Synthesis, structure, and photochemical reaction of 9,10-dihydro-9-silaanthracene derivatives carrying bulky substituents

Article abstract of DOI:10.1016/S0022-328X(00)00196-0

Some of 9-aryl-9,10-dihydro-9-silaanthracenes (1) were prepared and the alkylation of the compounds gave trans-9-aryl-10-alkyl-9,10-dihydro-9-silaanthracenes exclusively. Upon photolysis of a 9-phenyl derivative, 9-phenyl-9-silaanthracene was confirmed by

Full text of DOI:10.1016/S0022-328X(00)00196-0

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Journal of Organometallic Chemistry 604 (2000) 20–26
Synthesis, structure, and photochemical reaction of
9,10-dihydro-9-silaanthracene derivatives carrying bulky
substituents
Kozaburo Nishiyama a,*, Makoto Oba a, Hidenori Takagi a, Isao Fujii b,
Noriaki Hirayama b, Narisu c, Hiroaki Horiuchi c, Tetsuo Okutsu c,
Hiroshi Hiratsuka c
a Department of Material Science and Technology, Tokai Uni6ersity, Numazu, Shizuoka 410-0395, Japan
b Biological Science and Technology, Tokai Uni6ersity, Numazu, Shizuoka 410-0395, Japan
c Department of Chemistry, Gunma Uni6ersity, Kiryu, Gunma 376-8515, Japan
Received 13 December 1999; received in revised form 3 March 2000; accepted 14 March 2000
Abstract
Some of 9-aryl-9,10-dihydro-9-silaanthracenes (1) were prepared and the alkylation of the compounds gave trans-9-aryl-10-
alkyl-9,10-dihydro-9-silaanthracenes exclusively. Upon photolysis of a 9-phenyl derivative, 9-phenyl-9-silaanthracene was con-
firmed by spectroscopic analysis. Also, structural studies of the dihydro compounds were performed by NMR and X-ray. © 2000
Elsevier Science S.A. All rights reserved.
Keywords: Silaaromatics; Structure of dihydro-9-silaanthracene; Photolysis of dihydro-9-silaanthracene
1. Introduction
disilaanthracene, assumed as either a precursor of
silaaromatics or a new reducing agent. In addition, the
structural chemistry of these compounds is also attrac-
tive for us. We have previously reported first photo-
chemical formation of 9-silaanthracenes from
9,10-dihydro-9-silaanthracene in rigid glass [5] and re-
ductive reactions of organic halides using 9,10-dihy-
dro-9,10-disilaanthracene [6]. In our preliminary
communication, 9-methyl- and 9-phenyl-9,10-dihydro-
9-silaanthracene (1a and b) gave 9-silaanthracene
derivative (2a and b) on UV irradiation and, espe-
cially, the latter 1b resulted in the silaanthracene
derivative 2b effectively (Scheme 1). Therefore, we at-
tempted to establish a general synthetic route of the
precursor of the silaanthracene framework and silaan-
thracene itself having a sterically bulky group around
the silicon atom. In this paper, we would like to report
a synthesis of 9-aryl-9,10-dihydro-9-silaanthracene (1b–
h), the photolytic reaction of some of these compounds,
and a structural analysis using NMR and X-ray [7]
technique.
Although a number of unsaturated compounds con-
taining siliconꢀcarbon or siliconꢀsilicon double bonds
are well-known as a silene or disilene, only a few
silaaromatic compounds have been prepared apart
from silabenzene, disilabenzene, and 9-silaanthracenes
[1], which were confirmed by Maier et al. as matrix
isolation products or Diels–Alder adducts of flash py-
rolysis intermediates of the dihydro- or tetrahydro-
derivatives [2,3]. Recently, isolation of 2-silana-
phthalene having a sterically bulky substituent on the
silicon atom at room temperature has been reported
via dehydrohalogenation of the precursor by Tokitoh,
Okazaki, and co-workers [4]. A recent interest of our
group in regard to organosilicon compounds is the
chemistry of dihydro derivatives of 9-sila- and 9,10-
* Corresponding author. Fax: +81-559-681155.
