Synthesis and structure of the dithienostannole anion

Article abstract of DOI:10.1016/j.jorganchem.2009.08.026

Novel dithienostannoles were synthesized by the reactions of the corresponding dilithiobithiophenes with dichlorodiphenylstannane. A unique byproduct, 10-membered ring compound was also obtained. Reduction of type A dithienostannole with lithium afforded 2,2′-dilithio-3,3′-bithiophene, while reduction of type B dithienostannole with lithium afforded the corresponding dithienostannole anion. The structure and aromaticity of the dithienostannole anion are also discussed.

Full text of DOI:10.1016/j.jorganchem.2009.08.026

Journal of Organometallic Chemistry 694 (2009) 4056–4061
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis and structure of the dithienostannole anion
a
a
b
b
Masaichi Saito a, , Munenori Shiratake , Tomoyuki Tajima , Jing Dong Guo , Shigeru Nagase
*
a Department of Chemistry, Graduate School of Science and Engineering, Saitama University, Shimo-okubo, Sakura-ku, Saitama-city, Saitama 338-8570, Japan
b Department of Theoretical and Computational Molecular Science, Institute for Molecular Science, Myodaiji, Okazaki, Aichi 444-8585, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 14 July 2009
Received in revised form 18 August 2009
Accepted 18 August 2009
Available online 22 August 2009
Novel dithienostannoles were synthesized by the reactions of the corresponding dilithiobithiophenes
with dichlorodiphenylstannane. A unique byproduct, 10-membered ring compound was also obtained.
Reduction of type A dithienostannole with lithium afforded 2,20-dilithio-3,30-bithiophene, while reduc-
tion of type B dithienostannole with lithium afforded the corresponding dithienostannole anion. The
structure and aromaticity of the dithienostannole anion are also discussed.
Ó 2009 Elsevier B.V. All rights reserved.
Keywords:
Dithienostannole
Reduction
Lithium
Anion
Aromaticity
1. Introduction
2. Results and discussion
For a decade, there has been considerable interest in the an-
ions and dianions of Group 14 elements, which are heavier cong-
eners of the cyclopentadienyl anion [1]. After considerable works
on the synthesis of non-annulated Group metallole anions and
dianions, attention was next paid to the effect of benzannulation
of the metallole anions and dianions on their aromaticity [2–4].
The benzannulated metallole anions are non-aromatic, while
the metallole rings of the corresponding dianions have consider-
able aromatic characters. On the other hand, thiophene has long
2.1. Synthesis of two thiophene-annulated stannoles
Since we have already succeeded in the synthesis of stannole
dianions by the reduction of the corresponding diphenyl deriva-
tives [4,7], we chose dithienostannoles having two phenyl groups
on the tin atom as precursors of the corresponding anions and dia-
nions. Firstly, we tried the synthesis of type A dithienostannole 1
by the reaction of 2,20-dilithio-3,30-bithiophene (2), prepared from
2,20-dibromo-3,30-bithiophene [8] and butyllithium, with dichloro-
diphenylstannane. However, reaction of 2,20-dilithio-3,30-bithioph-
ene (2) with an equimolar amount of dichlorodiphenylstannane
afforded 10-membered ring compound 3 (12%), which arose from
two bithiophene and diphenylstannylene units, and 3,30-bithioph-
ene (4) (41%) (Scheme 1). The structure of 10-membered ring com-
pound 3 was finally confirmed by X-ray crystallographic analysis.
In contrast, reaction of 2,20-dilithio-3,30-bithiophene with an equi-
molar amount of dichlorodiphenylstannane in the presence of two
equivalents of copper(I) iodide [9] provided diphenyldithienostan-
nole 1 in 13% yield together with 3 (5%). Diphenyldithienostannole
1 was so unexpectedly extremely unstable under atmosphere that
we could not purify it at an elemental analysis level, even through
the NMR signals of 1 could be completely assigned.
played important roles as a building block of
pounds and has been applied to the synthesis of useful materials
[5]. In the course of the studies on the expansion of -conjugated
p-conjugated com-
p
compounds, quite recently, thiophene-annulated siloles have
been synthesized and been found to exhibit luminescent and
semiconducting properties [6]. Therefore, thiophene-annulation
of Group 14 metallole anions and dianions is worth considering
as a new annulation mode. We report herein the synthesis of
two types of thiophene-annulated stannoles (the annulation
modes are denoted as Types A and B, hereafter; Chart 1) and
their reduction, which is dependent on the annulation mode.
Theoretical calculations are also carried out to investigate on
the structure of the resulting new thiophene-annulated stannole
anion.
