Coordination geometry of monomeric, dimeric and polymeric organotin(IV) compounds constructed from 5-bromopyridine-2-carboxylic acid and mono-, di- or tri-organotin precursors

Article abstract of DOI:10.1016/j.molstruc.2012.11.052

Reactions of mono-, di-, tri-alkyltin chlorides or oxide with 5-bromopyridine-2-carboxylic acid result in five new organotin(IV) compounds, [MeSn(O₂CC₅NH₃Br)Cl₂(H ₂O)]·(C₂H₅)₂O (1), [(n-Bu)Sn(O₂CC₅NH₃Br)Cl₂(H ₂O)]·(C₂H₅)₂O (2), {[(n-Bu)₂Sn(O₂CC₅NH₃Br)] ₂O}₂ (3) [(n-Bu)₃Sn(O₂CC ₅NH₃Br)]_n (4) and [Ph₃Sn(O ₂CC₅NH₃Br)]_n (5), which have been characterized by single crystal X-ray diffraction, element analysis, IR, ¹H, ¹³C and ¹¹⁹Sn NMR. Three different coordination modes for the ligand are demonstrated in this group of compounds: (1) bidentate mode with the pyridyl nitrogen atom and carboxyl oxygen atom for mono-alkyltin compounds 1 and 2, in which six-coordinated tin center is also bound with two chlorine ions and one water molecule; (2) compound 3 is a tetranuclear centrosymmetric dimer with a central Sn₂O₂ four-membered ring. The four tin atoms are linked by two bridging carboxyl groups while the remaining two act as monodentate ligands to the endo- and exo-cyclic tin atoms; (3) for tri-alkyltin compounds 4 and 5, the bidentate bridging carboxylic group coordinates with two different tin atoms through the SnOCO → Sn bond, and the carboxylate bridge propagates 1D polymeric chains, typical for five coordinate tin. However, in compounds 3-5, the pyridyl nitrogen atoms do not participate in the coordination. For triorganotin(IV) polymers 4 and 5, the solution studies show the collapse of the intermolecular interactions observed in the solid state to yield monomeric species.

Full text of DOI:10.1016/j.molstruc.2012.11.052

Journal of Molecular Structure 1036 (2013) 244–251
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Coordination geometry of monomeric, dimeric and polymeric organotin(IV)
compounds constructed from 5-bromopyridine-2-carboxylic acid and mono-,
di- or tri-organotin precursors
a
a
a
Min Hong a,b, Han-Dong Yin a, , Yan-Wei Zhang , Jin Jiang , Chuan Li
⇑
a Shandong Provincial Key Laboratory of Chemical Energy Storage and Novel Cell Technology, School of Chemistry and Chemical Engineering, Liaocheng University, Liaocheng
252059, China
b State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing
210093, China
h i g h l i g h t s
"
"
"
"
Five new organotin(IV) compounds with 5-bromopyridine-2-carboxylic acid as the ligand were synthesized.
Monomeric, dimeric and polymeric organotin(IV) carboxylates were obtained.
In all compounds, there are three different coordination modes for the ligands.
For triorganotin(IV) polymers, the intermolecular interaction would rupture in solution.
a r t i c l e i n f o
a b s t r a c t
Article history:
Reactions of mono-, di-, tri-alkyltin chlorides or oxide with 5-bromopyridine-2-carboxylic acid result in
five new organotin(IV) compounds, [MeSn(O2CC5NH3Br)Cl2(H2O)]ꢀ(C2H5)2O (1), [(n-Bu)Sn(O2CC5NH3
Br)Cl2(H2O)]ꢀ(C2H5)2O (2), {[(n-Bu)2Sn(O2CC5NH3Br)]2O}2 (3) [(n-Bu)3Sn(O2CC5NH3Br)]n (4) and [Ph3
Sn(O2CC5NH3Br)]n (5), which have been characterized by single crystal X-ray diffraction, element analy-
sis, IR, 1H, 13C and 119Sn NMR. Three different coordination modes for the ligand are demonstrated in this
group of compounds: (1) bidentate mode with the pyridyl nitrogen atom and carboxyl oxygen atom for
mono-alkyltin compounds 1 and 2, in which six-coordinated tin center is also bound with two chlorine
ions and one water molecule; (2) compound 3 is a tetranuclear centrosymmetric dimer with a central
Sn2O2 four-membered ring. The four tin atoms are linked by two bridging carboxyl groups while the
remaining two act as monodentate ligands to the endo- and exo-cyclic tin atoms; (3) for tri-alkyltin com-
pounds 4 and 5, the bidentate bridging carboxylic group coordinates with two different tin atoms
through the SnAOAC@O ? Sn bond, and the carboxylate bridge propagates 1D polymeric chains, typical
for five coordinate tin. However, in compounds 3–5, the pyridyl nitrogen atoms do not participate in the
coordination. For triorganotin(IV) polymers 4 and 5, the solution studies show the collapse of the inter-
molecular interactions observed in the solid state to yield monomeric species.
