Synthesis, characterization, and photoreactions of 1,2-disiladigermacyclobutane

Article abstract of DOI:10.1002/hc.1060

A new four-membered ring compound having a Si₂Ge₂ skeleton, octaisopropyl-1,2-disiladigermacyclobutane (1), was synthesized by the reductive coupling of tetraisopropyl-1,2-dichlorosilagermane with sodium in toluene. The structure of 1, which has one Ge-Ge bond, one Si-Si bond, and two Ge-Si bonds in a ring; was confirmed by chemical derivatization; the reactions of 1 with m-chloroperoxy-benzoic acid and PCl₅ led to the selective cleavage of the Ge-Ge bond in 1. The selective extrusion of a germylene from 1 was observed at the initial stage of the photolysis using 254 nm light.

Full text of DOI:10.1002/hc.1060

Heteroatom Chemistry
Volume 12, Number 5, 2001
S
ynthesis, Characterization, and
Photoreactions of 1,2-
Disiladigermacyclobutane
1,2
2
2
Hisako Hashimoto, Yusuke Yagihashi, Lubov Ignatovich,
1,2
and Mitsuo Kira
1
Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku, Sendai 980-
8
578, Japan
2
Photodynamics Research Center, The Institute of Physical and Chemical Research (RIKEN), 519-
1
399, Aoba, Aramaki, Aoba-ku, Sendai 980-0845, Japan
Received 15 January 2001; revised 13 February 2001
the cyclic oligometalane systems having both silicon
and germanium in the ring have been limited so far,
while there have been reports on the syntheses and
structures of Si Ge [8], SiGe [9], Si Ge [10], Si Ge
ABSTRACT: A new four-membered ring compound
having a Si Ge skeleton, octaisopropyl-1,2-disiladi-
2
2
germacyclobutane (1), was synthesized by the reduc-
tive coupling of tetraisopropyl-1,2-dichlorosilager-
mane with sodium in toluene. The structure of 1,
which has one Ge–Ge bond, one Si–Si bond, and two
Ge–Si bonds in a ring, was confirmed by chemical de-
rivatization; the reactions of 1 with m-chloroperoxy-
2
2
3
4
[
11], Si Ge [12], and Si Ge [12] rings. The Si–Ge
4
2
5
mixed ring compounds are quite intriguing because
they are possible precursors not only for GeꢁSi dou-
bly bonded compounds [9] but also for Si–Ge co-
polymers with ordered Si/Ge sequences, which have
been expected to be polymers with a one-dimen-
sional superlattice [13]. We wish herein to report the
preparation, characterization, and photolysis of a
new four-membered cyclic oligometalane, octaiso-
propyl-1,2-disiladigermacyclobutane (1).
benzoic acid and PCl led to the selective cleavage of
5
the Ge–Ge bond in 1. The selective extrusion of a ger-
mylene from 1 was observed at the initial stage of the
photolysis using 254 nm light. ꢀ 2001 John Wiley &
Sons, Inc. Heteroatom Chem 12:398–405, 2001
INTRODUCTION
The chemistry of cyclic oligosilanes [1–3] and oli-
gogermanes [1,4–6] have been extensively studied
because of their possible cyclic r conjugation [1c,7]
and their importance as photochemical precursors
of reactive intermediates, such as silylenes, germy-
lenes, disilenes, and digermenes. However, studies of
RESULTS AND DISCUSSION
Synthesis and Characterization of 1,2-
Disiladigermacyclobutane
Dedicated to Prof. Naoki Inamoto on the occasion of his 72nd
birthday.
Correspondence to: Mitsuo Kira
2001 John Wiley & Sons, Inc.
Small ring oligosilanes and oligogermanes are gen-
erally synthesized by the reductive coupling of the
ꢀ
3
98

Synthesis, Characterization, and Photoreactions of 1,2-Disiladigermacyclobutane 399
corresponding ␣,x-dichlorooligometallane with al- oxadisiladigermacyclopentane 5 with two different
2
9
kali or alkaline-earth metals [1,2]. Reductive cou-
pling of tetraisopropyl-1,2-dichlorosilagermanewith
sodium in toluene at reflux, followed by recrystalli-
zation of the product from EtOH gave 1,2-disiladi-
germacyclobutane 1 in 23% yield.
resonances in the Si NMR spectrum as a sole oxi-
dation product (Equation 2). The results are com-
patible with the 1,2-isomer 1. The two oxidation
products obtained in this experiments are assigned
to two of three possible isomers of oxadisiladiger-
macyclopentanes 6a, 6b, and 6c, which should show
2
9
one, one, and two Si resonances, respectively
Equation 3). The major product is assigned to 6b
rather than 6a on the basis of its higher field Si
NMR resonance than that of 1 (9.3 ppm) [14].
