Solvothermal synthesis and characterizations of monophenyltin complexes in drum conformations

Article abstract of DOI:10.1016/j.poly.2009.10.013

A series of drum structures of organotin complexes with various carboxylic acids have been solvothermally synthesized and characterized by elemental analysis, FT-IR, NMR (¹H, ¹³C and ¹¹⁹Sn) spectra and X-ray crystallography. The molecular structure analyses reveal that all of the complexes have endo drum structures. Furthermore, each of the drum structures has a hole, in which atoms of a given radius could be held.

Full text of DOI:10.1016/j.poly.2009.10.013

Polyhedron 29 (2010) 881–885
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Solvothermal synthesis and characterizations of monophenyltin complexes
in drum conformations
a
a
a
Chun-Lin Ma a,b, , Yun Ren , Yue-Rong Wang , Ru-Fen Zhang
*
a Department of Chemistry, Liaocheng University, Liaocheng 252059, People’s Republic of China
b Taishan University, Taian 271021, People’s Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of drum structures of organotin complexes with various carboxylic acids have been solvother-
mally synthesized and characterized by elemental analysis, FT-IR, NMR (1H, 13C and 119Sn) spectra and
X-ray crystallography. The molecular structure analyses reveal that all of the complexes have endo drum
structures. Furthermore, each of the drum structures has a hole, in which atoms of a given radius could be
held.
Received 29 September 2009
Accepted 11 October 2009
Available online 20 October 2009
Keywords:
Organotin
Ó 2009 Elsevier Ltd. All rights reserved.
Carboxylic acids
Drum structures
Solvothermal synthesis
1. Introduction
and X-ray crystallography spectroscopy. All these complexes were
synthesized under the same conditions.
In recent years, organotin (IV) carboxylates have been one of the
most extensively studied class of anticancer compounds, not only
for their significant reduction in the growth rates of tumours
[1,2], but also for their interesting and various architectures and
topologies [3,4]. The latter has been actively investigated by a large
number of researchers, and a multitude of structural types, includ-
ing monomers, dimers, tetramers, oligomeric ladders, hexameric
drums, etc., have been discovered [5,6]. Most of them were synthe-
sized by conventional synthetic techniques. Recently, solvothermal
synthesis has become an effective method for preparing various
novel coordination complexes using simple inorganic or organo-
metallic compounds and organic ligands as starting materials. It
is also a superb technique for crystallizing these products that have
hardly arisen from other synthetic methods [7,8]. In our previous
work we have obtained 12- and 16-membered cyclic organotin
complexes using the solvothermal technique [9,10], and intrigued
by this method we chose triphenyltin chloride to react with seven
carboxylic acids, in the hope of obtaining novel structures. Herein,
we report the syntheses and characterizations of the seven struc-
tures, each with a drum configuration, resulting from solvothermal
synthesis. These complexes form hexameric organostannoxane
drums, which consist of a prismatic Sn6O6 core. All the complexes
were characterized by elemental, IR, FT-IR, NMR (1H, 13C and 119Sn)
2. Results and discussion
2.1. Syntheses
The following general procedure was used for the synthesis
of complexes 1–7. A mixture of the carboxylic acids, triphenyltin
(IV) chloride and KOH in
(V/V = 2:1) was heated under solvothermal conditions (130 °C).
They were heated in a sealed Teflon-lined stainless steel autoclave
for 3 days. After cooling down to room temperature, colorless crys-
tals were collected and washed with methanol. The synthetic
experiments of complexes 1–7 are shown in Scheme 1.
a mixture of CH3OH and H2O
2.2. IR spectra
In the infrared spectra, strong absorptions in the region of 433–
453 cmÀ1, which are absent in the spectra of the free carboxylic
acids, are assigned to the Sn–O stretching mode. Strong bands in
the region of 621–637 cmÀ1 for the complexes are assigned to
m(Sn–O–Sn), indicating the forming of a Sn–O–Sn bridged struc-
ture. All these values are consistent with those detected in a num-
ber of organotin (IV)-oxygen derivatives [11]. As reported for other
organotin complexes, IR spectroscopy can provide useful informa-
tion relating to the bond formation through the carboxylate moie-
ties in the organotin carboxylate complexes. It is possible to
distinguish the coordination mode of the –CO2 group. For the com-
* Corresponding author. Address: Department of Chemistry, Liaocheng Univer-
sity, Liaocheng 252059, People’s Republic of China. Tel.: +86 635 8230660; fax: +86
538 6715521.