Received 22 September 2012
Received in revised form 23 November 2012
Accepted 26 November 2012
Available online 3 December 2012
Keywords:
Organotin(IV) compound
5-Bromopyridine-2-carboxylic acid
X-ray crystallography
Structural characterization
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
number of tin atoms [5–7]. From the view of coordination chemis-
try, the bi-dentate or multi-dentate ligands with N, O and S donor
In recent years, organotin(IV) compounds have attracted con-
siderable interests, because of their applications in industry, agri-
culture, biology, especially in the fields of organic synthesis,
catalysts, pharmaceutics and antitumour activities [1–4]. In gen-
eral, the biochemical activity of organotin(IV) compounds is influ-
enced greatly by their molecular structure and the coordination
atoms may benefit the construction of more complicated and inter-
esting structures that have multiple tin atoms and molecular struc-
ture dimension, and increase coordination number as well as
diversified coordination modes [8–10]. These aspects have been
attracting the attention of a number of researchers and a multitude
of structural types have been discovered [11].
A large number of organotin(IV) carboxylates has been prepared
and structurally characterized during the last few decades in our
laboratory [12,13], and it is well known that the biological activity
⇑
Corresponding author. Tel./fax: +86 6358239121.
E-mail address: handongyin@163.com (H.-D. Yin).
0022-2860/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molstruc.2012.11.052

M. Hong et al. / Journal of Molecular Structure 1036 (2013) 244–251
245
of organotins is related to not only the coordination number, but
also the type of alkyl groups attached to the tin atom. The struc-
tural characterization of such organotin(IV) compounds may pro-
vide important clues to the structure–activity relationship of the
ligand and alkyl species and provide an invaluable insight to the
reaction mechanism that may, in turn, allow synthetic chemists
to further optimize reaction conditions [14–16]. Thus new rational
strategies to construct a variety of types of organotins(IV) are
required.
Studies reveal that the introduction of halogen atoms into the
antitumor agents will have a significan affect on their biological
activity [17–19]. As part of our interest to pyridine carboxylic acid
ligands, we intend to modify the composition of the organotin(IV)
5-bromopyridine-2-carboxylates with mono-, bi-, tri-alkyltin salts,
as well as adjust different coordination solvent molecules. Further-
more, the isolation and structural characterization of five tin coor-
dination monomeric, dimeric or polymeric compounds by X-ray
crystallography are presented. From previous reports it is known
that the reaction of organotin(IV) groups with 2-pyridinecarboxyl-
ate and its derivatives gives complexes with coordinative N ? Sn
bonds and five-membered C2NOSn chelate rings [20,21]. It is
expected that different alkyltin salts afford opportunities for
generating novel topologies.
COO), 574 (m, SnAC), 532 (m, SnAO), 429 (w, SnAN), 367 (m,
SnACl).
2.2.2. Synthesis of compound [(n-Bu)Sn(O2CC5NH3Br)Cl2(H2O)]
ꢀ(C2H5)2O (2)
Compound 2 was prepared by the similar method as compound
1. 5-Bromopyridine-2-carboxylic acid (0.202 g, 1 mmol) and so-
dium ethoxide (0.068 g, 1.0 mmol) were added to dry benzene
(20 ml) in a Schlenk flask and stirred for 0.5 h. n-Butyltin trichlo-
ride (0.28 g, 1.0 mmol) was then added and the reaction mixture
was refluxed for 10 h more and then filtered. The solvent was grad-
ually removed by evaporation under vacuum until a solid product
was obtained. The solid was then recrystallized from diethyl/petro-
leum ether to give colorless crystals suitable for single crystal
X-ray diffraction were obtained. Yield 71%. M.p.: 160–162 °C. Anal.
Calc. for C14H24BrCl2NO4Sn: C 31.15, H 4.48, N 2.59; Found: C
31.07,
d8.56–9.09 (m, 3H, PyAH), 3.47 (q, 4H, ACH2A), 1.72 (s, 2H, H2O),
1.57–1.63 (m, 4H, Sn-n-Bu- , b-CH2), 1.19–1.36 (m, 2H, Sn-n-Bu-
H 4.52, N
2.61%. 1H NMR (400 MHz, CDCl3, ppm):
a
c
-CH2), 1.11 (t, 6H, CH3), 0.92 (t, J = 6.8 Hz, 3H, Sn-n-Bu-d-CH3).
13C NMR (100 MHz, CDCl3, ppm): d15.3 (CH3), 25.7, 26.8, 39.7,
(ACH2A), 120.1, 135.8, 147.5, 150.3, 153.7 (PyAC), 157.4 (COO).
119Sn NMR (149 MHz, CDCl3, ppm): d-339.8. IR (KBr, cmꢁ1): 3331
(s, HAOAH), 1512, 1265 (s, COO), 552 (m, SnAC), 537 (m, SnAO),
434 (m, SnAN), 351 (m, SnACl).
2. Experimental
2.1. Materials and physical measurements
2.2.3. Synthesis of compound {[(n-Bu)2Sn(O2CC5NH3Br)]2O}2 (3)
5-Bromopyridine-2-carboxylic acid (0.202 g, 1 mmol) was
added to benzene solution (30 ml) of di-n-butyltin oxide
(0.2487 g, 1 mmol). The mixture was heated under reflux with stir-
ring for 10 h. The clear solution thus obtained was evaporated un-
der vacuum to form a solid, and recrystallized in dichloromethane/
hexane. Then the colorless crystals suitable for single crystal X-ray
diffraction were obtained. Yield: 85%. M.p.: 118–120 °C. Anal. Calc.
for C56H84Br4N4O10Sn4: C 38.05, H 4.79, N 3.17; Found: C 38.11, H
4.73, N 3.22%. 1H NMR (400 MHz, CDCl3, ppm): d8.31–9.16 (m, 12H,
Methyltin trichloride, n-butyltin trichloride, di-n-butyltin oxide,
tri-n-butyltin chloride, triphenyltin chloride, 5-bromopyridine-2-
carboxylic acid were purchased from Sigma–Aldrich Chemical Co.
and used without further purification. All the solvents used in
the reaction were of AR grade and dried using standard literature
procedures.