(
2
9
(1)
Although all the spectroscopic data obtained for
the product of the reaction depicted in Equation 1
were compatible with a disiladigermacyclobutane
structure, two possible isomers 1 (1,2-isomer) and 2
(2)
(
1,3-isomer) were not discriminated by these spec-
troscopic data. The molecular ion peak in the mass
spectrum was found at m/z ꢁ 546 with a satisfactory
2
9
fitting isotopic pattern due to two Ge atoms. The Si
7
3
and Ge NMR resonances for the product appeared
at 9.3 ppm and ꢂ54.2 ppm in CDCl , respectively.
3
The UV absorption band maximum was observed at
2
90 nm with the absorption coefficient of 440 in hex-
ane; the spectral feature is similar to those of octa-
isopropyltetrasilacyclobutane 3 (kmax 290 nm, e 200)
(3)
[
3
2b], and trisilagermacyclobutane 4 (kmax 300 nm, e
20) [10b]. The structure of the disiladigermacyclo-
The disiladigermacyclobutane obtained by the
reaction depicted in Equation 1 was also confirmed
butane was not determined by the X-ray analysis due
to the inevitable disorder in a single crystal.
as 1 by examining the chlorination with PCl in ben-
zene, which gave only 1,4-dichloro-1,4-digerma-2,3-
5
disilane 7 in 85% yield (Equation 4) [15].
(4)
It is suggested that, in the present Wurtz-type
coupling, the initial metal–metal coupling occurs ex-
clusively between the same metals (Ge–Ge or Si–Si)
to give 1; semiempirical molecular orbital (MO) cal-
culations (PM3) have shown that 2 is even more sta-
ble by 3.8 kcal/mol than 1.
Since disiladigermacyclobutane 1 has three dif-
ferent types of metal–metal bonds, Ge–Ge, Ge–Si,
and Si–Si, in a ring, the relative reactivities among
these bonds can be determined by examining the re-
actions of 1 with many reagents. In this respect, it is
interesting to note that both the chlorination with
The structure of the disiladigermacyclobutane
was determined to be the 1,2-isomer 1 by the follow-
ing chemical derivatizations. The oxidation of the
disiladigermacyclobutane by m-chloroperoxyben-
zoic acid (MCPBA) afforded two oxidation products
(
in a ratio of 95:5), and the major product showed
2
9
only one Si NMR resonance at ꢂ10.0 ppm. The
results indicate that the disiladigermacyclobutane
should not be the 1,3-isomer 2 because it should give
PCl and the oxidation with MCPBA occurred at the
5
Ge–Ge bond of 1 in a highly chemoselective manner.
The longer bond distance and the higher electron-

4
00 Hashimoto et al.
donating ability of the Ge–Ge bond compared with
the Si–Si and Si–Ge bonds may be responsible for
the observed relative reactivity.
presence of an excess amount of 2,3-dimethylbuta-
diene afforded 1,1-diisopropyl-1-germa-3,4-dimeth-
ylcyclopent-3-ene (22%) as a sole volatile product to-
gether with unreacted 1 (28%) after 10 minutes of
i
irradiation. No product derived from Pr Si: was de-
Photoreactions of Disiladigermacyclobutane 1
2
tected. It should also be noted that a small amount
Photolyses of 1 in the Presence of Trapping Re-
agents. When a hexane solution of 1 was irradiated
i
i
of ( Pr Si) Pr GeO was detected by GC-MS, when
2
2
2
2
the irradiated solution was exposured to air, indicat-
ing the concomitant formation of disilagermacyclo-
in the presence of Et SiH at room temperature,
3
i
Et SiGe Pr H formed in 9% as a single product
3
2
i
i
propane ( Pr Si) Pr Ge. The results are summarized
2
2
2
within 1 minute. After 4 minutes of irradiation, the
in Scheme 1.
i
yield of Et SiGe Pr H increased to 26%, with the for-
3
2
i
mation of Et SiSi Pr H in 5% yield. After irradiation
3
2
for 10 minutes, 83% of 1 was consumed to afford
Photolysis of 1 Monitored by UV–Vis Spectros-
copy. When the photoreaction of 1 in hexane at
room temperature using a 254 nm light was moni-
tored by UV–vis spectroscopy, a new absorption
band appeared at 420 nm. The intensity of the band
increased, and the solution turned yellow with in-
creasing irradiation time. The yellow color as well as
the 420 nm band disappeared slowly in an inert at-
i
i
Et SiGe Pr H and Et SiSi Pr H in 46 and 14% yields,
3
2
3
2
respectively. The photo-products were analyzed by
gas chromatography (GC) and gas chromatography–
mass spectrometry (GC-MS) techniques. The per-
cent consumption of 1 and the product yields were
plotted against irradiation time as shown in Figure
1
. When a hexane solution of 1 was irradiated in the
i
presence of EtOH, Pr Ge(OEt)H formed in 7%
2
yield within 1 minutes. After 10 minutes of irra-
i
i
diation, Pr Ge(OEt)H (36%), Pr Si(OEt)H (30%),
2
2
i
i
i
i
(
EtO) Pr SiSi Pr H (ca. 12%) [16], (EtO) Pr SiGe -
2
2
2
Pr H (ca. 8%) [16], and unreacted 1 (14%) were de-
2
tected in the product mixture (Figure 2). While the
germylene-derived product was the most prominent
product, the difference between the yields of the sil-
ylene- and germylene-derived products was smaller
in this experiment than that in the experiment with
Et SiH. The reason may be ascribed to the lower
3
trapping efficiency toward germylene than that to-
ward silylene of EtOH [6,17]. Photolysis of 1 in the
FIGURE 2 Time course of conversion (%) of 1 and product
yields in the photolysis of 1 in the presence of EtOH. ꢃ, 2b;
i
i
i
i
●
(
, Pr Ge(OEt)H; ꢀ, Pr Si(OEt)H; ▫, (EtO)Pr SiSiPr H; ꢄ,
2 2 2 2
i i
EtO)Pr SiGePr H.
