Synthesis and optical properties of spirobi(dithienometallole)s and spirobi(dithienothiametalline)s

Article abstract of DOI:10.1016/j.jorganchem.2012.03.012

Spiro-condensed dithienometalloles (metal = Si, Ge) and dithienothiametallines (metal = Si, Ge, Sn) were prepared by the ring closure reactions of dilithiated bithiophene and dithienyl sulfide with metal tetrachlorides, and their optical properties were s

Full text of DOI:10.1016/j.jorganchem.2012.03.012

Journal of Organometallic Chemistry 710 (2012) 53e58
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis and optical properties of spirobi(dithienometallole)s and
spirobi(dithienothiametalline)s
*
Kwang-Hoi Lee, Joji Ohshita , Daiki Tanaka, Yuta Tominaga, Atsutaka Kunai
Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, Higashi-Hiroshima 739-8527, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Spiro-condensed dithienometalloles (metal ¼ Si, Ge) and dithienothiametallines (metal ¼ Si, Ge, Sn)
were prepared by the ring closure reactions of dilithiated bithiophene and dithienyl sulfide with metal
tetrachlorides, and their optical properties were studied with respect to the UV absorption and emission
spectra. The absorption and emission maxima of them moved to higher energies by increasing the size of
the center metal from Si to Ge and Sn, and stepwise oxidation of the ring sulfur atom in the dithieno-
thiasiline system forming sulfoxide and sulfone linkages, making the fine tuning of the electronic states
possible.
Received 20 January 2012
Received in revised form
6 March 2012
Accepted 9 March 2012
Keywords:
Spiro-condensation
Metallole
Ó 2012 Elsevier B.V. All rights reserved.
Thiametalline
1. Introduction
their PL and carrier transporting properties (Chart 1). In these
compounds, the conjugation is markedly enhanced by the highly
Spiro-condensed compounds with orthogonal chromophores
are of interest [1]. The nonplanar structures of these compounds
would hinder the close packing of the chromophores in the solid
states to improve the solubility in organic solvents, the photo-
luminescence (PL) efficiency in the solid states, and also the
thermal stability of the amorphous phase, providing the opportu-
nity to utilize them in areas of organic electronic devices. Of those,
spirobifluorene has been extensively studied as a core fragment of
star-shaped molecules [2] and as a component of conjugated olig-
omers and polymers, and their use as organic light emitting diode
(OLED) and thin film transistor (TFT) materials, and also as micro-
porous materials has been explored [3]. Modification of the spiro-
fluorene system by the introduction of heteroatoms has been
studied. For example, it was demonstrated that silicon-cored
bi(silafluorene) derivatives could be used as efficient lumines-
cence materials [4]. Replacement of the phenylene rings of the
spirobifluorene by heteroaromatic systems such as N- [5] and S-
containing ones [6] has been also examined to modify the elec-
tronic states and the functionalities.
planar structures of the tricyclic systems, and also by the bonding
interaction between the metal
*- and bithiophene *-orbital
*e * conjugation), which lowers the LUMO energy levels.
Currently, these DTS [9] and DTG [8,10] systems attract much
attention as the donor-components of donoreacceptor type
conjugated photovoltaic polymers. We prepared also dithieno-
thiasilines (DTTSs) with a sulfide linkage and demonstrated the
hole-transporting properties of their vapor-deposited films,
being usable in multi-layered OLEDs [11]. In this paper, we report
the synthesis of spiro-condensed dithienometalloles (metal ¼ Si,
Ge) and dithienothiametallines (metal ¼ Si, Ge, Sn) [12]. To gain
insight into the role of the spiro-structure and the center
elements affecting the electronic states, we investigated their
optical properties and carried out theoretical calculations of
spiro-condensed dithienometallole models with C and Si as the
center element.
s
p
(
s
p
p
-
Recently, we have introduced dithienosilole (DTS) [7] and
-germole (DTG) [8] derivatives as functional materials based on
* Corresponding author.
Chart 1. General structures of DTS, DTG, and DTTS.
E-mail address: jo@hiroshima-u.ac.jp (J. Ohshita).
0022-328X/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2012.03.012

54
K.-H. Lee et al. / Journal of Organometallic Chemistry 710 (2012) 53e58
Scheme 1. Synthesis of spirobi(dithienometallole)s.
