Synthesis, spectroscopic properties, X-ray single crystal analysis and antimicrobial activities of organotin(IV) 4-(4-methoxyphenyl)piperazine-1- carbodithioates

Article abstract of DOI:10.1016/j.ica.2011.06.055

A series of mononuclear organotin(IV) complexes of the types, R ₃SnL {R = C₄H₉ (1), C₆H₁₁ (2), CH₃ (3) and C₆H₅ (4)}, R₂SnClL {R = C₄H₉

Full text of DOI:10.1016/j.ica.2011.06.055

Inorganica Chimica Acta 376 (2011) 381–388
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Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Synthesis, spectroscopic properties, X-ray single crystal analysis
and antimicrobial activities of organotin(IV) 4-(4-methoxyphenyl)piperazine-1-
carbodithioates
b
c
Zia-ur-Rehman a,b, Niaz Muhammad a, Saqib Ali a, , Ian S. Butler , Auke Meetsma
⇑
a Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan
b Department of Chemistry, McGill University, 801 Sherbrooke St. West, Montreal, Quebec, Canada H3A2K6
c Crystal Structure Center, Chemical Physics, Zernike, Institute for Advanced Materials, University of Groningen, Nijenborgh 4, NL-9747 AG Groningen, The Netherlands
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of mononuclear organotin(IV) complexes of the types, R3SnL {R = C4H9 (1), C6H11 (2), CH3 (3) and
C6H5 (4)}, R2SnClL {R = C4H9 (5), C2H5 (7) and CH3 (9)} and R2SnL2 {R = C4H9 (6), C2H5 (8) and CH3 (10)},
have been synthesized, where L = 4-(4-methoxyphenyl)piperazine-1-carbodithioate. The ligand-salt and
the complexes have been characterized by Raman, FT-IR and multinuclear NMR (1H, 13C and 119Sn) spec-
troscopy and elemental microanalysis (CHNS). The spectroscopic data substantiate coordination of the
ligands to the organotin moieties. The structures of complexes 4 and 6 have been determined by sin-
gle-crystal X-ray diffraction and illustrate the asymmetric bidentate bonding of the ligand. The packing
Received 25 November 2009
Received in revised form 19 May 2011
Accepted 30 June 2011
Available online 12 July 2011
Keywords:
4-(4-Methoxyphenyl)piperazine-1-
carbodithioates
Organotin(IV) complexes
NMR spectroscopy
X-ray diffraction
diagrams indicate OꢀꢀꢀH and
pꢀꢀꢀH intermolecular interactions in complex 4 and intermolecular S2CꢀꢀꢀH
interactions in complex 6, resulting in layer structures for both complexes. A subsequent antimicrobial
study indicates that the compounds are active biologically and may well be the basis for a new class
of fungicides.
Antimicrobial activities
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
approach to the development of new drugs. A judicious choice of
ligands can modulate the properties of the complexes produced.
Dithiocarboxylate ligands owe their special significance due to
their enormous industrial and biological applications as vulcaniza-
tion additives, stabilizers for PVC, fungicides, and antibacterial and
anticancer agents [1–5]. The diethyldithiocarboxylate anion,
S2CNEt2ꢁ, has found extensive clinical use as an antidote for copper
poisoning, i.e., Wilson’s disease [6], and in ameliorating nephrotox-
icity associated with platinum-based chemotherapy [7]. The anti-
bacterial effect of dithiocarboxylates was reported to arise by the
reaction of HS-groups with physiologically important enzymes by
transferring the alkyl group of the dithioester to the HS-function of
the enzyme [8]. Investigations of various types of compounds pos-
sessing aminoalkylation ability showed that substituted amino-
ethyl-N,N-dialkyldithiocarboxylates have cytostatic features
presumably via a similar mechanism proposed for antibacterial
action [9]. The study of metal complexes containing sulfur donor
ligands continues to increase at an unabated pace, chiefly because
of their close similarity to several important biomolecules, such as
amino acids and vitamins [10].The synthesis of metal complexes
with such types of active ligands is a research area of increased inter-
est to inorganic, pharmaceutical and medicinal chemists as an
As a result, metal-based dithiocarboxylates, such as ziram (zinc-
dimethyldithiocarboxylate) and zineb (zinc ethylene-1,2-bis-
dithiocarboxylate) are marketed as fungicides. These are protective
fungi cides for use on seed foliages and fruit and vegetable crops. The
recognition of the importance of Sn–S bond in biology has led to the
study of organotin compounds with dithiocarboxylates [11].
Organotin(IV) dithiocarboxylates continue to attract significant
attention, again because of their variety of biological applications,
such as fungicidal, bactericidal, insecticidal and antitumor activity
[12–15]. Moreover, the side-effects, such as localized irritation of
the skin with a mild burning sensation and redness and itching,
which are associated with commonly used fungicides has led to
the search for new fungicides that do not pose serious threats to
the environment or to human beings. The coupling of dithiocarba-
mate ligands with organotin moieties has generated interest
because of their dual structure and probable biological applications
[16]. We have shown recently that these types of complexes are
good DNA binders [17,18]. Because of the broad spectrum of biolog-
ical properties of dithiocarboxylates and organotin dithiocarboxy-
lates, we thought it would be worthwhile studying the structures
and antimicrobial activities of organotin(IV) 4-(4-methoxyphenyl)
piperazine-1-carbodithioates and report the results of this investi-
gation here.