Secondly, the synthesis of a type B dithienostannole was inves-
tigated. In contrast to the synthesis of 1, the corresponding dilith-
iobithiophene prepared from 4,40-dibromo-3,30-bithiophene [10]
reacted with dichlorodiphenylstannane without copper(I) iodide
to afford the synthesis of type B diphenyldithienostannole 5 in
* Corresponding author. Tel.: +81 48 858 9029; fax: +81 48 858 3698.
E-mail address: masaichi@chem.saitama-u.ac.jp (M. Saito).
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.08.026

M. Saito et al. / Journal of Organometallic Chemistry 694 (2009) 4056–4061
4057
Chart 1. Annulation modes of thiophene-annulated stannoles.
Scheme 1. Reactions of 2,20-dilithio-3,30-bithiophene
2 with dichlorodiphenyl-
stannane.
Fig. 1. ORTEP drawings of 3 with thermal ellipsoids plots (40% probability for non-
hydrogen atoms). All hydrogen atoms were omitted for clarity. Selected bond
lengths (Å) and angles (°): Sn(1)–C(1), 2.123(6); Sn(1)–C(8), 2.117(6); Sn(2)–C(4),
2.124(6); Sn(2)–C(5), 2.134(6); C(1)–Sn(1)–C(8), 116.7(2); C(4)–Sn(2)–C(5),
117.1(2).
Scheme 2. Preparation of type B dithienostannole 5.
61% yield (Scheme 2). The structure of diphenyldithienostannole 5
was finally confirmed by X-ray crystallographic analysis.
2.2. Molecular structures of10-membered ring compound 3 and type B
dithienostannole 5
There have appeared only a few reports on the molecular struc-
tures of monocyclic 10-membered ring compounds containing two
heavier Group 14 atoms and eight carbon atoms [11,12]. With re-
gards to the distannacyclodecane, the sole example of the X-ray
structural determination has been reported [12]. Therefore, the
structure of 3 is worthy of discussion. The 10-membered ring of
3 has a boat-like conformation (Fig. 1), completely different from
that of the previous example having a zigzag conformation where
two boat-like moieties are connected with each other from the
Fig. 2. ORTEP drawing of 5 with thermal ellipsoids plots (40% probability for non-
hydrogen atoms). All hydrogen atoms were omitted for clarity. Selected bond
lengths (Å) and angles (°): Sn(1)–C(1), 2.139(5); Sn(1)–C(4), 2.142(4); C(1)–C(2),
1.428(6); C(2)–C(3), 1.468(7); C(3)–C(4), 1.445(6); C(1)–C(5), 1.352(7); C(2)–C(6),
1.374(7); C(3)–C(8), 1.364(6); C(4)–C(7), 1.367(6); C(1)–Sn(1)–C(4), 83.25(18).
opposite directions [12]. The tinꢀcarbon distances in
3
(2.117(6)–2.139(6) Å) are in the normal range (2.14 Å) [13].

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M. Saito et al. / Journal of Organometallic Chemistry 694 (2009) 4056–4061
The structure of type B dithienostannole 5 is shown in Fig. 2.
occurred, in contrast to the reduction of hexaphenylstannole with
lithium, leading to reductive cleavage of the tinꢀphenyl bonds to
afford the stannole dianion [7]. However, a fate of the tin moiety
could not be discussed. Although the 119Sn NMR signals were ob-
served at ꢀ127, ꢀ120 and ꢀ106 ppm, we could assign only the sig-
nal at ꢀ106 ppm to Ph3SnLi [14]. According to the 1H NMR
spectrum, 2,20-dilithio-3,30-bithiophene (2) was found to be a ma-
jor product and signals in the aromatic region were complicated
[15].
Since no structural reports on the molecular structures of Type A
or B Group 14 metalloles have appeared to date, type B dithieno-
stannole 5 is the first example of these categories. The tricyclic
framework is almost planar and the tinꢀcarbon bond distances
in 5 (2.128(5)–2.142(4) Å) are in the normal range (2.14 Å) [13].
The carbonꢀcarbon distances in the central five-membered ring
are 1.428(6), 1.445(6) and 1.468(7) Å, which are expected from
the resonance form in the annulation mode of 5.