2. Results and discussion
two sets of 5,50-bis(trimethylsilyl)-2,20-bithiophene-3,30-diyl
segments in a 1:1 ratio, agreeing with the cyclic structure shown in
Fig. 1. Attempted X-ray single crystal structural analyses failed.
However, quantum chemical calculations at the B3LYP/LANL2DZ//
MOPAC/PM6 level indicated that this dimeric form is thermally
stable and contains ring strain less than sDTSn as demonstrated by
a thermodynamic equation of 2 sDTSn ¼ sDTSn-dimer þ 14.1 kcal/
mol.
2.1. Preparation of spirobi(dithienometallole) and
spirobi(dithienothiametalline) derivatives
Spiro-condensed dithienosilole and -germole (sDTS and sDTG)
derivatives were obtained as shown in Scheme 1. The reactions of
b,
b
0-dilithiated bithiophenes with 0.5 equiv of MCl4 (M ¼ Si or Ge)
afforded the corresponding spirobi(dithienometallole)s (sDTS1,
sDTS2, and sDTG1). Bromination and iodination of sDTS1 with Br2
and ICl readily afforded tetrahalospirobi(dithienosilole)s sDTS3 and
sDTS4, respectively. Because of the barely soluble properties of
tetraiodo compound sDTS4 in organic solvents, we employed tet-
rabromo compound sDTS3 for the further transformation, leading
to sDTS2 and sDTS5. These spiro-condensed compounds were
colorless or yellow solids and soluble in common organic solvents,
except for sDTS4.
Spirobi(dithienothiametalline)s including a tin derivative were
prepared by the reactions of bis[lithio(trimethylsilyl)thienyl]
sulfide with MCl4 as shown in Scheme 2, similarly to the prepara-
tion of sDTS and sDTG. No dimeric compound was obtained from
the reaction with SnCl4. It seems that sDTTSn having a six-
membered core possesses less strain than sDTSn. Oxidation of
sDTTS was carried out to give its oxides sDTTSO1 and sDTTSO2 by
selective mono- and dioxidation with mCPBA, similarly to that of
DTTS, reported previously [11].
In contrast to the reactions with SiCl4 and GeCl4, a complex
mixture was obtained with SnCl4, from which a compound whose
MALDI-TOF mass spectrum revealed the parent signal at m/z 1472
2.2. Quantum chemical calculations and optical measurements
corresponding to
a dimeric form of the expected tetrakis(-
First, we examined quantum chemical calculations for spi-
ro(dithienometallole)s with metal ¼ C and Si, to estimate the
effects of the core elements on their electronic states. Fig. 2 depicts
trimethylsilyl)spirobi(dithienostannole) (sDTSn) was isolated in
15% yield. The 1H and 13C NMR spectra indicated the existence of
Fig. 1. Chemical structure of sDTSn-dimer and its optimized geometry derived from MOPAC/PM6 calculations on Gaussian09 Program (hydrogen atoms and trimethylsilyl groups
are omitted for clarity).

K.-H. Lee et al. / Journal of Organometallic Chemistry 710 (2012) 53e58
55
Scheme 2. Synthesis of spirobi(dithienothiametalline) derivatives.
the HOMO and LUMO energy levels and profiles of the models,
derived from DFT calculations at the B3LYP/6-31G(d,p) level
[13e15]. The LUMO of sDTS0 lies at lower energy than that of
respectively, indicating the spiro-conjugation being operative in
these systems. However, the shifts (Dlmax in Table 1) were similar
for M ¼ Si and Ge, showing no significant effects of the center
elements on the spiro-conjugation. Although these spi-
robi(dithienometallole)s were photoluminiscent, the quantum
efficiencies were markedly lowered by spiro-condensation in both
sDTC0, indicating that the
s*ep* conjugation operates even in
these spiro-condensed systems, similarly to DTS0. On the other
hand, spiro-condensation decreases the HOMOeLUMO energy gap
for both sDTC0 and sDTS0, relative to those of DTC0 and DTS0,
respectively. This is probably due to the through-space interaction
the solution and the solid states (
F
¼ 0.10e0.17), compared to
simple dithienometalloles DTS1 and DTG1, despite our expectation
(Table 1).