IR spectra were recorded on a Nicolet-460 spectrophotometer
using KBr discs. 1H, 13C and 119Sn NMR spectra were recorded on
a Mercury Plus-400 NMR spectrometer; chemical shifts were given
in ppm relative to Me4Si and Me4Sn in CDCl3 solvent, and 13C and
119Sn NMR spectra were determined in the decoupling mode. The
spectra were acquired at room temperature (25 °C) unless other-
wise specified. Elemental analyses were performed with a PE-
2400II elemental analyzer.
PyAH), 1.60 (t, J = 8.0 Hz, 16H, Sn-n-Bu-a-CH2), 1.23–1.36 (m, 32H,
Sn-n-Bu-b,
c
-CH2), 0.91 (t, J = 7.2 Hz, 24H, Sn-n-Bu-d-CH3).
13C NMR (100 MHz, CDCl3, ppm): d14.1 (CH3), 26.3, 29.1, 42.3
(ACH2A), 113.8, 134.7, 145.6, 146.5, 151.3 (PyAC), 164.7, 169.5
(COO). 119Sn NMR (149 MHz, CDCl3, ppm): d-205.3, -220.8. IR
(KBr, cmꢁ1): 1635, 1617, 1435, 1391 (s, COO), 636 (m, SnAOASn),
563 (m, SnAC), 462, 541 (m, SnAO).
2.2. Synthesis of the compounds
2.2.1. Synthesis of compound [MeSn(O2CC5NH3Br)Cl2(H2O)]ꢀ(C2H5)2O
(1)
2.2.4. Synthesis of compound [(n-Bu)3Sn(O2CC5NH3Br)]n (4)
Compound 4 was prepared by the similar method as compound
1, 5-bromopyridine-2-carboxylic acid (0.202 g, 1.0 mmol) and so-
dium ethoxide (0.068 g, 1.0 mmol) were added to dry benzene
(20 ml) and stirred for 0.5 h. Tri-n-butyltin chloride (0.325 g,
1.0 mmol) was then added and the reaction mixture was refluxed
for 10 h more and then filtered. The solvent was gradually removed
by evaporating under vacuum until a solid product was obtained.
The solid was then recrystallized from diethyl/petroleum ether
and colorless block crystals suitable for X-ray diffraction were ob-
tained. Yield: 72%. M.p.: 156–160 °C. Anal. Calc. for C18H30BrNO2Sn:
C 44.03, H 6.16, N 2.85%; Found: C 44.15, H 6.09, N 2.86%. 1H NMR
(400 MHz, CDCl3, ppm): d8.47–9.05 (m, 3H, PyAH), 1.51–1.60 (m,
The reaction was carried out under nitrogen atmosphere with
the use of the the standard Schlenk technique. 5-Bromopyridine-
2-carboxylic acid (0.202 g, 1 mmol) and sodium ethoxide
(0.068 g, 1.0 mmol) were added to 20 mL absolute benzene and
heated under reflux with stirring for 0.5 h. After the addition of
methyltin trichloride (0.24 g, 1.0 mmol) to the reactor, the reaction
mixture was refluxed for 10 h more. The reaction solution obtained
after filtering was evaporated in vacuum to give a solid, which was
then recrystallized from diethyl/petroleum ether to give colorless
block crystals suitable for single crystal X-ray diffraction. Yield:
76%. M.p.: 179–180 °C. Anal. Calc. for C11H18BrCl2NO4Sn: C 26.54,
H 3.65, N 2.81; Found: C 26.73, H 3.52, N 2.75%. 1H NMR
(400 MHz, CDCl3, ppm): d8.48–9.24 (m, 3H, PyAH), 3.47 (q, 4H,
ACH2A), 1.61 (s, 2H, H2O), 1.22 (t, 6H, ACH3), 0.83 (s, 3H, SnACH3).
13C NMR (100 MHz, CDCl3, ppm): d13.8 (ACH3), 114.1, 138.8, 145.5,
148.3, 159.7 (PyAC), 157.4 (COO). 119Sn NMR (149 MHz, CDCl3,
ppm): d-358.6. IR (KBr, cmꢁ1): 3327 (s, HAOAH), 1538, 1299 (s,
6H, Sn-n-Bu-a-CH2), 1.44–1.51 (m, 6H, Sn-n-Bu-b-CH2) 1.23–1.36
(pq, 6H, Sn-n-Bu-
c
-CH2), 0.90 (t, J = 7.2 Hz, 9H, Sn-n-Bu-d-CH3).
13C NMR (100 MHz, CDCl3, ppm): d13.9 (CH3), 43.7 (ACH2A),
115.8, 138.7, 146.6, 148.5, 151.3 (PyAC), 162.4 (COO). 119Sn NMR
(149 MHz, CDCl3, ppm): d-137.1. IR (KBr, cmꢁ1): 1586, 1384
(s, COO), 562 (w, SnAC), 485 (m, SnAO).