2.4. Reduction of type B dithienostannole 5
2.3. Reduction of type A dithienostannole 1
Reduction of type B dithienostannole 5 with lithium in ether
and THF provided complex mixtures. However, when the reduction
was carried out in DME, the 119Sn NMR spectrum of the resulting
mixture showed only a signal at ꢀ211 ppm. After removal of insol-
uble materials in DME and concentration of the filtrate in a glove-
box, the 119Sn NMR spectrum of the residue still showed a signal at
ꢀ210 ppm. Treatment of the residue with iodomethane then affor-
ded methylphenyldithienostannole 6 in 23% yield [16], revealing
the formation of intermediary dithienostannole anion 7 (Scheme
4). After reduction of dithienostannole 5 with lithium in DME fol-
lowed by removal of insoluble materials in DME and concentration
of the filtrate in a glovebox, the residue was washed by hexane to
afford dithienostannole anion 7 in 75% yield. Although the effect of
solvents on the reduction of type B dithienostannole 5 is still diffi-
cult to explain, it results probably from stabilization of the lithium
atom by coordination with DME molecules [17].
Since type A dithienostannole 1 was very unstable and it could
not be purified by either gel permeation chromatography or col-
umn chromatography, reduction of
a crude product (ratio,
1:3 = ca. 10:3) was carried out. Monitoring the reduction by NMR
spectroscopy revealed the formation of 2,20-dilithio-3,30-bithioph-
ene (2) (Scheme 3). The formation of 2,20-dilithio-3,30-bithiophene
(2) was confirmed by its alternative synthesis from 2,20-dibromo-
3,30-bithiophene [8] and t-butyllithium. The formation of 2 clearly
shows that reductive cleavage of the tinꢀthiophene carbon bonds
Scheme 3. Reduction of type A dithienostannole 1.
2.5. NMR spectra of dithienostannole anion 7
The 1H NMR signals assignable to the thiophene protons of
dithienostannole anion 7 (6.57 and 6.80 ppm) shift to upfield, com-
pared with those of the starting stannole 5 (7.21 and 7.50 ppm),
suggesting very slight loss of aromaticity of the thiophene moieties
of 7, even though a simple solvent effect cannot be ruled out. In the
Scheme 4. Reduction of type B dithienostannole 5: formation of dithienostannole
anion 7.
13C NMR spectrum, a signal assignable to the
a-carbon of the
Fig. 3. Geometric optimization of dithienostannole anion 7.

M. Saito et al. / Journal of Organometallic Chemistry 694 (2009) 4056–4061
4059
Table 1
of dithienostannole anion 7 suggest that the central stannole ring
has non-aromatic character, while the thiophene rings are still aro-
matic. The optimized structure of dithienostannole anion 7, having
a lithium atom in the center of the stannole ring, suggests that
dithienostannole anion 7 would be a potential ligand for a transi-
tion metal. Further investigation on the synthesis of transition me-
tal complexes using dithienostannole anion 7 and the synthesis of
dithienostannole dianions is currently in progress.
Selected bond length (Å) in isomer B.
C1–C2
C2–C3
C3–C4
C3–C7
1.367
1.456
1.376
1.474
Sn–C2
Sn–C6
Sn–Li
2.326
2.326
2.612
stannole ring was observed in a low field (171.00 ppm), similar to
those of the stannole anions [18]. The 119Sn NMR signal of 7 was
observed at ꢀ211 ppm, which is in the upfield compared with that
of 5 (ꢀ168 ppm). Similar upfield shift was also observed from a
diphenylstannaindene and the corresponding anion [4a]. The 7Li
NMR signal of 7 was observed at ꢀ2.2 ppm, which is located be-
tween those of the aromatic stannole dianion (ꢀ4.4 ppm) [7] and
the non-aromatic stannole anion (ꢀ0.64 ppm) [18]. Therefore, the
structure and aromaticity of 7 is of considerable interest, even
though the X-ray crystallographic analysis could not be achieved.
4. Experimental
4.1. General procedures
All experiments were performed under an argon atmosphere
using usual glass apparatus or a glovebox. THF, diethyl ether,
DME and benzene-d6 were distilled over sodium/benzophenone
followed from potassium mirror. 1H NMR (400 MHz) and 13C
NMR (101 MHz) spectra were recorded on a Bruker DPX-400 or a
Bruker DRX-400 spectrometer. 119Sn NMR (149 MHz) and 7Li
NMR (156 MHz) spectra were recorded on a Bruker DPX-400 spec-
trometer. The J(C, Sn) couplings were observed in the 13C NMR
spectra as satellite signals. When the J(C, 117Sn/119Sn) coupling
constants were observed separately, each of them were calculated.
FAB mass spectra were recorded on a JEOL JMS-700AM. Wet col-
umn chromatography (WCC) was carried out with Kanto silica
gel 60N. Preparative gel permeation chromatography (GPC) was
carried out on an LC-918 (Japan Analytical Ind. Co., Ltd.) with
JAIGEL-1H and -2H columns with chloroform as the eluant. All
melting points were determined on a Mitamura Riken Kogyo
MEL-TEMP apparatus and were uncorrected. Elemental analyses
were carried out at the Microanalytical Laboratory of Molecular
Analysis and Life Science Center, Saitama University.