between the orthogonally arranged bithiophene
p-orbital in
HOMO, namely spiro-conjugation [16]. In their LUMOs, the inter-
For the spirobi(dithienothiametalline) derivatives, UV lmax
shifted to shorter wavelength in the order of M ¼ Si > Ge > Sn (UV
action through the
extent.
s* orbital of the center atom is involved to an
lmax ¼ 321 nm (3.86 eV,
3
¼ 25 000) for sDTTS, 312 nm (3.97 eV,
3
UV absorption and fluorescence data of the present spi-
robi(dithienometallole)s are listed in Table 1. Spiro-compounds
sDTS1 and sDTG1 exhibited red-shifted absorption maxima from
those of DTS1 [7a] and DTG1 (R ¼ SiMe3 and Ar]Ph in Chart 1),
3
¼ 28 300) for sDTTG, and 302 nm (4.11 eV,
¼ 21 000) for
sDTTSn), as shown in Fig. 3(a). The absorption band of sDTTS was at
longer wavelength by 4 nm than that of DTTS1 (R ¼ SiMe3 and Ar]
Ph in Chart 1) [11], due to the spiro-conjugation, but the shift was
Fig. 2. HOMO and LUMO profiles and relative energy levels for model compounds, derived from DFT calculations at B3LYP/6-31G(d,p) level.

56
K.-H. Lee et al. / Journal of Organometallic Chemistry 710 (2012) 53e58
Table 1
step-by-step oxidation of the bridging sulfur atom of
Optical properties of dithienometalloles.
spirobi(dithienothiasiline).
3. Experimental
3.1. General
Compound UV abs lmax/nm (/eV),
3
Dlmax/nm Emission lem/nm
(/eV)a
In THF
In THF (
F
)
As solids (F)
sDTS1
sDTS2
sDTS5
sDTG1
DTS1b
DTG1
366 (3.39), 25 900
366 (3.39), 21 200
368 (3.37), 24 100
358 (3.46), 26 000
356 (3.48), 10 200
350 (3.54), 8100
10 (0.9)
8 (0.8)
435 (0.17) 439 (0.06)
434 (0.10) 438 (0.07)
436 (0.10) 443 (0.07)
421 (0.09) 421 (0.05)
425 (0.69) ec
All reactions were carried out under a dry argon atmosphere.
THF and ether were dried over sodiumepotassium alloy and
distilled immediately before use. Methylene chloride was distilled
from CaH2 and stored at 0 ꢀC until use. NMR spectra were recorded
on a JEOL EX-270 or LA-400 spectrometer. EI mass spectra were
measured on a Hitachi M80B spectrometer, while MALDI-TOF mass
analysis was performed on a Shimadzu Kompact Muldi2 spec-
trometer. APPI mass spectra were measured on a Thermo Fisher
Scientific LTQ Orbitrap XL spectrometer at the Natural Science
Center for Basic Research and Development (N-BARD), Hiroshima
University. UVevis spectra were measured on a Hitachi U-3210
spectrophotometer, and emission spectra were recorded on a Shi-
madzu RF5000 spectrophotometer. The solution PL quantum effi-
ciencies were determined relative to a 9,10-diphenylanthracene
solution as the standard, while those in the solid states were
determined in an integration sphere attached by a Hamamatsu
Photonics C7473 Multi-Channel Analyzer.
409 (0.71) ec
a
Dlmax ¼ (lmax of sDTM1 ꢁ lmax of DTM1).
See Ref. [7a].
Not measured.
b
c
smaller than that of sDTS1 from DTS1. It was also found that the
electronic states were tunable by stepwise oxidation of the bridging
sulfur atoms of sDTTS, shifting the absorption edges from 356 nm
(3.48 eV) for sDTTS to 342 (3.63 eV,
(3.77 eV,
although the maximum of sDTTSO1 appeared at higher energy
than that of sDTTSO2 (Fig. 3(b)). No photoluminescence was
detected for these spirobi(dithienothiametalline) and the oxides
either in solutions or as solids.
