Synthesis, characterization and antibacterial activity of some new triphenyltin(IV) sulfanylcarboxylates: Crystal structure of [(SnPh 3)2(p-mpspa)], [(SnPh3)2(cpa)] and [(SnPh3)2(tspa)(DMSO)]

Article abstract of DOI:10.1016/j.jorganchem.2005.09.012

Five new triphenyltin(IV) sulfanylcarboxylates of the general formula [(SnPh₃)₂L] (L = pspa, tspa, fspa, p-mpspa or cpa, where p = 3-(2-phenyl)-, t = 3-(2-thienyl)-, f = 3-(2-furyl)-, p-mp = 3-(4-methoxyphenyl)-, spa = 2-sulfanylpropenoato and cpa = 2-cyclopentilyden-2- sulfanylacetate) have been synthesized by reacting triphenyltin(IV) hydroxide with the corresponding acid in ethanol/acetone. The complexes have been characterized by elemental analysis and mass spectrometry and by vibrational and NMR (¹H, ¹³C, ¹¹⁹Sn) spectroscopies. In the case of [(SnPh₃)₂(p-mpspa)] and [(SnPh₃) ₂(cpa)], X-ray structural studies showed that in both compounds each Sn atom is coordinated to three phenyl C atoms and to one S or O atom of the bridge ligand L. All five complexes are active against strains of Staphylococcus aureus, but are inactive against Escherichia coli and Pseudomonas aeruginosa. From a solution of [(SnPh₃)₂(tspa)] in DMSO-d₆ the new complex [(SnPh₃)₂(tspa)(DMSO)] was isolated. The single-crystal X-ray diffractometric study of this complex is also reported, showing that both Sn atoms are bridged by the tspa ligand, whereas the molecule of DMSO is coordinated to one of the tin atoms via the oxygen atom.

Full text of DOI:10.1016/j.jorganchem.2005.09.012

Journal of Organometallic Chemistry 691 (2006) 45–52
www.elsevier.com/locate/jorganchem
Synthesis, characterization and antibacterial activity of some new
triphenyltin(IV) sulfanylcarboxylates: Crystal structure of
[(SnPh3)2(p-mpspa)], [(SnPh3)2(cpa)] and [(SnPh3)2(tspa)(DMSO)]
a
b
a
c
´
´
´
Pedro Alvarez-Boo , Jose S. Casas , Marıa D. Couce , Rosa Farto ,
a
a
b,
a
*
´
´
´
´
Vanesa Fernandez-Moreira , Eduardo Freijanes , Jose Sordo , Ezequiel Vazquez-Lopez
a
Departamento de Quı´mica Inorga´nica, Universidade de Vigo, 36310 Vigo, Spain
Departamento de Quı´mica Inorga´nica, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain
b
c
Laboratorio de Microbiologı´a, Universidade de Vigo, 36310 Vigo, Spain
Received 27 July 2005; received in revised form 8 September 2005; accepted 10 September 2005
Available online 13 October 2005
Abstract
Five new triphenyltin(IV) sulfanylcarboxylates of the general formula [(SnPh3)2L] (L = pspa, tspa, fspa, p-mpspa or cpa, where p =
3-(2-phenyl)-, t = 3-(2-thienyl)-, f = 3-(2-furyl)-, p-mp = 3-(4-methoxyphenyl)-, spa = 2-sulfanylpropenoato and cpa = 2-cyclopentilyden-
2-sulfanylacetate) have been synthesized by reacting triphenyltin(IV) hydroxide with the corresponding acid in ethanol/acetone. The
complexes have been characterized by elemental analysis and mass spectrometry and by vibrational and NMR (1H, 13C, 119Sn) spectros-
copies. In the case of [(SnPh3)2(p-mpspa)] and [(SnPh3)2(cpa)], X-ray structural studies showed that in both compounds each Sn atom is
coordinated to three phenyl C atoms and to one S or O atom of the bridge ligand L. All five complexes are active against strains of
Staphylococcus aureus, but are inactive against Escherichia coli and Pseudomonas aeruginosa. From a solution of [(SnPh3)2(tspa)] in
DMSO-d6 the new complex [(SnPh3)2(tspa)(DMSO)] was isolated. The single-crystal X-ray diffractometric study of this complex is also
reported, showing that both Sn atoms are bridged by the tspa ligand, whereas the molecule of DMSO is coordinated to one of the tin
atoms via the oxygen atom.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Organotin(IV); Triphenyltin(IV); Sulfanylcarboxylato; Crystal structure; Antibacterial activity
1. Introduction
display cardiovascular activity [5]. In general, the struc-
ture–activity relationship in this kind of compounds is still
subject of controversy, but it seems been established that,
for instance, in the case of triorganotin carboxylates, those
containing trans-O2SnC3 moieties exhibit a greater biocidal
activity than those containing cis-O2SnC3 [6].
In previous work [7], we have reported the synthesis and
characterization of some organotin compounds, as well as
their biological activity. In continuing with this type of
studies, we describe in this paper the synthesis, structural
study and bacteriostatic activity of a new series of triphe-
nyltin(IV) complexes of the 3-(aryl)-2-sulfanylpropenoic
acids depicted in Scheme 1. The R groups of these acids
were chosen partly because of their possibility of modulate
The chemistry of the organotin(IV) derivatives is being
subject of study with growing interest [1], not only because
of the environmental consequences of the widespread use
of these compounds [2], but also as due to the increasingly
importance of their medical assays for bactericide and
antitumour purposes [3]. In this respect, various triorgano-
tins have been reported recently [4] to be effective against
mosquito larvae and adult mosquitoes responsible for ma-
laria and yellow fever, and also some phenyltin derivatives
*
Corresponding author.