246
M. Hong et al. / Journal of Molecular Structure 1036 (2013) 244–251
2.2.5. Synthesis of compound [Ph3Sn(O2CC5NH3Br)]n (5)
1, 2, 4 and 5, the ligand should be firstly deprotonated by the addi-
tion of sodium ethoxide for further coordinating with organo-
tin(IV) center. Reaction pathway for these compounds is shown
in Scheme 1. All five compounds have been characterized by
X-ray diffraction analysis, of which both compound 1 and 2 contain
one uncoordinated diethyl ether solvent molecule incorporated
from the recrystallization.
Compound 5 was prepared by the similar method as compound
1, 5-bromopyridine-2-carboxylic acid (0.202 g, 1.0 mmol) and so-
dium ethoxide (0.068 g, 1.0 mmol) were added to dry benzene
(20 ml) and stirred for 0.5 h. Triphenyltin chloride (0.385 g,
1.0 mmol) was then added and the reaction mixture was refluxed
for 10 h more and then filtered. The solvent was gradually removed
by evaporating under vacuum until a solid product was obtained.
The solid was then recrystallized from diethyl/petroleum ether
and colorless block crystals suitable for X-ray diffraction were
obtained. Yield: 83%. M.p.: 172–173 °C. Anal. Calc. for C24H18
BrNO2Sn: C 52.32, H 3.29, N 2.54%; Found: C 52.39, H 3.22, N
2.47%. 1H NMR (400 MHz, CDCl3, ppm): d8.53–9.25(m, 3H, PyAH),
7.49–7.67 (m, 15H, SnAC6H5). 13C NMR (100 MHz, CDCl3, ppm):
d114.3, 125.6, 126.3, 129.9, 131.6, 136.9, 141.4, 146.8, 149.1
(ArAC), 168.24 (COO). 119Sn NMR (149 MHz, CDCl3, ppm):
d-126.3. IR (KBr, cmꢁ1): 1558, 1359 (s, COO), 567 (m, SnAC), 487
(m, SnAO).
3.2. IR spectra
The IR spectra of compounds 1–5 reveal similarities. For all
compounds, the characteristic absorptions of ACOOH belonging
to the ligand at 3200–3500 cmꢁ1 disappear, indicating that it coor-
dinates to the tin atom in COOꢁ form. The
D
m[
m
as(COꢁ) –
m
s(COꢁ)]
2
2
values (239–247 cmꢁ1) for compounds 1 and 2 indicate that the
carboxylate groups adopt the monodentate coordination mode
[22]. In compounds 4 and 5 the
Dm ,
values are under 200 cmꢁ1
which indicates a bidentate coordination mode for the carboxylate
ligand. However, IR spectra reveal strong absorptions at 1635,
1617, 1435 and 1391 cmꢁ1 for compound 3, corresponding to the
symmetric and antisymmetric carboxylate stretches, which are
typical for tetranuclear diorganotin carboxylates. In the 462–
2.3. Determination of crystal structures
X-ray diffraction data for crystals were performed with graph-
541 cmꢁ1 region, medium absorptions are assigned to
v(SnAO)
ite-monochromated Mo K
Smart-1000 CCD diffractometer and collected by the
a
radiation (0.71073 Å) on the Bruker
-2h scan
x
[23]. The presence of two SnAO bands, which is more obvious for
compound 3, reflects different SnAO bond lengths, as proved by
the X-ray analysis. The dichlorotin derivatives 1 and 2 exhibit
technique at 298(2) K. The crystal structures were solved by direct
method and different Fourier syntheses using SHELXL-97 program,
and refined by full-matrix least-squares on F2. All non-hydrogen
atoms were refined anisotropically. All the hydrogen atoms were
put in calculated positions or located from the Fourier maps and
refined isotropically with the isotropic vibration parameters re-
lated to the non-hydrogen atom to which they are bonded. Crystal-
lographic data and experimental details of the structure
determinations are listed in Table 1.
v
(SnAO) (532 and 537 cmꢁ1) shifted to higher frequencies, reflect-
ing the different effects of Clꢁ and the organo ligands. Generally, a
powerful electron-withdrawing group, such as Cl, increases the
strength of the SnAO bonds. v(SnACl) for 1 and 2 are at about
360 cmꢁ1. Otherwise, in 1 and 2, the absorptions at ꢂ430 cmꢁ1
for
v(SnAN) have also been observed. A strong absorption at
636 cmꢁ1 for compound 3 is assigned to SnAOASn stretching
vibration, indicating that the existence of SnAOASn bridged
structure [23].
3. Results and discussion
3.1. Synthetic procedures of organotin(IV) compounds 1–5
3.3. 1H, 13C and 119Sn NMR spectra (CDCl3)
Compounds 1–5 were obtained by the reactions between equi-
molar of 5-bromopyridine-2-carboxylic acid with mono-, bi- or tri-
alkyltin salts in different solvents under the reflux conditions in
good yields, 71–85%. In the preparation procedures of compounds
In the 1H NMR spectra of compounds 1–5, the single resonance
for the proton of ACOOH is absent, indicating the carboxylic ligand
coordinated to tin atom in COOꢁ form. The protons of the pyridyl
ring for all compounds give broad signals at 8.31–9.25 ppm, which
Table 1
Crystal data and structure refinement details for compounds 1–5.