⇑
Corresponding author. Tel.: +92 (051) 90642130; fax: +92 (051) 90642241.
E-mail address: drsa54@yahoo.com (S. Ali).
0020-1693/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2011.06.055

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Zia-ur-Rehman et al. / Inorganica Chimica Acta 376 (2011) 381–388
2.1.2.4. Triphenyltin(IV) 4-(4-methoxyphenyl)piperazine-1-carbodithi
oate (4). Yield: 78%. M.p. 136–139 °C. Anal. Calc. for C30H30N2OS2Sn:
2. Experimental
2.1. Materials and methods
C, 58.36; H, 4.90; N, 4.54; S, 10.39. Found: C, 58.22; H, 4.83; N, 4.50; S,
10.33%. Raman (cmꢁ1): 269 (Sn–S). IR (cmꢁ1): 1005
m(Sn–C), 374 m
m
(C–S), 1480 m(C–N).
Reagents, triorganotin(IV) chlorides, diorganotin(IV) dichlorides
and 4-(4-methoxyphenyl)piperazine were obtained from Aldrich
Chemical Co., while CS2 was purchased from Riedal-de Haën.
Methanol was dried before use by the literature procedure [19].
Microanalyses were performed using a Leco CHNS 932 apparatus.
Infrared spectra were recorded as KBr pellets in the range from
4000–400 cmꢁ1 on a Bio-Rad Excaliber FT-IR, model FTS 300 MX
spectrometer (USA). Raman spectra ( 1 cmꢁ1) were measured with
an InVia Renishaw spectrometer, using argon-ion (514.5 nm) and
near-infrared diode (785 nm) laser excitation. WiRE 2.0 software
was used for the data acquisition and spectra manipulations.
NMR spectra (DMSO-d6) were obtained using a Hg-300 MHz spec-
trometer (1H and 13C) and a Varian Unity 500-MHz instrument
2.1.2.5. Chlorodi-n-butyltin(IV) 4-(4-methoxyphenyl)piperazine-1-
carbodithioate (5). Yield: 71%. Sticky material. Anal. Calc. for
C
20H33N2OS2SnCl: C, 44.83; H, 6.21; N, 5.23; S, 11.97. Found: C,
44.73; H, 6.17; N, 5.20; S, 11.90%. Raman (cmꢁ1): 437
(Sn–C), 388
(C–N), 511
m
m
m
(Sn–S), 274
(Sn–C).
m m(C–S), 1483 m
(Sn–Cl). IR (cmꢁ1): 995
2.1.2.6. Di-n-butyltin(IV) bis[4-(4-methoxyphenyl)piperazine-1-carbo
dithioate] (6). Yield: 75%. M.p. 141–142 °C. Anal. Calc. for
C
32H48N4O2S4Sn: C, 50.06; H, 6.30; N, 7.30; S, 16.71. Found: C,
49.96; H, 6.23; N, 7.27; S, 16.64%. Raman (cmꢁ1): 445
(Sn–C), 376
(Sn–S). IR (cmꢁ1): 999
(C–S), 1473 (C–N), 509 (Sn–C).
m
[
119Sn; SnMe4 (ext) ref.].
m
m
m
m
2.1.2.7. Chlorodiethyltin(IV) 4-(4-methoxyphenyl)piperazine-1-carbo
dithioate (7). Yield: 81%. M.p. 84–86 °C. Anal. Calc. for
2.1.1. Synthesis of 4-(4-methoxyphenyl)piperazinium 4-(4-
methoxyphenyl)piperazine-1-carbodithioate (L-salt)
C
16H25N2OS2SnCl: C, 40.06; H, 5.25; N, 5.84; S, 13.37. Found: C,
39.99; H, 5.23; N, 5.80; S, 13.31%. Raman (cmꢁ1): 487
(Sn–C),
(C–N),
To a 30 mL methanolic solution of 1-(4-methoxyphenyl)pipera-
zine (3 g, 15.6 mmol) was added CS2 (excess) dropwise with contin-
uous stirring maintained at 0 °C for 0.5 h. The resulting white
compound formed (Scheme 1a) was filtered and thoroughly washed
with methanol and diethyl ether, and then dried under vacuum.
(Yield: 85 %). M. p. 187–189 °C. Anal. Calc. for C23H32N4O2S2: C,
59.97; H, 7.00; N, 12.16; S, 13.92. Found: C, 59.71; H, 6.91; N,
m
383
501
m
(Sn–S), 257
m m(C–S), 1481 m
(Sn–Cl). IR (cmꢁ1): 988
m
(Sn–C).
2.1.2.8. Diethyltin(IV) bis[4-(4-methoxyphenyl)piperazine-1-carbodi-
thioate] (8). Yield: 80%. M.p. 138–142 °C. Anal. Calc. for
C
28H40N4O2S4Sn: C, 47.26; H, 5.67; N, 7.87; S, 18.02. Found: C,
47.16; H, 5.61; N, 7.84; S, 17.95%. Raman (cmꢁ1): 497
(Sn–C),
397 (C–S), 1475 (C–N), 503 (Sn–C).