E-mail address: nishiyam@wing.ncc.u-tokai.ac.jp (K. Nishiyama).
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(00)00196-0

K. Nishiyama et al. / Journal of Organometallic Chemistry 604 (2000) 20–26
21
from trans to the 9-aryl group, which was confirmed by
X-ray crystallographic analysis [7]. A similar reaction of
the compound 1g with 2-iodopropane furnished the
compound 1h in 30% yield.
These 9,10-dihydro-9-silaanthracenes, except for the
compound 1b, are unknown compounds and show sat-
isfactory 1H-, 13C-, and 29Si-NMR, IR, and HRMS
data.
2.2. Structure of the 9,10-dihydro-9-silaanthracens (1)
In the 1H-NMR spectra of the compounds 1c and 1d,
two kinds of methyl or isopropyl group of 9-aryl, which
correspond to ortho and para substituents on the aro-
matic ring, were observed as expected. For example,
compound 1d showed the sharp signals of the isopropyl
groups at l 1.02 (d, J=7 Hz, 12H) and 1.31 (d, J=7
Hz, 6H) at 22°C. The dihedral angle (q) between two
phenyl rings in the dihydroanthracene framework was
152°. This shows that two isopropyl groups at the 2-
and 6-positions of the Tip group are considered to be
equivalent. The aryl substituent exists as pseudo-equa-
torial on the silicon atom of the 1-silacyclohexadiene
ring. For 1c, two methyl groups at the 2- and 6-posi-
tions of the mesityl group are equivalent at l 2.34. On
the other hand, the signals of the t-butyl group of
9-(2,4,6-tri-t-butyl)phenyl derivative 1g appeared at l
1.07 (br, 9H), 1.39 (s, 9H), and 1.59 (br. 9H) at 22°C.
The very broad signals at l 1.07 and 1.59 were assigned
to be the t-Bu groups at 2- and 6-positions, and these
two t-butyl groups should be non-equivalent at 22°C,
namely, the bond rotation about SiꢀAr is very slow
because of steric hindrance between the t-Bu group and
the dihydroanthracene framework. From variable tem-
perature NMR measurement, these signals coalesced at
around 35°C and three kinds of very sharp singlets were
observed at l 0.99, 1.38, and 1.61 at −60°C (the bond
rotation about SiꢀAr was frozen at this temperature).
The dihedral angle q is 154°, similar to that of 1d.
Molecular structure of 1g is shown in Fig. 1 and the
emphasized structural feature of the Ttp group is illus-
trated in Fig. 2. The benzene ring of the aryl group is
found bent with an angle of 17°. From these investiga-
tions, it became clear that the SiꢀAr bond of 1b, 1c, and
1e, rotates freely but that of 1g is sterically restricted at
room temperature and the dihedral angle q of these
compounds is almost similar, not due to the aryl
substituent.
Scheme 1.
2. Results and discussion
2.1. Synthesis
According to the synthetic route for 9-phenyl-9,10-di-
hydro-9-silaanthracene (1b) [8], a reaction of 2,4,6-
trimethylphenyldichlorosilane
di-Grignard reagent, which was prepared from 2,2%-
(MesSiCl2H)
with
dichlorodiphenylmethane (3) with activated magnesium
[9],
gave
9-(2,4,6-trimethylphenyl)-9,10-dihydro-9-
silaanthracene (1c) in 28% yield (Scheme 2). On the
other hand, treatment of 2,4,6-triisopropylphenylsilane
(TipSiH3) with 2,2%-dilithiodiphenylmethane, which was
formed by dilithiation of 2,2%-dibromodiphenylmethane
with butyllithium, afforded 9-(2,4,6-triisopropylphenyl)-
9,10-dihydro-9-silaanthracene (1d) in 72% yield. With
the more bulky 2,4,6-tri-t-butylphenylsilane (TtpSiH3),
refluxing the reaction mixture overnight was necessary
to obtain the 9-(2,4,6-tri-t-butylphenyl)-9,10-dihydro-9-
silaanthracene (1g) in moderate yield (48%).