2.6. Theoretical calculations of dithienostannole anion 7
To gain insight into the structure and aromaticity of 7, the
geometry of 7 was optimized with hybrid density functional theory
at the B3LYP [19] level using the GAUSSIAN 03 program [20]. As indi-
cated in Fig. 3, three different lithiodithienostannoles (B-1, 2 and 3)
were found to be minima in the gas phase and one more isomer (B-
4) was also found in the solvent phase (diethylether) with polar-
ized continuum model (PCM) [21]. In the structure B-1, the most
stable in the gas phase, the lithium atom is located in the center
of the stannole ring and the phenyl ring is perpendicular to the tri-
cyclic framework. The tinꢀlithium bond distance (Table 1) is calcu-
lated to be 2.612 Å, which is slightly shorter than that of the
stannole dianion (2.758 and 2.769 Å) [7]. The carbonꢀcarbon dis-
tances in the central five-membered ring (1.456 and 1.474 Å) are
almost the same as those found in 5 (1.428(6) and 1.468(7) Å),
while the tinꢀcarbon bonds (2.326 Å) are about 0.2 Å longer than
those of 5. The distances of C1ꢀC2 and C3ꢀC4 bonds (1.367 and
1.376 Å, respectively) in the thiophene moieties suggest that the
thiophene rings have still considerable aromatic character. The
other three structures have almost the same energies as that of
B-1 in the gas phase with the differences less than 0.03 kcal/mol.
Among these structures, the structure B-3 is worth mentioning.
The lithium atom is located nearly above the thiophene ring with
the distances between the tin and lithium atoms of 2.623 and
2.884 Å, in the gas phase and the solvent phase, respectively, which
are comparable with the corresponding bond distances of B-1, and
the structure B-3 is the most stable in the solvent phase. Therefore,
the relatively upfield resonance in the 7Li NMR is probably caused
by the equilibrated structure B-3 in solution, where the lithium
atom is shielded by aromatic ring current of the thiophene ring.
To gain more insight into the aromaticity of dithienostannole anion
7, NICS values of the free dithienostannole anion were calculated
[22]. NICS(1) and NICS(ꢀ1) [23] values of the thiophene rings range
from ꢀ10.0 to ꢀ9.4 ppm, suggesting that they have still consider-
able aromatic character, while those of the central five-membered
ring are ꢀ0.21 and 0.55 ppm, respectively, suggesting that the
stannole ring is non-aromatic.
4.2. Reaction of 2,20-dilithio-3,30-bithiophene (2) with
dichlorodiphenylstannane
To a diethylether (10 mL) solution of 2,20-dilithio-3,30-bithiophene
(2), prepared from 2,20-dibromo-3,30-bithiophene [8] (131.1 mg,
0.40 mmol) and butyllithium (0.3 mL, 0.88 mmol; 2.66 M in hexane),
was added a THF (4 mL) solution of dichlorodiphenylstannane
(157.4 mg, 0.46 mmol) at room temperature and the resulting mix-
ture was heated under reflux. After removal of precipitates, the fil-
trate was concentrated and the residue was subjected to WCC
(hexane:ethyl acetate = 20:1) to afford 7,7,14,14-tetraphenyl-7,14-
dihydro[1,6]distannecino[2,3-b:5,4-b0:7,8-b00:10, 9-b000]tetrathioph-
ene (3) (21.7 mg, 13%) and 3,30-bithiophene (4) (27.3 mg, 41%). 3:
mp 147–148 °C (dichloromethane + hexane). 1H NMR(CDCl3):
d = 6.91(d, J(H, H) = 5 Hz, 4H, Cb), 7.27–7.34(m, 20H), 7.43(d, J(H,
H) = 5 Hz, 4H, C ); 13C NMR(CDCl3): d = 128.28(d, J(C, Sn) = 57 Hz),
a
129.03(d, J(C, Sn) = 12 Hz), 130.19(d, J(C, Sn) = 49 Hz), 131.90(d,
J(C, Sn) = 28 Hz), 132.85(s), 136.52(d, J(C, Sn) = 80 Hz), 137.88(s),
148.10(s, J(C, Sn) = 28 Hz); 119Sn NMR(CDCl3): d = ꢀ161.4. Anal.
Calc. for C40H28S4Sn2 (874.36): C, 54.94; H, 3.22. Found: C, 54.45;
H, 3.14%.
