Synthesis, characterization, and structure of some silicon containing diorganotin(IV) complexes of salicylaldehyde thiosemicarbazones

Article abstract of DOI:10.1080/10426507.2012.717144

Four diorganotin(IV) complexes, bis[(trimethylsilyl)methyl]tin salicylaldehyde thiosemicarbazonate monohydrate(1), bis[(trimethylsilyl)methyl] tin 3-methoxysalicylaldehyde thiosemicarbazonate (2), bis[(trimethylsilyl) methyl]tin 5-tert-butyl-3-methylsalicylaldehyde thiosemicarbazonate (3), and bis[(trimethylsilyl)methyl]tin 2-oxylnaphthaldehyde thiosemicarbazonate (4) have been synthesized by reactions of (Me₃SiCH₂) ₂SnCl₂ with the corresponding semicarbazone. The four complexes were characterized by IR and NMR spectroscopy and elemental analyses. The X-ray studies of compounds 1 and 4 showed that the thiosemicarbazone ligands act as tridentate ligands chelating to the central tin atoms, and thus the tin atoms were five coordinated in trigonal bipyramidal geometry for both compounds. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

Full text of DOI:10.1080/10426507.2012.717144

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Synthesis, Characterization, and
Structure of Some Silicon Containing
Diorganotin(IV) Complexes of
Salicylaldehyde Thiosemicarbazones
Qibao Wang a , Ruifang Ding a , Xinmin Wen a & Fujun Yin b
a Department of Pharmacy , Jining Medical College, Rizhao ,
Shandong , People's Republic of China
b School of Chemistry and Chemical Engineering , Huaihai Institute
of Technology , Lianyungang , Jiangsu , People's Republic of China
Accepted author version posted online: 09 Aug 2012.Published
online: 05 Jul 2013.
To cite this article: Qibao Wang , Ruifang Ding , Xinmin Wen & Fujun Yin (2013) Synthesis,
Characterization, and Structure of Some Silicon Containing Diorganotin(IV) Complexes of
Salicylaldehyde Thiosemicarbazones, Phosphorus, Sulfur, and Silicon and the Related Elements, 188:7,
895-903, DOI: 10.1080/10426507.2012.717144
To link to this article: http://dx.doi.org/10.1080/10426507.2012.717144
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Phosphorus, Sulfur, and Silicon, 188:895–903, 2013
Copyright ꢀC Jining Medical College
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426507.2012.717144
SYNTHESIS, CHARACTERIZATION, AND STRUCTURE
OF SOME SILICON CONTAINING DIORGANOTIN(IV)
COMPLEXES OF SALICYLALDEHYDE
THIOSEMICARBAZONES
Qibao Wang,1 Ruifang Ding,1 Xinmin Wen,1 and Fujun Yin2
1Department of Pharmacy, Jining Medical College, Rizhao, Shandong, People’s
Republic of China
2School of Chemistry and Chemical Engineering, Huaihai Institute of Technology,
Lianyungang, Jiangsu, People’s Republic of China
GRAPHICAL ABSTRACT
Abstract Four diorganotin(IV) complexes, bis[(trimethylsilyl)methyl]tin salicylaldehyde
thiosemicarbazonate monohydrate(1), bis[(trimethylsilyl)methyl]tin 3-methoxysalicylaldehyde
thiosemicarbazonate (2), bis[(trimethylsilyl)methyl]tin 5-tert-butyl-3-methylsalicylaldehyde
Received 17 June 2012; accepted 21 July 2012.
This work was supported by the Shandong Province Natural Science Foundation (No. ZR2010BL031) and
Domestic Visitor Foundation from the Education Commission of Shandong Province.
Address correspondence to Qibao Wang, Department of Pharmacy, Jining Medical College, No.669 Xueyuan
Road, Rizhao, Shandong, People’s Republic of China. E-mail: wqb wangqibao@163.com
895