2 2
FIGURE 1 Time course of conversion (%) of 1 and product
yields in the photolysis of 1 in the presence of Et SiH. ꢃ, 1;
3
i
i
●
, HPr GeSiEt ; ꢀ, HPr SiSiEt .
SCHEME 1
2
3
2
3

Synthesis, Characterization, and Photoreactions of 1,2-Disiladigermacyclobutane 401
mosphere but immediately upon exposure to air. No
other distinct absorption band was observed in the
visible region during the irradiation.
germacyclobutane in 3-MP, it was observed that the
absorption maximum found at 390 nm at 77 K
shifted to 420 nm at room temperature.
Irradiation of 1 with a 254 nm light in a 3-meth-
ylpentane (3-MP) glass matrix at 77 K produced two
absorption bands at 390 nm and 540 nm with a
shoulder at 300 nm within a few minutes (Figure 3).
During the irradiation, orange spots were observed
in the glass matrix. Upon melting, the spots as well
Photodegradation Pathways of Disiladigermacy-
clobutane 1. Based on the aforementioned exper-
imental results, the photoreaction pathways of 1 are
summarized as shown in Scheme 2. Thus, the reac-
tion proceeds through the selective formation of
as the absorption bands at 390 and 540 nm disap-
i
Pr Ge: and the corresponding disilagermacyclopro-
2
i
peared. The 540 nm band is assigned to Pr Ge:,
2
pane 8 at the initial stage. Subsequent photolysis of
which is reported to show a band maximum at 540
nm at 77 K [6c]. The assignment is in good accord
with the results of the trapping experiments afore-
mentioned, whereas, by the spectroscopic data
i
i
8
will generate Pr Ge: and Pr Si:, whose dimeriza-
2
2
tion and cross coupling afford the corresponding di-
metallenes, as shown in Scheme 2.
In contrast to the photolysis of perisopropyl-
i
i
alone, Pr Si: cannot be ruled out as the species re-
tetrasilacyclobutane, c-Si Pr , [2g], which produces
2
4
8
i
sponsible for the 540 nm band (vide infra); k
of
Pr Si: and hexaisopropyltrisilacyclopropane at the
initial stage, the germanium analog, c-Ge Pr , has
max
2
i
i
Pr Si: is reported to be 530 nm at room temperature
2
4
8
[
3b]. The absorption band observed at 390 nm at 77
been reported to decompose in three different man-
ners; a germylene extrusion, a homolytic germa-
nium-germanium bond scission leading to biradi-
cals, and formation of digermenes [6c]. Trisil-
i
i
K is attributable to one, two, or all of Pr GeꢁGe Pr
2
2
i
i
i
i
[
6c], Pr SiꢁSi Pr , and Pr GeꢁSi Pr , based on the
2
2
2
2
i
i
reported band maxima for Pr GeꢁGe Pr [6c] and
2
2
i
i
i
Pr SiꢁSi Pr [2c]; they are 390 nm at 77 K and 400
agermacyclobutanes, c-Si R GeRꢅ (R ꢁ Pr or
2
2
3
6
2
t
nm at room temperature, respectively.
CH Bu , Rꢅ ꢁ CH SiMe ), are reported to produce
2
2
3
A shoulder appeared at 300 nm during the pho-
tolysis of 1 at 77 K and it may be assigned to disila-
germacyclopropane and/or other trimetalacyclopro-
panes, whose absorption bands are reported to be
observed at around 300 nm [2b,4a].
the corresponding germylene and cyclotrisilane as
main products, together with a small amount of the
corresponding silylene upon irradiation [10b]. Bains
et al. have reported that photolysis of permesityldi-
silagermacyclopropane generates the corresponding
germylene and silagermene, the latter of which
isomerizes to a more stable silylgermylene; no for-
mation of the corresponding silylene and digermene
was observed [9]. Our present results, as well as lit-
erature reports [9,10b], indicate that extrusion of a
germylene is preferred to that of a silylene during
the photolysis of a cyclic oligometalane having both
silicon and germanium atoms.