4.3. Preparation of type A dithienostannole 1
3. Conclusions
To a diethylether (20 mL) solution of 2,20-dilithio-3,30-bithioph-
ene (2), prepared from 2,20-dibromo-3,30-bithiophene [8]
(703.4 mg, 2.17 mmol) and t-butyllithium (5.5 mL, 8.64 mmol;
1.57 M in pentane), was added copper(I) iodide (872.2 mg,
4.56 mmol) at ꢀ78 °C and the resulting mixture was stirred for
1.5 h at the same temperature. To the suspension was added a
diethylether (5 mL) solution of dichlorodiphenylstannane
(749.6 mg, 2.80 mmol) at ꢀ78 °C and the resulting mixture was
Reduction of the type A dithienostannole 1 with lithium affor-
ded 2,20-dilithio-3,30-bithiophene 2. In contrast, reduction of the
type B dithienostannole 5 with lithium afforded dithienostannole
anion 7, as evidenced by NMR spectroscopy and a trapping exper-
iment. Annulation mode of the dithienostannoles therefore af-
fected reactivity of the dithienostannoles. Theoretical calculations

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M. Saito et al. / Journal of Organometallic Chemistry 694 (2009) 4056–4061
stirred overnight, warming to room temperature. After removal of
insoluble materials in dichloromethane, the resulting mixture was
subjected to GPC to afford 7,7-diphenyl-7H-stannolo[2,3-b:5,4-
b0]dithiophene (1) (120.3 mg, 13%) and 3 (45.0 mg, 5%). Although
the NMR signals of 1 could be completely assigned, the elemental
analysis could not be carried out because of its unexpected unsta-
bility. The compound 1 gradually decomposed to complex mix-
tures during its purification. 1: 1H NMR(CDCl3): d = 7.34–7.43(m,
(475.7 mg, 1.38 mmol) at ꢀ78 °C and the resulting mixture was
stirred overnight, warming to room temperature. In a glovebox,
after removal of insoluble materials, the filtrate was concentrated
to give a mixture of 1 and 3 in the ratio of 10:3, estimated by
119Sn NMR spectroscopy. Since the 1H NMR spectrum of the crude
product revealed that other compounds besides 1 and 3 were also
formed and purification by recrystallization in a glovebox was dif-
ficult, the yield of 1 in the mixture could not be estimated. To a
diethylether (1 mL) solution of the mixture was added lithium
(120.1 mg, 17.3 mmol) and the mixture was stirred for 2 h. After
removal of insoluble materials, the residue was dissolved in ben-
zene-d6 and the formation of 2,20-dilithio-3,30-bithiophene (2)
was confirmed by NMR spectroscopy. The 119Sn NMR spectrum re-
vealed signals at ꢀ127, ꢀ120 and ꢀ106 ppm and the signal at
ꢀ106 ppm was assigned to Ph3SnLi [14].
6H), 7.48(d, J(H, H) = 5 Hz, 2H, C ), 7.60–7.63(m, 4H), 7.66(d, J(H,
a
H) = 5 Hz, 2H); 13C NMR(CDCl3): d = 123.38(d, J(C, Sn) = 47 Hz),
129.03(d, J(C, Sn) = 12 Hz), 130.07(d, J(C, Sn) = 14 Hz), 132.17(s),
134.71(d, J(C, Sn) = 18 Hz), 135.80(s), 136.89(d, J(C, Sn) = 47 Hz),
152.51(s, J(C, Sn) = 55 Hz); 119Sn NMR(CDCl3): d = ꢀ126.0. FAB MS
[M+H]: 439.
4.4. Preparation of type B dithienostannole 5
4.7. Alternative synthesis of 2,20-dilithio-3,30-bithiophene (2) from
To a diethylether (25 mL) solution of 4,40-dilithio-3,30-bithioph-
ene, prepared from 4,40-dibromo-3,30-bithiophene [10] (1008.8 mg,
3.11 mmol) and t-butyllithium (8.0 mL, 12.6 mmol; 1.57 M in pen-
tane), was added a diethylether (10 mL) solution of dichlorodiphe-
nylstannane (1166.0 mg, 3.39 mmol) at ꢀ78 °C and the resulting
mixture was stirred overnight, warming to room temperature.