896
Q. WANG ET AL.
thiosemicarbazonate (3), and bis[(trimethylsilyl)methyl]tin 2-oxylnaphthaldehyde thiosemi-
carbazonate (4) have been synthesized by reactions of (Me3SiCH2)2SnCl2 with the corre-
sponding semicarbazone. The four complexes were characterized by IR and NMR spectroscopy
and elemental analyses. The X-ray studies of compounds 1 and 4 showed that the thiosemi-
carbazone ligands act as tridentate ligands chelating to the central tin atoms, and thus the tin
atoms were five coordinated in trigonal bipyramidal geometry for both compounds.
Supplemental materials are available for this article. Go to the publisher’s online edition of
Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.
Keywords Organotin compounds; thiosemicarbazones; silicon; crystal structure; spectral
studies
INTRODUCTION
The use of organosilanes as bioactive agents in pharmaceutical applications have been
of long standing interest,1 and the design of bioactive organosilanes was often involved in
systematic replacement studies of a bioactive molecule’s stable carbon atoms with silicon,
based on the bioisosterism model.2 Chen et al. reported several silanediol analogs of a
carbinol-based inhibitor of the HIV protease, and studies showed that these analogs can
easily cross cell membranes and deliver their antiviral effects with less toxicity.3 Tacke also
reported two sila-substitutions of M3 subtype-preferring muscarinic antagonists. Studies
showed that these sila-substitutions display a pronounced selectivity for M3 versus M2
muscarinic receptors.4 Organotin(IV) complexes have been extensively studied as wood
preservatives, antitumorals, antibacterials, antifungals, and biocides, even if their toxicity
and their environmental effects are now limiting their uses.5 Previous studies mostly focused
on designing new types of organotin complexes by changing the ligands to minimize its
drawbacks.6 So far few studies have been conducted toward changing the carbon atoms of
the tin-bound alkyl groups based on bioisosterism.
On the other hand, thiosemicarbazones and their metal complexes present a
wide range of bioactivities, and their chemistry and pharmacological applications have
been investigated.7,8 We synthesized the silicon containing diorganotin(IV) compound
(Me3SiCH2)2SnCl2 and studied its reaction with salicylaldehyde thiosemicarbazones and
related ligands. The details of this study are reported herein.
RESULTS AND DISCUSSION
IR Spectroscopy
The IR bands of compounds 1–4 have been assigned by comparison with the IR
spectra of the free thiosemicarbazones. As a result, the ν(OH) and ν(C S) absorptions,
present in the spectra of the free thiosemicarbazones at 3627∼3633 and 847∼852 cm−1
,
disappeared in 1–4. Four new intense bands at 1539∼1555 cm−1 found in the spectra of
compounds 1–4 were assigned to new C N double bonds, which were C–N single bonds in
thiosemicarbazones.9 Moreover the ν(C S) absorption disappeared in 1–4, and four new
bands appeared at 761∼767 cm−1 assigned to ν(C–S). All of these indicate that the sulfur
atoms coordinate to the central tin atoms via thiolate rather than thione.10
NMR Spectroscopy
The absence of the OH and NH protons in compounds 1–4 indicate deprotonation,
which supports the evidence from IR spectroscopy that the ligands are O,N,S-coordinated