E-mail address: macl@lcu.edu.cn (C.-L. Ma).
plexes in this article, the Dm (Dm = mas(COO)–ms(COO)) values of
0277-5387/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2009.10.013

882
C.-L. Ma et al. / Polyhedron 29 (2010) 881–885
R
C
R
C
O
O
O
n
Ph
O
Ph
Sn
O
Ph
O
Sn
O
R
C
O
Sn
O
methanol/water (2:1)
130°C
S
O
RCOOH
Ph3SnCl
O
+
KOH
+
O
C
Sn
O
R
Ph
Sn
O
O
O
Ph
Ph
O
O
C
R
C
R
H
CH
S
C
1,
3,
4,
2,
7
5,
6,
O
Scheme 1.
complexes 1–7 (239.4–304.9 cmÀ1) reveal that the carboxylate
groups have bidentate coordination modes [12]. The conclusions
drawn from the IR data are consistent with the X-ray crystallogra-
phy spectroscopy data.
2.3. NMR spectra
The 1H NMR spectra show the expected integration and peak
multiplicities. In the spectra of the free ligands, resonances are ob-
served at about 10.12 ppm, and these are absent in the spectra of
the complexes, indicating the formation of Sn–O bonds in all the
complexes. In complexes 1–7, the chemical shifts of the signal
for the phenyl groups (d = 7.12–7.90 ppm) appear almost in the
same positions. The structural changes occurring in the ligands
upon deprotonation and coordination to the Sn atoms should be
reflected by the changes in the 13C NMR spectra of complexes 1–
7. If the ligands chelate Sn through the O atom from C–O, the IR
bands of the COO group should be shifted to a lower frequency
in the spectra of the complexes compared with the spectra of the
free ligands. 119Sn NMR chemical shift values may be used to give
tentative indications of the environment around the tin atoms.
ˇ
Holeeek et al. [13] have suggested d values from +200 to À60 for
four-coordinated, À90 to À190 for five-coordinated and À210 to
À400 ppm for six-coordinated tin atoms in solution. The 119Sn
NMR spectra of the complexes show single resonances indicating
the presences of only one type of tin atom, which is consistent with
other similar complexes [14].
Fig. 1. Molecular structure of complex 1 [The
drawn, but the other atoms are omitted for clarity.].
a
-carbon of the phenyl ring (Sn–Ph) is
2.21(6) Å) [16]. The Sn–O–Sn bond angles in the six-membered
rings, in the range 98.5(4)–135.0(6)°, are wider than those found
in the four-membered rings. It can be seen from the structures in
2.4. Description of crystal structures
Fig. 2, the four-membered [Sn2 (l3-O)2] rings are not planar, the
The molecular structure of complex 1 is shown in Fig. 1 (the
similar structures of complexes 2–7 are not displayed) and selected
bond lengths and angles for 1 are summarized in Table 2. The most
ubiquitous cages are the hexanuclear complexes, also known as
drums. The centrosymmetric structures are built around a Sn6O6
central stannoxane core which contains two puckered six-mem-
oxygen atoms are tilted toward the cavity of the drum. Thus the
interior of the drum can be considered as a crown made of six oxy-
gen atoms in a trigonal antiprismatic arrangement.
The 119Sn NMR of complexes 1–7 show a single peak character-
istic of this class of complexes, indicating that all the tin atoms of
the drum complexes are chemically equivalent. A single chemical
shift is seen in their 119Sn NMR spectra [17–19], where the tin
atoms are hexa-coordinated (5O, 1C) [20,21], with three of the coor-
dination sites being occupied by bridging tri-coordinated oxygen
atoms. While the oxygen atoms from the bridging carboxylate li-
gands occupy two of the coordination sites, the sixth coordination
site is occupied by a C atom from the phenyl group. The O5C donor
set defines a distorted octahedron, which is approved by the angles
in Table 2. In all the complexes, the distance between the planes de-
fined by the six tin atoms is about 2.32 Å. The corresponding dis-
tance between the planes defined by the oxygen atoms is about
1.84 Å. As seen in Fig. 2a and b, we can imagine a center residing
in the interior of the cavity, the center being defined by the crown
bered [Sn3
(
l3-O)3] rings as its top and bottom face (Fig. 1) [15].
