Synthesis and structural studies of organotin(IV) and organolead(IV) thiophene-2-thiocarboxylate

Article abstract of DOI:10.1002/ejic.201000692

A few organotin(IV) ([R₂SnCl₂], [R₃SnCl]; R = Me, Ph, nPr, or nBu) and organolead(IV) ([Ph₂PbCl₂], [Ph₃PbCl]) compounds that contain the thiophene-2-thiocarboxylate ligand have been synthesized and characterized by ¹H, ¹³C, ¹¹⁹Sn NMR; FTIR; and UV/Vis spectroscopy. The molecular structures of some of the compounds were studied by single-crystal X-ray diffraction. Structures and electronic transitions have been explained on the basis of DFT calculations. Organotin ([R₂SnCl₂], [R₃SnCl]; R = Me, Ph, nPr, and nBu) and organolead ([Ph₂PbCl₂], [Ph₃PbCl]) compounds that contain the thiophene-2-thiocarboxylate ligand have been synthesized and characterized by spectral and crystallographic studies. Structures and electronic transitions have been explained on the basis of DFT calculations.

Full text of DOI:10.1002/ejic.201000692

FULL PAPER
DOI: 10.1002/ejic.201000692
Synthesis and Structural Studies of Organotin(IV) and Organolead(IV)
Thiophene-2-thiocarboxylate
Suryabhan Singh,[a] Subrato Bhattacharya,*[a] and Heinrich Nöth[b]
Keywords: Tin / Lead / Thiocarboxylate / Thiophene / Density functional calculations / Structure elucidation
A few organotin(IV) ([R2SnCl2], [R3SnCl]; R = Me, Ph, nPr, or
nBu) and organolead(IV) ([Ph2PbCl2], [Ph3PbCl]) compounds
that contain the thiophene-2-thiocarboxylate ligand have
been synthesized and characterized by 1H, 13C, 119Sn NMR;
FTIR; and UV/Vis spectroscopy. The molecular structures of
some of the compounds were studied by single-crystal X-ray
diffraction. Structures and electronic transitions have been
explained on the basis of DFT calculations.
thiophene-2-thiocarboxylate. [While compiling our results,
a paper appeared that described the synthesis of this ligand
(by a different route) and its complexes[31]]. The thiophene
ring, being aromatic in nature, is expected to behave like a
phenyl group in which the bidentate bonding mode is a little
more favored as compared with the alkyl group of the
thiocarboxylate ligand due to the contributions of dianionic
canonical forms (as shown in Scheme 1.)
Introduction
Organotin compounds are well known for their synthetic
applications[1] and toxic effects.[2] A number of studies have
been carried out on the structures, bonding patterns, and
reactivities of these compounds that contain oxygen or sul-
fur ligands.[3] A number of papers related to studies focused
on organotin compounds that contain anisobidentate S,O-
donor ligands are also available.[4] Compounds that contain
thiocarbamate[5] and thio-β-diketonate[6] ligands were re-
ported some time ago. Our early studies with thiocarboxyl-
ate ligands have revealed that the ligand may bind to the
organotin center either monodentately through S or biden-
tately by using both O and S atoms.[7] Tani et al. have
studied the extent of Sn–O overlap in triphenyltin thioben-
zoate in which the primary bonding of the ligand is essen-
tially through the S atom.[8] Very recently, we have reported
studies on structures of a few organotin thiocarboxylates
and their reactivities.[9,10] It was observed that both struc-
ture and reactivity of organotin thiocarboxylates depend
not only on the organyl groups (on Sn) but also on the
terminal R groups of the RCOS– ligands.[10] Although we
have been able to establish effects of these factors, in a few
cases more structural data are essential before any generali-
zation can be made.[7,10]
Scheme 1. Dianionic canonical of the thiobenzoate group.
Further, the presence of a sulfur atom at the peripheral
position is expected to influence the crystal and molecular
structures. In light of the thiophilicity of organotin and
-lead centers, one may look for one or more possible modes
of bonding of the thiocarboxylate ligand (Scheme 2).
We thought it would be worthwhile to study the effect of
terminal groups on bonding on organotin(IV) by systemati-
cally changing the number/nature of organyl groups. Fur-
ther, a comparison with analogous organolead compounds
would shed light on the role of the metal atom. We report
herein the synthesis and structures of a few di- and tri-
organotin and -lead compounds that contain a new ligand,
Scheme 2. Possible bonding modes of thiophene-2-thiocarboxylate.
Results and Discussion
Syntheses and Characterization
All the complexes were synthesized by a simple one-step
reaction between sodium thiophene-2-thiocarboxylate and
organotin or -lead chlorides in methanol (Scheme 3). The
compounds were isolated in high yields and were found to
be quite stable under ambient conditions.