The 420 nm band observed during irradiation of
1
at room temperature would have the same origin
to the 390 nm band at 77 K; the large temperature
dependence may be attributed to the conformational
dependence of the absorption bands [18]. Actually,
in an independent photolysis of octaisopropyltetra-
EXPERIMENTAL
General Procedures
All the reactions were carried out under dry argon.
1
13
29
H, C, and Si NMR spectra were recorded on a
7
3
Varian UNITY 300 spectrometer. Ge NMR spectra
were recorded on a JEOL ␣-500 spectrometer. Mass
spectra were obtained on a Hitachi M-2500 mass
spectrometer or a Hewlett Packard HP5971A spec-
trometer. GC analysis was carried out using a Shi-
madzu GC-14A gas chromatograph. Preparative
gas–liquid chromatography (GLC) was performed
using an Ohkura Model-802 gas chromatograph. UV-
vis spectra were recorded on a Milton Roy Spec-
tronic 3000 Array spectrophotometer. Elemental
analyses were performed at the Instrumental Anal-
FIGURE 3 UV spectral change of 1 during irradiation with a
254 nm light in 3-MP at 77 K.

4
02 Hashimoto et al.
for C H ClSi: C, 63.54; H, 8.44. Found: C, 63.91; H,
1
2
19
8
.30.
i
i
Ph Pr GeSi Pr Ph
2
2
i
To a solution of Ph Pr GeCl (17.4 g, 63.9 mmol) in
2
tetrahydrofuran (THF) (40 mL) was added fine-cut
Li (1.33 g, 192 mmol), and the resulting dark red
solution was stirred at room temperature for 3
i
hours. The solution of Ph Pr GeLi was added drop-
2
i
wise to Ph Pr SiCl (17.4 g, 63.9 mol) in THF (60 mL)
2
at ꢂ70ЊC. The resulting light yellow solution was
gradually allowed to warm to room temperature.
Usual work-up and then distillation in vacuo gave
SCHEME 2
i
i
Ph Pr GeSi Pr Ph in 68% yield (18.8 g, 44.0 mmol):
2
2
1
b.p. ca. 210ЊC/2 mmHg. H NMR (CDCl , 299.9
ysis Center, Graduate School of Science, Tohoku
University.
3
MHz): d 1.10 (m, ꢂCH(CH ) , 12H), 1.18 (m,
3
2
ꢂCH(CH ) , 12H), 1.49 (m, ꢂCH(CH ) , 2H), 1.69
3
2
3 2
1
3
1
(
m, ꢂCH(CH ) , 2H), 7.2–7.5 (m, Ph, 10H). C{ H}
3
2
Materials
NMR (CDCl , 75.4 MHz): d 13.5, 17.1, 19.6, 19.8,
3
i
i
i
21.1, 21.2, 127.3, 127.50, 127.54, 128.3, 135.4, 136.8,
Ph Pr GeCl [19], Ph Pr SiCl [19], c-Si Pr [2h], and
2
i
2
4
8
2
9
73
140.9. Si NMR (CDCl , 59.6 MHz): d ꢂ2.0. Ge
c-Ge Pr [5a,5d] were prepared according to the lit-
3
4
8
ꢆ
NMR (CDCl , 17.2 MHz): d ꢂ48.3. MS: m/z 428 (M ,
erature procedures. 2,3-Dimethylbutadiene was pur-
chased and distilled before use. Ether, THF, and ben-
zene were dried over molecular sieves before use.
-Methylpentane (3-MP) was treated with concen-
trated H SO overnight to remove olefinic impuri-
3
ꢆ
i
ꢆ
i
ꢆ
2
), 385 (M ꢂ Pr, 29), 342 (M ꢂ 2 Pr, 16), 301 (M
i
ꢆ
i
ꢂ 3 Pr, 35), 259 (M ꢂ 4 Pr, 84), 121 (100). Anal.
calcd for C H GeSi: C, 67.47; H, 8.96. Found: C,
3
24 38
6
7.56; H, 9.01.
2
4
ties, dried over MgSO , and distilled under argon
4
from lithium aluminum hydride prior to use. EtOH
used for photoreactions was distilled from magne-
sium before use. Other materials were commercially
available and used without further purification.
i
i
Cl Pr GeSi Pr Cl
2
2
i
i
Into a suspension of Ph Pr GeSi Pr Ph (5.00 g, 11.7
mmol) and AlCl (30 mg, 0.22 mmol) in benzene (30
2
2
3
mL) was bubbled HCl gas with stirring at 80ЊC for 6
hours. A small amount of acetone was added to the
solution to stop the reaction. Filtration, evaporation
of the solvent in vacuo, and distillation gave
i
Ph Pr GeCl
2
1
3
H NMR (CDCl , 299.9 MHz) d 1.18 (d, J ꢁ 7.3 Hz,
3
HH
3
i
i
ꢂCH(CH ) , 6H), 1.23 (d, J ꢁ 7.3 Hz, ꢂCH(CH ) ,
Cl Pr
150ЊC/2 mmHg. H NMR (CDCl
(m, ꢂCH(CH , 12H), 1.28 (m, ꢂCH(CH
1.43 (m, ꢂCH(CH , 2H), 1.77 (m, ꢂCH(CH
, 75.4 MHz): d 16.9, 17.5, 17.8,
19.1, 19.3, 22.7. Si NMR (CDCl , 59.6 MHz): d 33.2.
