Synthesis, structure and biological activity of organotin derivatives with pyridylmethylthiobenzoic acid

Article abstract of DOI:10.1016/j.poly.2007.04.029

Reaction of 2-(2-pyridylmethylthio)benzoic acid (1) with R₂SnO (R = Et or ⁿBu) in a 1:1 molar ratio gives the dimeric compounds {[(2-PyCH₂SC₆H₄CO₂)SnR₂]₂O}₂. A similar reaction of 2-(4-pyridylmethylthio)benzoic acid (2) with Et₂SnO yields an analogous result. However, treatment of 2 with ⁿBu₂SnO in a 1:1 molar ratio only gives the diorganotin dicarboxylate (4-PyCH₂SC₆H₄CO₂)₂Sn(ⁿBu)₂. X-ray crystal structure analyses indicate that the pyridyl nitrogen atoms do not coordinate to the tin atoms in the dimer, whilst in the diorganotin dicarboxylate the tin atom has a seven-coordinate distorted pentagonal-bipyramidal geometry, and this compound forms a linkage coordination polymer through the interactions of the pyridyl nitrogen atoms with the adjacent tin atoms. In addition, treatment of 1 or 2 with (Ph₃Sn)₂O in a 2:1 molar ratio affords triphenyltin carboxylates, in which the tin atoms also show different coordination environments. In the solid state, triphenyltin 2-(2-pyridylmethylthio)benzoate is a monomer and the pyridyl nitrogen atom does not participate in coordination to the tin atom either, while the interactions between the pyridyl nitrogen atoms and the adjacent tin atoms link triphenyltin 2-(4-pyridylmethylthio)benzoate into a coordination polymer. Preliminary in vitro tests for fungicidal activity show that all these compounds display good activity to Physolospora piricola in a low concentration. Moreover, the triphenyltin carboxylates show a higher inhibition percentage than the diorganotin carboxylates.

Full text of DOI:10.1016/j.poly.2007.04.029

Polyhedron 26 (2007) 3743–3749
www.elsevier.com/locate/poly
Synthesis, structure and biological activity of organotin
derivatives with pyridylmethylthiobenzoic acid
*
Xiao-Yan Zhang, Hai-Bin Song, Qing-Shan Li, Xiu-Feng Liu, Liang-Fu Tang
Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, PR China
Received 14 March 2007; accepted 5 April 2007
Available online 5 May 2007
Abstract
n
Reaction of 2-(2-pyridylmethylthio)benzoic acid (1) with R2SnO (R = Et or Bu) in a 1:1 molar ratio gives the dimeric compounds
{[(2-PyCH2SC6H4CO2)SnR2]2O}2. A similar reaction of 2-(4-pyridylmethylthio)benzoic acid (2) with Et2SnO yields an analogous result.
n
However, treatment of 2 with Bu2SnO in a 1:1 molar ratio only gives the diorganotin dicarboxylate (4-PyCH2SC6H4CO2)2Sn(nBu)2.
X-ray crystal structure analyses indicate that the pyridyl nitrogen atoms do not coordinate to the tin atoms in the dimer, whilst in
the diorganotin dicarboxylate the tin atom has a seven-coordinate distorted pentagonal-bipyramidal geometry, and this compound forms
a linkage coordination polymer through the interactions of the pyridyl nitrogen atoms with the adjacent tin atoms. In addition, treatment
of 1 or 2 with (Ph3Sn)2O in a 2:1 molar ratio affords triphenyltin carboxylates, in which the tin atoms also show different coordination
environments. In the solid state, triphenyltin 2-(2-pyridylmethylthio)benzoate is a monomer and the pyridyl nitrogen atom does not par-
ticipate in coordination to the tin atom either, while the interactions between the pyridyl nitrogen atoms and the adjacent tin atoms link
triphenyltin 2-(4-pyridylmethylthio)benzoate into a coordination polymer. Preliminary in vitro tests for fungicidal activity show that all
these compounds display good activity to Physolospora piricola in a low concentration. Moreover, the triphenyltin carboxylates show a
higher inhibition percentage than the diorganotin carboxylates.
ꢀ 2007 Elsevier Ltd. All rights reserved.
Keywords: Organotin carboxylate; Thiobenzoic acid; Pyridyl; Crystal structure; Biological activity
1. Introduction
groups [5–18]. Due to the presence of additional coordinat-
ing atoms, some organotin carboxylates with fascinating
structures, such as hexameric cyclic diorganotin carboxyl-
ate [6,7], have been isolated. It is a real pity that as a kind
of polyfunctional S,N,O-ligand, pyridylalkylthiobenzoic
acid has drawn little attention, although compounds with
the pyridylalkylthiophenyl group have been reported to
display significant biological properties, such as drugs for
brain protection or inhibitors of angiogenesis and vascular
permeability [19,20]. As a continuation of our studies on
biologically active organotin compounds [21,22], we have
synthesized organotin carboxylates of pyridylmethylthio-
benzoic acid (Scheme 1), and their structures have been
characterized by multinuclear NMR and X-ray crystallog-
raphy. The antibacterial activity of these new organotin
carboxylates has also been tested in vitro.