In conclusion, spiro-condensed dithienometalloles (metal ¼ Si
and Ge) and dithienothiametallines (metal ¼ Si, Ge, and Sn) were
readily prepared by simple ring closure reactions of dilithiated
bithiophene and dithienyl sulfide derivatives with metal tetra-
chlorides. It must be noted that the electronic states of these
compounds were finely tuned by changing the center elements and
3
¼ 23 000) and 329 nm
3
¼ 20 000) for sDTTSO1 and sDTTSO2, respectively,
3.2. Preparation of spiro-condensed dithienometallole and
dithienothiametalline by ring closure
To a solution of 3,30-dilithio-5,50-bis(trimethylsilyl)-2,20-bithio-
phene [7a], prepared by the reaction of 8.50 g (18.2 mmol) of 3,30-
dibromo-5,50-bis(trimethylsilyl)-2,20-bithiophene and 23.0 mL
(36.3 mmol) of a 1.58 M n-butyllithium/hexane solution in 80 mL of
THF at ꢁ80 ꢀC, was added 1.54 g (9.08 mmol) of SiCl4 at the same
temperature. After being refluxed for 3 h, the mixture was hydro-
lyzed with water and extracted with ether. The extract was dried
over anhydrous magnesium sulfate and the organic solvent was
evaporated. The residue was chromatographed on a silica gel
column with n-hexane as an eluent to afford crude solids that were
recrystallized from n-hexane/chloroform to give 4.80 g (82% yield)
of sDTS1 [12] as pale yellow crystals: mp > 300 ꢀC; MS m/z 644
a
sDTTSn sDTTG
sDTTS
(Mþ); 1H NMR (
phene ring H); 13C NMR (
(thiophene CH), 142.14 (qC), 157.24 (qC); 29Si NMR
d
in CDCl3) 0.32 (s, 36H, MeSi), 7.07 (d, 4H, thio-
in CDCl3) 0.05 (MeSi), 136.91 (qC), 137.16
in
d
(d
CDCl3) ꢁ6.65 (MeSi), ꢁ33.14 (center Si). Anal. Calcd for C28H40S4Si5:
250
300
350
C, 52.11; H, 6.25. Found: C, 52.14; H, 6.26.
Wavelength (nm)
Other spirobi(dithienometallole)s and -(dithienothiametalline)s
were prepared in a fashion similar to that above. Dþata for sDTS2
[12]: colorless solid; mp 223e225 ꢀC; MS m/z 588 (M ); 1H NMR (
d
b
in CDCl3) 0.37 (d, 24H, J ¼ 3.6 Hz, MeSi), 4.53 (septet, 4H, J ¼ 3.6 Hz,
HSi), 7.09 (s, 4H, thiophene ring H); 13C NMR (
d
in CDCl3) ꢁ2.82
sDTTSO1 sDTTSO2 sDTTS
(MeSi), 136.96 (qC), 138.17 (thiophene CH), 138.58 (qC), 157.69 (qC).
Anal. Calcd for C24H32S2Si5: C, 48.92; H, 5.47. Found: C, 49.11; H,
5.55. Data for sDTG1: pale yellow solid; mp >300 ꢀC; MS m/z 690
(Mþ); 1H NMR (
phene ring H); 13C NMR (
CH), 138.12 (qC), 142.16 (qC), 153.83 (qC); 29Si NMR
d
in CDCl3) 0.34 (s, 36H, MeSi), 7.13 (d, 4H, thio-
in CDCl3) 0.03 (MeSi), 136.84 (thiophene
in
d
(d
CDCl3) ꢁ6.55 (MeSi). HRMS Calcd for C28H40GeS4Si4: 690.0302.
Found: 690.0273. Data for sDTSn-dimer: colorless solid; mp
>300 ꢀC; TOF-MS m/z 1472 (Mþ); 1H NMR (
d
in CDCl3) 0.30 (s, 36H,
MeSi), 0.37 (s, 36H, MeSi), 6.74 (s, 4H, thiophene ring H), 7.50 (s, 4H,
thiophene ring H); 13C NMR (
in CDCl3) 0.11 (MeSi), 0.22 (MeSi),
137.76 (qC), 138.67 (thiophene CH), 139.73 (thiophene CH), 139.79
(qC), 141.46 (qC), 142.74 (qC), 148.49 (qC), 154.39 (qC); 29Si NMR (
d
250
300
350
Wavelength (nm)
d
in CDCl3) ꢁ6.75 (MeSi, two peaks may be overlapped). Anal. Calcd
Fig. 3. UV spectra of spirobi(dithienothiametalline)s (a) and spirobi(dithienothiasiline)
oxides (b).