2
GeS Pr Cl in 75% yield (3.02 g, 8.77 mmol): b.p.
2
3
2
HH
3 2
3
1
6
7
1
1
9
H), 1.81 (sept, J ꢁ 7.3 Hz, ꢂCH(CH ) , 2H), 7.3–
.6 (m, Ph, 5H). C{ H} NMR (CDCl , 75.4 MHz): d
8.1 and 18.2 (ꢂCH(CH ) ), 19.6 (ꢂCH(CH ) ),
28.2, 129.6, 133.6, and 135.1 (Ph). MS: m/z 272 (M ,
3
, 299.9 MHz): d 1.19
, 12H),
, 2H).
HH
3 2
1
3
1
)
)
3
3
2
3 2
)
)
3
2
3 2
3
2
3 2
ꢆ
13
1
C{ H} NMR (CDCl
3
ꢆ
i
ꢆ
i
29
), 229 (M ꢂ Pr, 100), 187 (M ꢂ 2 Pr, 26), 151
3
ꢆ
i
ꢆ
ꢆ
i
ꢆ
(
M
ꢂ Pr ꢂ Ph, 85). Exact mass (m/z) calcd for
MS: m/z 344 (M , 2), 301 (M ꢂ Pr, 5), 259 (M ꢂ
2 Pr, 35), 217 (M ꢂ 3 Pr, 4), 173 (4), 115 (100). Exact
mass (m/z) calcd for C H Cl GeSi: 344.0556.
i
ꢆ
i
C H ClGe: 272.0394. Found: 272.0403.
1
2
19
1
2
28
2
Found: 344.0531.
i
Ph Pr SiCl
2
1
3
H NMR (CDCl , 299.9 MHz) d 1.02 (d, J ꢁ 7.3 Hz,
3
HH
i
Preparation of c-Si Ge Pr (1)
3
2
2
8
ꢂCH(CH ) , 6H), 1.10 (d, J ꢁ 7.3 Hz, ꢂCH(CH ) ,
3
2
HH
3 2
3
6
7
1
1
H), 1.42 (sept, J ꢁ 7.3 Hz, ꢂCH(CH ) , 2H), 7.3–
.7 (m, Ph, 5H). C{ H} NMR (CDCl , 75.4 MHz): d
3.8 (ꢂCH(CH ) ), 16.7 and 17.0 (ꢂCH(CH ) ),
27.8, 130.0, 132.2, and 134.3 (Ph). Si NMR (CDCl ,
To a mixture of Na dispersion (0.88 g, 38 mmol) and
18-crown-6 (0.47 g, 1.8 mmol) in toluene (15 mL)
HH
3 2
1
3
1
3
i
i
was added Cl Pr GeSi Pr Cl (5.00 g, 14.4 mmol) in
3
2
3
2
2
2
2
9
toluene (6 mL) at room temperature. The mixture
was heated to 110ЊC and stirred for about 1 hour.
Addition of hexane, filtration, evaporation of the sol-
3
ꢆ
ꢆ
5
9.6 MHz): d 26.8. MS: m/z 226 (M , 5), 183 (M ꢂ
i
ꢆ
i
Pr, 41), 155 (100), 141 (M ꢂ 2 Pr, 17). Anal. Calcd

Synthesis, Characterization, and Photoreactions of 1,2-Disiladigermacyclobutane 403
i
ꢆ
i
ꢆ
vent in vacuo, and then recrystallization of the resi-
ꢂ 3 Pr, 28), 221 (M ꢂ Ge Pr Cl, 58), 179 (M ꢂ
2
5
i
due from EtOH gave colorless crystals of 1 in 23%
Ge Pr Cl, 70), 93 (100). Anal. calcd for
C H Cl Ge Si : C, 46.72; H, 9.15. Found: C, 46.61;
H, 8.81.
2
6
1
yield (0.643 g, 1.18 mmol). 1: m.p. 204–206ЊC. H
2
4
56
2
2
2
3
NMR (CDCl , 299.9 MHz): d 1.26 (d, J ꢁ 7.0 Hz,
3
HH
3
SiCH(CH ) , 24H), 1.34 (d,
J
ꢁ 7.4 Hz,
3
2
HH
3
GeCH(CH ) , 24H), 1.53 (sept, JHH ꢁ 7.0 Hz,
SiCH(CH ) , 4H), 1.83 (sept, JHH ꢁ 7.4 Hz,
GeCH(CH ) , 4H). C{ H} NMR (CDCl , 75.4 MHz):
d 15.2, 19.0, 22.2, 22.5, 23.7, 23.9. Si NMR (CDCl3,
3
2
3
Photolysis of 1 at Room Temperature
3
2
1
3
1
3
2
3
A cyclohexane (1 mL) solution of 1 (5.0 mg, 9.2 ꢇ
2
9
ꢂ6
1
0
mol) in a quartz UV cell with a optical length
7
3
5
9.6 MHz): d 9.3. Ge NMR (CDCl , 17.2 MHz): d
3
of 1 cm was degassed by Ar bubbling and then irra-
diated with a spiral low-pressure mercury arc lamp
110 W) at room temperature. The photoreaction
ꢂ54.2. UV(hexane): k 290 nm (e 440). MS: m/z 546
max
ꢆ
ꢆ
i
ꢆ
i
(
M , 8), 503 (M ꢂ Pr, 15), 461 (M ꢂ 2 Pr, 51), 59
(
(
100). Anal. calcd for C H Ge Si : C, 52.79; H,
2
4
56
2
2
was monitored by UV spectroscopy.