We next carried out the introduction of an alkyl
group into the 10-position in order to create more
crowded environment around the Si atom. After treat-
ment of the compound 1d with butyllithium, the resul-
tant carbanion was quenched by iodomethane or
2-iodopropane to afford the corresponding 10-alkylated
compound 1e or 1f in 51 or 60% yield, respectively. The
incorporation of the alkyl group exclusively occurred
For 1e and 1f, the incorporation of the alkyl group
exclusively occurred from trans to the 9-aryl group. By
introducing the alkyl group into the 10-position of 1,
however, the rotation about the SiꢀAr bond depended
upon the alkyl substituent. The rotation of the aryl
group of compound 1f, obtained from 1d by introduc-
tion of an isopropyl group at the 10-position, was
restricted at 22°C, as checked by NMR. Also, the
Scheme 2.

22
K. Nishiyama et al. / Journal of Organometallic Chemistry 604 (2000) 20–26
Table 1
dihedral angle q of the compound 1f (141°) is 10°
smaller than that of 1d, due to compression by the
isopropyl group at the 10-position. The values of the
dihedral angle q and chemical equivalency of the ortho
substituents on the aryl ring of 1c–h are compiled in
Table 1.
Dihedral angle q between two phenyl rings in the dihydroanthracene
framework and chemical equivalency of the ortho substituents of the
aryl group
Compound
Dihedral angle a (°)
Ortho substituents b
1c
1d
1e
1f
1g
1h
Equivalent
Equivalent
Equivalent
Nonequivalent
Nonequivalent
Nonequivalent
152
158
141
154
2.3. Photolysis of 9,10-dihydro-9-silaanthracenes
It is well known that anthracene is easily produced
by the photolysis of 9,10-dihydroanthracene. As men-
tioned above, Maier et al. observed 9-silaanthracene
produced by flash pyrolysis [3]. We studied the photo-
chemical formation of 9-silaanthracene derivatives for
9,10-dihydro-9-silaanthracene (1i) [10] and 9-phenyl-
9,10-dihydro-9-silaanthracene (1b). By photolysis of 1b,
9-phenyl-9-silaanthracene (2b) was formed. This was
confirmed by comparing absorption spectrum with that
reported for 9-phenyl-9-silaanthracene produced by
a Determined by X-ray analysis [7].
b Observed in 400 MHz 1H-NMR at 22°C.
flash thermolysis technique [3]. The 407 nm band was
assigned to the Lb transition by the results of fluores-
1
cence polarization measurements and the calculated
results by CNDO/S-CI method [11]. Although forma-
tion of 9-silaanthracene (2i) from 1i was also confirmed
by the observation of its absorption band at 400 nm, its
yield was very small. From these results, it is considered
that steric hindrance and electron-donating ability of a
substituent group at the 9-position play an important
role in the formation process of 9-silaanthracene
derivatives. Here we have studied the photolysis of the
9,10-dihydro-9-silaanthracene derivatives having
a
2,4,6-triisopropylphenyl or 2,4,6-tri-t-butylphenyl
group at the 9-position, which are considered to be
much more bulky and/or have electron-donating
ability.
Fig. 3a–d show absorption spectra of 1i, 1b, 9-(2,4,6-
triisopropylphenyl)-9,10-dihydro-9-silaanthracene (1d),
and
9-(2,4,6-tri-t-butylphenyl)-9,10-dihydro-9-silaan-
thracene (1g) in 3MP (3-methylpentane) at 77 K before
(dotted line) and after (full line) the photolysis with
253.7 nm light, respectively. Upon photolysis of 1d, a
new absorption peak appeared at 405 nm, and this
absorption band is assigned to the 1Lb band of the
corresponding 9-silaanthracene, although its formation
amount was relatively smaller. In the case of 1g, a
broad absorption band was slightly observed at 408
nm.
Formation yields of the corresponding 9-silaan-
thracenes are in the order of 1b\1i\1d\1g. These
results indicate that electron-donating power or bulki-
ness of the substituent is not the only important factor
for the formation of a 9-silaanthracene derivative.