SILICON CONTAINING DIORGANOTIN(IV) COMPLEXES
897
and existing in the thiol form. The chemical shift of the protons of azomethine (CH N)
groups exhibit signals at 8.49∼9.40 ppm as singlet for 1–4. The singlets at 0.03∼0.05 ppm
were assigned to SiMe3 protons. The double dublets at 0.52∼0.55 ppm were assigned to
SnCH2 protons, and the spin–spin coupling constant JSn–H is 58∼86 Hz.
13C NMR signals for each carbon atom appear at their usual positions and compare
well with the reported values.11,12
The 119Sn chemical shift values in compounds 1–4 are found to be in the range of
–107.6 to –111.7 ppm. The appearance of chemical shift values in this region indicates
five-coordination environment around the central tin atoms in compound 1–4.13
X-Ray Studies
Crystallographic data for compounds 1 and 4 are listed in Table 1. The crystal data
were collected on a Bruker APEX II CCD area-detector diffractometer. The diffractometer
was equipped with graphite-monocromators, using MoKα radiation (λ = 0.71073 Å). The
structures were solved by direct methods and anisotropically refined except the hydrogen
atoms. Hydrogen atoms were placed into calculated positions and refined using a riding
model with fixed isotropic thermal parameters. Structures were solved and refined using
SHELXS-9714 and SHELXL-97,15 respectively. Additional information to the structure is
given in Table 1 and selected bond distances and angles can be seen in Table 2.
Table 1 Crystallographic data and refinement details for compound 1 and 4
Data
1
4
Formula
C16H31N3O2SSi2Sn
504.37
C20H31N3OSSi2Sn
536.41
M (g·mol−1
)
Temperature (K)
296 (2)
293 (2)
Crystal dimensions (mm)
0.27 × 0.20 × 0.15
Monoclinic
P2(1)/c
0.25 × 0.21 × 0.13
Monoclinic
C2/c
Crystal system
Space group
Unit cell
a (Å)
17.179 (2)
13.8752 (19)
10.0618 (14)
96.891 (2)
2381.0 (6)
4
38.814 (18)
7.206 (3)
19.538 (9)
111.096 (5)
5098 (4)
8
b (Å)
c (Å)
β (◦)
V (Å3)
Z
Dcalc (g·cm−3
)
1.407
1.275
1.398
1.193
Linear absorption coefficient (mm−1
)
F(000)
1032
2192
Index ranges
16 ≤ h ≤ 20
–16 ≤ k ≤ 16
–11 ≤ l ≤ 9
11,404
46 ≤ h ≤ 46
–8 ≤ k ≤ 8
–23 ≤ l ≤ 23
16,126
Reflections collected
Independent reflections
Refined parameters
4172
244
4487
268
Absorption correction
Max./min. transmission
Goodness-of fit (F2)
Final R indices (I > 2σ (I))
R indices(all data)
Multiscan
0.8318, 0.7247
1.110
Multiscan
0.8603, 0.7547
1.302
0.0338
0.0433
0.1015
0.1257