After removal of insoluble materials in dichloromethane, the
resulting mixture was subjected to WCC (hexane:ethyl ace-
tate = 20:1) to afford 4,4-diphenyl-4H-stannolo[2,3-c:4,5-c0]dithi-
ophene (5) (829.4 mg, 61%). 5: mp 182 °C (dichloromethane +
ethanol)(decomp). 1H NMR(CDCl3): d = 7.37–7.41(m, 6H), 7.51(d,
J(H, H) = 2 Hz, 2H), 7.55(d, J(H, H) = 2 Hz, 2H), 7.60–7.63(m, 4H);
13C NMR(CDCl3): d = 116.55(d, J(C, Sn) = 48 Hz), 129.14(d, J(C,
Sn) = 59 Hz), 129.83(d, J(C, Sn) = 13 Hz), 132.07(d, J(C, Sn) = 60 Hz),
136.74(s, J(C, 117Sn/119Sn) = 567/593 Hz), 137.26(s, J(C, Sn) =
45 Hz), 142.56(s, J(C, 117Sn/119Sn) = 463/484 Hz), 147.90(s, J(C,
117Sn/119Sn) = 66/69 Hz); 119Sn NMR(CDCl3): d = ꢀ153.5. Anal. Calc.
for C20H14S2Sn (437.18): C, 54.95; H, 3.23. Found: C, 54.92; H,
3.09%.
2,20-dibromo-3,30-bithiophene
To a diethylether (15 mL) solution of 2,20-dibromo-3,30-bithi-
ophene [8] (234.9 mg, 0.72 mmol) was added t-butyllithium
(1.85 mL, 2.90 mmol; 1.57 M in pentane) at ꢀ78 °C and the result-
ing mixture was stirred for 1 h, warming to room temperature.
After removal of volatile substances, the residue was dissolved in
benzene-d6. 2: 1H NMR(C6D6): d = 7.99(d, J(H, H) = 4 Hz, 2H),
8.05(d, J(H, H) = 4 Hz, 2H); 13C NMR(CDCl3): d = 127.90(d),
136.02(d), 153.93(s), 159.68(s).
4.8. Reduction of type B dithienostannole 5 in diethylether
In a glovebox, to a diethylether (1 mL) solution of type B dithi-
enostannole 5 (90.5 mg, 0.21 mmol) was added lithium (16.2 mg,
2.33 mmol) at room temperature and the resulting mixture was
stirred for 9 h. After removal of insoluble materials, monitoring
the residue by NMR spectroscopy revealed the formation of a com-
plex mixture.
4.5. X-ray crystallographic analysis of 3 and 5
4.9. Reduction of type B dithienostannole 5 in THF
Crystals suitable for X-ray diffraction were obtained by recrys-
tallization in dichloromethane and hexane solution of 3 and in
dichloromethane and ethanol solution of 5. The intensity data were
collected at ꢀ170 °C on a Bruker SMART APEX equipped with a CCD
In a glovebox, to a THF (2 mL) solution of type B dithienostan-
nole
5 (104.2 mg, 0.24 mmol) was added lithium (22.2 mg,
3.20 mmol) at room temperature and the resulting mixture was
stirred for 3 h. After removal of insoluble materials, the filtrate
was treated with iodomethane (0.19 mL, 3.08 mmol). Although
the resulting mixture was complicated, purification of the residue
by GPC afforded 4-methyl-4-phenyl-4H-stannolo[2,3-c:4,5-
c0]dithiophene (6) (0.3 mg, 0.3%). 6: 1H NMR(CDCl3): d = 0.80(s,
J(H, Sn) = 61, 64 Hz, 3H), 7.33–7.38(m, 2H), 7.43(d, J(H, H) = 5 Hz,
4H), 7.48–7.50(m, 3H); 13C NMR(CDCl3): d = ꢀ8.82(q), 115.77(d),
128.62(d), 129.40(d), 131.39(d), 136.30(d), 138.51(s), 143.43(s),
147.49(s); 119Sn NMR(CDCl3): d = ꢀ114.5. Anal. Calcd for
C15H12S2Sn (375.11): C, 48.03; H, 3.23. Found: C, 48.24; H, 3.17%.
area detector with graphite-monochromated Mo K
a radiation
(k = 0.71073 Å) and graphite monochromator. 3: Formula
C40H28S4Sn2, FW = 874.36, crystal dimension 0.15 ꢁ 0.10 ꢁ
0.10 mm, monoclinic, space group P21/c, Z = 8, a = 11.997(2) Å,
b = 35.517(7) Å, c = 17.429(3) Å, b = 107.901(5)°, V = 7067(2) Å3,
Dcalcd = 1.643 g cmꢀ3
,
R1 = 0.056 (I > 2r(I), 8488 reflections),
wR2 = 0.087 (for all reflections) for 12 812 reflections and 829
parameters, GOF = 1.008. 5: Formula C20H14S2Sn, FW = 437.18,
crystal dimension 0.10 ꢁ 0.10 ꢁ 0.08 mm, monoclinic, space group
P21/c, Z = 8, a = 8.3266(4) Å, b = 17.7263(8) Å, c = 23.7621(11) Å,
b = 98.094(1)°, V = 3472.3(3) Å3, Dcalcd = 1.673 g cmꢀ3, R1 = 0.042
4.10. Reduction of type B dithienostannole 5 in DME
(I > 2r(I), 5278 reflections), wR2 = 0.092 (for all reflections) for
6276 reflections and 461 parameters, GOF = 1.067.