(Sn–S). IR (cmꢁ1): 978
12.12; S, 13.67%. Raman (cmꢁ1): 638
(C–N). IR (cmꢁ1): 1033
(C–S), 1457 m
m
(C–S), 1185
(C–N). 1H NMR (ppm):
m(C@S), 1430
m
m
m
m
m
m
m
0
2.91–2.89, 2.48–2.46 (m, 8H, H2, 2,2a, 2 a), 4.43–4.40, 3.18–3.17 (m,
´
8H, H3, 3 ,3a,3 a), 6.92–6.77 (m, 8H, Ar-H), 8.4 (s, 2H, NH2). 13C NMR
(ppm): 210.1 (C-1), 48.2, 44.3 (C-2, 20, 2a, 20a), 50.9, 50.4 (C-3, 30,
3a, 30a), 152.3, 152.1, 140.5, 140.2, 123.9, 123.4, 121.1, 121.0,
118.4, 118.3, 112.4, 112.1 (Ar-C).
0
0
2.1.2.9. Chlorodimethyltin(IV) 4-(4-methoxyphenyl)piperazine-1-car-
bodithioate (9). Yield: 82%. M.p. 166–168 °C. Anal. Calc. for
C
14H21N2OS2SnCl: C, 37.23; H, 4.69; N, 6.20; S, 14.20. Found: C,
37.13; H, 4.62; N, 6.17; S, 14.13%. Raman (cmꢁ1): 530
(Sn–C),
(C–N),
m
381
521
m
(Sn–S), 257
m m(C–S), 1485 m
(Sn–Cl). IR (cmꢁ1): 977
2.1.2. General procedure for the synthesis of complexes
m(Sn–C).
Triorganotin(IV) chloride or diorganotin(IV) dichloride in dry
methanol (30 mL) was added dropwise to a ligand-salt in dry meth-
anol (40 mL) in the appropriate molar ratio and the mixture was
refluxed for 6 h with constant stirring. The 4-(4-methoxyphenyl)-
piperazinium chloride was allowed to settle and was removed by
filtration. The filtrate was rotary evaporated to afford the desired
product, which was then recrystallized from a chloroform–ethanol
(3:2) mixture (Scheme 1b). All the complexes are air stable and
are soluble in common organic solvents.
2.1.2.10. Dimethyltin(IV) bis[4-(4-methoxyphenyl)piperazine-1-carbo
dithioate] (10). Yield: 72%. M.p. 174–176 °C. Anal. Calc. for
C
26H36N4O2S4Sn: C, 45.68; H, 5.31; N, 8.20; S, 18.76. Found: C,
45.59; H, 5.27; N, 8.16; S, 18.67%. Raman (cmꢁ1): 507
(Sn–C),
390 (C–S), 1474 (C–N), 506 (Sn–C).
(Sn–S). IR (cmꢁ1): 989
m
m
m
m
m
2.1.3. X-ray crystallographic studies
The X-ray diffraction data were collected on a Bruker SMART
APEX CCD diffractometer, equipped with a 4 K CCD detector. Data
integration and global cell refinement was performed with the pro-
gram SAINT. The program suite SAINTPLUS was used for space group
determination (XPREP). The structure was solved by Patterson meth-
od; extension of the model was accomplished by direct method
2.1.2.1. Tri(n-butyl)tin(IV) 4-(4-methoxyphenyl)piperazine-1-carbodi-
thioate (1). (Yield: 70%). M.p. 170–171 °C. Anal. Calc. for C24H42N2O
S2Sn: C, 51.71; H, 7.59; N, 5.03; S, 11.50. Found: C, 51.59, H, 7.53, N,
5.00, S, 11.43%. Raman (cmꢁ1): 471
997 (C–S), 1475 (C–N), 510
m
(Sn–C), 391
m
(Sn–S). IR (cmꢁ1):
and applied to different structure factors using the program DIRDIF
.
m
m
m(Sn–C).
All refinement calculations and graphics were performed with the
program PLUTO and PLATON package [20].
2.1.2.2. Tricyclohexyltin(IV) 4-(4-methoxyphenyl)piperazine-1-carbo
dithioate (2). Yield: 73%. M.p. 144–145 °C. Anal. Calc. for C30H48
N2OS2Sn: C, 56.69; H, 7.61; N, 4.41; S, 10.09. Found: C, 56.58; H,
2.1.4. Antibacterial activity
The synthesized compounds were tested for antibacterial
activity against five different bacterial strains including, Escherichia
coli, Salmonella typhi, Pseudomonas aeruginosa, Stephlococcus aureus,
and Streptococcus using the agar well diffusion method [21]. Strep-
tomycin was used as standard drug and the wells (6 mm in diame-
ter) were dug in the media with the help of a sterile metallic borer.
Two to eight hours old bacterial inoculums containing approxi-
mately 104–106 colony forming units (CFU)/mL were spread on
the surface of a nutrient agar with the help of a sterile cotton swab.
7.52; N, 4.37; S, 10.03%. Raman (cmꢁ1): 484
m
(Sn–C), 380
m(Sn–
S). IR (cmꢁ1): 1015
m(C–S), 1478 m(C–N), 502 m(Sn–C).