E-mail address: qijsordo@usc.es (J. Sordo).
0022-328X/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.09.012

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P. Alvarez-Boo et al. / Journal of Organometallic Chemistry 691 (2006) 45–52
46
O
(2.DMSO), 279012 (4) and 279013 (5) contain the supple-
mentary crystallographic data for this paper. These data
can be obtained free of charge from The Cambridge Crys-
tallographic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif.
3
CH
2
C
1
R
C
OH
SH
Antibacterial activity was initially assayed by Muller-
¨
6
5
5
6
6 5
Hinton agar diffusion methods. Discs of paper 5 mm in
diameter were loaded with 20 ll of a 2 mg/ml solution of
the substance to be tested in 9:1 ethanol–water; control
discs were loaded with solvent alone. The discs were placed
7
7
4
7
4
4
R
=
8
9
O
S
H2pspa
H2tspa
H2fspa
on dishes of Muller-Hinton agar inoculated with Esche-
¨
H3CO
richia coli (CECT 101), Pseudomonas aeruginosa (CECT
110) or Staphylococcus aureus (CECT 240) and incubated
for 24 h at 37 ꢁC. The bacterial growth inhibition zones
were recovered. All the assays were carried out in duplicate.
The ligands were also assayed as negative control. For
those products which showed activity, minimum inhibitory
concentration (MIC), defined as the lowest concentration
of active compound which inhibits the growth of the tested
organism under optimal concentration, was determined
6
5
4
5
7
6
3
8
4
7
9
H2cpa
H2-p-mpspa
Scheme 1.
intermolecular interactions, and partly because of their
likely influence on the hydrophilicity and lipophilicity of
the complexes prepared, which are of great importance
for pharmaceutical activity.
using serial dilutions in Muller-Hinton broth as described
¨
in the literature [11]. A portion of 0.1 ml of nutrient broth
containing 108 cells mlÀ1 of the sensitive bacterial culture
was added to solutions of the compounds at concentrations
from 80 to 0 lg mlÀ1. Results were observed after 18 h of
incubation at 35 ꢁC. Serial dilutions of 90% ethanol were
assayed as experimental control. Minimal bactericidal con-
centration (MBC), defined as the lowest concentration of
compound that totally kills the tested bacterium, was also
2. Experimental
2.1. Methods and materials
Triphenyltin(IV) hydroxide and rhodanine (Aldrich-
Chemie) were used as supplied. Elemental analyses were
performed with a Carlo Erba 1108 apparatus. The IR spec-
tra were recorded on a Bruker IFS 66v FT-IR spectrometer,
and the Raman spectra were recorded on the same spec-
assayed by spreading with a swab on Muller-Hinton agar
¨
plates with subcultures of tubes that showed inhibitory ac-
tion. The plates were incubated for 24 h at 35 ꢁC.
2.2. Synthesis of the compounds
1
trometer using an FRA-106 accessory. H and 13C NMR
spectra were obtained in CDCl3 on a Bruker AMX300 spec-
trometer operating at 300.14 and 75.48 MHz, respectively,
and referred to SiMe4. 119Sn NMR spectra in the same sol-
vent were recorded on a Bruker AMX500 apparatus oper-
ating at 186.50 MHz, and referred to SnMe4, all of them
at room temperature. Mass spectra were recorded on a Kra-
tos MS50TC spectrometer connected to a DS90 data system
and operating under EI (70 eV, 250 ꢁC) and FAB condi-
tions (Xe, 8 eV) using as liquid matrix 3-nitrobenzyl alco-
hol. Crystallographic data were recorded at room
temperature on a Bruker CCD Smart apparatus using Mo
3-Aryl-2-sulfanylpropenoic acids were prepared by con-
densation of the appropriated aldehyde with rhodanine
[12], subsequent hydrolysis in NaOH 1 M and ulterior acid-
ification with aqueous HCl 1 M [13]. For the preparation
of 2-cyclopentilyden-2-sulfanylacetic acid, in the condensa-
tion reaction a ketone (cyclopentanone) was used instead
[14].
The complexes were synthesized by reacting the corre-
sponding acid in ethanol/acetone (1:1 v/v) with triphenyl-
tin(IV) hydroxide in the same solvent, in a donor/
acceptor 1:2 mole ratio, as indicated in Scheme 2.
˚
Ka radiation (k = 0.71073 A). An absorption correction
was made by means of the SADABS program [8], and the
structure solution was carried out using the SHELX-97 pro-
gram [9]. The DMSO molecule in 2.DMSO had a disor-
dered sulphur atom. This was modelled successfully using
two alternative sites with the same occupancy factors
(50%). Least-squares full-matrix refinements on F2 were
performed using the program SHELXL97 [9], and the illustra-
tions were obtained with the PLATON package [10]. The crys-
tal data, experimental details and refinement results are
summarized in Table 1. CCDC reference numbers 279011
2.2.1. [(SnPh3)2(pspa)] (1)
To a solution of 0.100 g (0.55 mmol) of 3-(2-phenyl)-2-
sulfanylpropenoic acid in 10 ml of ethanol/acetone (1:1 v/v),
0.407 g (1.11 mmol) of triphenyltin(IV) hydroxide dis-
solved in 10 ml of the same solvent were added. After
refluxing for 5 h the solution was concentrated to about
1/2 the original volume in a Dean-Stark apparatus. The
resulting precipitate was filtered off and dried in vacuo.