[a] Departmentof Chemistry, Faculty of Science, Banaras Hindu
University,
Varanasi 221005, India
E-mail: s_bhatt@bhu.ac.in
[b] Department of Chemistry, University of Munich,
Butenandstrasse 5–13, 81377 Munich, Germany
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119Sn NMR spectral studies were carried out to under-
stand the structure of compounds 1a–1c. The single reso-
nance observed in the spectra of all the three compounds
rules out any possibility of the existence of more than one
isomer in solution. The peak at δ = –190.10 ppm in the
spectrum of 1c indicates a five-coordinate environment
around the tin center.[11] 119Sn signals for four-coordinate
compounds are observed in the range of δ = +200 to
–60 ppm.[11] Signals at δ = –69.68 and –77.71 ppm, respec-
tively, in the cases of 1a and 1b indicate higher (Ͼ4) coordi-
nation numbers around the tin atom, which is possibly due
to the existence of weak Sn–O bonds (the primary bonding
of ligands is through the sulfur atoms).
Scheme 3. Synthetic route for organotin and -lead compounds.
The IR spectra showed a strong absorption between 1609
This could be further substantiated by variable-tempera-
and 1557 cm–1 due to C=O stretching vibrations. Two other ture (VT) 119Sn NMR spectroscopic studies (Table 1). At
strong bands were observed in the 1196–1226 and 1045– –30 °C, 1b showed a signal at δ = –83.77 ppm, which shifted
1053 cm–1 regions. These two correspond to ν(th–C) and downfield on an increase in the temperature. Similar tem-
ν(C–S) vibrations, respectively. The infrared spectral fea- perature-dependent shifts in the NMR spectroscopic signals
tures that corroborate the bonding modes of the ligand have have also been observed for 1a and 1c. Such shifts in 119Sn
been studied in the case of monoorganotin thiobenzoates.[7] NMR spectroscopic signals evince weakening of Sn–O in-
Shifts in the positions of C=O, Ph–C, and C–S bond teractions with an increase in temperature.
stretching vibrations can be used as a diagnostic tool to
Table 1. Variable-temperature 119Sn NMR spectroscopic data of
1a–1c.
detect the coordination mode of the ligand. A CO stretch-
ing band observed around 1600 cm–1 offers strong evidence
Compound
T [°C]
δ(119Sn) [ppm]
for the existence of a double bond between the two atoms.
A lowering in this frequency is indicative of M···O bonding.
Similarly, from the ν(C–S) band, an inference can be drawn
about the nature of the C–S bond; on chelation, the ν(C–
S) band shifts to a higher wavenumber. Furthermore, the
ν(Ph–C) absorption around 1200 cm–1 is also indicative of
monodentate attachment of the ligand, since, on chelation,
this band shifts to a higher frequency as has been observed
in [Cl2Sn(SOCPh)2].[7] From the spectroscopic data of com-
pounds 1–4, one may conclude that bonding of the ligands
in these complexes is mainly through the sulfur atoms; how-
ever, in 1a–c and 3 significant M···O interactions are ex-
pected.
1a
+24
+46
–30
0
+24
+46
+24
+46
–69.66
–64.40
–83.77
–80.10
–77.71
–73.52
–190.10
–186.76
1b
1b
Crystal and Molecular Structures
All the complexes except 2a (liquid) and 2b (insoluble
solid) have been characterized by single-crystal X-ray dif-
fraction. Suitable single crystals of 1a were grown from a
chloroform solution by layering with n-hexane. The com-
pound crystallized in the triclinic system with P1 space
group. A molecular structure and atomic labeling scheme
of 1a are depicted in Figure 1.
1
In the H NMR spectrum of thiophene-2-thiocarboxylic
acid, two doublets (δ = 7.67, 7.75 ppm) and a triplet (δ =
7.13 ppm) were observed due to the thiophene ring protons,
which showed small shifts after complexation. Similarly, the
four signals observed due to thiophene carbon atoms (δ =
128.03, 133.88, 134.09, 141.54 ppm) in the 13C NMR spec-
trum of the free acid were also observed in the complexes.
One would expect the signals of the carbon atoms at the
2- and 5-positions of the thiophene ring to show smaller
downfield shifts relative to those of the ones in the free acid
if the thiophene sulfur atom is involved in bonding with the
metal atom. Small changes were observed in the δ values of
C-2 of the ring, but the signal of the carbon atom at posi-
tion 5 appeared at the same position. The shift in the for-
mer case may also arise due to bonding with the metal atom
through the S/O-donor atoms. As expected, significant
changes in the chemical-shift values of the COS carbon
atom were noticed in the complexes when compared to that
Figure 1. Molecular structure of 1a.