Moreover, the reactivity of these compounds might be
dependent upon the structure of the ground state, as
suggested by structural analysis.
,
Fig. 1. Molecular structure of 1g. Important bond lengths (A) and
angles (°): Si(9)ꢀC(1a)=1.869(3), Si(9)ꢀC(8a)=1.871(3), Si(9)ꢀ
C(11)=1.896(3); C(1a)ꢀSi(9)ꢀC(8a)=104.2(1), C(1a)ꢀSi(9)ꢀC(11)=
112.0(1), C(8a)ꢀSi(9)ꢀC(11)=122.8(1), Si(9)ꢀC(11)ꢀC(12)=117.4(2),
Si(9)ꢀC(11)ꢀC(16)=122.7(2), C(12)ꢀC(11)ꢀC(16)=116.8(3).
Other attempts for generation of silaanthracene,
i.e., 1,4-dehydrochlorination and 1,4-dehydrogenation,
were made, but the product was not the compound
expected.
Fig. 2. Emphasized structural feature of Ttp group of compound 1g.

K. Nishiyama et al. / Journal of Organometallic Chemistry 604 (2000) 20–26
23
Fig. 3. Absorption spectra of 1i (a), 1b (b), 1d (c), and 1g (d) in 3MP at 77 K before (dotted line) and after (full line) photolysis with 253.7 nm
light.
3. Experimental
3.2. Materials and sol6ents
3.1. General
Most of the starting materials and reagents were
commercial products and were used as accepted. 2,2%-
Dichlorodiphenylmethane (3) [8], 2,2%-dibromodi-
phenylmethane (4) [12], 2,4,6-trimethylphenyldichloro-
silane [13], 2,4,6-triisopropylphenylsilane [14], and
2,4,6-tri-t-butylphenylsilane [15] were prepared accord-
ing to the literature. Solvents were distilled over sodium
in the presence of benzophenone.
GC measurements were performed on a Shimadzu
GC-18A and
a GL Sciences GC-380 gas chro-
matograph using a 50 m×0.25 mm methyl silicone
capillary column (Quadrex). TLC was carried out on
Merck silica gel 60 F254. Flash column chromatography
was performed on Merck silica gel 60 (230–400 mesh).
Infrared spectra were recorded on a Perkin–Elmer 1600
infrared spectrometer. H-, 13C-, and 29Si-NMR spectra
3.3. 9-(2,4,6-Trimethylphenyl)-9,10-dihydro-9-
silaanthracene (1c)
1
were measured on a Varian UNITY-400 spectrometer.
All chemical shifts are reported as l-values (ppm)
relative to residual chloroform (lH 7.26), the central
peak of deuteriochloroform (lC 77.0) or tetramethylsi-
lane (lSi 0.0). GC-MS was measured with the direct
combination of GC (Hewlett–Packard GC 5890 Series
II with a 25 m×0.25 mm methyl silicone capillary
column) and a JEOL JMS-AX-500 spectrometer with
DA7000 data system.
To Mg turnings (560 mg, 24.0 mmol) was added
1,2-dibromoethane (4.51 g, 24.0 mmol) in THF (40 ml),
and the mixture was refluxed under argon atmosphere
for 1 h. After the solution was cooled to room temper-
ature (r.t), K (1.75 g, 45.0 mmol), KI (1.66 g, 10.0
mmol) was added and refluxed for 2 h. Then, 2,2%-
dichlorodiphenylmethane (3, 1.89 g, 8.00 mmol) was

24
K. Nishiyama et al. / Journal of Organometallic Chemistry 604 (2000) 20–26
purified by flash chromatography on silica gel and
elution with hexane gave 9-silaanthracene 1g (840 mg,
48%) as colorless plates, m.p. 172–173°C. 1H-NMR
(CDCl3): l 1.07 (br, 9H), 1.39 (s, 9H), 1.59 (br. 9H),
4.08 and 4.21 (ABq, J=18 Hz, 2H), 5.65 (s, 1H), 7.17
(m, 2H), 7.31 (m, 6H), 7.52 (br, 2H). 13C-NMR
(CDCl3): l 31.2, 34.1, 34.8, 39.6, 41.6, 121.4, 122.9,
125.4, 127.9, 128.9, 135.1, 135.6, 143.7, 151.2, 161.7.