Colourless. Yield: 32%. Mp: 300 ꢁC. Anal. Calc. for
C45H36O2SSn2: C, 61.54; H, 4.13; S, 3.64. Found: C,

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P. Alvarez-Boo et al. / Journal of Organometallic Chemistry 691 (2006) 45–52
47
Table 1
Crystal and structure refinement data for complexes 2.DMSO, 4 and 5
[(SnPh3)2(tspa)(DMSO)]
[(SnPh3)2(p-mpspa)]
[(SnPh3)2(cpa)]
Empirical formula
Formula weight
Crystal system
C
962.33
Triclinic
45H40O3S3Sn2
C46H38O3SSn2
908.20
Triclinic
C43H38O2SSn2
856.17
Monoclinic
P2(1)/c
ꢀ
ꢀ
Space group
P1
P1
Unit cell dimensions
˚
a (A)
11.1262(7)
12.1475(8)
18.5999(13)
95.2370(10)
97.8690(10)
117.2200(10)
2180.4(3)
10.448(2)
10.968(2)
18.864(4)
105.791(5)
97.519(5)
102.734(5)
1986.5(8)
2
1.518
1.349
17.8683(13)
18.6039(14)
11.4215(9)
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
90.305(2)
3
˚
Volume (A )
3796.7(5)
4
1.498
1.405
1712
Z
2
Calculated density (Mg mÀ3
Absorption coefficient (mmÀ1
F(000)
)
1.466
1.326
964
)
908
Crystal size (mm)
(h) Range for data collection(ꢁ)
Index ranges
0.30 · 0.25 · 0.22
1.91–28.02
À13 6 h 6 14
À15 6 k 6 9
À24 6 l 6 24
12804
0.12 · 0.17 · 0.25
1.97–28.19
À13 6 h 6 13
À14 6 k 6 13
À24 6 l 6 18
11009
0.04 · 0.16 · 0.22
1.58–28.04
À19 6 h 6 23
À24 6 k 6 23
À15 6 l 6 13
20653
Reflections collected
Independent reflections
Completeness to h = 28.19ꢁ
Absorption correction
Maximum and minimum transmission
Refinement method
8948 [Rint = 0.0261]
84.8%
None
1.000/0.811
Full-matrix least-squares on F2
8948/0/439
0.903
7734 [Rint = 0.0871]
79.2%
8470 [Rint = 0.0803]
Multi-scan
1.000/0.602
Full-matrix least-squares on F2
7734/0/458
0.791
Semi-empiric
1.000/0.841
Full-matrix least-squares on F2
8470/0/433
Data/restraints/parameters
Goodness-of-fit on F2
0.564
Final R indices [I > 2(r)(I)]
R1 = 0.0616
wR2 = 0.1660
R1 = 0.1184
wR2 = 0.1865
1.680 and À1.143
R1 = 0.0814
wR2 = 0.1841
R1 = 0.2160
wR2 = 0.2234
2.400 and À1.274
R1 = 0.0417
wR2 = 0.0900
R1 = 0.1644
wR2 = 0.1451
0.474 and À0.331
R indices (all data)
À3
˚
Largest difference peak and hole (e A
)
Co, 122.9 Cm, 123.7 Cp. 119Sn NMR (CDCl3):
d
O
O
(ppm) = À94.6 (s); À121.3 (s).
EtOH/acet.
(1:1 v/v)
OH
R
+ 2SnPh3OH
OSnPh3
R
2.2.2. [(SnPh3)2(tspa)] (2)
SH
SSnPh3
To a solution containing 0.100 g (0.54 mmol) of 3-(2-thi-
enyl)-2-sulfanylpropenoic acid in 10 ml of ethanol/acetone
(1:1 v/v), 0.395 g (1.08 mmol) of triphenyltin hydroxide in
10 ml of the same solvent were added. The resulting orange
solution was refluxed for 5 h in a Dean-Stark apparatus.
After stirring for a further 12 h term a solid was formed;
this was filtered off and dried in vacuo. Colour: yellow.
Yield: 30%. Mp: 300 ꢁC. Anal. Calc. for C43H34O2S2Sn2:
C, 58.41; H, 3.88; S, 7.25. Found: C, 57.03; H, 3.81; S,
7.01%. The main signals in the EI spectrum are at m/z
(ion, intensity): 351 [SnPh3]+ (100); 274 [SnPh2]+ (22);
197 [SnPh]+ (96); 120 [Sn]+ (76). Apart from these signals,
the EI spectrum shows signals for H2tspa and its fragments
and the FAB spectrum shows the same metallated signals
and another one at 655 [M-3Ph]+ (27%). IR (Raman)
(cmÀ1): 1590s, masym(CO2); 1333s (1333s), msym(CO2); 272s,
Scheme 2.