The two [Sn3
(l3-O)3] rings are connected further by six Sn–O
bonds provided by tri-coordinated O atoms, thus the side faces of
the drum are characterized by six puckered four-membered [Sn2
(l3-O)2] rings. Alternate tin atoms are held together by the coordi-
nation action of bidentate carboxylate groups to form a symmetri-
cal bridge between two carboxylate ligands. This represents the
signature structural feature of stannoxane clusters. The structure
features of various ‘drum’ complexes are similar. In general, the
Sn–O bond lengths inside the core range between 2.08 and
2.14 Å, and these distances are comparatively shorter than the
Sn–O bonds to the bridging carboxylate ligands (2.16(3)–

C.-L. Ma et al. / Polyhedron 29 (2010) 881–885
883
Table 1
fication. The melting points were obtained with an X-4 digital mi-
cro-melting-point apparatus and were uncorrected. Infrared-
spectra were recorded on a Nicolet-5700 spectrophotometer using
KBr discs. 1H, 13C and 119Sn NMR spectra were obtained on a Varian
Mercury Plus 400 MHz NMR spectrometer. The chemical shifts are
reported in ppm with respect to the references and are quoted rel-
ative to external tetramethylsilane (TMS) for 1H and 13C NMR and
tetramethyltin for 119Sn NMR. 13C spectra are broadband proton
decoupled. Element analyses were performed with a PE-2400II
apparatus.
Crystal data and structure refinement parameters for complex 1.
Complex
1
Empirical formula
Formula weight
Wavelength (Å)
Crystal system
Space group
a (Å)
C66H72O24Sn6
1961.38
0.71073
monoclinic
P2(1)/n
13.5887(12)
17.171(2)
15.0363(14)
90
b (Å)
c (Å)
a
(°)
b (°)
95.324(2)
90
3493.2(6)
2
1.865
2.190
c
(°)
3.2. Syntheses of complexes 1–7
V (Å3)
Z
3.2.1. [PhSn(O) (O3C5H7)]6 (1)
Dcalc (Mg/m3)
(mmÀ1
)
Complex 1 was synthesized by mixing ( )-tetrahydro-2-fural
acid (0.12 g 1.0 mmol), KOH (0.056 g, 1.0 mmol), triphenyltin chlo-
ride (0.056 g, 1.0 mmol), CH3OH (10 ml) and H2O (5 ml), which
were heated in a Teflon-lined autoclave at 130 °C for 3 days. After
cooling down to room temperature, colorless crystals were col-
lected and washed with methanol. Yield: 71%; M.p. 257–259 °C.
Anal. Calc. for C66H72O24Sn6: C, 40.41; H, 3.70; Found: C, 40.22;
H, 3.59%. IR (KBr, cmÀ1): 1580 (COO)as, 1385 (COO)s, 459 (Sn–C),
436 (Sn–O), 626 (Sn–O–Sn). 1H NMR (CDCl3, ppm) d: 7.13–7.73
l
F(0 0 0)
Crystal size (mm)
Reflections collected
Unique reflections [Rint
1920
0.23 Â 0.16 Â 0.12
17 305
]
6128 [Rint = 0.0427]
6128/1422/470
1.639
R1 = 0.0647, wR2 = 0.1664
R1 = 0.1239, wR2 = 0.1941
Data/restraints/parameters
Goodness-of-fit (GOF) on F2
Final R indices [I > 2
R indices (all data)
r
(I)]
(30H, C6H5), 4.34 (6H, CH–COO), 2.19 (12H, b-CH2), 1.96 (12H, c-
CH2), 3.94 (12H, d-CH2). 13C NMR (CDCl3, ppm) d: 176.3 (COO),
81.3 (C2, tetrahydro-2-fural), 30.5 (C3, tetrahydro-2-fural), 25.6
(C4, tetrahydro-2-fural), 69.9 (C5, tetrahydro-2-fural), 128.1 (p-C),
128.9 (m-C), 135.1 (o-C), 142.6 (i-C). 119Sn NMR (CDCl3, ppm) d:
À285.4.
Table 2
Selected bond lengths (Å) and angles (°) for complex 1.
Complex 1
Sn(1)–O(10)
Sn(1)–O(12)#1
Sn(1)–O(11)
Sn(1)–C(16)
Sn(1)–O(1))
2.08(7)
2.08(7)
2.10(8)
2.12(1)
2.16(8)
2.16(8)
103.8(3)
177.1(4)
86.9(3)
86.3(3)
78.6(4)
Sn(2)–C(22)
Sn(2)–O(11)
Sn(2)–O(2)
Sn(2)–O(10)
Sn(3)–O(10)
Sn(3)–O(12)
O(10)–Sn(2)–C(22)
O(12)–Sn(2)–O(11)
O(4)–Sn(2)–O(2)
O(12)–Sn(3)–C(28)
O(11)#1–Sn(3)–O(10)
2.12(1)
2.10(7)
2.15(9)
2.10(7)
2.10(7)
2.10(7)
178.3(4)
103.9(3)
78.2(3)
179.2(4)
103.1(3)
3.2.2. [PhSn(O) (O2C7H9)]6 (2)
Sn(1)–O(8)#1
Complex 2 was synthesized in the same way as 1 and the color-
less crystals were collected and washed with methanol. Yield: 65%;
M.p. 233–235 °C. Anal. Calc. for C78H84O18Sn6: C, 46.14; H, 4.19.