Organotin carboxylates have attracted considerable
attention due to their wide applications in many fields,
for example as pesticidal, bactericidal and antitumor
agents [1–3]. In these organotin carboxylates, the coordina-
tion number and environment of the tin atom can be easily
controlled by adjusting the steric and electronic factors of
the carboxylic acid ligands and substituents linked to the
tin atom [3,4]. In recent years, a vast amount of investiga-
tion has focused on organotin carboxylates of functional-
ized carboxylic acids with additional O, S or N donor
*
Corresponding author. Fax: +86 22 23502458.
E-mail address: lftang@nankai.edu.cn (L.-F. Tang).
0277-5387/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2007.04.029

3744
X.-Y. Zhang et al. / Polyhedron 26 (2007) 3743–3749
Table 1
˚
Selected bond distances (A) and angles (ꢁ) for compounds 4 and 5
Compound 4a
Compound 5b
Sn1–O1
Sn1–O5
Sn1–O5A
Sn1ꢁ ꢁ ꢁO3
Sn1ꢁ ꢁ ꢁSn1A
Sn2–O5
Sn2–O2A
Sn2–O3
Sn2ꢁ ꢁ ꢁO4
C3–S1
C8–S1
C1–O1
C1–O2
C14–O3
C14–O4
2.257(3)
2.166(3)
2.043(3)
2.83(1)
3.302(4)
2.045(3)
2.266(4)
2.195(3)
2.77(1)
1.780(6)
1.815(6)
1.264(6)
1.260(6)
1.311(6)
1.223(6)
Sn1–O1
Sn1–O1A
Sn1–O5A
Sn1ꢁ ꢁ ꢁO2
Sn1ꢁ ꢁ ꢁSn1A
Sn2–O1
Sn2–O2
Sn2–O4
Sn2–O3
C11–S1
C16–S1
C9–O2
2.161(2)
2.034(2)
2.253(3)
3.045(4)
3.300(1)
2.045(2)
2.213(2)
2.253(3)
2.531(2)
1.768(3)
1.823(4)
1.294(4)
1.244(4)
1.258(4)
1.240(4)
Scheme 1. The structures of pyridylmethylthiobenzoic acid 1 and 2.
2. Results and discussion
2.1. Reaction of 2-(2-pyridylmethylthio)benzoic acid (1)
n
with R2SnO (R = Et or Bu)
Upon treatment of 2-(2-pyridylmethylthio)benzoic acid
C9–O3
C22–O4
C22–O5
n
with R2SnO (R = Et or Bu) in a 1:1 molar ratio in anhy-
drous benzene, dimeric compounds {[(2-PyCH2SC6H4-
CO2)SnR2]2O}2 [R = Et (3) and nBu (4)] were yielded,
which have been characterized by elemental analyses, IR
as well as NMR spectra. The NMR spectra of these two
compounds are consistent with their structures as dimeric
distannoxanes. For instance, the 119Sn spectra of these
compounds verify the presence of endo- and exo-cyclic tin
atoms. A pair of resonances of equal intensities is observed
at ꢀ207.92 and ꢀ209.58 ppm for 3 as well as at ꢀ194.13
and ꢀ193.13 ppm for 4. These values are comparable with
those reported for other dimeric distannoxanes with cyclic
Sn2O2 units [13,21–23], and correspond to a five-coordi-
nated or weakly six-coordinated tin atom. In addition,
the 1H and 13C NMR spectra of these two compounds also
support the suggested structures, and exhibit two sets of
ethyl signals for 3 and butyl signals for 4.
C27–Sn1–C31
O1–Sn1–O5
O5A–Sn1–C27
C27–Sn1–O5
C31–Sn1–O1
C35–Sn2–C39
O3–Sn2–O2A
O5–Sn2–C35
O5–Sn2–C39
C3–S1–C8
Sn1–O5–Sn2
Sn1–O5–Sn1A
O1–C1–O2
O3–C14–O4
a
139.3(2)
165.1(1)
107.9(1)
99.7(1)
C1–Sn1–C3
O1–Sn1–O5A
O1A–Sn1–C3
C1–Sn1–O1
C1–Sn1–O5A
C5–Sn2–C7
O2–Sn2–O4
O1–Sn2–C7
O1–Sn2–O3
C11–S1–C16
Sn1A–O1–Sn2
Sn1A–O1–Sn1
O2–C9–O3
137.0(1)
165.7(1)
109.7(1)
94.8(1)
83.5(1)
82.9(1)
141.7(3)
170.4(1)
112.6(2)
105.0(1)
103.5(3)
120.8(1)
103.3(1)
123.9(5)
120.2(5)
146.9(1)
171.6(1)
109.4(1)
139.11(8)
103.4(1)
133.2(1)
103.71(9)
120.2(3)
123.8(3)
O4–C22–O5
Symmetry code of ‘‘A’’ is 1 ꢀ x, 2 ꢀ y, 1 ꢀ z.
b
Symmetry code of ‘‘A’’ is 1 ꢀ x, ꢀy, 2 ꢀ z.