61.23; H, 3.84; S, 3.55%. The main signals in the EI spec-
trum are at m/z (ion, intensity): 351 [SnPh3]+ (94); 274
[SnPh2]+ (37); 197 [SnPh]+ (100); 120 [Sn]+ (93%). Besides
these signals the EI spectrum shows signals for H2pspa and
its fragments and the FAB spectrum shows the same met-
allated signals and another one at 801 [M-Ph]+ (2%).
IR (Raman) (cmÀ1): 1595s, masym(CO2); 1330s (1331w),
m
sym(CO2); 280w, masym(Sn–C); 235w (235w), msym(Sn–C);
390m, m(Sn–S); 446m, m(Sn–O). [masym(CO2) À msym
1
(CO2)] = 265. H NMR (CDCl3): d (ppm) = 8.04 (s, 1H,
C(3)H); 8.09 (d, 2H, C(5)H); 7.41 (t, 2H, C(6)H); 7.29 (t,
1H, C(7)H); 7.47–7.00 (m, 12H, Pho); 7.36–7.32 (m, 18H,
Phm,p). 13C NMR (CDCl3): d (ppm) = 134.1 C(2), 131.2
C(3), 136.9 C(4), 125.0 C(5), 125.6 C(6), 123.3 C(7), 131.2
m
asym(Sn–C); 234m, msym(Sn–C); 343m (341w), m(Sn–S);
1
445s (447w), m(Sn–O). [masym(CO2) À msym(CO2)] = 257. H

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P. Alvarez-Boo et al. / Journal of Organometallic Chemistry 691 (2006) 45–52
48
NMR (CDCl3): d (ppm) = 8.27 (s, 1H, C(3)H); 7.59 (d, 1H,
C(5)H); 7.11 (d, 1H, C(6)H); 7.74 (s, 1H, C(7)H); 7.50
(m, 12H, Pho); 7.36 (m, 18H, Phm,p). 13C NMR (CDCl3):
d (ppm) = 173.1 C(1), 126.1 C(2), 122.9 C(3), 140.4
C(4), 132.4 C(5), 127.8 C(6), 128.8 C(7), 141.4 Ci, 136.4
Co [2J(119Sn–13C), 42.6 Hz], 128.6 Cm [3J(119Sn–13C), 63.8
Hz], 130.1 Cp. 119Sn NMR (CDCl3): d (ppm) = À98.4 (s);
À109.8 (s).
the EI spectrum shows signals for H2-p-mpspa and its frag-
ments and the FAB spectrum shows the same metallated
signals and another one at 120 [Sn]+ (11%). IR (Raman)
(cmÀ1): 1586s, masym(CO2); 1327s (1328s), msym(CO2);
274m, masym(Sn–C); 236m (238w), msym(Sn–C); 356w,
m(Sn–S); 453s, m(Sn–O). [masym(CO2) À msym (CO2)] = 259.
1H NMR (CDCl3): d (ppm) = 8.05 (d, 1H, C(3)H); 8.07
(d, 1H, C(5)H); 7.21 (d, 2H, C(6)H); 3.80 (s, 3H, OCH3);
7.48 (m, 12H, Pho); 7.33 (m, 18H, Phm,p). 13C NMR
(CDCl3): d (ppm) = 173.9 C(1), 137.3 C(2), 142.2 C(3),
132.7 C(4), 130.2 C(5), 113.6 C(6), 159.9 C(7), 55.3
OCH3, 136.7 Ci, 136.4 Co [2J(119Sn–13C), 45.1 Hz], 128.2
Cm, 128.7 Cp. 119Sn NMR (CDCl3): d (ppm) = À96.9 (s);
À121.6 (s).
From a DMSO-d6 solution of a fraction of this product
suitable crystals for X-ray diffraction were obtained. The
structural study by single-crystal X-ray diffraction showed
this solid to be the new and unexpected complex 2.DMSO
where a DMSO molecule is attached to one Sn atom via the
oxygen atom.
2.2.3. [(SnPh3)2(fspa)] (3)
2.2.5. (SnPh3)2(cpa)] (5)
To the brown solution obtained by adding 0.100 g
(0.59 mmol) of 3-(2-furyl)-2-sulfanylpropenoic acid to
10 ml of a mixture ethanol/acetone (1:1 v/v), 0.432 g
(1.18 mmol) of triphenyltin hydroxide in 10 ml of the same
solvent were added. By refluxing for 4 h in a Dean-Stark
apparatus, the azeotropic mixture was eliminated, after
which the solution was stirred for 12 h. The resulting solid
was filtered off and vacuum dried. Colour: brown. Yield:
32%. Mp: 178 ꢁC. Anal. Calc. for C43H34O3SSn2: C,
59.49; H, 3.95; S, 3.69. Found: C, 58.22; H, 3.86; S,
3.66%. The main signals in the EI spectrum are at m/z
(ion, intensity): 351 [SnPh3]+ (93); 274 [SnPh2]+ (29); 197
[SnPh]+ (96); 120 [Sn]+ (91). Besides these signals the EI
spectrum shows signals for H2fspa and its fragments and
the FAB spectrum shows the same metallated signals.