Selected bond lengths and angles are given in Table 2.
of the free acid (δ = 182.18 ppm). From these data, it ap- There are two molecules in the unit cell that lie almost per-
pears that there is no significant bonding between the metal pendicular to each other (the interplanar angle between the
atom and the ring sulfur atom.
two C2S2O2Sn units is 81.54°). The central tin atom is sur-
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Organotin(IV) and Organolead(IV) Thiophene-2-thiocarboxylate
rounded by two carbon, two sulfur, and two oxygen atoms. other with an interplanar angle of 44.92°. This indicates
The thiocarboxylate ligands are bonded to the metal atom that the delocalization of the thiophene π-electrons does not
mainly through the S atoms and have longer distances be- extend up to the donor atoms (O/S) by conjugation, and as
tween the oxygen and tin atoms. The average Sn–O distance a result the bidentate binding of the ligand is not favored.
2.778 Å is significantly longer than the corresponding dis-
An alternative and better description of the geometry
tances in the earlier reported molecule [Cl2Sn(SCOPh)2] thus can be made by considering the Sn–O distances as
with distorted octahedral structure. The geometry around nonbonding interactions only. The Sn1 atom is tetrahe-
Sn1 may be described as skewed trapezoidal-bipyramidal. drally surrounded by two sulfur and two carbon atoms. The
The C11–Sn1–C12 angle is 125.5(3)°, which corresponds to C–Sn–S bond angles (which vary between 105.43 and
the geometry of the transition state in the cis/trans pathway 112.88°) are very close to the ideal tetrahedral angle. The
of the skewed trapezoidal-bipyramidal structures.[12] How- large deviation of the C–Sn–C angle is due to the capping
ever, the O1–Sn1–O2 angle (153.49°) is quite smaller than of the CCS faces by the oxygen atoms.[13]
that of the transition state (160–170°), and the two SCO
There are two types of intermolecular hydrogen bonds,
units of two thiocarboxylate groups deviate slightly from one between a methyl hydrogen atom and the thiophene
planarity (the interplanar angle is 14.74°). Notably, the two sulfur atom (2.985 Å) along the b axis and the other be-
thiophene rings are twisted to opposite directions from each tween a hydrogen atom of the thiophene ring and a car-
bonyl oxygen atom (2.654 Å). Sulfur, which has less elec-
tronegativity, forms weaker hydrogen bonds relative to oxy-
gen, and the C–H donor strength is known to vary along
the order C(sp)–H Ͼ C(sp2)–H Ͼ C(sp3)–H.[14] The S···HC(sp3)
distance in the present case indicates a strong hydrogen
bond. Due to two types of hydrogen bonding, it acquires a
sheetlike structure along the a axis (Figure 2).
Table 2. Selected bond lengths and angles of the complexes.
Bond lengths [Å]
1a
1b
1c
3
Sn1–S1
Sn1–C11
S1–C1
2.467(16)
2.105(6)
1.745(5)
1.469(7)
2.473(3)
2.136(10)
1.751(10)
1.453(13)
2.480(7)
2.135(3)
1.756(3)
1.457(4)
2.574(3)
2.207(10)
1.767(12)
1.456(13)
2.550(5)
2.189(15)
2.170(15)
1.50(2)
Sn1–S3
Sn1–C12
O1–C1
2.470(17)
2.085(6)
1.227(6)
C1–C2
Sn1–S1
Sn1–C6
S1–C1
Sn1–S1
Sn1–C6
O1–C1
2.473(3)
2.136(10)
1.243(12)
C1–C2
Sn1–S1
Sn1–C11
S1–C1
Sn1–S2
Sn1–C17
O1–C1
2.483(7)
2.122(2)
1.228(3)
C2–C1
Pb1–S1
Pb1–C11
S1–C1
Pb1–S2
Pb1–C17
O1–C1
2.586(3)
2.182(9)
1.234(14)
2.743(8)
1.751(18)
2.202(17)
1.21(2)
C2–C1
Pb1–O1
S01–C01
Pb01–C12
O01–C01
4
Pb01–S01
Pb01–C06
Pb01–C18
C01–C02
Bond angles [°]
1a
1b
1c
3
S1–Sn1–S3
C12–Sn1–S1
C1–S1–Sn
C2–C1–S1
S1–Sn1–S1
C6–Sn1–S1
C1–S1–Sn1
C2–C1–S1
S1–Sn1–S2
C17–Sn1–S1
C1–S1–Sn1
C2–C1–S1
S1–Pb1–S2
C17–Pb1–S1
C1–S1–Pb1
C2–C1–S1
O1–Pb1–O2
88.88(5)
105.43(19) C11–Sn–C12
189.94(17) O1–C1–S1
C11–Sn1–S1
112.75(18)
125.5(3)
121.6(4)
122.6(4)
108(3)
115.9(4)
87.73(12)
111.5(3)
90.2(3)
117.4(7)
89.73(2)
110.59(7)
87.07(9)
118.5(2)
89.05(9)
108.1(3)
87.7(3)
O1–C1–C2
C6–Sn1–S1
C6–Sn1–C6
O1–C1–S1
O1–C1–C2
C11–Sn1–S1
C17–Sn1–C11
O1–C1–S1
O1–C1–C2
C11–Pb1–S1
C17–Pb–C11
O1–C1–S1
O1–C1–C2
S1–Pb1–O1
Figure 2. Packing of 1a along the a axis showing hydrogen bonds.