In order to prove the role of these heteroatoms in the
carboxylate ligands, the structure of 4 has also been con-
firmed further by X-ray crystallography, and presented in
Fig. 1. Selected bond distances and angles are listed in
Table 1. As seen in Fig. 1, the pyridyl nitrogen atoms do
not coordinate to the tin atoms. The crystallographically
unique carboxylic ligands display different coordination
modes. One acts as a monodentate ligand by the carboxyl-
ate oxygen, while the other is a bridging bidentate ligand
by two oxygen atoms of the carboxyl group. Each tin atom
adopts a five-coordinate distorted trigonal bipyramidal
geometry with two oxygen atoms (O1 and O5 for Sn1 as
well as O3 and O2A for Sn2) occupying the axial positions.
The axial O–Sn–O angles (O1–Sn1–O5 165.1(1)ꢁ and O3–
Sn2–O2A 170.4(1)ꢁ) significantly derivate from 180ꢁ. Some
weak intramolecular Snꢁ ꢁ ꢁO interactions are also observed.
˚
The Snꢁ ꢁ ꢁO distances (Sn1ꢁ ꢁ ꢁO3 2.83(1) A, Sn2ꢁ ꢁ ꢁO4
˚
2.77(1) A) are significantly shorter than the sum of the
˚
van der Waal’s radii for the Sn and O atom of 3.57 A [9],
but are markedly longer than the covalent Sn–O distance,
˚
˚
such as Sn1–O1 (2.257(3) A) and Sn1–O5 (2.166(3) A).
2.2. Reaction of 2-(4-pyridylmethylthio)benzoic acid (2)
n
with R2SnO (R = Et or Bu)
The reaction of 2-(4-pyridylmethylthio)benzoic acid
with Et2SnO in a 1:1 molar ratio in anhydrous benzene also
gives
a
dimeric compound, {[(4-PyCH2SC6H4CO2)-
SnEt2]2O}2 (5). Although its 119Sn NMR spectrum only
shows a broad single resonance peak at ꢀ193.17 ppm (pos-
sibly owing to coincidental overlapping), the 13C NMR
spectrum clearly shows two sets of signals for the ethyl
Fig. 1. The molecular structure of 4 with the thermal ellipsoids at the 30%
probability level. Hydrogen atoms are omitted for clarity. Symmetric
operation of ‘‘A’’ is 1 ꢀ x, 2 ꢀ y, 1 ꢀ z.

X.-Y. Zhang et al. / Polyhedron 26 (2007) 3743–3749
3745
˚
carbons, consistent with the structure of a dimeric distan-
noxane, like in 4. However, treatment of 2-(4-pyridylmeth-
ylthio)benzoic acid with nBu2SnO in a 1:1 molar ratio
under similar reaction conditions only yields the diorgano-
tin dicarboxylate (4-PyCH2SC6H4CO2)2Sn(nBu)2 (6). Its
1H and 13C NMR spectra exhibit only one set of butyl sig-
nals. In addition, the 119Sn NMR spectrum of 6 displays
one resonance at ꢀ155.56 ppm, markedly different from
those of 3–5, but comparable with those reported for
related diorganotin dicarboxylates [10,22,23]. Although
the tin atom in this compound is seven-coordinate in the
solid state (see Fig. 3), this 119Sn NMR chemical shift is
not consistent with that of a seven-coordinate tin centre
[8,16], suggesting that the seven-coordinate structure of
tin is not retained, and extensive dissociation may occur
in solution. It is known that the steric hindrance of the car-
boxylic acid or alkyl groups of tin significantly affects the
coordinate environment of the tin atom in organotin carb-
oxylates [8,9,24]. So the greater bulkiness of the butyl
group compared to that of the ethyl group possibly plays
a key role in the formation of 6 in this reaction.
Sn1ꢁ ꢁ ꢁO3 distance (2.83(1) A) in 4, implying weaker non-
bonded Snꢁ ꢁ ꢁO interactions in 5. Additionally, it is note-
worthy pointing out these two compounds have short
˚
˚
Sn1ꢁ ꢁ ꢁSn1A separations (3.302(4) A in 4 and 3.300(1) A
in 5) [12,25].
The molecular structure of 6 is presented in Fig. 3, and
selected bond distances and angles are listed in Table 2.