Compound
1
2
3
4
5
Empirical formula
Formula weight
Crystal system
Space group
a (Å)
C
11H18BrCl2NO4Sn
C14H24BrCl2NO4Sn
539.84
C28H42Br2N2O5Sn2
883.84
Triclinic
P–1
11.390(2)
13.145(3)
13.782(3)
112.139(2)
111.375(2)
94.370(2)
1724.4(6)
2
C18H30BrNO2Sn
491.03
Monoclinic
P2(1)/n
12.726(3)
10.727(2)
16.007(4)
90
93.409
90
2181.3(8)
4
C24H18BrNO2Sn
550.99
Monoclinic
P2(1)/n
12.945(3)
12.333(3)
13.420(3)
90
91.985(3)
90
2141.3(9)
4
497.76
Triclinic
P–1
Monoclinic
P2(1)/c
17.979(2)
10.0792(16)
11.7368(18)
90
90.1450(10)
90
2126.9(5)
4
7.4621(16)
9.472(2)
14.361(3)
70.897(2)
89.188(2)
70.113(2)
896.5(3)
2
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
Z
F(000)
484
1.844
1.51–25.01
4656
184
0.0476
0.0395
0.1132
0.1057
1.004
104
1.686
2.32–25.00
10410
208
0.1148
0.0694
0.2617
0.1983
868
1.702
1.73–25.01
8701
352
0.0797
0.0520
0.1506
0.1289
984
1.495
1.99–25.01
11083
211
0.1114
0.0606
0.2068
0.1625
1.000
1080
1.709
2.15–25.01
9993
262
0.0372
0.0253
0.0594
0.0550
1.055
Dcalc (g cmꢁ3
h Range (°)
)
Number of reflections
Number of paramters
R factor all
R factor [I > 2
wR2
r
(I)]
wR2 [I > 2
Goodness-of-fit (GOF)
r(I)]
1.011
1.041

M. Hong et al. / Journal of Molecular Structure 1036 (2013) 244–251
247
Scheme 1. Reaction pathway of compounds 1–5.
are consistent with values reported in other organotin(IV) com-
pounds with pyridyl carboxylic acid as ligands [24–26]. The methyl
protons of mono-methyltin(IV) derivative 1 appear as sharp sing-
The 13C NMR spectral data for the R groups attached to the tin
atom, where R = CH3, n-Bu and Ph, were assigned by comparison
with related analogues as model compounds [24–26]. The posi-
tions of the pyridyl carbon signals undergo minor variations in
the compounds compared with those observed in the free acid.
The carboxylate carbon shifts to a lower field region in all the com-
pounds, indicating participation of the carboxylic group in coordi-
nation to tin(IV).
lets at 0.83 ppm with well-defined satellites. The
and -CH2 protons of mono-n-butyltin compounds appear as mul-
tiplets, and d-CH3 appears as a triplet with 3J[1H, 1H] = 6.8 Hz. The
-CH2 protons of di-n-butyltin compounds appear as a triplet at
a-CH2, b-CH2
c
a
1.60 ppm with 3J[1H, 1H] = 8.0 Hz; the b-CH2 and
c-CH2 protons ap-
pear as multiplets, and d-CH3 appears as a triplet with 3J[1H,
1H] = 7.2 Hz. In the tri-n-tributyltin(IV) complex, the d-CH3 appears
The 119Sn NMR spectra were recorded in CDCl3 solution, a non-
coordinating solvent. The chemical shift values obtained for the
monoorganotin(IV) derivatives 1 and 2 (see Section 2) lie in the
normal range expected for six-coordinate tin compounds, which
is similar to that found in the compound {[(n-Bu)SnCl2]ꢁ[4-NHC5
as a triplet at 0.90 ppm with 3J[1H, 1H] = 7.2 Hz,
c
-CH2 as a pseudo-
-CH2 and b-CH2 protons as
multiplets at 1.51–1.60 ppm and 1.44–1.51 ppm, respectively.
quintet at 1.23–1.36 ppm, and the
a
Fig. 1. Dimeric structure (with thermal ellipsoids at 30% probability) of compound 1 linked by intermolecular OAHꢀ ꢀ ꢀO hydrogen bonds (dotted line) among the coordinated
water molecule, diethyl ether solvent and the carboxyl oxygen atoms, and its numbering scheme. All H atoms are omitted for clarity.

248
M. Hong et al. / Journal of Molecular Structure 1036 (2013) 244–251
Fig. 2. Supramolecular structure (with thermal ellipsoids at 30% probability) of compound 2 showing the 1D chain linked by intermolecular OAHꢀ ꢀ ꢀO hydrogen bonds (dotted
line) among the coordinated water molecule, diethyl ether solvent and the carboxyl oxygen atoms, and its numbering scheme. All H atoms are omitted for clarity.
Table 3
Table 2
Selected bond lengths (Å) and angles (°) for compound 3.
Selected bond lengths (Å) and angles (°) for compounds 1 and 2.