898
Q. WANG ET AL.
Table 2 Selected bond lengths (Å) and angles (◦) for compounds 1 and 4
Compound 4
Compound 1
Sn(1)–O(1)
Sn(1)–C(13)
Sn(1)–C(9)
Sn(1)–N(1)
Sn(1)–S(1)
S(1)—C(8)
O(1)–C(1)
N(1)–C(7)
2.078 (3)
2.133 (4)
2.148 (4)
2.264 (3)
2.5242 (10)
1.749 (4)
1.348 (4)
1.301 (5)
1.388 (4)
1.303 (5)
Sn(1)–O(1)
Sn(1)–C(13)
Sn(1)–C(17)
Sn(1)–N(1)
Sn(1)–S(1)
S(1)–C(12)
O(1)–C(3)
N(1)–C(1)
2.104 (8)
2.129 (13)
2.154 (14)
2.190 (9)
2.569 (4)
1.722 (12)
1.331 (14)
1.323 (13)
1.423 (12)
1.297 (14)
1.381 (14)
90.0 (5)
98.2 (4)
127.1 (6)
81.0 (3)
114.0 (4)
118.9 (5)
157.6 (2)
98.6 (4)
N(1)–N(2)
N(2)–C(8)
N(3)–C(8)
N(1)–N(2)
N(2)–C(12)
N(3)–C(12)
1.337 (5)
O(1)–Sn(1)–C(13)
O(1)–Sn(1)–C(9)
C(13)–Sn(1)–C(9)
O(1)–Sn(1)–N(1)
C(13)–Sn(1)–N(1)
C(9)–Sn(1)–N(1)
O(1)–Sn(1)–S(1)
C(13)–Sn(1)–S(1)
C(9)–Sn(1)–S(1)
N(1)–Sn(1)–S(1)
100.63 (13)
87.82 (13)
122.35 (16)
80.58 (11)
97.40 (14)
140.06 (13)
142.83 (8)
110.80 (12)
91.58 (11)
76.27 (8)
O(1)–Sn(1)–C(13)
O(1)–Sn(1)–C(17)
C(13)–Sn(1)–C(17)
O(1)–Sn(1)–N(1)
C(13)–Sn(1)–N(1)
C(17)–Sn(1)–N(1)
O(1)–Sn(1)–S(1)
C(13)–Sn(1)–S(1)
C(17)–Sn(1)–S(1)
N(1)–Sn(1)–S(1)
93.1 (4)
76.6 (2)
In the solid structure of compound 1 (shown in Fig. 1), the thiosemicarbazone ligand
acts as tridentate ligand chelating to the central tin atom, and thus the tin atom is five
coordinated in a trigonal bipyramidal geometry. In the coordination polyhedron two carbon
atoms, C(9) and C(13) of the trimethylsilylmethyl groups, and the imine N(1) atom occupy
the equatorial plane, whereas the S(1) and O(1) atoms occupy the axial positions. Bond
lengths of C(7)–N(1) 1.276 Å, N(1)–N(2) 1.380 Å, C(8)–N(2) 1.346 Å, and C(8)–S(1)
1.689 Å were found in the uncoordinated ligand,16 while in compound 1 the C(7)–N(1)
[1.301(5) Å], C(8)–N(2) [1.303(5) Å], and C(8)–S(1) [1.749(4) Å] bond lengths are quite
different from those of the ligand. The shortening of the C(8)–N(2) and lengthening of the
C(9)–S(1) show that deprotonation of the imine N(2) atom results from a conversion from
thione to thiolate,17–19 which accords with the results of IR and NMR spectra. The same
changes were also found in compound 4.
In the crystal structure of compound 1, the N–H···N hydrogen bonding interac-
tions cause two neighboring molecules to become a dimer, and the O–H···O and O–H···S
hydrogen bonds between the dimers and the water molecules lead to a one-dimensional
chain structure (Figure 2). Significant contacts are represented by N(3)–H(3A)···N(2) (–x
◦
◦
+ 1, –y + 1, –z) 3.067 Å, 167.72 ; N(3)–H(3B)···O(2) (x, y, z – 1) 2.871 Å, 152.3 ;
O(2)–H(2A)···O(1) 2.812 Å, 160.58 ◦; and O(2)–H(2B)···S(1) (x, –y + 0.5, z + 0.5) 3.384
Å, 171.44 ◦.
The X-ray structure determination of compound 4 revealed similar molecular struc-
tures as compound 1 (Figure 3), and the bond lengths and angles were also similar with
those of the compound 1.

SILICON CONTAINING DIORGANOTIN(IV) COMPLEXES
899
Figure 1 Crystal structure of compound 1. Ellipsoids are drawn at the 30% probability level. H atoms, not
involved in hydrogen bonding, are omitted for clarity.
EXPERIMENTAL
Materials
All air-sensitive and volatile materials were handled either in vacuo or under Argon
by using standard Schlenk techniques. (Me3SiCH2)2SnPh2 was prepared by a published
procedure.20 Salicylaldehyde, 3-methoxysalicylaldehyde, 2-hydroxy-1-naphthaldehyde, 5-
tert-butyl-3-methyl-salicylaldehyde, and thiosemicarbazide were used as received from
Figure 2 One-dimensional chain structure with intermolecular hydrogen bonds of compound 1.

900
Q. WANG ET AL.
Figure 3 Crystal structure of compound 4. Ellipsoids are drawn at the 30% probability level. H atoms, not
involved in hydrogen bonding, are omitted for clarity.
commercial sources. The solvents used in the reactions were of AR grade and dried using
standard literature procedures. IR spectra were recorded on a Bruker TENSOR 27 spec-
trometer, NMR spectra on Bruker AMX 400 in CDCl3. 1H and 13C signals were referred to
TMS via the solvent signals (7.27 for 1H in CDCl3), and 119Sn to external neat Sn(CH3)4.
Preparation of Ligands
The thiosemicarbazones were prepared by reacting equimolar amounts of
thiosemicarbazides and respective salicylaldehyde/substituted salicylaldehydes in a 1:1
ethanol–water mixture (Equation 1). The products were recrystallized from ethanol.