The tin atom has a seven-coordinate distorted pentago-
nal-bipyramidal geometry, with four oxygen atoms of
two chelating carboxylate ligands and the pyridyl nitrogen
atom occupying the equatorial plane and two butyl groups
lying in axial positions with an axial angle C27–Sn1–C31of
167.0(1)ꢁ. The Sn1 atom lies in the plane formed by the Sn1
The distannoxane structure for 5 and dicarboxylate
structure for 6 are also supported by their X-ray diffraction
analyses. The molecular structure of 5 is presented in
Fig. 2, and selected bond distances and angles are listed
in Table 1. To a first approximation, the molecular struc-
ture of 5 is similar to that of 4. For instance, they both have
tetranuclear distannoxane structures, and the pyridyl nitro-
gen atoms do not participate in coordination to the tin
atoms in either of these two compounds. On the other
hand, some noticeable differences exist between 4 and 5.
In 5, one tin atom (Sn1) adopts a five-coordinate distorted
trigonal bipyramidal geometry, while the other tin (Sn2) is
in a six-coordinate distorted octahedral geometry. The
coordination modes of the carboxylic ligands are also dif-
ferent in these two compounds. One carboxylic ligand in
5 acts as a bidentate bridging ligand, while the other is a
bidentate chelating ligand. In addition, the Sn1ꢁ ꢁ ꢁO2 dis-
Fig. 3. The molecular structure of 6 with the thermal ellipsoids at the 30%
probability level. Hydrogen atoms are omitted for clarity. Symmetric
operation of ‘‘A’’ is 0.5 ꢀ x, 0.5 + y, 0.5 ꢀ z.
Table 2
˚
˚
Selected bond distances (A) and angles (ꢁ) for compounds 6 and 8
tance (3.045(4) A) in 5 is longer than the corresponding
Compound 6a
Compound 8b
Sn1–O1
Sn1–O2
Sn1–N2A
S(1)–C(7)
S(1)–C(8)
C1–O1
2.227(3)
2.420(3)
2.510(4)
1.771(5)
1.812(5)
1.267(5)
1.251(5)
Sn1–O2
Sn1ꢁ ꢁ ꢁO1
Sn1–N1A
C6–S1
C7–S1
C13–O1
C13–O2
2.149(2)
3.040(3)
2.524(2)
1.816(3)
1.768(3)
1.224(4)
1.300(4)
C1–O2
C27–Sn1–C31
C27–Sn1–O4
C31–Sn1–O3
O4–Sn1–O1
O4–Sn1–O2
O2–Sn1–O3
C31–Sn1–N2A
O4–Sn1–N2A
C7–S1–C8
167.0(1)
95.6(1)
90.3(1)
C14–Sn1–C20
C20–Sn1–C26
C26–Sn1–O2
C20–Sn1–N1A
O2–Sn1–N1A
C6–S1–C7
124.2(1)
112.6(1)
90.1(1)
84.2(1)
85.7(1)
140.0(1)
164.4(1)
83.2(1)
138.3(1)
103.2(2)
120.2(4)
175.27(9)
102.3(1)
123.1(3)
O1–C13–O2
O1–C1–O2
a
Fig. 2. The molecular structure of 5 with the thermal ellipsoids at the 30%
probability level. Hydrogen atoms are omitted for clarity. Symmetric
operation of ‘‘A’’ is 1 ꢀ x, ꢀy, 2 ꢀ z.
Symmetry code of ‘‘A’’ is 0.5 ꢀ x, 0.5 + y, 0.5 ꢀ z.
Symmetry code of ‘‘A’’ is ꢀ0.5 + x, 0.5 ꢀ y, 0.5 + z.
b

3746
X.-Y. Zhang et al. / Polyhedron 26 (2007) 3743–3749
O1, O2, O3, O4 and N2A atoms, and only deviates from
˚
the plane by 0.0101 A. Furthermore, this compound forms
a linkage coordination polymer through the interactions of
the pyridyl nitrogen atoms with the adjacent tin atoms. The
˚
Sn1–N2A bond distance is 2.510(4) A, comparable with
those reported in other related seven-coordinate organotin
dicarboxylates [8,12,16].
2.3. Reaction of 1 and 2 with (Ph3Sn)2O
Reaction of pyridylmethylthiobenzoic acids 1 and 2 with
(Ph3Sn)2O in a 2:1 molar ratio gives triphenyltin carboxy-
lates (2-PyCH2SC6H4CO2)SnPh3 (7) and (4-PyCH2SC6H4-
CO2)SnPh3 (8), which have also been characterized by
elemental analyses, IR, NMR spectra and X-ray crystallog-
raphy. The molecular structure of 7 is presented in Fig. 4,
and indicates that the tin is in a distorted tetrahedral geom-
etry. The carboxylate group acts as unidentate ligand. Like
4 and 5, the pyridyl nitrogen atom in 7 does not participate
in coordination to the tin atom. Additionally, other weak
non-bonded interactions, such as intramolecular Snꢁ ꢁ ꢁO
Fig. 5. The molecular structure of 8 with the thermal ellipsoids at the 30%
probability level. Hydrogen atoms are omitted for clarity. Symmetric
operation of ‘‘A’’ is ꢀ0.5 + x, 0.5 ꢀ y, 0.5 + z.