IR (Raman) (cmÀ1): 1590s, masym(CO2); 1335s (1337m),
To 0.050 g (0.32 mmol) of 2-cyclopentilyden-2-sulfanyl-
acetic acid solved in 10 ml of ethanol/acetone (1:1 v/v),
0.232 g (0.64 mmol) of triphenyltin hydroxide in 10 ml of
the same solvent were added. After 12 h stirring, the yellow
suspension was refluxed for a further 5 h and concentrated
by means of a Dean-Stark apparatus to 1/2 the original
volume. The formed solid was filtered off and vacuum
dried. From the mother liquor crystals suitable for X-ray
analysis were separated. Colourless. Yield: 36%. Mp:
211 ꢁC. Anal. Calc. for C43H38O2SSn2: C, 60.32; H, 4.47;
S, 3.74. Found: C, 59.85; H, 4.77; S, 3.31%. The main sig-
nals in the EI spectrum are at m/z (ion, intensity): 351
[SnPh3]+ (100); 274 [SnPh2]+ (11); 197 [SnPh]+ (47); 120
[Sn]+ (19). Besides these signals the EI spectrum shows sig-
nals for H2(fspa) and its fragments and the FAB spectrum
shows the same metallated signals and another one at 781
[M-Ph]+ (62%). IR (Raman) (cmÀ1): 1594s, masym(CO2);
m
sym(CO2); 273m, masym(Sn–C); 236m (236w), msym(Sn–C);
353m (352w), m(Sn–S); 450m (473w), m(Sn–O). [masym
1346s,
m
sym(CO2); 272s,
masym(Sn–C); 237m (239w),
1
(CO2) À msym (CO2)] = 255. H NMR (CDCl3): d (ppm) =
m
m
sym(Sn–C); 360m, m(Sn–S); 446s, m(Sn–O). [masym(CO2) À
1
8.05 (d, 1H, C(3)H); 7.58 (d, 1H, C(5)H); 7.33 (d, 1H,
C(6)H); 7.61 (d, 1H, C(7)H); 7.51 (m, 12H, Pho); 7.39 (m,
18H, Phm,p). 13C NMR (CDCl3): d (ppm) = 172.7 C(1),
126.6 C(2), 123.6 C(3), 142.0 C(4), 129.3 C(5), 127.8 C(6),
128.7 C(7), 143.1 Ci, 136.3 Co [2J(119Sn–13C), 43.0 Hz],
128.4 Cm [3J(119Sn–13C), 58.6 Hz], 130.1 Cp. 119Sn NMR
(CDCl3): d (ppm) = À93.1 (s); À122.1 (s).
sym(CO2)] = 248. H NMR (CDCl3): d (ppm) = 2.65 (m,
4H, C(4)2H); 1.60 (m, 4H, C(5)2H); 1.60 (m, 4H,
C(6)2H); 2.65 (m, 4H, C(7)2H); 7.48 (m, 12H, Pho); 7.34
(m, 18H, Phm,p). 13C NMR (CDCl3): d (ppm) = 166.6
C(1), 129.9 C(2), 138.2 C(3), 38.4 C(4), 27.7 C(5), 25.7
C(6), 36.4 C(7), 141.1 Ci, 136.8 Co [2J(119Sn–13C),
48.0 Hz], 128.8 Cm [3J(119Sn–13C), 58.7 Hz], 128.4 Cp.
119Sn NMR (CDCl3): d (ppm) = À99.1 (s); À109.7 (s).
2.2.4. [(SnPh3)2(p-mpspa)] (4)
From 0.100 g (0.48 mmol) of 3-(4-methoxyphenyl)-2-
sulfanylpropenoic acid solved in 10 ml of ethanol/acetone
(1:1 v/v) and 0.349 g (0.96 mmol) of triphenyltin hydroxide
in 10 ml of the same solvent a yellowish solution was
formed. After 12 h stirring the solution was refluxed for
5 h in a Dean-Stark apparatus and reduced in volume to
ca. 10 ml. The formed solid was filtered off, and the filtrate
was air-evaporated, yielding crystals suitable for X-ray
analysis. Colour: yellow. Yield: 34%. Mp: 184 ꢁC. Anal.
Calc. for C46H38O3SSn2: C, 60.83; H, 4.22; S, 3.53. Found:
C, 60.35; H, 3.83; S, 3.42%. The main signals in the EI
spectrum are at m/z (ion, intensity): 351 [SnPh3]+ (100);
274 [SnPh2]+ (12); 197 [SnPh]+ (16). Besides these signals
3. Results and discussion
3.1. X-ray studies
3.1.1. Structure of 2.DMSO
Fig. 1 shows an ORTEP representation of the molecular
structure for this complex, and selected bond distances and
angles are listed in Table 2.
The asymmetric unit contains two metal centres, each
one of them surrounded by 5 atoms in a distorted trigo-
nal-bipyramidal environment, where the tspa ligand acts
as a bridge between the two metal atoms: as an O-donor
ligand with respect to Sn(2) and as an S,O-donor chelating

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P. Alvarez-Boo et al. / Journal of Organometallic Chemistry 691 (2006) 45–52
49
tions in the bipyramid. So that, the C(131)–Sn(1)–O(2)
[166.5(2)ꢁ] and the S(1)–Sn(1)–O(2) [74.91(13)ꢁ] angles have
values quite different from the theoretically expected 180ꢁ
and 90ꢁ, respectively.