In a glovebox, to a DME (1 mL) solution of type B dithienostan-
nole
5 (31.7 mg, 0.07 mmol) was added lithium (5.7 mg,
4.6. Reduction of type A dithienostannole 1
0.82 mmol) at room temperature and the reaction mixture was
stirred overnight. After removal of insoluble materials, the filtrate
was treated with iodomethane (0.17 mL, 2.75 mmol). The reaction
mixture was purified by GPC to afford 6 (6.2 mg, 23%).
To a diethylether (36 mL) solution of 2,20-dilithio-3,30-bithioph-
ene (2), prepared from 2,20-dibromo-3,30-bithiophene [8]
(439.4 mg, 1.36 mmol) and t-butyllithium (3.5 mL, 5.49 mmol;
1.57 M in pentane), was added copper(I) iodide (529.2 mg,
2.57 mmol) at ꢀ78 °C and the resulting mixture was stirred for
1.5 h at the same temperature. To the suspension was added a
diethylether (5 mL) solution of dichlorodiphenylstannane
4.11. Isolation of dithienostannole anion 7
In a glovebox, to a DME (1 mL) solution of type B ditheinostan-
nole
5 (34.9 mg, 0.08 mmol) was added lithium (6.3 mg,

M. Saito et al. / Journal of Organometallic Chemistry 694 (2009) 4056–4061
4061
[4] (a) For Sn: M. Saito, M. Shimosawa, M. Yoshioka, K. Ishimura, S. Nagase,
Organometallics 25 (2006) 2967;
0.91 mmol) at room temperature and the reaction mixture was
stirred overnight. After removal of insoluble materials, the filtrate
was concentrated and the residue was washed with hexane to af-
ford 4-lithio-4-phenyl-4H-stannolo[2,3-c:4,5-c0]dithiophene (7)
(38.2 mg, 75%). 7: 1H NMR(DME with (CD3)2C@O in a sealed tube
for NMR lock): d = 6.36(tt, J(H, H) = 2, 7 Hz, 1H), 6.45(dd, J(H,
H) = 7, 7 Hz, 2H), 6.57(d, J(H, H) = 2 Hz, 2H), 6.80(d, J(H, H) = 2 Hz,
2H), 7.06(dd, J(H, H) = 2, 7 Hz, 2H); 13C NMR(DME with (CD3)2C@O
in a sealed tube for NMR lock): d = 111.56(d, J(C, Sn) = 17 Hz),
123.44(d), 124.27(d, J(C, Sn) = 18 Hz), 126.17(d, J(C, Sn) = 41 Hz),
137.47(d, J(C, Sn) = 52 Hz), 153.09(s), 166.34(s), 171.01(s); 119Sn
NMR(DME with (CD3)2C@O in a sealed tube for NMR lock):
d = ꢀ210.6; 7Li NMR(DME with (CD3)2C@O in a sealed tube for
NMR lock): d = ꢀ2.2.
(b) M. Saito, M. Shimosawa, M. Yoshioka, K. Ishimura, S. Nagase, Chem. Lett. 35
(2006) 940.
[5] (a) For very recent examples, see: M.R. Harpham, O. Süzer, C.-Q. Ma, P.
Bäeuerle, T. Goodson III, J. Am. Chem. Soc. 131 (2009) 973;
(b) J.-C. Li, H.-Y. Lee, S.-H. Lee, K. Zong, S.-H. Jin, Y.-S. Lee, Synth. Met. 159
(2009) 201.
[6] J. Ohshita, Y. Kurushima, K.-H. Lee, A. Kunai, Y. Ooyama, Y. Harima,
Organometallics 26 (2007) 6591.
[7] M. Saito, R. Haga, M. Yoshioka, K. Ishimura, S. Nagase, Angew. Chem., Int. Ed. 44
(2005) 6553.
[8] M.J. Marsella, K. Yoon, F.S. Tham, Org. Lett. 3 (2001) 2129.
[9] Even though the mechanism for the formation of type A dithienostannole 1
using copper(I) iodide is still unclear, the expected 1,4-dicopper-1,3-butadiene
would function as a key intermediate, see: C. Wang, J. Yuan, G. Li, Z. Wang, S.
Zhang, Z. Xi, J. Am. Chem. Soc. 128 (2006) 4564.
[10] A. Rajca, M. Miyasaka, M. Pink, H. Wang, S. Rajca, J. Am. Chem. Soc. 126 (2004)
15211.