˚
˚
3.045(4) A). The Sn–N distance is 2.524(2) A, also similar
˚
with that in 6 (2.510(4) A) and other related polymeric tri-
phenyltin derivatives containing pyridyl carboxylate
˚
ligands, such as 4-PyCO2SnPh3 (2.512(6) A) [26,27].
The IR and NMR spectra of compounds 7 and 8 are
also consistent with their structures. For instance, the con-
siderable differences between the asymmetric and symmet-
ric stretching vibrations of the carboxylate groups
(292 cmꢀ1 in 7 and 301 cmꢀ1 in 8) indicate that they act
as unidentate ligands [27,28]. The 119Sn NMR spectrum
of 7 displays one resonance at ꢀ103.44 ppm, very close
to the values reported for the corresponding four-coordi-
nated triphenyltin carboxylates, such as 105.97 ppm in
Ph3SnO2CCH2CH2COC6H4C6H5 [29]. Although the tin
atom in 8 is five-coordinate in the solid state (see Fig. 5),
its 119Sn NMR chemical shift (ꢀ107.52 ppm) is similar to
that of 7, indicating that the polymeric five-coordinate
organotin structure is lost in solution. This result has also
been observed in 6 and other polymeric or oligomeric
organotin derivatives [30].
i
˚
(Sn1ꢁ ꢁ ꢁO2 2.737(3) A) and intermolecular Sꢁ ꢁ ꢁS (S1ꢁ ꢁ ꢁS1
˚
3.617(4) A, symmetry code: i = 1 ꢀ x, 2 ꢀ y, 2 ꢀ z) interac-
tions, have also been observed in this compound.
Like compound 6, 8 forms a linkage coordination poly-
mer through the interactions of the pyridyl nitrogen atoms
with the adjacent tin atoms, as shown in Fig. 5. In 8, how-
ever, the tin atom adopts a five-coordinate distorted trigo-
nal bipyramidal geometry with one oxygen atom and the
pyridyl nitrogen atom occupying the axial positions with
an axial angle O2–Sn1–N1A of 175.27(9)ꢁ (see Table 2).
˚
The non-bonded Snꢁ ꢁ ꢁO distance (Sn1ꢁ ꢁ ꢁO1 3.040(3) A) is
significantly longer than the corresponding Snꢁ ꢁ ꢁO dis-
˚
tances in 4 and 7 (Sn1ꢁ ꢁ ꢁO3 2.83(1) A in 4 and Sn1ꢁ ꢁ ꢁO2
˚
2.737(3) A in 7), but is similar to that in 5 (Sn1ꢁ ꢁ ꢁO2
2.4. Biological activity
Preliminary in vitro tests for fungicidal activity of
compounds 3–8 have been carried out by the fungi
growth inhibition method [31]. These compounds are dis-
solved in DMF at a concentration of 50 ppm. The data
are summarized in Table 3, and show that all com-
pounds display certain activity to Physolospora piricola
at a low concentration. Moreover, the triphenyltin carb-
Table 3
The fungicidal activities of compounds 3–8
Compound
Inhibition ratio (%) (50 ppm)
Fig. 4. The molecular structure of 7 with the thermal ellipsoids at the 30%
probability level. Hydrogen atoms are omitted for clarity. Selected bond
3
4
5
6
7
8
˚
distances [A] and angles [ꢁ]: Sn1–O1 = 2.058(2), Sn1ꢁ ꢁ ꢁO2 = 2.737(3),
Gibbereila zeae
Alternaria solani
0
0
0
45.6
0
0
0
0
39.7
0
0
0
0
0
23.5
0
51.4
0
60.8
70.0
50.0
70.6
64.0
47.8
23.5
56.3
85.2
64.0
Sn1–C1 = 2.120(3), Sn1–C2 = 2.127(3), Sn1–C3 = 2.126(3), C6–O1 =
i
˚
1.304(4), C6–O2 = 1.237(4), C20–S1 = 1.819(4), S1ꢁ ꢁ ꢁS1 = 3.617(4) A;
Cercospora arachidicola
Physolospora piricola
Fusarium oxysporum
C1–Sn1–C3 = 119.4(1), C2–Sn1–O1 = 98.6(1), C1–Sn1–O1 = 106.4(1),
O1–C6–O2 = 120.2(3), C7–S1–C20 = 104.3(1)ꢁ (symmetry code: i =
1 ꢀ x, 2 ꢀ y, 2 ꢀ z).
39.7
0

X.-Y. Zhang et al. / Polyhedron 26 (2007) 3743–3749
3747
oxylates 7 and 8 are more active than the other diorg-
anotin derivatives, similar to the results reported previ-
ously by Alt [32]. In addition, compound 8 shows the
highest inhibition percentage for Physolospora piricola
(85.2%) in vitro.