1
0.34. Found: C, 52.36; H, 10.39.
Oxidation of 1 with MCPBA
Photolysis of 1 in a 3-MP Matrix at 77 K
ꢂ4
A CCl (15 mL) solution of 1 (120 mg, 0.220 mmol)
A 3-MP solution of 1 in (1 ꢇ 10 M) in a quartz UV
4
and MCPBA (22 mg, 0.13 mmol) was stirred for 1.5
hours at room temperature. Evaporation of the sol-
vent gave colorless crystals of oxadisiladigermacy-
clopentane in 90% yield (111 mg, 0.198 mmol),
which was recrystallized from EtOH (3 mL). The
GC-MS spectrum of the crystals indicated the exis-
tence of two isomers in a ratio of 95:5. The spectro-
cell was degassed by freeze-pump-thaw cycles (three
cycles). The cell was sealed and placed into a liquid
nitrogen Dewar with a quartz window. The resulting
matrix was irradiated with a 110 W low-pressure
mercury arc lamp. The UV spectra were measured
periodically during the irradiation.
1
scopic data for the major isomer: H NMR (CDCl ,
3
2
99.9 MHz): d 1.20 (m, ꢂCH(CH ) , 48H), 1.50 (m,
Photolysis of 1 in the Presence of Trapping
3
2
1
3
1
ꢂCH(CH ) , 8H). C{ H} NMR (CDCl , 75.4 MHz) d
Reagents
3
2
3
2
9
1
5
1
3.6, 19.6, 19.7, 22.1, 22.2, 22.6. Si NMR (CDCl3,
A degassed cyclohexane (1 mL) solution of 1 (5.0 mg,
9.6 MHz) d ꢂ10.0. UV(hexane): kmax 222 nm (e
ꢂ6
9
.2 ꢇ 10 mol) with hexadecane as an internal ref-
ꢆ
6900), 242 nm (e 9700). MS: m/z 562 (M , 2), 519
erence (10 lL) in a quartz tube was irradiated in the
ꢆ
i
ꢆ
i
ꢆ
i
(
M ꢂ Pr, 35), 477 (M ꢂ 2 Pr, 5), 435 (M ꢂ 3 Pr,
ꢂ3
presence of a trapping reagent (1.1 ꢇ 10 mol) with
ꢆ
i
3
3), 393 (M ꢂ 4 Pr, 84), 349 (68), 117 (100). Anal.
a 110 W low-pressure mercury arc lamp at room
temperature. The time-course of the reaction was
followed with GC and GC-MS periodically. The main
products were identified by comparing their GC re-
tention times and MS fragmentation patterns with
those of the authentic samples.
calcd for C H OGe Si : C, 51.29; H, 10.04. Found:
2
4
56
2
2
2
9
C, 51.18; H, 9.69. Based on the single Si resonance
that appeared at a much higher magnetic field than
that of 1, the major isomer was assigned to 6b. The
spectroscopic data for the minor isomer were not
obtained except for the mass spectrometric data.
Dichlorination of 1 with PCl5
Authentic Samples of the Products of
Photoreactions of 1 in the Presence of Trapping
Reagents
A solution of 1 (100 mg, 0.183 mmol) and PCl (49.8
mg, 0.239 mmol) in benzene (20 mL) was stirred for
5
i
i
1
.5 hours at room temperature. Usual workup and
Pr Ge(OEt)H [6c]. Ph Pr GeH was prepared in
2
2
i
i
then distillation in vacuo gave Si Ge Pr Cl in 85%
92% yield by the reduction of Ph Pr GeCl (1.00 g,
2
2
8
2
2
1
yield (94.0 mg, 0.152 mmol). H NMR (CDCl , 299.9
3.67 mmol) by LiAlH (0.074 g, 1.95 mmol) in ether
3
4
3
MHz): d 1.25 (m, ꢂCH(CH ) , 48H), 1.65 (sept, J
(10 mL). Dephenylchlorination of the resulting
3
2
HH
3
i
ꢁ
7.4 Hz, SiCH(CH ) , 4H), 1.84 (sept, J ꢁ 7.4
Ph Pr GeH by the use of HCl gas in the presence of
3
2
HH
2
1
3
1
Hz, GeCH(CH ) , 4H). C{ H} NMR (CDCl , 75.4
a catalytic amount of AlCl in benzene (20 mL) af-
3
2
3
3
2
9
i
MHz): d 15.2, 19.8, 20.5, 21.6, 22.1, 24.8. Si NMR
forded crude Pr GeClH (ca. 0.40 g, 2.0 mmol), which
2
1
(
CDCl , 59.6 MHz): d 2.4. UV(hexane): k 250 nm (e
was characterized by MS and H NMR spectroscopy.