Sn(1)AC(17)
Sn(1)AO(5)
Sn(1)AC(13)
Sn(1)AO(5)#1
Sn(1)AO(1)
Sn(1)AO(3)#1
C(17)ASn(1)AO(5)
O(5)ASn(1)AC(13)
C(17)ASn(1)AO(5)#1
O(5)ASn(1)AO(5)#1
C(13)ASn(1)AO(5)#1
C(17)ASn(1)AO(1)
O(5)ASn(1)AO(1)
C(13)ASn(1)AO(1)
C(17)ASn(1)AO(3)#1
C(13)ASn(1)AO(3)#1
O(5)#1ASn(1)AO(3)#1
2.111(7)
2.112(4)
2.127(7)
2.182(5)
2.347(5)
2.516(5)
Sn(2)AO(5)
Sn(2)AC(25)
Sn(2)AC(21)
Sn(2)AO(3)
Sn(2)AO(2)
1.991(4)
2.109(9)
2.121(8)
2.207(5)
2.222(6)
1
Sn(1)AC(7)
Sn(1)AO(1)
Sn(1)AO(3)
C(7)ASn(1)AO(1)
C(7)ASn(1)AO(3)
O(1)ASn(1)AO(3)
O(1)ASn(1)AN(1)
O(3)ASn(1)AN(1)
C(7)ASn(1)ACl(1)
2.113(6)
2.124(3)
2.202(4)
94.1(2)
Sn(1)AN(1)
Sn(1)ACl(1)
Sn(1)ACl(2)
N(1)ASn(1)ACl(1)
C(7)ASn(1)ACl(2)
O(1)ASn(1)ACl(2)
N(1)ASn(1)ACl(2)
Cl(1)ASn(1)ACl(2)
O(3)ASn(1)ACl(1)
2.263(4)
2.413(1)
2.424(2)
88.45(10)
100.5(2)
94.63(1)
83.80(1)
95.55(5)
85.53(9)
95.8(2)
102.9(2)
O(1)ASn(1)AO(3)#1
O(5)ASn(2)AC(25)
O(5)ASn(2)AC(21)
C(25)ASn(2)AC(21)
O(5)ASn(2)AO(3)
C(25)ASn(2)AO(3)
C(21)ASn(2)AO(3)
O(5)ASn(2)AO(2)
C(25)ASn(2)AO(2)
C(21)ASn(2)AO(2)
130.73(2)
115.0(3)
117.9(3)
127.1(4)
76.40(2)
94.1(3)
97.9(3)
94.42(2)
89.3(3)
79.45(1)
74.37(1)
79.30(1)
102.1(2)
100.2(2)
99.2(3)
74.62(2)
97.6(2)
84.6(3)
87.83(2)
85.2(3)
83.9(2)
85.0(2)
66.83(2)
2
Sn(1)AO(1)
Sn(1)AC(7)
Sn(1)AO(3)
O(1)ASn(1)AC(7)
O(1)ASn(1)AO(3)
C(7)ASn(1)AO(3)
O(1)ASn(1)AN(1)
O(3)ASn(1)AN(1)
O(3)ASn(1)ACl(1)
2.110(8)
2.146(1)
2.199(8)
95.2(5)
83.7(3)
90.1(5)
73.7(3)
79.0(3)
88.8(3)
Sn(1)AN(1)
Sn(1)ACl(2)
Sn(1)ACl(1)
O(1)ASn(1)ACl(2)
C(7)ASn(1)ACl(2)
N(1)ASn(1)ACl(1)
N(1)ASn(1)ACl(2)
C(7)ASn(1)ACl(1)
Cl(2)ASn(1)ACl(1)
2.256(9)
2.399(3)
2.406(3)
89.6(2)
103.3(4)
88.4(2)
86.8(2)
101.6(5)
93.74(1)
86.8(3)
Symmetry code: #1 1 ꢁ x, 1 ꢁ y, 1 – z.
suggesting there are either five- or six-coordinate tin atoms in
the distannoxane [28,29], which also reveals that the dimeric
structure found in the solid state (vide infra) are retained in
solution. However, 119Sn NMR spectra of compounds 4 (ꢁ137.1)
H4CON2CH(C6H4O-2)]+ we reported previously [27]. The solution
119Sn NMR spectra of 3 shows two peaks at d = ꢁ205.3, ꢁ220.8,
Fig. 3. The 1D chain structure of compound 3 (with thermal ellipsoids at 30% probability) formed by intermolecular CAHꢀ ꢀ ꢀO hydrogen-bonding interactions along the a-axis,
and its numbering scheme. Part hydrogen and n-butyl carbon (except SnAC) atoms are omitted for clarity.

M. Hong et al. / Journal of Molecular Structure 1036 (2013) 244–251
249
Fig. 4. A perspective view of the 1D chain polymeric structure of compound 4 (with thermal ellipsoids at 30% probability) and its numbering scheme.
Fig. 5. A perspective view of the 1D chain polymeric structure of compound 5 (with thermal ellipsoids at 30% probability) and its numbering scheme.
Table 4
and 5 (ꢁ126.3) are consistent with monomeric structures in solu-
Selected bond lengths (Å) and angles (°) for compounds 4 and 5.
tion [29,30], which is characteristic for a tetrahedral geometry.
4
Sn(1)AC(7)
Sn(1)AC(15)
Sn(1)AC(11)
2.116(2)
2.121(2)
2.136(2)
Sn(1)AO(1)
Sn(1)AO(2)#1
2.266(7)
2.336(8)
3.4. X-ray crystallography
C(7)ASn(1)AC(15)
C(7)ASn(1)AC(11)
C(15)ASn(1)AC(11)
C(7)ASn(1)AO(1)
C(15)ASn(1)AO(1)
123.8(6)
C(11)ASn(1)AO(1)
C(7)ASn(1)AO(2)#1
C(15)ASn(1)AO(2)#1
C(11)ASn(1)AO(2)#1
85.3(5)
89.5(6)
96.8(5)
83.5(5)
3.4.1. Crystal structures of compounds 1 and 2
117.2(6)
119.0(6)
94.4(5)
89.8(5)
When the reaction of 5-bromopyridine-2-carboxylic acid with
methyltin trichloride or n-butyltin trichloride was carried out,
compound 1 and 2 were obtained. As illustrated in Figs. 1 and 2,
compounds 1 and 2 present the similar crystal structures, both
including two parts, the organotin(IV) moieties and one uncoordi-
nated diethyl ether solvent molecule. Selected bond distances and
angles of compounds 1 and 2 are listed in Table 2.