2.1.2.3. Trimethyltin(IV) 4-(4-methoxyphenyl)piperazine-1-carbodithi
oate (3). Yield: 68%. M.p. 162–164 °C. Anal. Calc. for C15H24N2O S2
Sn: C, 41.78; H, 5.61; N, 6.50; S, 14.87. Found: C, 41.64; H, 5.56;
N, 6.47; S, 14.77%. Raman (cmꢁ1): 507
m
(Sn–C), 380
m(Sn–S). IR
(cmꢁ1): 1015
m(C–S), 1474 m(C–N), 530 m(Sn–C).

Zia-ur-Rehman et al. / Inorganica Chimica Acta 376 (2011) 381–388
383
Scheme 1. (a) Numbering scheme for ligand-salt and organic moieties attached to Sn; (b) synthesis of ligand-salt and its organotin(IV) derivatives.
The recommended concentration of the test sample (1 mg/mL in
DMSO) was introduced into the respective wells. Other wells sup-
plemented with DMSO and reference antibacterial drug served as
negative and positive controls, respectively. The plates were incu-
bated immediately at 37 °C for 20 h. The activity was determined
by measuring the diameter of the inhibition zone (in mm), showing
complete inhibition. Growth inhibition was calculated with refer-
ence to the positive control.
2.1.5. Antifungal activity
The agar tube dilution protocol [21] method was employed to
test the antifungal activities of the synthesized compounds against
four different strains of fungi, using Clotrimazole as standard drug.
Stock solutions of pure compounds (200 lg/mL) were prepared in
sterilized DMSO. Sabouraud dextrose agar was prepared by mixing
Sabouraud (32.5 g), glucose agar (4%) and agar–agar (20 g) in
500 mL of distilled water followed by dissolution at 90–95 °C on

384
Zia-ur-Rehman et al. / Inorganica Chimica Acta 376 (2011) 381–388
a water bath. The media (4 mL) was dispensed into screw-capped
tubes and autoclaved at 121 °C for 15 min. Known amounts of test
compounds were added from the stock solution to non-solidified
Sabouraud agar media (50 °C). The contents of the tubes were then
solidified at room temperature and inoculated with 4 mm diame-
ter portion of inoculums derived from a 7 days old respective fun-
gal culture. For non-mycelial growth, an agar surface streak was
employed. The tubes were incubated at 27–29 °C for 7–10 days
and growth in the compound containing media was determined
by measuring the linear growth (in mm) and growth inhibition
with reference to the respective control.
In the IR spectra of organotin(IV) dithiocarbamates, two types of
bands have particular structural significance. The first lies in the
region 1450–1580 cmꢁ1, which is primarily associated with the
‘‘thioureide’’ band due to the
m
(N–CSS) vibration; the second, which
(C–S)
appears in the region 940–1060 cmꢁ1, is associated with a
m
vibration [23]. In the present study, the N–CSS band was observed
at 1457 cmꢁ1 for the ligand and was shifted appreciably (ꢂ20
cmꢁ1) upon coordination to the organotin moieties owing to the in-
crease in double bond character of the N–CSS bond [24]. This shift
may be due to electron delocalization toward the Sn center. This
suggestion is further supported by the shift of the m(N–CSS) band
The inhibition of fungal growth, expressed in percentage terms,
was determined using the Vincent equation [22]:
to still higher energies in the chlorodiorganotin derivatives owing
to the presence of the electron-withdrawing chloride group. In all
the complexes, the presence of a solitary C–S vibration indicates
bidentate coordination of the dithiocarbamato group [25].
Inhibition % ¼ 100ðC ꢁ TÞ=C
where C is the diameter of fungal growth for a control and T is the
diameter of fungal growth for the sample.
3.2. Multinuclear NMR spectra
In the 1H NMR spectra of the complexes (Table 1), the presence
of proton resonances for the ligand moiety as well as for the
organotin groups confirmed the formation of the complexes. In
every case, the ligand protons appeared as four sets of signals as
expected; two multiplets due to the piperazine moiety, a singlet
due to the methoxy protons and a multiplet in the aromatic region
due to the phenyl ring protons. The proton chemical shift assign-
ments of the methyltin derivatives (3, 9 and 10) is clear-cut from
the multiplicity pattern and the 2J [119Sn, 1H] coupling constants.
The C–Sn–C angles, calculated by applying Lockhart’s equation
[26], given in Table 3, support the tetrahedral, trigonal bipyramidal
3. Results and discussion
3.1. Vibrational spectra
In the Raman spectra of the complexes, the presence of a new
peak below 400 cmꢁ1, attributable to a
m(Sn–S) vibration, signifies
coordination of ligand to the organotin moiety. In the chlorodiorg-
anotin derivatives, an additional peak around 260 cmꢁ1 is observed,
which can be assigned to m(Sn–Cl) stretching, and suggests the sub-
stitution of one chloride group during the reactions.
Table 1
1H NMR dataa,b of complexes 1–10.