3
max
ꢆ
i
ꢆ
i
i
1
1
3
4700). MS: m/z 573 (M ꢂ Pr, 2), 540 (M ꢂ PrCl,
Without purification, Pr GeClH was treated with a
2
ꢆ
i
ꢆ
i
), 469 (M ꢂ Ge PrCl), 423 (M ꢂ Ge Pr Cl, 13),
small excess of NaOEt in EtOH (3 mL) at room tem-
perature. Filtration of NaCl, concentration of the fil-
2
ꢆ
i
i
ꢆ
i
39 (M ꢂ Ge Pr Cl ꢂ 2 Pr, 22), 297 (M ꢂ Ge Pr Cl
2
2

4
04 Hashimoto et al.
trate, and then preparative GLC gave the pure title
compound in 8% overall yield (0.060 g, 0.29 mmol)
ꢂCH(CH ) , 6H), 1.45 (m, ꢂCH(CH ) , 2H), 3.28 (br
3
2
3 2
3
13
1
t, J ꢁ 2.7 Hz, GeH, 1H). C{ H} NMR (CDCl , 75.4
HH
3
i
i
1
29
based on the starting Ph Pr GeCl. Pr Ge(OEt)H: H
MHz): d 5.3, 8.3, 14.7, 22.4, 22.5. Si NMR (CDCl ,
2
2
3
3
ꢆ ꢆ
NMR (CDCl , 299.9 MHz): d 1.13 (d, J ꢁ 7.5 Hz,
59.6 MHz): d 5.6. MS: m/z 276 (M , 7), 233 (M ꢂ
ꢆ ꢆ
3
HH
3
i
i
i
ꢂCH(CH ) , 6H), 1.17 (d, J ꢁ 7.2 Hz, ꢂCH(CH ) ,
Pr, 16), 191 (M ꢂ 2 Pr, 38), 160 (M ꢂ Et ꢂ 2 Pr,
3
2
HH
3 2
3
6
(
ꢁ
H), 1.20 (t, J ꢁ 7.0 Hz, ꢂOCH CH , 3H), 1.42
sept, J ꢁ 7.5 Hz, ꢂCH(CH ) , 2H), 3.75 (q, J
7.0 Hz, OCH CH , 2H), 4.95 (br t, J ꢁ 1.8 Hz,
GeH, 1H). H NMR (C D , 299.9 MHz): d 1.08 (d, J
100). Anal. calcd for C H GeSi: C, 52.40; H, 10.99.
HH
2
3
12 30
3
3
Found: C, 52.63; H, 10.86.
HH
3
2
HH
3
2
3
HH
1
3
i
Pr Si(SiEt )H. A cyclohexane (8 mL) solution
6
6
HH
2
3
3
i
ꢁ
7.5 Hz, ꢂCH(CH ) , 6H), 1.15 (d, J ꢁ 6.9 Hz,
of c-Si Pr (100 mg, 0.219 mmol) and Et SiH (3.0
3
2
HH
4
8
3
3
ꢂCH(CH ) , 6H), 1.24 (t, J ꢁ 6.9 Hz, ꢂOCH CH ,
mL, 19 mmol) was irradiated with a 125 W low-pres-
sure mercury arc lamp for 17 hours at room tem-
3
2
HH
2
3
3
3
H), 1.29 (m, ꢂCH(CH ) , 2H), 3.78 (q, J ꢁ 6.9
Hz, ꢂOCH CH , 2H), 5.09 (br s, GeH, 1H). C{ H}
3
2
HH
1
3
1
i
perature. Pure Pr Si(SiEt )H was obtained in 43%
2
3
2
3
1
NMR (C D , 75.4 MHz): d 17.1, 18.8 and 19.0, 19.5,
yield (22 mg, 0.094 mmol) by preparative GLC. H
NMR (CDCl , 299.9 MHz): d 0.70 (q, J ꢁ 7.8 Hz,
ꢂCH CH , 6H), 0.99 (t, J ꢁ 7.8 Hz, ꢂCH CH ,
6
6
ꢆ
ꢆ
i
3
6
3.3. MS: m/z 206 (M , 3), 163 (M ꢂ Pr, 40), 119
2
HH
ꢆ
i
3
(
M
ꢂ 2 Pr, 100). Exact mass (m/z) calcd. for
2
3
HH
2
3
3
C H GeO: 206.0733. Found: 206.0741.