for C56H80S8Si8Sn2: C, 45.70; H, 5.48. Found: C, 45.73; H, 5.50. Data

K.-H. Lee et al. / Journal of Organometallic Chemistry 710 (2012) 53e58
57
for sDTTS: colorless solid; mp 242e244 ꢀC; MS m/z 708 (Mþ); 1H
NMR ( in CDCl3) 0.25 (s, 36H, MeSi), 7.20 (s, 4H, thiophene ring H);
13C NMR (
139.94 (qC), 148.13 (qC). Anal. Calcd for C28H40S6Si5: C, 47.40; H,
5.68. Found: C, 47.32; H, 5.91. Data for sDTTG: colorless solid; mp
of a mixture of cis- and trans-isomers of sDTTSO1 with respect to
the two SeO bonds, as colorless solids: mp 269e272 ꢀC; MS m/z 740
d
d
in CDCl3) ꢁ0.05, 131.56 (qC), 139.20 (thiophene CH),
(Mþ); 1H NMR (
d
in CDCl3) 0.28 (s, 18H, MeSi), 0.29 (s, 18H, MeSi),
7.07 (s, 2H, thiophene ring H), 7.45 (s, 2H, thiophene ring H); 13C
NMR (
in CDCl3) ꢁ0.20 (two MeSi signals are overlapped), 133.83
(qC), 133.95 (qC), 139.20 (thiophene CH), 140.51 (thiophene CH),
148.40 (qC), 148.43 (qC), 160.42 (qC), 161.22 (qC); 29Si NMR (
in
d
256e258 ꢀC; MS m/z 754 (Mþ); 1H NMR (
d
in CDCl3) 0.27 (s, 36H,
MeSi), 7.09 (s, 4H, thiophene ring H); 13C NMR (
d
in CDCl3) ꢁ0.06
d
(MeSi), 133.08 (qC), 138.38 (thiophene CH), 140.53 (qC), 145.21 (qC).
Anal. Calcd for C28H40GeS6Si4: C, 44.60; H, 5.35. Found: C, 44.96; H,
5.87. Data for sDTTSn: colorless solid; mp 275e277 ꢀC; MS m/z 754
CDCl3) ꢁ4.76 (MeSi), ꢁ4.82 (MeSi), ꢁ53.05 (center Si). Anal. Calcd
for C28H40O2S6Si5: C, 45.36; H, 5.44. Found: C, 45.50; H, 5.32.
Compound sDTTSO2 was synthesized in 90% yield in a fashion
similar to that above using 4þequiv of mCPBA: colorless solid; mp
(Mþ); 1H NMR (
phene ring H); 13C NMR (
d
in CDCl3) 0.28 (s, 36H, MeSi), 7.22 (s, 4H, thio-
in CDCl3) 0.07 (MeSi), 137.19 (qC), 139.81
d
278e280 ꢀC; MS m/z 772 (M ); 1H NMR (
d
in CDCl3) 0.30 (s, 36H,
in CDCl3) ꢁ0.24 (MeSi),
137.33 (qC), 139.16 (thiophene CH), 148.16 (qC), 156.94 (qC); 29Si
NMR (
(thiophene CH), 142.10 (qC), 146.69 (qC). Anal. Calcd for
C28H40S6Si4Sn: C, 42.03; H, 5.04. Found: C, 41.93; H, 5.14.
MeSi), 7.21 (s, 4H, thiophene); 13C NMR (
d
d
in CDCl3) ꢁ4.19 (MeSi), ꢁ55.21 (center Si). Anal. Calcd for
3.3. Halogenation of sDTS1
C28H40O4S6Si5: C, 43.48; H, 5.21. Found: C, 43.44; H, 5.24.