29Si-NMR (CDCl3): l −46.5. IR (KBr): wSiꢀH 2156.3
cm−1. HRMS (EI): m/z 440.2942 [M+, Calc. for
C31H40Si 440.2899].
added to the resulting black suspension of activated Mg
and the mixture was heated to reflux for 3 h, after
which 2,4,6-trimethylphenyldichlorosilane (2.11 g, 9.60
mmol) was added at r.t. After being stirred at r.t.
overnight, the reaction mixture was quenched with
aqueous NH4Cl and extracted with ether. The organic
layer was dried over MgSO4 and evaporated. The crude
product was purified by flash chromatography on silica
gel and elution with hexane gave 9-silaanthracene (1c)
(690 mg, 28%) as colorless plates, m.p. 107–109°C.
1H-NMR (CDCl3): l 2.24 (s, 3H), 2.34 (s, 6H), 4.13
and 4.29 (ABq, J=18 Hz, 2H), 5.66 (s, 1H), 6.92 (s,
2H), 7.17 (m, 2H), 7.34 (m, 2H), 7.41 (m, 4H). 13C-
NMR (CDCl3): l 21.2, 24.2, 41.6, 124.9, 125.8, 128.2,
128.9, 129.4, 132.1, 134.3, 140.4, 145.6, 146.5. 29Si-
3.6. 10-Methyl-9-(2,4,6-triisopropylphenyl)-9,10-
dihydro-9-silaanthracene (1e)
NMR (CDCl3): l −47.5. IR (KBr): wSiꢀH 2139.1 cm−1
.
To a solution of 9-silaanthracene (1d) (1.45 g, 3.64
mmol) in THF (25 ml) was added 1.7 M t-butyllithium
in pentane (3.30 ml, 5.61 mmol) at −78°C under Ar
atmosphere. After the solution was stirred for 1 h,
iodomethane (2.28 g, 16.1 mmol) was added. After
being stirred at r.t. overnight, the reaction mixture was
quenched with H2O and extracted with ether. The
organic layer was dried over MgSO4 and evaporated.
The crude product was purified by flash chromatogra-
phy on silica gel and elution with hexane gave 9-silaan-
thracene 1e (767 mg, 51%) as a colorless solid, m.p.
146–148°C. 1H-NMR (CDCl3): l 0.97 (d, J=7 Hz,
12H), 1.31 (d, J=7 Hz, 6H), 1.50 (d, J=7 Hz, 3H),
2.93 (sep, J=7 Hz, 1H), 3.09 (sep, J=7 Hz, 2H), 4.30
(q, J=7 Hz, 1H), 5.89 (s, 1H), 7.06 (s, 2H), 7.16 (m,
2H), 7.36 (m, 2H), 7.40 (m, 4H). 13C-NMR (CDCl3): l
23.8, 24.4, 29.1, 33.5, 34.4, 48.4, 121.3, 124.1, 125.4,
128.0, 129.7, 132.1, 135.2, 150.7, 151.4, 157.7. 29Si-
HRMS (EI): m/z 314.1526 [M+, Calc. for C22H22Si
314.1491].
3.4. 9-(2,4,6-Triisopropylphenyl)-9,10-
dihydro-9-silaanthracene (1d)
To a solution of 2,2%-dibromodiphenylmethane (4,
10.0 g, 30.7 mmol) in ether (150 ml) was added 1.6 M
butyllithium in hexane (43 ml, 68.8 mmol) at 0°C under
Ar atmosphere. After the solution was stirred at r.t. for
1 h, 2,4,6-triisopropylphenylsilane (10.78 g, 46.1 mmol)
was added at r.t. After being stirred at r.t. overnight,
the reaction mixture was quenched with aqueous
NH4Cl and extracted with ether. The organic layer was
dried over MgSO4 and evaporated. The crude product
was recrystallized from ethanol to give 9-silaanthracene
(1d) (8.61 g, 72%) as colorless plates, m.p. 160–162°C.