122.9(8)
120.3(8)
122.3(9)
107.22(7)
127.59(9)
119.4(2)
122.1(3)
105.4(2)
133.8(4)
120.5(8)
122.3(10)
58.90(18)
88.1(3)
Molecular structures and atomic labeling schemes of 1b
and 1c are depicted in Figure 3. Both compounds 1b and
1c have similar structures. Notable features include better
planarity of the two thiocarboxylate groups relative to that
in 1a. The SCO units are rather coplanar, whereas the twists
between the thiophene rings are less significant (5.40° in 1b
and 10.68° in 1c). Both O···H- and S···H-type hydrogen
bonds are present in 1b; however, these are in the same di-
rection. As a result, the molecules form long strips along
the b axis (Figure 4) Apart from the H···O hydrogen bond-
ing, there is significant CH···π(phenyl) interaction in 1c
(Figure 5).
117.2(8)
153.1(2)
143.63(18) C11–Pb1–O1
88.0(3)
S2–Pb1–O1
C17–Pb1–O1
C01–S01–Pb01 98.7(6)
C12–Pb01–S01 108.7(4)
C06–Pb01–C12 118.0(6)
C12–Pb01–C18 115.8(6)
4
C06–Pb01–S01 105.4(4)
C18–Pb01–S01 92.7(4)
C06–Pb01–C18 112.6(6)
O01–C01–S01
O01–C01–C02 121.4(14)
Compound 3 is isostructural to 1c (Figure 6). Small dif-
ferences in bond lengths and angles arise due to the differ-
ence in size and electronegativities of SnIV and PbIV, which
do not necessitate further comment. There are two distinct
123.2(4)
C02–C01–S01
115.4(11)
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S. Singh, S. Bhattacharya, H. Nöth
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Figure 5. Intermolecular hydrogen bonding and CH–π interactions
in 1c.
Figure 3. Molecular structures of 1b and 1c.
In compound 4 (Figure 6), the central Pb atom is bonded
with three carbon atoms and one sulfur atom and has a
distorted tetrahedral coordination geometry around it. The
angles subtended at Pb range from 92.7(4) to 118.0(6)°. The
thiocarboxylate ligand is bonded to the metal atom through
the S atom only. The oxygen atom is quite far away from
the Pb center (3.191 Å), and there is no possibility of any
bonding between the two.
This is the only molecule that shows a weak interaction
of the thiophene sulfur atom with the neighboring Pb atom.
The intermolecular S–Pb distance is 3.74 Å, which is
slightly shorter than the sum of the van der Waals radii of
the Pb and S atoms (3.82 Å) (Figure 7). The corresponding
M–S distances in compounds 1–3 vary within a range of
5.324–6.988 Å, thus ruling out any possibility of an interac-
Figure 4. Arrangement of 1b molecules forming a strip.
CH···π interactions; one that involves the phenyl ring (as in tion between the two atoms. Possibly, there is also a π–π
the case of 1c) and the other that uses the π-electrons of interaction between a phenyl ring and a thiophene ring of
the thiophene ring. H···O hydrogen bonds between a pair the adjacent molecule. The two rings have a displaced paral-
of molecules are present as observed in the tin compounds lel arrangement[15] with a centroid–centroid distance of
1a–1c.
4.04 Å.
Figure 6. Molecular structures of 3 and 4.
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Organotin(IV) and Organolead(IV) Thiophene-2-thiocarboxylate
noncovalent and weak. Besides the sulfur atom, which is
the primary bonding site with the metal atom, the thio-
carboxylate ligand possesses two other atoms that can poss-
ibly act as donor sites. These are the oxygen atom of the
thiocarboxylate group and the sulfur atom of the thiophene
ring. As described in the preceding sections, no
M···S(thiophene) interaction was detected in the molecular
structures of the complexes except in 4. It was found by
natural bond orbital (NBO) analysis that the sulfur atom
of the thiophene ring has +0.5 natural charges, and as a
result a dative bond formation is not favored. Thus, there
is no bonding interaction of the thiophene sulfur atom with
the metal ions. In the case of 4, although there is a weak
interaction between the lead atom and the sulfur atom of
the thiophene ring, the stabilization energies associated with
nsǞπ*Pb electron delocalizations are very low (2.47 and
3.34 kcalmol–1, which are even less than commonly ob-
served hydrogen-bonding energies). Calculations on a pair
of molecules in the gas phase also supported the existence
of very weak interactions. The energy difference between a
pair of molecules and two isolated molecules is
–2.62 kcalmol–1.