SILICON CONTAINING DIORGANOTIN(IV) COMPLEXES
901
(Me3SiCH2)2SnCl2·H2O. The syntheses of (Me3SiCH2)2SnCl2·H2O via hydrolysis
of (Me3SiCH2)2SnCl2 was reported by Beckmann.13 In this report, (Me3SiCH2)2SnCl2·H2O
was prepared by reaction of (Me3SiCH2)2SnPh2 (0.447 g, 1 mmol) with excess conc. HCl
(15 mL, 37%) in 30 mL CHCl3. The reaction mixture was stirred and maintained at 70 ◦C
for 24 h. The organic layer was separated and the aqueous layer extracted with CHCl3 (3
× 30 mL). The organic extracts were combined, the solvent was removed under vacuum,
and the residue was crystallized from CH2Cl2/hexane to give colorless crystals (0.269 g,
◦
73.9%), m.p. 46–48 C, 119Sn NMR: δ –51.7. The data were in agreement with those
reported in the literature (m.p. 48–49 ◦C, 119Sn NMR: δ –53.9).13
Preparation of the Tin Complexes
The tin complexes 1–4 were prepared by reaction of the ligands with
(Me3SiCH2)2SnCl2·H2O (equ. 1).
Bis[(trimethylsilyl)methyl]tin salicylaldehyde thiosemicarbazonate monohy-
drate (1). To a solution of salicylaldehyde thiosemicarbazone (0.215 g, 1.10 mmol)
in 30 mL THF (tetrahydrofuran) was added sodium ethoxide (0.119 g, 2.20 mmol)
under stirring. The mixture was stirred for 2 h and then a 10 mL a THF solution of
(Me3SiCH2)2SnCl2·H2O (0.347 g, 1.00 mmol) was added. The yellow reaction mixture
was refluxed for 24 h under inert conditions. The volatiles were removed and the residue
was crystallized from acetonitrile to give yellow crystals 0.418 g, yield 83%. IR: νC
N
1614, 1549 cm−1, νC–S 764 cm−1. 1H NMR: δ 0.05 (s, 18H, SiMe3), 0.53 (dd, 4H, 2JSn–H
= 58 Hz, SnCH2), 1.71 (s, 2H, H2O), 4.93 (s, 2H, NH2), 6.69 (d, 1H, aromatic-H), 6.71
(d, 1H, aromatic-H), 7.10 (dd, 1H, aromatic-H), 7.30 (t, 1H, aromatic-H), 8.51 (s, 1H,
CH N). 13C NMR: δ 1.2 (SiMe3), 13.2 (CH2Sn), 116.6, 116.8, 121.5, 133.7, 134.7,
161.1 (aromatic-C), 166.0 (CH N), 167.9 (C N). 119Sn NMR: δ –107.6. Anal. Calcd. for
C16H31N3O2SSi2Sn: C, 38.10; H, 6.19; N, 8.33; Found: C, 38.03; H, 6.11; N, 8.40.
Bis[(trimethylsilyl)methyl]tin 3-methoxylsalicylaldehyde thiosemicarbazonate
(2). The preparation follows the procedure described for compound 1, yield 80%. IR: νC
N
1617, 1542 cm−1, νC–S 762 cm−1. 1H NMR: δ 0.05 (s, 18H, SiMe3), 0.52 (dd, 4H, 2JSn–H
=
63 Hz, SnCH2), 3.71 (s, 3H, OCH3), 4.92 (s, 2H, NH2), 6.52 (br, 1H, aromatic-H), 6.75 (d,
1H, aromatic-H), 7.23 (dd, 1H, aromatic-H), 8.50 (s, 1H, CH N). 13C NMR: δ 1.2 (SiMe3),
13.1 (CH2Sn), 57.3 (OCH3), 111.2, 112.7, 117.7, 144.2, 151.4, 160.4, (aromatic-C), 164.3
(CH N), 167.2 (C N). 119Sn NMR: δ –109.3. Anal. Calcd. for C17H31N3O2SSi2Sn : C,
39.54; H, 6.05; N, 8.14; Found: C, 39.48; H, 6.16; N, 8.20.
Bis[(trimethylsilyl)methyl]tin 5-tert-butyl-3-methylsalicylaldehyde thiosemicar-
bazonate (3). The preparation follows the procedure described for compound 1, yield 75%.
1
IR: νC 1611, 1539 cm−1, νC–S 761 cm−1. H NMR: δ 0.03 (s, 18H, SiMe3), 0.52 (dd,
N
4H, 2JSn–H = 86 Hz, SnCH2), 1.42 (s, 9H, C(CH3)3), 2.24 (s, 3H, CH3), 4.89 (s, 2H, NH2),
6.76 (s, 1H, aromatic-H), 7.16 (s, 1H, aromatic-H), 8.49 (s, 1H, CH N). 13C NMR: δ 1.2
(SiMe3), 12.9 (CH2Sn), 20.5[(CH3)3], 29.6 (CH3), 34.8 [C–(CH3)3], 116.6, 124.9, 128.5,
131.6, 133.5, 140.5 (aromatic-C), 163.0 (CH N), 167.5 (C N). 119Sn NMR: δ –117.7.
Anal. Calcd. for C21H39N3OSSi2Sn: C, 45.32; H, 7.06; N, 7.55; Found: C, 45.27; H, 6.99;
N, 7.51.
Bis[(trimethylsilyl)methyl]tin 2-oxylnaphthaldehyde thiosemicarbazonate (4).
The preparation follows the procedure described for compound 1, yield 73%. IR: νC
N
1609, 1555 cm−1, νC–S 767 cm−1. 1H NMR: δ 0.05 (s, 18H, SiMe3), 0.55 (dd, 4H, 2JSn–H
= 60 Hz, SnCH2), 4.90 (s, 2H, NH2), 6.90 (d, 1H, aromatic-H), 7.28 (dd, 1H, aromatic-H),