1H-NMR (CDCl3): l 1.02 (d, J=7 Hz, 12H), 1.31 (d,
J=7 Hz, 6H), 2.93 (sep, J=7 Hz, 1H), 3.17 (sep, J=7
Hz, 2H), 4.15 and 4.32 (ABq, J=18 Hz, 2H), 5.71 (s,
1H), 7.09 (s, 2H), 7.18 (m, 2H), 7.34 (m, 2H), 7.40 (m,
2H), 7.43 (m, 2H). 13C-NMR (CDCl3): l 23.8, 24.6,
33.7, 34.4, 41.6, 121.4, 123.7, 125.5, 128.1, 129.3, 133.2,
134.8, 144.7, 151.5, 157.7. 29Si-NMR (CDCl3): l −
49.3. IR (KBr): wSiꢀH 2143.4 cm−1. HRMS (EI): m/z
398.2421 [M+, Calc. for C28H34Si 398.2430].
NMR (CDCl3): l −50.8. IR (KBr): wSiꢀH 2149.9 cm−1
.
HRMS (EI): m/z 412.2548 [M+, Calc. for C29H36Si
412.2586].
3.7. 10-Isopropyl-9-(2,4,6-triisopropylphenyl)-9,10-
dihydro-9-silaanthracene (1f)
To a solution of 9-silaanthracene (1d) (1.19 g, 3.00
mmol) in THF (25 ml) was added 1.7 M t-butyllithium
in pentane (2.25 ml, 3.83 mmol) at −78°C under Ar
atmosphere. After the solution was stirred for 1 h,
2-iodopropane (601 mg, 3.60 mmol) was added. After
refluxing overnight, the reaction mixture was quenched
with H2O and extracted with ether. The organic layer
was dried over MgSO4 and evaporated. The crude
product was purified by flash chromatography on silica
gel and elution with hexane gave 9-silaanthracene 1f
(790 mg, 60%) as a colorless solid, m.p. 171–173°C.
1H-NMR (CDCl3): l 0.49 (d, J=7 Hz, 6H), 0.79 (d,
J=7 Hz, 6H), 1.30 (d, J=7 Hz, 6H), 1.41 (d, J=7 Hz,
6H), 2.00 (m, 2H), 2.92 (sep, J=7 Hz, 1H), 3.64 (d,
3.5. 9-(2,4,6-Tri-t-butylphenyl)-9,10-
dihydro-9-silaanthracene (1g)
To a solution of 2,2%-dibromodiphenylmethane (4,
1.30 g, 4.00 mmol) in ether (20 ml) was added 1.6 M
butyllithium in hexane (6.2 ml, 9.92 mmol) at 0°C
under Ar atmosphere. After the solution was stirred at
r.t. for 1 h, 2,4,6-tri-t-butylphenylsilane (1.66 g, 6.00
mmol) was added at r.t. After refluxing overnight, the
reaction mixture was quenched with aqueous NH4Cl
and extracted with ether. The organic layer was dried
over MgSO4 and evaporated. The crude product was

K. Nishiyama et al. / Journal of Organometallic Chemistry 604 (2000) 20–26
25
ethanol solution at r.t. Diffraction data using a crystal
with the dimensions of 0.5×0.1×0.1 mm were col-
lected on Nonius CAD4 Turbo four-circle diffracto-
meter. Of a total of 6035 reflections collected up to
q=74.11° (−20BhB20, −13BkB0, −18BlB0)
in ꢀ–2q scan mode using graphite monochromated
Cu–Ka radiation, 5515 were independent (Rint=0.015).
These data were corrected empirically for absorption
(with maximum 0.998 and minimum 0.968 transmis-
sion). Hydrogen atoms were fixed on calculated posi-
tions. Non-hydrogen atoms were refined anisotropically
based on F by full-matrix least-squares method. The
final R1 and wR2 for 3644 reflections with I\3s(I) are
0.0632 and 0.0916, respectively. An ORTEPII drawing is
shown in Fig. 1.