Found: C, 46.37; H, 3.97%. IR (KBr, cmÀ1): 1552 (COO)as, 1356
(COO)s, 454 (Sn–C), 433 (Sn–O), 624 (Sn–O–Sn). 1H NMR (CDCl3,
ppm) d: 5.67 (12H, C@CH), 1.72–2.31 (36H, CH2, cyclohexene),
2.66 (6H, CH–COO), 7.25–7.78 (30H, C6H5). 13C NMR (CDCl3,
ppm) d: 176.7 (COO), 138.8 (i-C), 128.8 (p-C), 130.9 (m-C), 136.4
(o-C), 126.9 (C3-cyclohexene), 125.7 (C4-cyclohexene), 39.4 (C1-
cyclohexene), 28.3 (C2-cyclohexene), 25.9 (C5-cyclohexene), 24.8
(C6-cyclohexene). 119Sn NMR (CDCl3, ppm) d: À301.7.
O(10)–Sn(1)–O(12)#1
O(11)–Sn(1)–C(16)
O(10)–Sn(1)–O(1)
O(12)#1–Sn(1)–O(8)#1
O(1)–Sn(1)–O(8)#1
Symmetry code for complex 1: #1 Àx + 1,Ày + 1,Àz + 1.
of six oxygen atoms, which is in a trigonal antiprismatic arrange-
ment, where the average O–O distance is 2.63 Å and the average
distance from the center of the cavity to the O atoms is 2.10 Å. On
the basis of a van der Waals radius of 1.40 Å for oxygen, the interior
of the cavity could thus host a species with a radius of approxi-
mately 0.70 Å. The entrance to the cavity is defined by three oxygen
atoms arranged in an approximate equilateral triangle with an
average edge length (oxygen center to oxygen center) of 3.27 Å.
Again with 1.40 Å as the van der Waals radius of the oxygen, species
with radii up to about 0.50 Å could gain entrance to the cavity. Thus,
encapsulation of ions as large as Li+ [22] might be possible.
In summary, through hydrothermal reactions, we have obtained
seven new organotin drum structures derived from triphenyltin
chloride and carboxylate acids. In all of complexes 1–7, the tri-
phenyltin groups become monophenyltin groups due to Sn–C
cleavage under the condition of high temperature. These results
indicate that organotin drum structures can be obtained by solvo-
thermal synthesis, which give us a new method to synthesize sim-
ilar structures.
3.2.3. [PhSn(O) (O2C13H15)]6Á2MeOH (3)
Complex 3 was synthesized in the same way as 1 and the color-
less crystals were collected and washed with methanol. Yield: 75%;
M.p. 220–222 °C. Anal. Calc. for C116H128O20Sn6: C, 54.34; H, 5.05.
Found: C, 54.52; H, 4.82%. IR (KBr, cmÀ1): 1594 (COO)as, 1388
(COO)s, 460 (Sn–C), 436 (Sn–O), 621 (Sn–O–Sn). 1H NMR (CDCl3,
ppm) d: 3.35 (2H, OH), 2.57 (6H, CH3), 7.21–7.42 (60H, C6H5),
1.21–1.84 (54H, cycloclopentyl), 3.38 (6H, CH–COO). 13C NMR
(CDCl3, ppm) d: 176.6 (COO), 127.6-–38.7 (Ph), 43.4 (CH, cyclocl-
opentyl), 25.0–31.8 (CH2, cycloclopentyl), 57.9 (CH–COO). 119Sn
NMR (CDCl3, ppm) d: À304.9.
3.2.4. [PhSn(O) (O2C8H9)]6 (4)
Complex 4 was synthesized in the same way as 1 and the color-
less crystals were collected and washed with methanol. Yield: 72%;
M.p. 241–243 °C. Anal. Calc. for C84H84O18Sn6: C, 48.18; H, 3.82.
Found: C, 47.89; H, 4.07%. IR (KBr, cmÀ1): 1631 (COO)as, 1433
(COO)s, 504 (Sn–C), 453 (Sn–O), 627 (Sn–O–Sn). 1H NMR (CDCl3,
ppm) d: 7.12–7.41 (30H, C6H5), 1.65–5.98 (54H, norbornene). 13C
NMR (CDCl3, ppm) d: 174.6 (COO), 138.2, 135.8, 50.0, 49.7, 46.7,
43.8, 29.9 (norbornene-C). 119Sn NMR (CDCl3, ppm) d: À277.2.