Regarding the two Sn–O bond lengths between the
bridge ligand and both metal centres, their values are
˚
˚
2.453(5) A for Sn(1)–O(2), and 2.137(5) A for Sn(2)–O(1),
˚
whereas the sum of the covalent radii is 2.13 A [15]. As ex-
pected, the oxygen atom more weakly bound to Sn is closer
˚
to C than the other one [1.237(8) vs. 1.283(8) A]. The Sn–C
bond lengths, on the other hand, are unremarkable, being
all of them in the range found for other compounds of this
˚
type and close to the sum of the covalent radii (2.17 A). Fi-
nally, the oxygen atom [O(2)] attached to Sn(1) is located at
˚
3.382(5) A from Sn(2); although the sum of the van der
˚
Waals radii is 3.70 A, that value is out of the range
reported as corresponding to an Sn–O bond [2.263(6)–
3.071(2) A] [16]. Nevertheless, the existence of a weak inter-
action between both atoms (which would be responsible of
the previously discussed slight distortion of the Sn bipyra-
midal environment) cannot be discarded.
Fig. 1. Molecular structure of complex 2.DMSO. Ellipsoids at 30%
probability.
˚
Table 2
˚
Selected bond lengths (A) and angles (ꢁ) for 2.DMSO
Bond
Angle
3.1.2. Structure of [(SnPh3)2(p-mpspa)] (4)
Sn(1)–C(121)
Sn(1)–C(111)
Sn(1)–C(131)
Sn(1)–S(1)
Sn(1)–O(2)
Sn(2)–C(211)
Sn(2)–C(221)
Sn(2)–O(1)
Sn(2)–C(231)
Sn(2)–O(1D)
O(2)–C(1)
2.131(8)
2.146(7)
2.187(8)
2.439(2)
2.453(5)
2.105(10)
2.122(8)
2.137(5)
2.177(6)
2.321(7)
1.237(8)
1.283(8)
3.382(5)
C(121)–Sn(1)–C(111)
C(121)–Sn(1)–C(131)
C(111)–Sn(1)–C(131)
C(121)–Sn(1)–S(1)
C(111)–Sn(1)–S(1)
C(131)–Sn(1)–S(1)
C(121)–Sn(1)–O(2)
C(111)–Sn(1)–O(2)
C(131)–Sn(1)–O(2)
S(1)–Sn(1)–O(2)
C(211)–Sn(2)–C(221)
C(211)–Sn(2)–O(1)
C(221)–Sn(2)–O(1)
C(211)–Sn(2)–C(231)
C(221)–Sn(2)–C(231)
O(1)–Sn(2)–C(231)
C(211)–Sn(2)–O(1D)
C(221)–Sn(2)–O(1D)
O(1)–Sn(2)–O(1D)
C(231)–Sn(2)–O(1D)
115.2(3)
104.0(3)
102.4(3)
121.5(2)
115.2(2)
92.3(2)
79.9(2)
87.1(2)
166.5(2)
74.91(13)
119.5(4)
95.2(3)
Fig. 2 shows an ORTEP representation of this complex,
and Table 3 lists some selected bond lengths and angles.
The asymmetric unit contains two SnPh3 moieties bridged
by the p-mpspa ligand. Each Sn atom is surrounded by
three phenyl C atoms and one atom of the bridge ligand:
the oxygen atom O(1) is bound to Sn(2), and the sulphur
atom (S) to Sn(1). Moreover, the O(2) atom is separated
˚
˚
by 2.914(9) A from Sn(2) and 2.556(9) A from Sn(1).
Although neither of these interactions may be considered
to represent a strong bonding interaction, these distances
are short enough [16] to make this oxygen atom stereo-
chemically active around the two Sn atoms, and so that
responsible for the resulting geometry in both cases, which
compares with a trigonal bipyramid rather than a tetrahe-
dron. In fact, the coordination sphere around Sn(2) may be
thought to be formed by the O(2) atom of the ligand in one
O(1)–C(1)
Sn(2)–O(2)
98.5(3)
115.3(3)
121.9(3)
94.1(2)
87.2(4)
84.8(3)
174.2(3)
80.1(4)
ligand in its attachment to Sn(1). So that, the coordination
polyhedron around Sn(2) is formed by 2 oxygen atoms
(from DMSO and tspa, respectively) located on the apical
positions of the bipyramid, and 3 phenyl carbon atoms in
the equatorial sites. A considerable distortion arises from
the presence of the bridge ligand, as indicated by the
O(1)–Sn(2)–O(1D) angle value [174.2(3)ꢁ instead of the ex-
pected 180ꢁ]. In the same way, the bond angles in the equa-
torial plane take values slightly different from 120ꢁ
[115.3(3), 121.9(3), 119.5(4)ꢁ], whereas the angles between
the apical positions and the equatorial plane have values
such as 80.1(4) or 98.5(3)ꢁ.
The polyhedron around Sn(1) is even more distorted, as
expected from the presence of the tspa chelating ligand, the
sulfanyl S(1) atom of which is located in the equatorial plane,
occupying the carboxylic O(2) atom one of the apical posi-
Fig. 2. Molecular structure of complex 4. Ellipsoids at 30% probability.