To a solution of 4.00 g (6.20 mmol) of sDTS1 in 60 mL of ether,
3.69 g (24.80 mmol) of bromine was added at ꢁ80 ꢀC. After the
mixture was stirred for 30 min at room temperature, the solvent
was evaporated to give crude solids that were washed with n-
hexane (50 mL ꢂ 3) to give 3.40 g (82% yield) of sDTS3 [12]: yellow
3.6. Preparation of DTG1
To a solution of 3,3-dilithio-5,50-bis(trimethylsilyl)-2,20-bithio-
phene [12], prepared from the reaction of 0.47 g (1.00 mmol) of
3,30-dibromo-5,50-bis(trimethylsilyl)-2,20-bithiophene and 1.27 mL
(2.01 mmol) of a 1.58 M n-butyllithium/hexane solution in 15 mL of
ether at ꢁ80 ꢀC, was added 0.39 g (1.0 mmol) of Ph2GeBr2 dissolved
in 5 mL of ether at the same temperature. After being refluxed for
1 h, the mixture was hydrolyzed with water and extracted with
ether. The extract was dried over anhydrous magnesium sulfate and
organic solvent was evaporated. The residue was chromatographed
on a silica gel column with n-hexane/chloroform (10:1) as an eluent
to afford crude solids that were recrystallized from ethanol to give
0.29 g (54% yield) of DTG1 as pale yellow solids: mp 135e136 ꢀC;
solid; mp >300 ꢀC; MS m/z 668 (Mþ); 1H NMR (
d
in CDCl3), 6.87 (s,
4H, thiophene); 13C NMR (
d in CDCl3) 112.85 (CeBr), 132.18 (thio-
phene CH), 132.22 (qC), 153.27 (qC). Anal. Calcd for C16H4Br4S4Si: C,
28.29; H, 0.60. Found: C, 28.53; H, 0.65. sDTS4 was obtained in 85%
yield in a fashion similar to that above using ICl instead of Br2. Data
for sDTS4: greenish powder; mp >300 ꢀC; APPI MS m/z 859.51540
(Mþ, Calcd for C16H4I4S4Si: 859.51383). Anal. Calcd for C16H4I4S4Si:
C, 22.34; H, 0.47. Found: C, 22.46; H, 0.60. Solubility of sDTS4 in
organic solvents was too low to perform its NMR analysis.
MS m/z 536 (Mþ); 1H NMR (
d in CDCl3) 0.32 (s, 18H, MeSi), 7.26
3.4. Silylation of spirobi(dithienosilole)
(s, 2H, thiophene ring H), 7.35e7.40 (m, 6H, m- and p-Ph), 7.58 (dd,
4H, J ¼ 7.4 and 1.5 Hz, o-Ph); 13C NMR (
d in CDCl3) 0.11 (MeSi),
To a solution of tetralithiospiro(dithienosilole), prepared by the
reaction of 0.40 g (0.60 mmol) of sDTS3 and 1.90 mL (3.00 mmol) of
a 1.58 M n-butyllithium/hexane solution in 40 mL of THF at ꢁ80 ꢀC
was added 0.58 g (3.50 mmol) of PhSiMe2Cl at this temperature.
After being stirred overnight at room temperature, the mixture was
hydrolyzed with water and extracted with ether. The extract was
dried over anhydrous magnesium sulfate and the solvent was
evaporated. The residue was chromatographed on a silica gel
column with n-hexane/chloroform (4:1) as an eluent to afford
crude solids that were recrystallized from chloroform/ethanol to
give 0.27 g (50% yield) of sDTS5 as colorless solid [12]: mp
128.47, 129.66, 134.47, 134.71 (Ph), 136.30 (thiophene CH), 141.92
(thiophene qC), 142.22 (thiophene qC), 153.07 (thiophene qC); 29Si
NMR (
d
in CDCl3) ꢁ6.70 (MeSi). Anal. Calcd for C26H30GeS2Si2: C,
58.32, H, 5.65. Found: C, 58.30; H, 5.62.
Acknowledgments
This work was supported in part by a Grant-in-Aid for Scientific
Research (No. 23350097) from the Ministry of Education, Culture,
Sports, Science and Technology, Japan.
204e205 ꢀC; TOF-MS m/z 893 (M þ Hþ); 1H NMR (
d in CDCl3), 0.56
References
(s, 24H, MeSi), 7.04 (s, 4H, thiophene ring H); 7.33e7.38 (m, 12H, m-
and p-Ph), 7.56 (dd, 8H, J ¼ 7.5 and 1.9 Hz, o-Ph); 13C NMR (
d in
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136.96 (thiophene qC), 137.54 (Ph qC), 138.37 (thiophene CH),
140.04 (thiophene qC), 157.76 (thiophene qC); 29Si NMR (
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CDCl3) ꢁ11.73 (MeSi), ꢁ39.37 (center Si). Anal. Calcd for
C48H48S4Si5: C, 64.52; H, 5.41. Found: C, 64.33; H, 5.46.
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HMe2SiCl afforded compound sDTS2 in 40% yield.
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