1H
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
2,20
3.20–3.14
(m)
4.35–4.31
(m)
3.15–3.12
(m)
4.36–4.33
(m)
3.19 (bs)
3.16–3.13
(m)
4.26–4.42
(m)
3.19–3.16
(m)
4.14–4.11
(m)
3.16–3.13
(m)
4.28–4.25
(m)
3.20–3.16
(m)
4.15–4.12
(m)
3.19–3.16
(m)
4.15 (bs)
3.16–3.13
(m)
4.21 (bs)
3.17 (bs)
3,30
3.19 (bs)
3.17 (bs)
Ar-H
6.92–6.80
(m)
6.91–6.83
(m)
6.90–6.81
(m)
6.93–6.84
(m)
6.90–6.81
(m)
6.92–6.83
(m)
6.92–6.82
(m)
6.91–6.82
(m)
6.91–6.82
(m)
6.91–6.79 (m)
OCH3 3.66 (s)
3.76 (s)
2.02–1.25
(m)
2.02–1.25
(m)
3.76 (s)
0.65 s
[58, 56]
–
3.78 (s)
–
3.76 (s)
1.98–1.31
(m)
1.98–1.31
(m)
1.98–1.31
(m)
0.94 (t),(7.5) 0.94 (t),(6.9)
3.77 (s)
2.12–1.38
(m)
2.12–1.38
(m)
3.76 (s)
1.84 (q)
3.77 (s)
1.85 (q),(7.8) 1.46 (s) [79]
3.76 (s)
3.66 (s)
1.03 (s)
[112, 107]
–
a
b
c
d
1.63–1.08
(m)
1.63–1.08
(m)
1.63–1.08
(m)
0.83 (t),(7.5) 2.02–1.25
(m)
7.86–7.63
(m)
7.47–7.37
(m)
7.47–7.37
(m)
1.48 (t),(7.5) 1.49 (t),(7.8)
–
–
–
2.02–1.25
(m)
–
–
2.12–1.38
(m)
–
–
–
–
–
–
aChemical shift (d) in ppm. 2J [119Sn, 1H], 3J (1H, 1H) in Hz are listed in square brackets and parenthesis, respectively. Multiplicity is given as s = singlet, d = doublet,
m = muliplet, bs = broad signal. bNumbering in accordance with Scheme 1a.
Table 2
13C and 119Sn NMR dataa,b of complexes 1–10.
13C
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
1
197.6
43.5
47.6
154.3145.1,
118.7, 115.1
199.2
50.7
51.9
154.6145,
119,114.7
55.8
201.2
45.1
50.3
154.7145.4,
119.2114.7
55.8
196.6
50.7
52.5
154.8144.7,
119.5114.8
55.8
197.4
50.6
51.8
154.8144.4,
119.3114.8
55.8
26.5 [601,
589]
28
27.5
13.9
–191.5
200.8
50.7
51.3
154.7144.9,
119.1114.8
55.8
26.6
[787, 771]
34.8
197.5
50.6
51.8
202.4
50.6
51.8
199.7
41
47.5
154.2145,
118.7115
55.8
25
[568, 547]
–
–
–
190.6
50.6
51.3
154.2144.7,
119.2114.8
55.7
2,20
3,30
Ar-C
155.4144.4, 155,144.8,
119.4,
55.7
21.5
[532, 509]
10.4
–
119.3114.8
55.7
21.5
[620, 595]
10.5
–
OCH3 55.8
a
24 [341, 315]
35
ꢁ0.6
142.4
25 [950, 937]
[337, 314]
32.3 [17]
29.5 [67]
27.2
[382, 366]
–
b
c
d
28.6 [28.4]
27 [75]
14.4
137
–
–
–
–
–
128.8
129.4
–181
28.8
14.1
–345
–
–
119Sn 31.4
–24
–26.6
–185
–217.9
–186.6
–238.7
a
Chemical shifts (d) in ppm. nJ [119Sn, 13C] in Hz are listed in square brackets.
Number in accordance with 1a.
b

Zia-ur-Rehman et al. / Inorganica Chimica Acta 376 (2011) 381–388
385
Table 3
(C–Sn–C) angles (°) based on NMR parameters of selected complexes.
Table 4
Crystal data and structure refinement parameters for compounds 4 and 6.
Compound
number
1J (119Sn, 13C)
(Hz)
2J (119Sn, 1H)
(Hz)
Angle (°)
4
6
Empirical formula
Formula mass
Crystal system
Space group
a (Å)
C
30H30N2OS2Sn
(C16H24N2OS2)2Sn
767.74
monoclinic
C2/c, 15
32.768(4)
6.9313(9)
18.877(2)
124.2004(13)
3546.0(7)
4 (0.5)
1J
2J
617.42
monoclinic
P21/n, 14
10.0253(8)
29.974(2)
10.3297(8)
117.9951(9)
2740.9(4)
4 (1)
1
2
3
5
6
7
8
9
10
341
337
382
601
787
532
620
568
950
–
106.6
106.3
110.2
129.5
145.7
123.4
131
–
58
–
–
–
–
111.4
b (Å)
c (Å)
b (°)
V (Å3)
Z (Z0)
79
112
126
160
124
164.6
Crystal size (mm)
T (K)
0.35 ꢃ 0.24 ꢃ 0.07 0.51 ꢃ 0.46 ꢃ 0.37
100(1)
24 147
6767
1.111
5418
100(1)
14 351
4040
0.99
3727
Total reflections
Independent reflections all
and octahedral environments around the Sn atoms for complexes
3, 9 and 10, respectively. The nJ [119Sn, 1H] coupling constants for
the remaining complexes could not be determined because of their
complex multiplet patterns. Trigonal bipyramidal geometry can be
proposed for the triphenyltin compound on the basis of the value
obtained for the ortho protons chemical shift minus those for the
meta and para protons [27].