3.2. Reaction of pyridylmethylthiobenzoic acid with R2SnO
(R = nBu or Et)
A mixture of pyridylmethylthiobenzoic acid 1 or 2
(1 mmol) and R2SnO (1 mmol) in anhydrous benzene
(40 ml) was stirred and heated at reflux for 8 h to yield a
clear solution. After removing the benzene in vacuo, the
crude product was recrystallized from a suitable solvent.
3. Experimental
Multinuclear NMR spectra were obtained with a Bruker
AV300 or Mercury 300BB spectrometer using CDCl3 as
solvent unless otherwise noted, and the chemical shifts were
reported in ppm with respect to reference standards (inter-
3.2.1. Preparation of {[(RCO2)SnEt2]2O}2
(R = 2-(2-pyridylmethylthio)phenyl) (3)
This compound was obtained by the reaction of 1 with
Et2SnO. The reaction time was 15 h. The crude product
was recrystallized from benzene/hexane to afford white crys-
tals of 3. Yield: 65%; mp 167–169 ꢁC. 1H NMR: d = 8.54 (d,
2H, C5H4N), 7.90, 7.60–7.52, 7.36–7.14 (d, m, m, 2H, 4H,
8H, C5H4N and C6H4), 4.30 (s, 4H, CH2), 1.67–1.61, 1.41–
1.33 (m, m, 8H, 12H, SnCH2CH3) ppm. 13C NMR:
d = 173.13 (COO), 157.96, 153.17, 151.99, 149.29, 137.01,
131.82, 131.59, 126.16, 124.18, 123.18, 122.26 (C5H4N and
C6H4), 39.24 (CH2), 23.17, 21.28, 10.31, 10.06 (ethyl car-
bons) ppm. 119Sn NMR: d = ꢀ207.92, ꢀ209.58 ppm. IR
(cmꢀ1): mas (COO) 1591, 1572, ms (COO) 1399, 1346. Anal.
Calc. for C34H40N2O5S2Sn2: C, 47.58; H, 4.70; N, 3.26.
Found: C, 47.26; H, 4.25; N, 3.15%.
1
nal SiMe4 for H NMR and 13C NMR spectra, external
SnMe4 for 119Sn NMR). IR spectra were obtained on a
Bio-Rad FTS 6000 spectrometer using KBr discs. Elemen-
tal analyses were carried out on a Perkin–Elmer 2400C
analyzer. Melting points were measured with an X-4 digital
micro melting-point apparatus and were uncorrected.
3.1. Preparation of pyridylmethylthiobenzoic acids
These acids were prepared by a slight modification of
the method in the literature [20]. To a solution of KOH
(0.241 mol) in 50 ml of EtOH and 10 ml of water, thiosal-
icylic acid (73.1 mmol) and chloromethylpyridine–HCl
(73.2 mmol) were added. The reaction mixture was stirred
at room temperature for 2 h, and then water (100 ml) was
added. The water solution was extracted with diethyl ether
(3 · 50 ml), and the organic phase was discarded to remove
unreacted starting materials. The water phase was acidified
to a pH value of 4 with 2 M HCl to give a white precipitate,
which was filtered off, washed by water, and dried in air to
yield pyridylmethylthiobenzoic acid, which could be crys-
tallized with a large amount of alcohol.
3.2.2. Preparation of {[(RCO2)Sn(nBu)2]2O}2
(R = 2-(2-pyridylmethylthio)phenyl) (4)
This compound was obtained by the reaction of 1 with
nBu2SnO, and was recrystallized from ether to afford white
crystals of 4. Yield: 62%; mp 92–94 ꢁC. 1H NMR: d = 8.55
(d, 2H, C5H4N), 7.85–7.10 (m, 14H, C5H4N and C6H4),
4.30 (s, 4H, CH2), 1.77–1.55, 1.34–1.21 (m, m, 16H, 8H,
SnCH2CH2CH2), 0.85–0.73 (m, 12H, CH3) ppm. 13C
NMR: d = 172.98 (COO), 157.81, 157.51, 149.09, 139.91,
136.68, 131.27, 131.03, 126.21, 124.05, 122.97, 121.98
(C5H4N and C6H4), 39.14 (CH2), 30.08, 28.47, 27.64,
27.37, 26.87, 26.82, 13.59, 13.53 (butyl carbons) ppm.
119Sn NMR: d = ꢀ194.13, ꢀ195.13 ppm. IR (cmꢀ1): mas
(COO) 1591, 1575, ms (COO) 1406, 1346. Anal. Calc. for
C42H56N2O5S2Sn2: C, 51.98; H, 5.82; N, 2.89. Found: C,
51.67; H, 5.89; N, 2.70%.
3.1.1. Preparation of 2-(2-pyridylmethylthio)benzoic acid
(1)
This acid was obtained by the reaction of thiosalicylic
acid with 2-chloromethylpyridine–HCl. Yield: 72%; mp
173 ꢁC (dec.). 1H NMR (DMSO): d = 8.53 (d, 1H,
C5H4N), 7.89 (d, 1H, C5H4N), 7.77–7.48, 7.28–7.20 (m,
m, 4H, 2H, C5H4N and C6H4), 4.31 (s, 2H, CH2) ppm.