X-ray single-crystal structural analyses reveal that both 1 and 2
are simple mononuclear compounds. In these two compounds, the
Sn center is six-coordinated, being bound to one alkyl carbon atom,
two chlorine atoms and one water oxygen atom, as well as one
nitrogen and one oxygen atom from the bidentate ligand. The
geometry around the tin atom is distorted octahedral, with the al-
kyl carbon atom and the pyridyl nitrogen atom being in trans posi-
tion, the two chlorine atoms and two oxygen atoms lying in the
molecular plane. The bond lengths of SnAO, SnAN, SnACl, and
SnAC, and their corresponding angles between two neighboring
bonds (listed in Table 2) are consistent with those of similar
mono-n-butyltin compound {[(n-Bu)SnCl2]ꢁ[4-NHC5H4CON2CH
(C6H4O-2)]+ we reported previously [27].
5
Sn(1)AC(19)
Sn(1)AC(7)
Sn(1)AC(13)
C(19)ASn(1)AC(7)
C(19)ASn(1)AC(13)
C(7)ASn(1)AC(13)
C(19)ASn(1)AO(1)
C(7)ASn(1)AO(1)
2.128(3)
2.131(3)
2.144(3)
138.61(1)
106.56(1)
113.42(1)
96.44(9)
Sn(1)AO(1)
Sn(1)AO(2)#1
2.205(2)
2.396(2)
C(13)ASn(1)AO(1)
C(19)ASn(1)AO(2)#1
C(7)ASn(1)AO(2)#1
C(13)ASn(1)AO(2)#1
87.36(1)
85.53(9)
86.59(1)
86.49(1)
95.66(1)
Symmetry code: (#1 for 4) 3/2 ꢁ x, 1/2 + y, 1/2 ꢁ z; (#1 for 5) 3/2 ꢁ x, ꢁ1/2 + y, 1/
2 ꢁ z.
Intermolecular hydrogen-bonding interactions among the
water molecules, uncoordinated solvent diethyl ether molecules
and carboxyl oxygen atoms result in a dimeric structure for
compound 1 (see Fig. 1) or a 1D infinite supramolecular chain for

250
M. Hong et al. / Journal of Molecular Structure 1036 (2013) 244–251
compound 2 (see Fig. 2) [hydrogen bonding data: O3ꢀ ꢀ ꢀO4#1,
2.693 Å for 1 and 2.680 Å for 2; O3ꢀ ꢀ ꢀO2#2, 2.648 Å for 1 and
2.659 Å for 2; (#1 for 1) 2 ꢁ x, 1 ꢁ y, 1 ꢁ z; (#2 for 1) 2 ꢁ x, 1 ꢁ y,
2 ꢁ z; (#1 for 2) x, 3/2 ꢁ y, ꢁ1/2 + z; (#2 for 2) x, 3/2 ꢁ y, 1/2 + z].
disparity in the Sn-O bond distances not withstanding. The axial
positions are occupied by O1 and O2#1 [#1: ꢁx + 3/2, y + 1/2,
ꢁz + 1/2] and axial angle is 168.8(2)°. The sum of the angles sub-
tended at the tin atom in the equatorial plane is 360.18°, so that
the atoms Sn1, C7, C11 and C15 are almost in the same plane.
As mentioned before there are a considerable number of crystal
structure determinations for compounds of the general formula
R3Sn(O2CR0) for triorganotin(IV) mono-carboxylates, and these
are known to adopt a variety of coordination geometries [30].
The overwhelming majority of structures are monomeric, and
these may be described as cis-R3SnO2, depending on the magnitude
of the intramolecular Snꢀ ꢀ ꢀO interaction; or polymeric with
trans-R3SnO2 geometry as the carboxylate ligands are bidentate
bridging. The cyclo-oligomeric species have also been reported,
such as cyclotetrameric or cyclohexameric structures [29], which
depend on the steric factors associated the tin- and carboxylate-
bound R groups and global crystal packing considerations, and
may be thought as being intermediate between the monomeric
and polymeric extremes described above.
3.4.2. Crystal structure of compound 3
Molecular structure of compound 3 is shown in Fig. 3; for clar-
ity, the b,
c and d carbon atoms of the n-butyl groups have been
omitted. Selected bond distances and angles are listed in Table 3.