Figure 7. Pair of molecule 4 showing interaction between S (thio-
phene) and Pb. Thermal ellipsoid plot at 30% probability.
Theoretical Studies
Natural Bond Orbital Analyses
Theoretical calculations have been performed by using
the density functional theory (DFT) method[16] to under-
stand the nature of bonding, particularly those that are
In the case of 1c, the oxygen atom of each thiocarboxyl-
ate group has a substantial interaction with the tin atom
(Sn1–O1 2.63 Å) due to considerable charge transfers from
both the nonbonding orbitals (lone pairs) of the oxygen
atom to the tin atom. The stabilization energies associated
with electron transfers from nO33 to σ*Sn–S24 and σ*Sn–S25
orbitals are 11.03 and 9.75 kcalmol–1, respectively. Since 1a
and 1b are structurally similar to 1c, one would expect sim-
ilar Sn···O interactions in these compounds. An analogous
result was also found in the case of 3, in which the energy
due to electron transfers from nO14 to σ*Pb–S9 and σ*Pb–S18
orbitals is 9.08 and 10.79 kcalmol–1, respectively. In the
Figure 9. Selected molecular orbitals for 3 (orbital contour value =
0.05).
Figure 8. Selected orbitals for 1c (orbital contour value = 0.05).
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S. Singh, S. Bhattacharya, H. Nöth
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case of 4, however, the Pb–O distance is quite large and the arise due to inter- and intraligand charge transfers (Fig-
total stabilization energy associated with nOǞσ*Pb–S delo- ure 8).
calizations is only 3.07 kcalmol–1, thus indicating very weak
The results of TD-DFT calculations on compound 3
interaction between the two atoms. Although Tani et al. (Figure 9) revealed that the lower energy band calculated at
have reported[8] the existence of a weak interaction between 321 nm is due to the admixture of intraligand πǞπ* and
the metal atom and the oxygen atom that lead to short M– nǞπ* transitions in which the comparatively higher-energy
O distances in RC(O)S-MR3-type compounds on the basis band calculated at 266 nm is due to electron transfers from
of very low stabilization energies (2.05 kcalmol–1), we have a coordinated sulfur atom of the thiocaboxylate moiety and
recently shown that such interactions may not be responsi- (C–C)π orbitals of the phenyl ring to two different orbitals,
ត
ble for closeness of the two atoms.[17] This is because the namely, an antibonding orbital of the thiocarboxylate
energies associated with crystal packing and π-stacking are group and an RY* of Pb.
often larger and influence the structure to a greater extent.
The calculations reveal that, in the case of 4 (Figure 10),
the lower-energy band (calculated at 304 nm) is due to the
intermolecular πǞπ* transitions from a phenyl ring of the
triphenyllead moiety to the π*-orbitals of thiophene and
phenyl rings of another molecule. However, a comparatively
higher-energy band calculated at 256 nm is due to intramo-
lecular ligand-to-metal charge transfers from a sulfur atom
of the thiocarboxylate group and a π-orbital of the thio-
phene ring to the Pb–S antibonding orbitals.
TD-DFT Calculations
The results of time-dependent DFT calculations on 1c at
the B3LYP[18,19] level revealed that all absorption bands
Nonlinear Optical Properties
The nonlinear optical property of 4 was calculated by
double numerical differentiation of energies (finite-field per-
turbation method). Hyperpolarizability is given by the coef-
ficients in the Taylor series expansion of the energy in the
external electric field.[20] If the external electric field is weak
and homogeneous the expansion is [Equation (1)]:
1
1
E = E0 – μαFα – /2ααβFαFβ – /6βαβγFαFβFγ ...
(1)
in which E0 is the energy of unperturbed molecules, Fα is
the field of origin, and μα, ααβ, and βαβγ are the components
of dipole moment, polarizability, and first hyperpolarizabil-
ity, respectively. The mean first hyperpolarizabilty is defined
as shown in Equation (2):[21]
2
2
2 1/2
β0 = (βx + βy + βz )
(2)
in which the βx, βy, and βz components can be described by
βx = βxxx + βxyy + βxzz, βy = βyyy + βyxx + βyzz, and βz =
βzzz + βzxx + βzyy
.
The solvent parameters used were those of chloroform.
The β0 value calculated for one molecule of 4 was found
to be 8.70ϫ10–30 esu in chloroform, which is less than p-
nitroaniline (pNA, Table 3). The value marginally increases
for a pair of molecules (as shown in Figure 7), which was
calculated to be 9.86ϫ10–30 esu. This small increase in the
hyperpolarizability is possibly due to weak interactions be-
tween the sulfur atom of the thiophene ring of one molecule
and the lead atom of the other molecule.