l
(Mo K
a
) (mmꢁ1
)
For Fo P 4.0
R(F) = (||Fo| ꢁ |Fc||)/ |Fo| For
r
(Fo)
P
P
0.0365
0.0267
Fo > 4.0
r
(Fo)
P
wR(F2) = [ [w(Fo2 ꢁ F2c )2]/
0.0866
0.0731
P
[w(F2o )2]]1/2
Goodness-of-fit (GOF)
1.019
2.40–28.28
6767/0/326
1.077
2.65–27.48
4040/0/197
Clearly resolved 13C NMR signals were obtained for all the dis-
tinct carbon atoms present in the compounds (Table 2). In the li-
gand, the NCS2 carbon resonance appeared at about 210.1 ppm,
which then shifted upfield in the complexes by ꢂ10 ppm. The up-
field shift in the NCS2 carbon signal is an indication of deshielding
of this carbon upon complexation of the ligand to the positive Sn
center. In organotins, the coordination number of the Sn atom
can be extracted from the 1J [119Sn, 13C] coupling constant values
using Lockhart’s equation, 1J [119Sn, 13C] = 11.4h ꢁ 875, [28]. The
calculated values for complexes 1, 2 and 3 are 341, 337 and
382 Hz, respectively, characteristic of tetrahedral geometry around
Sn [29]. The geometrical assignment for the triphenyltin derivative
can be made on the basis of the 13C chemical shift of the ipso-
carbon, i.e., 142.4 ppm, which is in accord with trigonal bipyrami-
dal geometry [30]. The 1J [119Sn, 13C] coupling constants indicate
five (5 and 7–9) and six-coordinated (6 and 10) geometry around
Sn as shown in Table 3 [31,32].
h Range for data collections (°)
Data/restraints/parameters
trigonal bipyramidal geometry in solution. These data are consis-
tent with earlier reports [33].
3.3. Crystal structures of compounds 4 and 6
An ORTEP view of molecule 4, including the atom numbering
scheme, is shown in Fig. 1. Relevant bond lengths and bond angles
are collected together in Table 4, while Table 5 summarizes the
crystal data. The Sn atom is coordinated by an asymmetrically
bound ligand and the
a-carbon atoms of three phenyl groups.
The coordination environment is best described as being based
on distorted trigonal bipyramidal geometry with the sulfur atom
involved in forming the longer SnꢀꢀꢀS2 bond occupying one of the
axial positions. The geometry around Sn atom can be characterized
a)/60, where b is the largest of the basal
angles around the Sn atom. For compound 4, this angle is
The 119Sn NMR chemical shifts for complexes 1, 2 and 3 are com-
patible with tetrahedral geometry. Complexes 6 and 10 exhibited
119Sn NMR signal at ꢁ345 ppm, characteristic of a six-coordinate
Sn atom. In the rest of the complexes, the 119Sn values indicate
by the value of
s
= (b ꢁ
S2–Sn–C19 = 154.67(8)°. The second largest of the basal angles
Fig. 1. ORTEP drawing of compound 4 with atomic numbering scheme. All atoms are represented by their displacement ellipsoids drawn at the 50% probability level; hydrogen
atoms have been omitted to improve clarity.

386
Zia-ur-Rehman et al. / Inorganica Chimica Acta 376 (2011) 381–388
Table 5
Table 6
Selected bond lengths (Å) and bond angles (°) for 4.
Selected bond lengths (Å) and bond angles (°) for 6.