13C NMR (DMSO): d = 167.3 (CO2H), 157.1, 149.0,
140.8, 136.9, 132.3, 130.9, 127.8, 125.8, 124.0, 123.3,
122.3 (C5H5N and C6H4), 37.8 (CH2) ppm. IR (cmꢀ1):
m(C@O) 1688.8 s.
3.2.3. Preparation of {[(RCO2)SnEt2]2O}2
(R = 2-(4-pyridylmethylthio)phenyl) (5)
This compound was obtained by the reaction of 2
(1 mmol) with Et2SnO (1 mmol), and was recrystallized
from benzene/hexane to afford white crystals of 5. Yield:
64%; mp 174–177 ꢁC. 1H NMR: d = 8.46 (d, 4H,
C5H4N), 7.81 (d, 2H, C6H4), 7.29–7.19, 7.09–7.03 (m, m,
6H, 4H, C5H4N and C6H4), 4.03 (s, 4H, CH2), 1.59–1.46,
1.33–1.25 (m, m, 8H, 12H, SnCH2CH3) ppm. 13C NMR:
d = 172.90 (COO), 150.21, 148.61, 136.37, 132.67, 131.48,
128.33, 126.32, 124.49, 123.42 (C5H4N and C6H4), 34.67
(CH2), 22.92, 20.97, 10.03, 9.76 (ethyl carbons) ppm.
119Sn NMR: d = ꢀ193.17 (br) ppm. IR (cmꢀ1): mas
(COO) 1592, 1573, ms (COO) 1459, 1398. Anal. Calc. for
3.1.2. Preparation of 2-(4-pyridylmethylthio)benzoic acid
(2)
This acid was obtained similarly to 1 using thiosalicylic
acid and 4-chloromethylpyridine–HCl. Yield: 70%; mp
180 ꢁC (dec.). 1H NMR (DMSO): d = 8.48 (d, 2H,
C5H4N), 7.87 (d, 2H, C5H4N), 7.48–7.39, 7.21–7.17 (m,
m, 3H, 1H, C6H4), 4.23 (s, 2H, CH2) ppm. 13C NMR
(DMSO): d = 167.3 (CO2H), 149.6, 146.3, 140.0, 132.3,
130.9, 128.1, 125.9, 124.3, 124.1 (C5H5N and C6H4), 34.3
(CH2) ppm. IR (cmꢀ1): m(C@O) 1690.1 s.

3748
X.-Y. Zhang et al. / Polyhedron 26 (2007) 3743–3749
C34H40N2O5S2Sn2: C, 47.58; H, 4.70; N, 3.26. Found: C,
47.62; H, 4.57; N, 3.23%.
white crystals of 7. Yield: 78%; mp 103–105 ꢁC. 1H
NMR: d = 8.57, 8.15 (d, d, 1H, 1H, C5H4N), 7.97–7.76
(m, 6H, C6H5), 7.61, 7.52–7.33, 7.19–7.12 (t, m, m, 1H,
12H, 2H, C6H5, C5H4N and C6H4), 4.34 (s, 2H, CH2)
ppm. 13C NMR: d = 172.87 (COO), 157.62, 149.10,
141.11, 138.48, 137.43, 137.04, 136.91, 132.93, 132.38,
130.15, 128.93, 126.08, 124.17, 122.98, 122.14 (C6H5,
C5H4N and C6H4), 38.97 (CH2) ppm. 119Sn NMR:
d = ꢀ103.44 ppm. IR (cmꢀ1): mas (COO) 1622, ms (COO)
1330. Anal. Calc. for C31H25NO2SSn: C, 62.65; H, 4.24;
N, 2.36. Found: C, 62.38; H, 4.55; N, 2.43%.
3.2.4. Preparation of (RCO2)2Sn(nBu)2
(R = 2-(4-pyridylmethylthio)phenyl) (6)
This compound was obtained by the reaction of 2
n
(1 mmol) with Bu2SnO (1 mmol), and was recrystallized
from ethyl acetate/hexane to afford white crystals of 6.
1
Yield: 68%; mp 174–176 ꢁC. H NMR: d = 8.58 (d, 4H,
C5H4N), 8.17 (d, 2H, C6H4), 7.44–7.38, 7.24–7.19 (m, m,
6H, 4H, C5H4N and C6H4), 4.15 (s, 4H, CH2), 1.90–1.84,
1.80–1.73, 1.44–1.37 (m, m, m, 4H, 4H, 4H,
SnCH2CH2CH2), 0.88 (t, 6H, CH3) ppm. 13C NMR:
d = 175.58 (COO), 149.89, 146.11, 140.30, 132.60, 132.52,
128.62, 125.92, 124.62, 124.03 (C5H4N and C6H4), 36.23
(CH2), 26.73, 26.26, 26.19, 13.57 (butyl carbons) ppm.