Table 3. Calculated dipole moment and hyperpolarizabilities of 4.
System
μ
βx
βy
βz
β0
pNA
4
7.53 –13.70
0.03
–3.22 –6.03
–6.48 0.72
0.04
13.72
8.70
9.86
single molecule 2.05
paired molecules 4.10
–5.39
–7.39
Figure 10. Selected molecular orbitals for 4 (orbital contour value
= 0.05).
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Eur. J. Inorg. Chem. 2010, 5691–5699

Organotin(IV) and Organolead(IV) Thiophene-2-thiocarboxylate
mentary crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Conclusion
Organotin ([R2SnCl2], [R3SnCl]; R = Me, Ph, nPr, and
nBu) and organolead ([Ph2PbCl2], [Ph3PbCl]) compounds
of the thiocarboxylate ligand that contain a donor atom at
the terminal R group (thiophene) have been synthesized. In
all the compounds the binding of the thiocarboxylate ligand
is primarily through the sulfur atom of the thiocarboxylate
group; however, M···O interactions are strong enough to
affect the molecular geometry. Notably, significant interac-
tion of the terminal sulfur atom (thiophene) with the metal
atom is absent in all the cases except in [Ph3Pb(SCOth)], in
which weak intermolecular interaction is present that
amounts to a maximum energy lowering of 3.34 kcalmol–1.
The molecules exhibited electronic transitions in the UV
region due to inter- and intraligand charge transfers; how-
ever, in the case of [Ph3Pb(SCOth)], intermolecular πǞπ*
transitions were responsible for an absorption at 304 nm.
Theoretical calculations revealed that hyperpolarizability of
this molecule is 8.7ϫ10–3 esu in chloroform, which in-
creases slightly in its dimeric form.
Thiophene-2-thiocarboxylic Acid: For the synthesis, a method sim-
ilar to that reported for thiobenzoic acid[24] was applied. Thio-
phene-2-carbonyl chloride (2.930 g, 20.0 mmol) was added drop-
wise with stirring to a solution of KSH (5.760 g, 40.0 mmol) in
methanol (30.0 mL) over a period of 30 min. The reaction mixture
was stirred for 1 h, and then the precipitated KCl was removed by
filtration. The filtrate was dried under reduced pressure, and the
residue was dissolved in water (50 mL), which was washed with
benzene (20 mL). The aqueous solution was acidified with 6 n HCl
and extracted with diethyl ether (2ϫ 30 mL). The ethereal layer
wasdried with anhydrous sodium sulfate overnight, then filtered
and dried under reduced pressure. A yellow oily liquid was ob-
tained. Yield: 2.275 g (79%). The sodium salt of the acid was ob-
tained by treating it with sodium methoxide in a stoichiometric
ratio.
[Me2Sn(SCOth)2] (1a): A methanolic (5 mL) solution of sodium
thiophene-2-thiocarboxylate (0.339 g 1.02 mmol) was added with
stirring to a stirred solution of dimethyltin(IV) dichloride (0.123 g,
0.56 mmol) in methanol (5 mL). After stirring the reaction mixture
for 2 h, the solvent was evaporated under reduced pressure. The
yellow residue was dried under vacuum, dissolved in chloroform,
and separated from the sodium chloride by filtration. The filtrate
was layered with n-hexane and kept for crystallization. After 2 d,
light yellow crystals were obtained. Yield: 0.195 g (80%). M.p. 108–
110 °C. C12H12O2S4Sn (435.16): calcd. C 33.12, H 2.78; found C
Experimental Section
General: All the reactions were carried out under ambient condi-
tions. Solvents were purified by using standard methods. Organotin
and -lead chlorides and thiophene-2-carbonyl chloride were pur-
chased from Sigma Aldrich and used as received. IR spectra were
recorded with Varian 3100 FTIR instruments. NMR spectra were
obtained with a JEOL AL300 FT NMR spectrometer. Elemental
analyses were performed with an Exeter model E-440 CHN ana-
lyser. Electronic absorption spectra were recorded with a Shimazdu
33.41, H 2.76. IR (KBr): ν = 1575 [ν(CO)], 1217 [ν(th–C)], 1048
˜
1
[ν(C–S)] cm–1. H NMR (CDCl3): δ = 1.21 (6 H of Me), 7.09–7.87
(6 H of thiophene rings) ppm. 13C NMR (CDCl3): δ = 5.22, 5.25
(Me), 128.18–143.12 (thiophene ring), 192.92, 192.97 (COS) ppm.
119Sn NMR (CDCl3): δ = –69.68 ppm.