J=9 Hz, 1H), 3.97 (sep, J=7 Hz, 1H), 5.91 (s, 1H),
6.92 (s, 1H), 7.16 (m, 2H), 7.18 (s, 1H), 7.33 (m, 4H),
7.41 (m, 2H). 13C-NMR (CDCl3): l 21.7, 23.7, 24.9,
32.8, 33.8, 34.3, 37.1, 61.4, 120.5, 121.8, 124.6, 125.2,
128.5, 129.7, 132.9, 135.3, 148.7, 151.2, 157.5. 29Si-
NMR (CDCl3): l −49.5. IR (KBr): wSiꢀH 2146.1 cm−1
.
HRMS (EI): m/z 440.2861 [M+, Calc. for C31H40Si
440.2899].
3.8. 10-Isopropyl-9-(2,4,6-tri-t-butylphenyl)-9,10-
dihydro-9-silaanthracene (1h)
To a solution of 9-silaanthracene (1g) (970 mg, 2.21
mmol) in THF (20 ml) was added 1.7 M t-butyllithium
in pentane (1.85 ml, 3.15 mmol) at −78°C under Ar
atmosphere. After the solution was stirred for 1 h,
2-iodopropane (500 mg, 2.90 mmol) was added. After
refluxing overnight, the reaction mixture was quenched
with H2O and extracted with ether. The organic layer
was dried over MgSO4 and evaporated. The crude
product was purified by flash chromatography on silica
gel and elution with hexane gave 9-silaanthracene (1h)
(321 mg, 30%) as a colorless solid, m.p. 130–132°C.
1H-NMR (CDCl3): l 0.68 (d, J=7 Hz, 6H), 0.79 (s,
9H), 1.39 (s, 9H), 1.69 (s, 9H), 1.88 (m, 1H), 3.57 (d,
J=9 Hz, 1H), 5.83 (s, 1H), 7.14 (m, 2H), 7.27 (m, 6H),
7.42 (d, J=1.9, 1H), 7.54 (d, J=1.9, 1H). 13C-NMR
(CDCl3): l 21.9, 31.2, 33.7, 33.8, 34.2, 34.8, 36.7, 39.4,
39.6, 61.6, 122.3, 122.9, 123.3, 125.2, 128.3, 129.8,
135.8, 147.9, 151.0, 160.6, 162.7. 29Si-NMR (CDCl3): l
−47.4. IR (KBr): wSiꢀH 2172.1 cm−1. HRMS (EI): m/z
482.3332 [M+, Calc. for C34H46Si 482.3369].
4. Supplementary material
Crystallographic data for the strucutural analysis has
been deposited with the Cambridge Cristallographic
Data Centre, CCDC reference numbers 140081. Copies
of this information may be obtained free of charge
from the Director, CCDC, 12 Union Road, Cambridge,
CB2 1EZ, UK (fax: +44-1223-336033; e-mail: de-
posit@ccdc.cam.ac.uk or www: http://www.ccdc.cam.
ac.uk).
Acknowledgements
One of the authors (K.N.) gratefully acknowledges
financial support of a Grant-in-Aid for Scientific Re-
search (No. 09640646) from the Ministry of Education,
Science, Sports and Culture of Japan.
3.9. Photolysis of 9,10-dihydro-9-silaanthracenes
Photolysis was carried out at low temperature using
the 266 nm light; output of fourth harmonics from the
Nd3+: YAG laser with 8 ns-pulse width. Liquid nitro-
gen cryostat (Oxford DN-1704) and temperature con-
troller (Oxford ITC-1) were used for measurements at
various temperatures between 77 and 100 K.
Absorption spectra were measured by using a Hitachi
U3300 spectrophotometer. Fluorescence emission and
excitation spectra were measured using a Hitachi M850
fluorescence spectrometer with band pass of 3 or 5 nm
for both excitation and emission.
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26
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