119Sn NMR: d = ꢀ155.56 ppm. IR (cmꢀ1): mas (COO)
1615, ms (COO) 1401. Anal. Calc. for C34H38N2O4S2Sn: C,
56.60; H, 5.31; N, 3.88. Found: C, 56.39; H, 5.20; N, 3.64%.
3.3.2. Preparation of RCO2SnPh3
(R = 2-(4-pyridylmethylthio)phenyl) (8)
This compound was obtained by the reaction of 2 with
(Ph3Sn)2O, and recrystallized from benzene/hexane to
afford slight yellow crystals of 8. Yield: 80%; mp 186–
1
188 ꢁC. H NMR: d = 8.49, 7.18 (d, d, 2H, 2H, C5H4N),
8.11 (d, 1H, C6H4), 7.95–7.74 (m, 6H, C6H5), 7.47–7.29
(m, 12H, C6H5 and C6H4), 4.08 (s, 2H, CH2) ppm. 13C
NMR: d = 172.38 (COO), 149.88, 146.24, 139.88, 138.43,
137.00, 132.61, 132.03, 130.16, 128.92, 128.35, 126.38,
124.72, 124.02 (C6H5, C5H4N and C6H4), 36.49 (CH2)
ppm. 119Sn NMR: d = ꢀ107.52 ppm. IR (cmꢀ1): mas
(COO) 1632, ms (COO) 1331. Anal. Calc. for
C31H25NO2SSn: C, 62.65; H, 4.24; N, 2.36. Found: C,
62.58; H, 4.47; N, 2.24%.
3.3. Reaction of pyridylmethylthiobenzoic acid with
(Ph3Sn)2O
A mixture of pyridylmethylthiobenzoic acid 1 or 2
(2 mmol) and (Ph3Sn)2O (1 mmol) in anhydrous benzene
(40 ml) was stirred and heated at reflux for 6 h to yield a
clear solution. After removing the benzene in vacuo, the
crude product was recrystallized from a suitable solvent.
4. Crystal structure determinations
3.3.1. Preparation of RCO2SnPh3
(R = 2-(2-pyridylmethylthio)phenyl) (7)
This compound was obtained by the reaction of 1 with
(Ph3Sn)2O, and recrystallized from ether/hexane to afford
Crystals of 4 and 7 suitable for X-ray analyses were
obtained by slowly cooling their hot ether/hexane solu-
tions. Crystals of 6 suitable for X-ray analysis were
Table 4
Crystal data and refinement parameters for compounds 4–8
Compound
4
5
6
7
8
Formula
C
84H112N4O10S4Sn4
C68H80N4O10S4Sn4
1716.36
0.34 · 0.28 · 0.10
113(2)
C34H38N2O4S2Sn
721.47
0.20 · 0.16 · 0.10
294(2)
C31H25NO2SSn
594.27
0.22 · 0.20 · 0.12
293(2)
C31H25NO2SSn
594.27
0.28 · 0.22 · 0.20
293(2)
Formula weight
Crystal size (mm)
T (K)
1940.78
0.22 · 0.20 · 0.04
294(2)
˚
k (MoKa) (A)
0.71070
triclinic
0.71070
monoclinic
P21/c
14.740(2)
17.587(3)
15.064(2)
90
117.268(2)
90
3471.0(9)
2
0.71073
monoclinic
C2/c
32.462(4)
10.067(1)
20.558(3)
90
92.845(2)
90
6710.0(15)
8
0.71073
triclinic
0.71073
monoclinic
P21/n
9.7463(7)
16.939(1)
16.117(1)
90
91.455(1)
90
2659.9(3)
4
Crystal system
ꢀ
ꢀ
Space group
P1
P1
˚
a (A)
12.122(5)
13.418(5)
16.026(6)
100.607(2)
106.862(4)
109.755(5)
2229.7(15)
1
9.289(1)
9.466(1)
16.039(3)
95.858(3)
102.746(3)
99.226(3)
1343.9(4)
2
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
V (A )
Z
Dcalc (g cmꢀ3
F(000)
)
1.445
988
1.256
1.642
1720
1.602
1.428
2960
0.925
1.469
600
1.056
1.484
1200
1.068
l (mmꢀ1
)
Number of unique reflections (Rint
)
10039(0.0396)
6317
479
8972(0.0420)
8074
422
5914(0.0419)
3947
390
5418(0.0244)
3895
325
4703(0.0269)
3501
408
Number of observed reflections (I > 2r(I))
Number of parameters
Goodness of fit
1.033
1.087
1.042
1.039
1.010
Residuals R, Rw
0.0497, 0.1165
0.0389, 0.1032
0.0386, 0.0889
0.0385, 0.0650
0.0300, 0.0782

X.-Y. Zhang et al. / Polyhedron 26 (2007) 3743–3749
3749
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