UV-1700 PhermaSpec spectrophotometer. Single-crystal X-ray [nPr2Sn(SCOth)2] (1b): A solution of sodium thiophen-2-thiocarb-
data of 1a and 4 were collected with Enraf Nonius Kappa and
Bruker SMART APEX CCD diffractometers, respectively, whereas
those of 1b, 1c, and 3 were collected with an Xcalibur Oxford Dif-
fractometer by using graphite-monochromated Mo-Kα radiation (λ
= 0.7107 Å). Data collections for 1a and 4 were carried out at
100 K, whereas those for 1b, 1c, and 3 were carried out at 293 K.
The SHELX program[22] was used for structure solution and refine-
ment. A summary of crystallographic data and structure solutions
are listed in Table 4. The molecular structure plot of the compound
was created with Diamond software.[23] CCDC-771048 (1a) -771049
(1b), 771050 (1c), 771051 (3), and -771052 (4) contain the supple-
oxylate (0.208 g, 1.25 mmol) in methanol (5.0 mL) was added with
stirring to a stirred solution of [nPr2SnCl2] (0.191 g, 0.628 mmol) in
methanol (10 mL). The reaction mixture was stirred for 1 h, during
which a white precipitate appeared, which was collected by fil-
tration. The solid was dried and dissolved in chloroform, layered
with petroleum ether (boiling range 60–80 °C), and kept for
crystallization. After 2 d, colorless crystals suitable for single-crys-
tal X-ray diffraction were obtained. Yield: 0.290 g (89%). M.p. 86–
88 °C. C16H20O2S4Sn (491.26): calcd. C 39.11, H 4.10; found C
40.23, H 4.24. IR (KBr): ν = 1571 [ν(CO)], 1213 [ν(th–C)], 1047
˜
[ν(C–S)] cm–1. 1H NMR (CDCl3): δ = 1.04 (6 H of nPr), 1.81 (4 H
Table 4. Crystallographic data of compounds.
1a
1b
1c
3
4
Empirical formula
T [K]
Crystal system
Space group
a [Å]
b [Å]
c [Å]
C12H12O2S4Sn
100
triclinic
P1
5.9330(12)
7.6190(15)
18.418(4)
90.03
832.6(3)
2
C16H20O2S4Sn
293
monoclinic
C2/c
15.4722(10)
6.0028(4)
21.2495(12)
103.553(6)
1918.6(2)
4
C22H16O2S4Sn
293
C22H16O2PbS4
293
C23H18OPbS2
100
triclinic
triclinic
monoclinic
P21/n11
11.785(4)
13.402(5)
14.743(5)
63.463(6)
2083.4(13)
4
¯
¯
P1
P1
10.1857(3)
10.7413(3)
11.8598(3)
107.174
1138.51(5)
2
10.4143(6)
10.6226(7)
11.7566(8)
104.481(6)
1156.24(13)
3
β [°]
V [Å3]
Z
μ [mm–1]
2.030
1.772
1.505
7.672
8.308
R indices [IϾ2σ(I)]
R indices (all data)
GOF on F2
0.0240
0.0269
1.007
0.0781
0.0815
1.238
0.0363
0.0496
1.055
0.0698
0.1059
1.077
0.0503
0.0948
1.001
Eur. J. Inorg. Chem. 2010, 5691–5699
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
5697

S. Singh, S. Bhattacharya, H. Nöth
FULL PAPER
of nPr), 1.95 (4 H of nPr), 7.09–7.88 (6 H of thiophene ring) ppm.
ring and 15 H of phenyl ring) ppm. 13C NMR (CDCl3): δ = 127.79–
13C NMR (CDCl3): δ = 17.85 (CH3 of nPr), 19.55 and 27.56 (CH2 157.63 (thiophene ring and phenyl ring), 188.27 (COS) ppm.
of nPr), 128.13–143.30 (thiophene ring), 193.24 (COS) ppm. 119Sn
NMR (CDCl3): δ = –77.71 ppm.
Theoretical Calculations: The optimized geometry of tributyltin
thiophene-2-thiocarboxylate was calculated by using the B3LYP ex-
change correlation functional. The effective core potential (ECP)
standard basis set LANL2DZ(d,p)[25] was utilized for Sn atoms,
whereas the 6-31g**[26] basis set was used for C, H, O, and S atoms.
The energies and intensities of the 20 lowest-energy spin-allowed
electronic excitations were calculated by using TD-DFT at the same
level of theory. Natural bond orbital (NBO) calculations were per-
formed by using the LANL2DZ(d,p) basis set for all the atoms.
