg(II) for four coordi-nation and the stability of the 18 electron configuration aroundHg(II).

2.6.3. Antibacterial activityThe 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 thetested samples to those of reference antibiotics, the inhibitory po-tency of the tested complexes were found to be remarkable (Table6). 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 groupsexerts a number of changes on antibacterial activity of the testedcomplexes. Generally antibacterial activity of compounds is attrib-uted mainly to its major components. However, today it is knownthat the synergistic or antagonistic effect of one compound in min-

or percentage of mixture has to be considered [36–38]. Also, wecan consider that the coordination may facilitate the ability of acomplex to cross the lipid layer of the bacterial cell membraneand in this way may be effected the mechanisms of growth anddevelopment of bacteria [39,40]. The above results indicate thatthe 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

The present study describes the synthesis and characterizationof some mercury (II) complexes of ambidentate sulfonium ylides.On the basis of the physico-chemical and spectroscopic data isclear 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 binuclearstructure for complex 3 similar to that observed for phosphoniumanalog and a zig-zag polymer chain for complex 6 that is quitenew. It seems the bridge splitting only occurs in the longer andweaker iodo bridges of complex 6. The complex 6 is the firstone-dimensional polymer mercury complex of an a-keto stabilizedsulfonium ylide to be observed. A comparison of important bondlengths reveals a significant difference between the Hg–C bond

Table 4Antibacterial activities of [HgX2(Me2SCHC(O)C6H4-p-NO2)]2 (X = Cl (1), Br (2), I (3)).

Microorganism Inhibition zone (mm)

Concentration (1 mg ml�1) Concentration (0.1 mg ml�1) Concentration (0.01 mg ml�1)

1 2 3 1 2 3 1 2 3

P. vulgaris (�) 17 ± 0.28a 16 ± 0.22a 12 ± 0.18a 15 ± 0.36b 10 ± 0.24b 10 ± 0.32b 10 ± 0.28c 7 ± 0.00c 8 ± 0.14c

E. coli (�) 21 ± 0.64a 20 ± 0.34a 19 ± 0.15a 18 ± 0.14b 12 ± 0.18b 14 ± 0.26b 12 ± 0.34c 7 ± 0.16c 7 ± 0.00c

B .cereus (+) 22 ± 0.58a 22 ± 0.45a 20 ± 0.33a 13 ± 0.11b 10 ± 0.18b 13 ± 0.14b 8 ± 0.14c 7c ± 0.24c 7 ± 0.00c

S. aureus (+) 25 ± 0.26a 22 ± 0.55a 25 ± 0.33a 18 ± 0.16b 11 ± 0.25b 12 ± 0.16b 11 ± 0.25c Na 7 ± 0.11c

B. megaterium (+) 20 ± 0.22a 15 ± 0.18a 19 ± 0.38a 16 ± 0.24b 8 ± 0.00b 7 ± 0.11b 7 ± 0.00c 7 ± 0.00c NaS. marcescens (�) 14 ± 0.12a 11 ± 0.14a 11 ± 0.44a 11 ± 0.24b 9 ± 0.14b 9 ± 0.22b 10 ± 0.18c Na Na

Experiment was performed in triplicate and expressed as mean ± SD. Values with different superscripts within each column (for any bacteria in different concentrations) aresignificantly different (P < 0.05).Na, no active.

Table 5Antibacterial 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 (�) 17 ± 0.18a 16 ± 0.25a 17 ± 0.56a 10 ± 0.24b 10 ± 0.16b 11 ± 0.36b Na 7 ± 0.26c 9 ± 0.12c

E. coli (�) 21 ± 0.34a 20 ± 0.33a 20 ± 0.44a 15 ± 0.46b 10 ± 0.14b 10 ± 0.28b 13 ± 0.28c 7 ± 0.14c 7 ± 0.00c

B. cereus (+) 15 ± 0.26a 22 ± 0.33a 22 ± 0.66a 10 ± 0.26b 10 ± 0.11b 14 ± 0.18b Na 7 ± 0.00c 8 ± 0.22c

S. aureus (+) 25 ± 0.66a 22 ± 0.43a 25 ± 0.48a 10 ± 0.15b 10 ± 0.22b 13 ± 0.15b 7 ± 0.15c 8 ± 0.00c NaB. megaterium (+) 22 ± 0.54a 20 ± 0.38a 21 ± 0.25a 16 ± 0.36b 10 ± 0.33b 10 ± 0.34b 7 ± 0.00c 8 ± 0.18c 7 ± 0.14c

S. marcescens (�) 14 ± 0.15a 14 ± 0.22a 12 ± 016a 10 ± 0.22b 10 ± 0.14b 9 ± 0.15b 8 ± 0.24c 7 ± 0.14c 8 ± 0.16c

Experiment was performed in triplicate and expressed as mean ± SD. Values with different superscripts within each column (for any bacteria in different concentrations) aresignificantly different (P < 0.05).Na, no active.

Table 6Antibacterial activity of antibiotics as positive controls and DMSO solve as negative control.

Microorganism Inhibition zone (mm)

Positive controls Negative controls

Gentamaicen Penicillin Nitrofurantion Neomycin DMSO

P. vulgaris (�) 30 ± 0.14 Na 15 ± 0.22 22 ± 0.16 NaE. coli (�) Na Na 25 ± 0.22 20 ± 0.33 NaB. cereus (+) 25 ± 0.18 Na 10 ± 0.12 20 ± 0.36 NaS. aureus (+) 35 ± 0.24 Na 30 ± 0.34 25 ± 0.45 NaB. megaterium (+) 25 ± 0.33 Na 20 ± 0.28 20 ± 0.55 NaS. marcescens (�) 27 ± 0.18 Na 18 ± 0.14 22 ± 0.28 Na

Experiment was performed in triplicate and expressed as mean ± SD.Na, no active.

6 S.J. Sabounchei et al. / Polyhedron 53 (2013) 1–7

lengths that is attributed to Lewis basicity of dialkylsulfoniumylide ligands versus triarylphosphonium ylide ligands. Resultsfrom the present study clearly demonstrate that the complexes ex-hibit significant antibacterial activity, which may help to informthe design of improved antibacterial agents.

Acknowledgements

We are grateful to the Bu-Ali Sina University for a grant and Mr.Zebarjadian for recording the NMR spectra. F. Akhlaghi B. thanksthe University of Melbourne for hosting her as an exchange visitor.

Appendix A. Supplementary data

CCDC 881005 and 881003 contains the supplementary crystal-lographic data for complexes 3 and 6. These data can be obtainedfree of charge via http://www.ccdc.cam.ac.uk/conts/retriev-ing.html, or from the Cambridge Crystallographic Data Centre, 12

Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223 336 033; ore-mail: deposit@ccdc.cam.ac.uk. Supplementary data associatedwith 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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