´
P. Alvarez-Boo et al. / Journal of Organometallic Chemistry 691 (2006) 45–52
50
Table 3
˚
Selected bond lengths (A) and angles (ꢁ) for complex 4
Bond
Angle
Sn(2)–C(211)
Sn(2)–O(1)
Sn(2)–C(221)
Sn(2)–C(231)
Sn(2)–O(2)
O(1)–C(1)
2.110(9)
2.064(8)
2.082(15)
2.120(15)
2.914(9)
1.289(14)
1.240(14)
2.133(15)
2.139(15)
2.164(14)
2.441(4)
2.556(9)
C(221)–Sn(2)–O(2)
C(231)–Sn(2)–O(2)
C(211)–Sn(2)–C(231)
O(1)–Sn(2)–C(231)
C(221)–Sn(2)–C(231)
C(211)–Sn(2)–O(2)
O(1)–Sn(2)–O(2)
C(211)–Sn(2)–O(1)
C(211)–Sn(2)–C(221)
O(1)–Sn(2)–C(221)
C(131)–Sn(1)–C(121)
C(131)–Sn(1)–C(111)
C(131)–Sn(1)–O(2)
C(131)–Sn(1)–S
77.8(4)
85.4(5)
111.8(5)
102.4(5)
111.8(6)
146.6(3)
48.9(3)
O(2)–C(1)
Sn(1)–C(131)
Sn(1)–C(111)
Sn(1)–C(121)
Sn(1)–S
99.0(4)
115.0(5)
115.5(4)
116.0(5)
103.1(6)
85.4(5)
116.4(4)
169.0(4)
77.9(4)
Sn(1)–O(2)
C(111)–Sn(1)–O(2)
C(121)–Sn(1)–O(2)
S–Sn(1)–O(2)
Fig. 3. Molecular structure of complex 5. Ellipsoids at 30% probability.
72.8(2)
C(111)–Sn(1)–S
C(111)–Sn(1)–C(121)
96.9(4)
104.0(5)
and one atom of the cpa bridge ligand, the S atom in the
case of Sn(1) and the O atom in the case of Sn(2). As in
the p-mpspa complex commented above, the non-coordi-
nating O(2) atom of the cpa ligand plays an important role
in the resulting geometry around the two Sn atoms, since
the Sn(1)–O(2) and Sn(2)–O(2) distances are 2.743(5) and
apical position of a bipyramid, and one phenyl C atom
[C(211)] in the other, the equatorial positions being occu-
pied by the other two phenyl C atoms and the O(1) atom of
the p-mpspa ligand. The bite of the ligand makes the
O–Sn–O angle much narrower than 90ꢁ [48.9(3)ꢁ]. The other
metal atom, Sn(1), is surrounded in a similar but more reg-
ular way by three phenyl C atoms, the sulphur atom of the
ligand and the bridge atom O(2). This last atom occupies
one of the apical positions, whereas one of the C atoms
[C(111)] is located at the second one. When compared
the structure of this compound with that of the DMSO
complex commented above, the Sn–S bond lengths are al-
most identical in both species, and they are in the range
found in other similar systems [17]; by contrast, the Sn–O
distance is in this case much shorter than there. This differ-
ence may be explained taking into account that in the
DMSO complex this ligand provides to the Sn atom with
electronic charge enough to make less necessary the prox-
imity of the metal to the other O atom. Besides, in the for-
mer complex this O atom occupies an apical position of the
pseudo-bipyramid, whereas in the latter it is located on an
equatorial site. For the description of the bonding in the
five-coordinate Sn compounds, a three-centre orbital model
is usually adopted [18]. According to this model, (and
assuming that the contribution of tin 5d orbitals to the
bonding is very low), the three equatorial bonds are formed
by sp2 hybrid orbitals, whilst the remaining 5p orbital par-
ticipates in a weaker bond with the substituents on the api-
cal positions using a three-centre molecular orbital of the
linear type.
˚
2.824(5) A, respectively. Therefore, we may consider the
existence of a trigonal-bipyramidal environment around
each Sn atom. The bridge ligand constrains the angles
around Sn(1) to narrow; for instance, 166.9(2)ꢁ for
C(111)–Sn(1)–O(2) (instead of 180ꢁ) or 112.6(18)–
117.1(3)ꢁ in the equatorial plane (instead of 120o). Again,
the environment around Sn(2) is less regular, and we can
find values for the bond angles such as 50.50(16)ꢁ [O(1)–
Sn(2)–O(2)], instead of 90ꢁ. On the other hand, the bond
lengths, in each metal centre, between the Sn atom and
the O atom located in the apical position are quite different
˚
to each other [2.743(5) and 2.824(5) A, respectively], but in
Table 4
o
˚
Selected bond lengths (A) and angles ( ) for complex 5
Bond
Angle
Sn(1)–C(111)
Sn(1)–O(2)
Sn(1)–C(121)
Sn(1)–C(131)
Sn(1)–S(1)
2.166(8)
2.743(5)
2.123(8)
2.128(7)
2.432(2)
2.056(5)
2.110(8)
2.119(8)
2.126(7)
2.824(5)
C(121)–Sn(1)–C(131)
C(121)–Sn(1)–C(111)
C(131)–Sn(1)–C(111)
C(121)–Sn(1)–S(1)
C(131)–Sn(1)–S(1)
C(111)–Sn(1)–S(1)
C(121)–Sn(1)–O(2)
C(131)–Sn(1)–O(2)
C(111)–Sn(1)–O(2)
S(1)–Sn(1)–O(2)
O(1)–Sn(2)–C(221)
O(1)–Sn(2)–C(231)
C(221)–Sn(2)–C(231)
O(1)–Sn(2)–C(211)
C(221)–Sn(2)–C(211)
C(231)–Sn(2)–C(211)
O(1)–Sn(2)–O(2)
117.1(3)
106.0(3)
105.5(3)
112.63(18)
115.1(2)
97.79(19)
84.6(2)
Sn(2)–O(1)
Sn(2)–C(221)
Sn(2)–C(231)
Sn(2)–C(211)
Sn(2)–O(2)
75.4(2)
166.9(2)
70.54(11)
106.4(3)
112.0(2)
118.5(3)
95.5(3)
110.2(3)
111.8(3)
50.50(16)
86.9(2)
3.1.3. Structure of [(SnPh3)2(cpa)] (5)
The structure of this complex and the numbering scheme
is showed in Fig. 3, whereas selected bond lengths and an-
gles are listed in Table 4.