The first static hyperpolarizabilty (β0) for compound 4 was calcu-
lated by using the finite field perturbation method by implementing
the PCM model.[27,28] The solvent parameters were those of chloro-
form. X-ray coordinates were used for the calculation of electronic
excitation, natural bond orbital, and hyperpolarizability, except for
2a, which was optimized. All the theoretical calculations were per-
formed by using the Gaussian 03 W set of programs.[29] Molecular
orbital plots were generated by using the program MOLDEN.[30]
[Ph2Sn(SCOth)2] (1c): The same procedure as for 1b, but instead
of [nPr2SnCl2], [Ph2SnCl2] (0.219 g, 0.637 mmol) and sodium thio-
phene-2-thiocarboxylate (0.211 g, 1.27 mmol) were used. Colorless
crystals were obtained from a chloroform solution layered with pe-
troleum ether (boiling range 60–80 °C). Yield: 0.283 g (80%). M.p.
162–164 °C. C22H16O2S4Sn (559.30): calcd. C 47.24, H 2.88; found
C 46.90, H 2.90. IR (KBr): ν = 1559 [ν(CO)], 1226 [ν(th–C)], 1053
˜
[ν(C–S)] cm–1. 1H NMR (CDCl3): δ = 7.06–8.06 (6 H of thiophene
ring and 10 H of phenyl ring) ppm. 13C NMR (CDCl3): δ = 128.13–
142.58 (thiophene ring and phenyl ring), 190.90 (COS) ppm. 119Sn
NMR (CDCl3): δ = –190.10 ppm.
[nBu3Sn(SCOth)] (2a): A solution of sodium thiophene-2-thiocar-
boxylate (0.109 g, 0.659 mmol) in methanol (5.0 mL) was added
with stirring to
a stirred solution of [nBu3SnCl] (0.214 g,
0.657 mmol) in methanol (5.0 mL). A light yellow solution was ob-
tained. The reaction mixture was stirred for 2 h. It was then dried
under reduced pressure, and the residue was dissolved in chloro-
form to separate NaCl by filtration. The filtrate was dried under
reduced pressure, then in vacuo to obtain a viscous yellow-orange
Acknowledgments
Financial support in the form of a grant (to S. B.) and a fellowship
(to S. S.) from the Council of Scientific and Industrial Research,
India are gratefully acknowledged.
liquid. Yield: 0.219 g (76%). IR (KBr): ν = 1606 [ν(CO)], 1204
˜
[ν(th–C)], 1045 [ν(C–S)] cm–1. 1H NMR (CDCl3): δ = 0.88–1.66
(27 H of nBu), 7.05–7.84, (3 H of thiophene ring) ppm. 13C NMR
(CDCl3): δ = 6.99, 13.61, 15.09, and 28.72 (nBu) 127.77–144.73
(thiophene ring), 188.52 (COS) ppm. 119Sn NMR (CDCl3): δ =
–80.68 ppm.
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[Ph3Sn(SCOth)] (2b): The same procedure was applied as for 1c,
except [Ph3SnCl] (0.207 g, 0.536 mmol) and sodium thiophene-2-
thiocarboxylate (0.089 g, 0.536 mmol) were used. A yellow insolu-
ble precipitate was obtained. Yield: 0.209 g (79%). C23H18OS2Sn
(493.20): calcd. C 56.01, H 3.68; found C 55.43, H 3.64. IR (KBr):
ν = 1609 [ν(CO)], 1205 [ν(th–C)], 1069 [ν(C–S)] cm–1.
˜
[Ph2Pb(SCOth)2] (3): A solution of sodium thiophene-2-thiocar-
boxylate (0.155 g, 0.936 mmol) was added with stirring to stirred
suspension of [Ph2PbCl2] (0.202 g, 0.468 mmol) in methanol
(10 mL). A white precipitate appeared immediately. The reaction
mixture was stirred for another 1 h, and the precipitate was filtered
off. The latter was dried under vacuum, dissolved in chloroform,
and kept for crystallization. After 2 d, colorless crystals were ob-
tained that were suitable for single-crystal X-ray diffraction. Yield:
0.266 g (88%). M.p. 156–158 °C. C22H16O2PbS4 (647.81): calcd. C
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˜
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1218 [ν(th–C)], 1050 [ν(C–S)] cm–1. H NMR (CDCl3): δ = 7.06–
8.21 (6 H of thiophene rings and 10 H of phenyl rings) ppm. 13C
NMR (CDCl3): δ = 127.99–158.04 (thiophene ring and phenyl
ring), 192.99 (COS) ppm.
[Ph3Pb(SCOth)] (4): A solution of sodium thiophene-2-thiocarbox-
ylate (0.143 g, 0.862 mmol) was added with stirring to a stirred tur-
bid solution of [Ph3PbCl] (0.408 g, 0.861 mmol) in methanol
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for single-crystal X-ray diffraction. Yield: 0.449 g (90%). M.p. 120–
122 °C. C23H18OPbS2 (581.71): calcd. C 47.49, H 3.12; found C
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Published Online: November 12, 2010
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