902
Q. WANG ET AL.
7.48 (t, 1H, aromatic-H), 7.69 (d, 1H, aromatic-H), 7.74 (d, 1H, aromatic-H), 7.93 (d, 1H,
aromatic-H), 9.40 (s, 1H, CH N). 13C NMR: δ 1.2 (SiMe3), 12.6 (CH2Sn), 107.0, 112.6,
119.1, 122.9, 124.2, 127.4, 129.1, 133.6, 136.2, 156.8 (aromatic-C), 166.3 (CH N), 168.2
(C N). 119Sn NMR: δ –111.2. Anal. Calcd. for C20H31N3OSSi2Sn: C, 44.78; H, 5.82; N,
7.83; Found: C, 44.85; H, 5.91; N, 7.76.
CONCLUSION
Four silicon containing diorganotin (IV) complexes of thiosemicarbazones have been
synthesized by reaction of (Me3SiCH2)2SnCl2 with the corresponding semicarbazone. The
four complexes have been characterized by IR, NMR, and elemental analysis. The X-ray
studies of compounds 1 and 4 showed that the thiosemicarbazone ligands act as tridentate
ligand chelating to the central tin atoms, and thus the tin atom is five coordinated in a
trigonal bipyramidal geometry for both compounds.
SUPPLEMENTARY MATERIAL
Crystallographic data (excluding structure factors) for the structures in this paper have
been deposited with the Cambridge Crystallographic Data Centre, CSD numbers CCDC
884067 to complex 1, CCDC 884066 to complex 2. Copies of the data can be obtained, free
of charge, via www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge Crystal-
lographic Data Centre, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +441223
336033; e-mail: deposit@ccdc.cam.ac.uk.
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