The asymmetric unit is formed by two metal centres,
each one of them surrounded by three phenyl C atoms
C(221)–Sn(2)–O(2)
C(231)–Sn(2)–O(2)
C(211)–Sn(2)–O(2)
82.7(2)
145.8(2)

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P. Alvarez-Boo et al. / Journal of Organometallic Chemistry 691 (2006) 45–52
51
Table 5
both cases they are longer than the sum of their covalent
radii. In the cpa ligand, as expected, the shorter C–O bond
corresponds to the non-coordinating oxygen atom,
whereas the Sn–C bond distances are unremarkable.
Antibacterial activity against Staphylococcus aureus of the complexes:
diameters of the bacterial growth inhibition zones, MIC and MBC values
Diameter (mm) MIC (lg mlÀ1
)
MBC (lg mlÀ1
)
[(SnPh3)2(pspa)]
[(SnPh3)2(tspa)]
[(SnPh3)2(fspa)]
[(SnPh3)2(p-mpspa)] 1.8
[(SnPh3)2(cpa)] 1.7
1.7
2.1
2.0
0.9
2.5
2.5
5.0
5.0
5.0
15.0
15.0
22.0
60.0
3.2. Spectroscopic studies
The vibrational patterns of the complexes have been ana-
lyzed in the light of the X-ray diffraction structural results.
Thus, while the spectra of the ligands H2pspa, H2tspa,
H2fspa, H2-p-mpsa and H2cpa show the bands characteristic
of the SH and OH groups at about 2560–2580 and 1395–
1440 cmÀ1, respectively, the lack of these bands in the com-
plexes spectra confirms the di-deprotonation of the ligand
upon coordination. This coordination to Sn via the S and
O atoms is also revealed by the presence of (Sn–S) and
(Sn–O) stretching bands at about 360 and 450 cmÀ1, respec-
tively. On the other hand, the masym(COO) and msym(COO)
vibrations of the carboxylato group give rise to bands at
about 1590 and 1335 cmÀ1, respectively, with calculated
values for Dm(=masym À msym) in the range 248–265 cmÀ1, as
expected from the monodentate or asymmetric bidentate
behaviour of the carboxylate ligand [19,20].
In the case of the only sensitive strain, S. aureus, the
MIC and MBC values were also determined for the differ-
ent complexes. Table 5 shows the diameter, in mm, of the
bacterial growth inhibition zone for each complex assayed
together with the MIC and MBC values in lg mlÀ1. The
MIC results, in the range 0.9–5.0 lg mlÀ1, are much lower
as compared, for instance, to antibiotic ampicillin (MIC
12.5 lg mlÀ1), and similar to the values reported for antibi-
otic norfloxacin (MIC 3.0 lg mlÀ1) against the same bacte-
rium [5].
The MBC values confirmed the results obtained on
Muller-Hinton broth.
¨
The 1H NMR spectra of the complexes show, apart
from the absence of the C(1)OH and C(2)SH signals due
to the di-deprotonation of the ligand, the signals of the
phenyl groups attached to Sn in the range 7.30–7.90 ppm,
as usually occurs in this type of triphenyltin(IV) com-
pounds. Regarding the 13C NMR spectra, the C(1) signal
is shifted downfield, with respect to the ligand spectra, at
about 174 ppm, indicating the monodentate behaviour of
the carboxylato group. This signal, nevertheless, was not
found in the case of [(SnPh3)2(pspa)], which spectrum is
of poor quality due to the low solubility of this complex
in CDCl3. Besides, the coordination to Sn via the S atom
causes a shielding of C(3), while the other signals of the li-
gand remain practically unchanged upon coordination. Fi-
nally, the 119Sn NMR spectra show, in all cases, two signals
(indicating the existence of two different coordination envi-
ronments around the Sn atoms) in the usual range for four-
coordinate Sn complexes [21], denoting the cleavage in
solution of the weak Sn–O bond commented above. One
of these signals, attributable to the Ph3SnS moiety, occurs
at À90 to À100 ppm, while the other, due to the Ph3SnO
polyhedron, appears between À110 and À120 ppm.
Acknowledgements
We thank the EU Directorate General for Regional Pol-
icies and the Directorate General for Research of the Span-
ish Ministry of Science and Technology for financial
support under ERDF programs (Project BQU2002-
04524-C02-02), and the Xunta de Galicia, Galicia (Spain)
(Project PGIDIT03PXIC30103PN).
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