3. Experimental
3.1. Materials and measurements
Triphenyltin (IV) chloride and the seven carboxylic acids were
commercially available, and they were used without further puri-

884
C.-L. Ma et al. / Polyhedron 29 (2010) 881–885
Fig. 2. (a) Framework of the drum structure (except tin and oxygen atoms, all the other atoms are omitted for clarity). (b) The filled graph of the framework.
3.2.5. [PhSn(O) (O2C8H11)]6 (5)
M.p. 196–198 °C. Anal. Calc. for C96H84O18Sn6: C, 51.52; H, 3.78.
Found: C, 51.76; H, 3.55%. IR (KBr, cmÀ1): 1621 (COO)as, 1419
(COO)s, 455 (Sn–C), 441 (Sn–O), 630 (Sn–O–Sn). 1H NMR (CDCl3,
ppm) d: 7.22–7.54 (60H, C6H5), 4.38–6.33 (24H, butyric). 13C
NMR (CDCl3, ppm) d: 177.1 (COO), 140.8, 129.5, 128.9 (ph-C),
55.9, 117.9, 136.1 (butyric-C). 119Sn NMR (CDCl3, ppm) d: À254.4.
Complex 5 was synthesized in the same way as 1 and the color-
less crystals were collected and washed with methanol. Yield: 66%;
M.p. 243–245 °C. Anal. Calc. for C84H96O18Sn6: C, 47.60; H, 4.83.
Found: C, 47.87; H, 4.61%. IR (KBr, cmÀ1): 1633 (COO)as, 1436
(COO)s, 469 (Sn–C), 443 (Sn–O), 633 (Sn–O–Sn). 1H NMR (CDCl3,
ppm) d: 7.33–7.90 (30H, C6H5), 1.31–3.32 (66H, norbornane). 13C
NMR (CDCl3, ppm) d: 177.3 (COO), 47.1, 43.9, 40.3, 39.2, 33.9,
31.4, 28.7 (norbornane-C). 119Sn NMR (CDCl3, ppm) d: À239.4.
3.3. X-ray crystallographic studies of complexes 1, 2, 3, 4, 5, 6 and 7
Crystals were mounted in Lindemann capillaries under nitro-
gen. Diffraction data were collected on a Smart CCD area-detector
3.2.6. [PhSn(O) (O2C14H11S)]6 (6)
Complex 6 was synthesized in the same way as 1 and the color-
less crystals were collected and washed with methanol. Yield: 78%;
M.p. 193–195 °C. Anal. Calc. for C120H96O18S6Sn6: C, 52.48; H, 3.54;
S, 6.75. Found: C, 52.76; H, 3.33; S, 6.98%. IR (KBr, cmÀ1): 1632
(COO)as, 1432 (COO)s, 461 (Sn–C), 450 (Sn–O), 637 (Sn–O–Sn). 1H
NMR (CDCl3, ppm) d: 7.17–7.83 (90H, C6H5), 4.70 (6H, CH–COO).
with graphite monochromated Mo Ka radiation (k = 0.71073 Å). A
semi-empirical absorption correction was applied to the data.
The structures were solved by direct methods using SHELXS-97 and
refined against F2 by full matrix least-squares using SHELXL-97.
Hydrogen atoms were placed in calculated positions. Crystal data
and experimental details of the structure determinations are listed
in Table 1.
13C NMR(CDCl3, ppm) d: 177.4 (COO), 57.2 (
(ph-C). 119Sn NMR (CDCl3, ppm) d: À261.2.
a-C), 124.5–138.9
Acknowledgment
3.2.7. [PhSn(O) (O2C10H9)]6 (7)
Complex 7 was synthesized in the same way as 1 and the color-
less crystals were collected and washed with methanol. Yield: 86%;
We thank the National Nature Science Foundation of China
(20971096) for financial supported.

C.-L. Ma et al. / Polyhedron 29 (2010) 881–885
885
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CCDC 728576, 728582, 728579, 728578, 728581, 728583 and
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plexes 1, 2, 3, 4, 5, 6 and 7, respectively. These data can be obtained
free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.
html, or from the Cambridge Crystallographic Data Centre, 12 Un-
ion Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-
mail: deposit@ccdc.cam.ac.uk. Supplementary data associated
with this article can be found, in the online version, at doi:10.
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