As is the case of the other known carboxystannoxanes [28,30],
the complex is a tetranuclear centrosymmetric dimer with a cen-
tral Sn2O2 four-membered ring. The four tin atoms are linked by
two bridging carboxyl groups while the remaining two act as
monodentate ligands to the endo- and exo-cyclic tin atoms. Consid-
eration of the axial angles O(2)ASn(1)AO(3)#1 [#1: ꢁx + 1, ꢁy + 1,
ꢁz + 1] [130.73(17)°] and O(2)ASn(2)AO(3) [170.81(18)°] and the
SnAO distances lead to the conclusion that the two tin atoms are
in different environments. Both tin atoms are coordinated by two
n-butyl moieties which form CASnAC angles of 154.3(3)° and
127.1(4)°, respectively. In the case of the exocyclic Sn(2) atom,
the coordination is completed by O(2), O(3) and O(5) with dis-
tances of 2.222(6), 2.207(5) and 1.991(4) Å, respectively. For the
endocyclic Sn(1) atom, the O(1), O(5) and O(5) #1 atoms all coor-
dinate at distances of 2.347(5), 2.112(4) and 2.182(5) Å, and there
is a longer but significant interaction of 2.516(5) Å to O(3)#1. In the
case of Sn(2), O(1) is 3.603 Å from the tin atom. However, O(4) is
appreciably closer at 3.361 Å, but it appears that the interaction
is very weak. Thus it may be concluded that the exocyclic tin atom
Sn(1) is best described as five-coordinated, and the endocyclic
Sn(2) as pseudo-six-coordinated. As we know, this chemistry
structure is very common for the other diorganotin(IV) pyridine-
2-carboxylates [28,30], but is thoroughly different from those of
diorganotin(IV) pyridyl 3- or 4-carboxylates. The place of carboxyl
group on the pyridyl ring has an important effect on the coordina-
tion geometry of the central tin atoms, such as in the previous re-
ported dibutyltin or dimethyltin 5-bromopyridine-3-carboxylates,
the tin atoms are coordinated by four carboxyl oxygen atoms and
one pyridyl nitrogen atom besides two alkyl carbon atoms, and
the infinite one-dimensional polymeric chain structures have been
formed by the bridging of the pyridine-3-carboxyl ligands [31,32].
As shown in Fig. 3, an infinite 1D chain is formed along a axis
direction via the intermolecular CAHꢀ ꢀ ꢀO hydrogen bonds between
oxygen atom O4 of the monodentate ligand and the hydrogen atom
of pyridinyl ring (hydrogen bonding data: C4ꢀ ꢀ ꢀO4#2, 3.189 Å; #2
1 ꢁ x, 2 ꢁ y, 1 ꢁ z).
4. Conclusion
In conclusion, this work has shown that 5-bromopyridine-
2-carboxylic acid and different alkyltin salts can result in the for-
mation of various topological organotin(IV) compounds. When
mono-alkyltin chlorides and the ligand are used as the starting
materials, novel mono-organotin compounds 1 and 2 are produced,
in which the ligand present bidentate, one oxygen atom of ACO2ꢁ
ion and one pyridyl nitrogen atom. When di-n-butyltin oxide is
used as the starting material, a typical dimeric tetranuclear com-
pound 3 results, which contains two different coordination envi-
ronment tin atoms; and the two types of tin atoms are linked by
the bridging bidentate and the monodentate ACOꢁ2 oxygen atoms.
For tri-organotin compounds 4 and 5, the bidentate carboxylic
group connects contiguous tin atoms, which result in the forma-
tion of 1D bridging infinite polymeric chains. In addition, in com-
pounds 1, 2 and 3 independent units are connected by the
intermolecular OAHꢀ ꢀ ꢀO or CAHꢀ ꢀ ꢀO hydrogen bonds into the
dimer or infinite supermolecular chain. The effect of the introduc-
tion of bromine atom to the pyridyl group in organotin(IV) com-
pounds on their antitumor activities is in progress.
Acknowledgments
We acknowledge the National Natural Foundation of China
(21105042), the National Basic Research Program (No.
2010CB234601), the Natural Science Foundation of Shandong
Province (ZR2011BM007, ZR2010BQ021) and the Liaocheng Uni-
versity Funds for Young Scientists (31805) for financial support.
And this work was supported by Shandong ‘‘Tai–Shan Scholar Re-
search Fund’’.
3.4.3. Crystal structures of compounds 4 and 5
One-dimensional chain polymers 4 and 5 have been synthe-
sized by the reaction of 5-bromopyridine-2-carboxylic acid with
tri-n-butyltin chloride or tri-phenyltin chloride. The 1D poly-
meric chain solid state structures 4 and 5 are shown in Figs. 4
and 5. Selected geometric parameters are collected in Table 4.
Due to the identical coordination geometry for 4 and 5, struc-
tural analysis would be carried out by taking compound 4 for
example.
The polymeric structure of 4 arises as the carboxylate ligands
are typical bidentate bridging, albeit forming the relative symmet-
ric bond distances of approximately 2.266(7) and 2.336(8) Å,
which is comparable with literature reports [2.214(3)–2.410(3) Å]
for the polymeric structure resulting from bridging coordination
of the mono-carboxyl ligand [23], but is different obviously from
the values of two asymmetric SnAO bonds [2.160(3) and
2.64.0(3) Å] in the cyclotetrameric tri-n-butyltin(IV) carboxylate
derived from (Z)-3-(4-nitrophenyl)-2-phenyl-2-propenoic acid
[19]. The individual tin atom coordination geometry is based on
a trans-R3SnO2 trigonal bipyramid with the above-mentioned
Appendix A. Supplementary material
CCDC-871010 (for 1), -871009 (for 2), -871011 (for 3), -871013
(for 4), and -871012 (for 5) contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge via http://www.ccdc.cam.ac.uk/data_request/cif, or from
the Cambridge Crystallographic Data Centre, 12 Union Road, Cam-
bridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: depos-
it@ccdc.cam.ac.uk. Supplementary data associated with this
article can be found, in the online version, at http://dx.doi.org/
10.1016/j.molstruc.2012.11.052.

M. Hong et al. / Journal of Molecular Structure 1036 (2013) 244–251
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