[11] Y. Miyake, M. Wu, M.J. Rahman, Y. Kuwatani, M. Iyoda, J. Org. Chem. 71 (2006)
6110.
4.12. Computational details
[12] (a) A.G. Davies, M.-W. Tse, J.D. Kennedy, W. McFarlane, G.S. Pyne, M.F.C. Ladd,
D.C. Povey, J. Chem. Soc., Chem. Commun. (1978) 791;
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[13] K.M. Mackay, in: S. Patai (Ed.), The Chemistry of Organic Germanium, Tin and
Lead Compounds, Wiley, Chichester, 1995 (Chapter 2).
[14] M. Saito, Y. Okamoto, M. Yoshioka, Appl. Organomet. Chem. 19 (2005) 894.
[15] According to our experiences, diphenyl-substituted stannoles are more stable
Geometry optimization was carried out with density functional
theory (DFT) at the B3LYP level using the GAUSSIAN 03 program [20].
The basis set employed was [4333111/433111/43] augmented by
two d polarization functions (d exponents 0.253 and 0.078) for
Sn [7,24] and 6-311G** for C, H, Li and S. To estimate the solvation
energy, the geometry of dithienostannole anion 7 was reoptimized
at the same level in the presence of the solvent (dithylether) with
polarized continuum model (PCM) [21].
than the corresponding methyl-substituted stannoles and type
A
dithienostannole 1 was very unstable. Therefore, type A methyl-substituted
stannoles are thought to be more unstable than 1 and trapping experiments
with electrophiles such as iodomethane were not carried out. Even 2,20-
dibromo-3,30-bithiophene[8] is very unstable and should be used as soon as
possible after the preparation.
Acknowledgments
[16] Although the yield of 6 was not high, the119Sn NMR spectrum of the crude
product revealed two signals at ꢀ114 and ꢀ92 ppm, the former of which was a
main signal, assigned to methylphenyldithienostannole 6. Therefore, the
moderate yield of 6 was probably caused by loss of mass during the workup
process.
This work was partially supported by Grant-in-Aids for Scien-
tific Research (No. 20038010 for M.S. and No. 18066017 for S.N.)
in Priority Areas ‘‘Molecular Theory for Real Systems” and the
Nanotechnology Support Project from the Ministry of Education,
Culture, Sports, Science, and Technology of Japan.
[17] The lithium atom is known to be coordinated with DME molecules, for
example, see: M. Saito, S. Imaizumi, T. Tajima, K. Ishimura, S. Nagase, J. Am.
Chem. Soc. 129 (2007) 10974.
[18] R. Haga, M. Saito, M. Yoshioka, Eur. J. Inorg. Chem. (2007) 1297.
[19] (a) A.D. Becke, J. Chem. Phys. 98 (1993) 5648;
Appendix A. Supplementary material
(b) C. Lee, W. Yang, R.G. Parr, Phys. Rev. B 37 (1988) 785.
[20] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman,
J.A. Montgomery, Jr., T. Vreven, K.N. Kudin, J.C. Burant, J.M. Millam, S.S. Iyengar,
J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G.A.
Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa,
M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J.E. Knox,
H.P. Hratchian, J.B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R.E.
Stratmann, O. Yazyev, A.J. Austin, R. Cammi, C. Pomelli, J.W. Ochterski, P.Y.
Ayala, K. Morokuma, G.A. Voth, P. Salvador, J.J. Dannenberg, V.G. Zakrzewski, S.
Dapprich, A.D. Daniels, M.C. Strain, O. Farkas, D.K. Malick, A.D. Rabuck, K.
Raghavachari, J.B. Foresman, J.V. Ortiz, Q. Cui, A.G. Baboul, S. Clifford, J.
Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R.L.
Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng, A. Nanayakkara, M.
Challacombe, P.M.W. Gill, B. Johnson, W. Chen, M.W. Wong, C. Gonzalez, J.A.
Pople, GAUSSIAN 03, Revision E. 01, Gaussian Inc., Wallingford, CT, 2004.
[21] (a) B. Mennucci, J. Tomasi, J. Chem. Phys. 106 (1997) 5151;
(b) M.T. Cances, B. Mennucci, J. Tomasi, J. Chem. Phys. 107 (1997) 3032;
(c) M. Cossi, V. Barone, B. Mennucci, J. Tomasi, Chem. Phys. Lett. 286 (1998)
253;
CCDC 728387 and 728422 contain the supplementary crystallo-
graphic data for compounds 3 and 5, respectively. These data can
be obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif. Supplemen-
tary data associated with this article can be found, in the online
version, at doi:10.1016/j.jorganchem.2009.08.026.
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