Sn–S1
2.4957(7)
2.144(3)
2.161(3)
1.702(3)
Sn–S2
Sn–C19
S1–C12
2.9170(8)
2.170(3)
1.758(3)
Sn–S1
2.9685(6)
2.136(3)
2.5235(6)
1.697(2)
Sn–S2
2.5235(6)
2.9685(6)
2.136(3)
1.743(2)
Sn–C13
Sn–C25
S2–C12
Sn–C14
Sn–S2_a
S1–C13
Sn–S1a
Sn–C14a
S2–C13
S1–Sn–S2
65.83(2)
90.98(8)
92.39(8)
88.14(8)
119.04(11)
94.49(9)
117.80(17)
119.9(2)
121.8(2)
125.8(2)
S1–Sn–C13
S1–Sn–C25
S2–Sn–C19
C13–Sn–C19
C19–Sn–C25
Sn–S2–C12
Sn–C13–C14
Sn–C19–C20
Sn–C25–C26
105.49(8)
129.23(9)
154.67(8)
104.09(12)
100.07(11)
81.89(10)
121.0(2)
S1–Sn–S2
64.96(1)
147.35(2)
85.61(6)
147.60(2)
104.34(6)
104.34(6)
64.96(1)
108.09(6)
94.51(7)
S1–Sn–C14
S1–Sn–S2a
S2–Sn–C14
S2–Sn–S2a
C14–Sn–S1a
C14–Sn–C14a
S1a–Sn–C14a
Sn–S1–C13
82.36(6)
147.60(2)
108.09(6)
83.01(2)
85.61(6)
136.24(8)
82.36(6)
80.88(7)
S1–Sn–C19
S2–Sn–C13
S2–Sn–C25
C13–Sn–C25
Sn–S1–C12
S1–C12–S2
Sn–C13–C18
Sn–C19–24
Sn–C25–C30
S1–Sn–S1a
S1–Sn–C14a
S2–Sn–S1a
S2–Sn–C14a
C14–Sn–S2a
S1a–Sn–S2a
S2a–Sn–C14a
Sn–S2–C13
120.0(2)
116.3(2)
sulfur atom S1 is 353.7°, a marked deviation from the ideal angle
of 360°. The unsymmetrical coordination mode of the ligand can
also be easily visualized from the two Sn–S bond lengths, the
shorter Sn–S1 distance [2.4957(7) Å] and the longer Sn–S2 one
[2.9170(8) Å], i.e., a difference of 0.421 Å. The shorter Sn–S bond
is close in length to the sum of the covalent radii of Sn and S
(2.42 Å), while the longer bond is much shorter than is the sum
of the van der Waal’s radii of the two atoms (4.0 Å). The S–C bond
lengths [S1–C12 = 1.758(3) Å and S2–C12 = 1.702(3) Å] also show
the anisobidentate nature of the ligand. The packing diagram for
complex 4 (Fig. 2) indicates that the molecules are held together
through two types of intermolecular interactions, viz., CH3OꢀꢀꢀH
around the Sn atom,
a
, for 4 is S1–Sn–C25 = 129.23(9)°. So the cal-
culated
s value for compound 4 is 0.42. Based on the value of s, the
structure is biased towards square pyramidal geometry [34]. Pre-
sumably, this occurs because of the wide S1–Sn–C25 angle, i.e.,
129.23(9)°, which involves the more tightly bound sulfur atom
and the relatively close approach of the less tightly bound sulfur
atom, i.e., 2.9170(3) Å. Therefore, the C19 atom of one phenyl
group and the S2 of the ligand moiety are in the quasi-axial posi-
tions, while the C13 and C25 atoms of the other two phenyl groups
and S1 atom are in the planar positions. The sum of the equatorial
angles involving the two a-carbons of the phenyl groups and the
Fig. 2. Packing diagram of 4 illustrating CH3OꢀꢀꢀH and pꢀꢀꢀH intermolecular interactions that are 0.1 Å less than van-der-Waals contacts of the connected atoms.
Fig. 3. ORTEP drawing of compound 6 with atomic numbering scheme. All atoms are represented by their displacement ellipsoids drawn at the 50% probability level; hydrogen
atoms have been omitted to improve clarity.

Zia-ur-Rehman et al. / Inorganica Chimica Acta 376 (2011) 381–388
387
Fig. 4. Packing diagram of compounds 6 showing intermolecular S2CꢀꢀꢀH and CH3OꢀꢀꢀH interactions that are 0.1 Å less than van-der-Waals contacts of the connected atoms.
and
p
ꢀꢀꢀH interactions. These interactions are weak and are less
dithiocarboxylate ligands are nearly coplanar but are badly dis-
torted from square-planar geometry [cis S–Sn–S angles range from
64.96(1)° to 147.60(2)°]. In both anisobidentate ligands, each short
Sn–S bond is associated with a long C–S bond and vice versa; this is
with a consequence of the bonding asymmetry of the ligands. The
bond angles subtended at the Sn atom by the methylene carbons
and S2 and S2a atoms range from 108.09(6)° to 104.34(6)° demon-
strating that the Sn–C bonds are bent toward the longer Sn-S
bonds. This is obviously a result of repulsion between the bonding
electron pairs around the central Sn atom. Electronic and steric
arguments have also been invoked to account for the distortion
of similar structures from the regular octahedral geometry. Thus,
the coordination geometry about the Sn atom in compound 6 is
best described as being distorted skew trapezoidal-bipyramidal.
The geometry and bond lengths of SnC2S4 core are comparable
than the van der Waal’s radii of the connected atoms by 0.1 Å.
The structure of compound 6 is shown in Fig. 3. Crystal data and
selected interatomic parameters are presented in Tables 4 and 6,
respectively. The Sn atom is coordinated by two butyl groups
and two 4-(4-methoxyphenyl) piperazine-1-carbodithioate li-
gands, with the latter adopting similar behavior in coordination
modes. The two dithiocarboxylate ligands are anisobidentically
chelated to Sn, with one long and one short Sn–S bond
(av = 2.9685(6) Å and 2.5235(6) Å, respectively). The longer Sn–S
distances are significantly less than is the sum of the van der
Waal’s radii (4.0 Å), and the coordination number of Sn can be
unambiguously assigned as six. The overall geometry at Sn is, how-
ever, highly distorted from trans octahedral: the C–Sn–C angle is
only 136.24(8)°, and the Sn and four NCS2 sulfur atoms of the
Table 7
Antibacterial activity data of ligand and its organotin(IV) derivatives.a,b
Bacterium
Clinical implication
Zone of Inhibition (mm)
L-salt
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
Ref. Drug
Escherichia coli
Salmonella typhi
Pseudomonas aeruginosa
Staphlococcus aureus
Streptococcus
Infection of wounds, urinary tract and dysentery
Typhoid fever, localized infection
Infection of wounds, eyes, septicemia
Food poisoning, scaled skin syndrome, endrocarditis
Strep throat
29
18
8
9
30
30
30
14
4
12
22
3
6
0
21
25
23
22
30
28
28
6
5
30
23
29
16
25
23
22
24
13
24
26
30
31
23
28
30
26
31
20
26
28
22
24
19
24
18
20
19
15
16
18
34
31
24
38
38
31
a
In vitro, agar well diffusion method, conc. 1 mg/mL of DMSO.
Reference drug, Streptomycin.
b
Table 8
Antifungal activitya of ligand and its organotin(IV) derivatives.
Sample
Tested fungi
Aspergillus nigar
Linear growth
Aspergillus flavus
Helminthosporium solani
Alternia solani
% Inhibition
Linear growth
% Inhibition
Linear growth
% Inhibition
Linear growth
% Inhibition
Controlb
L-salt
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
85
16
54
20
13
41
76
51
83
44
73
16
60
–
86
86
10
61
20
10
81
81
86
86
82
86
86
–
0.0
87
12
10
69
83
12
80
77
78
78
86
79
51
90
10
12
80
83
11
80
60
79
51
80
40
48
–
81.2
36.5
76.5
84.7
51.8
10.6
40.0
2.4
48.2
14.1
81.2
29.4
86.2
88.5
20.7
4.6
86.2
8.0
11.5
10.3
10.3
1.1
88.9
86.7
11.1
7.8
87.8
11.1
33.3
12.2
43.3
11.1
55.6
46.7
88.4
29.1
76.7
88.4
5.8
5.8
0.0
0.0
4.7
0.0
39.5
9.2
41.4
Clotrimazole
a
Concentration: 200
Control = DMSO.
lg/mL of DMSO.
b

388
Zia-ur-Rehman et al. / Inorganica Chimica Acta 376 (2011) 381–388
with those that are usually observed for most octahedral
complexes [35,36]. An analysis of the crystal packing for this
compound (Fig. 4) shows that the molecules are held together by
S2CꢀꢀꢀH and CH3OꢀꢀꢀH interactions, that are 0.1 Å less than
van-der-Waals contacts of the connected atoms. No secondary
SnꢀꢀꢀS interactions are noted, as is usually the case for monoclinic
forms of diorganotin(IV) dithiocarboxylates [12].
complexes 4 and 6 with a distorted square pyramidal and a
skew-trapezoidal geometry, respectively.
The square-pyramidal geometry is unique because this kind of
geometry is not previously reported in the literature for triphenyl-
tin(IV) derivatives. The antimicrobial activities of the complexes
are, in broad terms, excellent and far exceed the level for the li-
gand-salt. The influence of the tin is clearly visible in the antibac-
terial activity. Such a study will be helpful in designing novel
antifungal metal-based drugs.
3.4. Antibacterial and antifungal activities
Acknowledgements
The antibacterial activities of ligand-salt and complexes were
tested by agar well diffusion method [21] against five different
strains of bacteria are shown in Table 7. The ligand-salt and the
complexes exhibited good activities against the test bacteria. The
organotin derivatives are more active than is the ligand-salt. i.e.,
complexation increases the bactericidal potency. This situation
can be understood in term of chelation theory, which states that
the polarity of the metal ion is reduced upon complexation, which
results in an increase the lipophilicity of the metal complexes, thus
facilitating their ability to cross the cell membrane more easily
[37]. Among the triorganotin(IV) derivatives examined here, the
bactericidal activities of complexes 1, 3 and 4 are fairly good. Com-
plex 1 exhibited lower activity against S. aureus and Streptococcus.
Complex 2 is the least active, while complex 3 is active against all
the bacterial strains. In general, the chlorodiorganotin(IV) com-
plexes are more active than are their counterparts without chloride
substituents. The most probable reason is that chloro group might
decrease the hydrophobic character of the complexes, rendering
them biologically active [38]. In order to check the idea whether
the precursors, organotin(IV) chloride, are more or less active then
the corresponding organotin(IV) derivatives of the ligand; we se-
lect (C6H5)3SnCl, (CH3)3SnCl, (CH3)2SnCl2 and (C2H5)2SnCl2, and
screened them against E. coli. The zone of inhibition of the precur-
sors is 10, 15, 50 and 34 mm, respectively. The activity of
(C6H5)3SnCl and (CH3)3SnCl is less than their corresponding trior-
ganotin(IV) derivatives of the ligand, whereas as for the other
two precursors the case is reversed. By comparing antibacterial re-
sults of our compounds with the previously reported organotin(IV)
compounds [39,40] show the supremacy of the former.
We thank the Higher Education Commission of Pakistan and the
NSERC (Canada) for financial support.
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The present paper describes the synthesis, characterization and
antimicrobial activities of ten new organotin(IV) 4-(4-methoxy-
phenyl)piperazine-1-carbodithioates. X-ray single crystal study
proved a dimeric and a supramolecular molecular structure for