9H), 1.09 (d, J ꢁ 5.4 Hz, ꢂCH(CH ) , 12H), 1.14
8
20
HH
3 2
3
(
m, ꢂCH(CH ) , 2H), 3.39 (t, J ꢁ 2.7 Hz, SiH,
3
2
HH
i
13
1
Pr Si(OEt)H [2c].
2
A solution of freshly dis-
1H). C NMR (CDCl , 75.4 MHz): d 4.7 (t, J ꢁ 117
Hz, CH CH ), 8.3 (q, J ꢁ 125 Hz, CH CH ), 11.1
(d, J ꢁ 123 Hz, ꢂCH(CH ) ), 20.8 (q, J ꢁ 125
3
CH
1
tilled (EtO) SiH (5.00 g, 30.4 mmol) in ether (4 mL)
3
2
3
CH
2
3
i
1
1
was added to an PrMgCl solution at 0ЊC, which was
CH
3
2
CH
i
ꢆ
ꢆ
prepared from PrCl (5.02 g, 63.9 mmol) and Mg
Hz, CH(CH ) ). MS: m/z 230 (M , 14), 201 (M ꢂ Et,
3
ꢆ
2
i
ꢆ
i
(
1.56 g, 63.9 mmol) in ether (40 mL). The mixture
4), 187 (M ꢂ Pr, 4), 159 (M ꢂ Et ꢂ Pr, 8), 145
ꢆ
i
i
was stirred overnight and filtered. Concentration of
the filtrate and then preparative GLC gave
(M ꢂ 2 Pr, 9), 115 (SiEt or PrSiH, 100). Exact
3
mass (m/z) Calcd for C H Si : 230.1886. Found:
1
2
30
2
i
1
Pr Si(OEt)H in 17% yield (0.829 g, 5.17 mmol). H
230.1899.
2
NMR (CDCl , 299.9 MHz): d 1.0 (m, ꢂCH(CH ) ,
3
3 2
3
2
(
H), 1.02 (d, J ꢁ 4.8 Hz, ꢂCH(CH ) , 12H), 1.20
1,1-Diisopropyl-1-germa-3,4-dimethylcyclopent-
3-ene [6c,10b]. The title compound was prepared
using a literature method [10b]: After stirring of a
mixture of lithium powder (91 mg, 13 mmol),
HH
3 2
3
3
t, J ꢁ 6.9 Hz, OCH CH , 3H), 3.76 (q, J ꢁ 6.9
HH
2
3
HH
1
3
1
Hz, OCH CH , 2H), 4.12 (br s, SiH, 1H). C{ H}
2
3
NMR (CDCl , 75.4 MHz): d 12.4, 17.9, 18.3, 61.3. MS:
m/z 160 (M , 7), 117 (M ꢂ Pr, 37), 89 (100). Exact
mass (m/z) calcd for C H SiO: 160.1283. Found
3
ꢆ
ꢆ
i
i
Pr GeCl (1.00 g, 4.35 mmol) and 2,3-dimethylbu-
2
2
tadiene (0.715 g, 8.70 mmol) in a mixed solvent of
ether (20 mL) and THF (2 mL) for 12 hours at room
temperature, hexane was added to the mixture to
permit removal of unreacted lithium by filtration.
Concentration of the filtrate and preparative GLC
gave the pure titled compound in 26% yield (0.272
8
20
1
60.1290.
i
Pr Ge(SiEt )H. To a solution of Et SiCl (0.554
g, 3.67 mmol) in THF (5 mL) was added Ph Pr GeLi
at room temperature, which was prepared by the re-
action of Ph Pr GeCl (1.00 g, 3.67 mmol) with Li (76
mg, 11 mmol) in THF (5 mL). After having been
stirred for 1.5 hours the mixture was treated with
hexane and then filtered. Crude Ph Pr GeSiEt ob-
tained by evaporation of the filtrate, was dissolved
in benzene (30 mL), and HCl gas was passed in for
2
3
3
i
2
i
1
g, 1.13 mmol). H NMR (CDCl , 299.9 MHz): d 1.06
2
3
3
(d, JHH ꢁ 7.2 Hz ꢂCH(CH ) , 12H), 1.28 (m,
3
2
ꢂCH(CH ) , 2H), 1.43 (s, GeCH ꢂ, 4H), 1.69 (s,
3
2
2
i
13
ꢂCCH ꢁ, 6H). C NMR (CDCl , 75.4 MHz): d 13.8
2
3
3
3
1
1
(d, J ꢁ 120 Hz, CH(CH ) ), 19.50 (q, J ꢁ 124
Hz, ꢂC(CH )ꢁ), 19.56 (q, JCH
ꢂCH(CH ) ), 20.1 (t, J ꢁ 127 Hz, CH ), 131.1 (s,
CH
3
2
CH
1
ꢁ
124 Hz,
3
1
2
hours at room temperature. Filtration and then
distillation under reduced pressure (200–210ЊC/1
mmHg) gave Cl Pr GeSiEt (0.545 g, 1.76 mmol). Re-
3
2
CH
2
ꢆ
ꢆ
i
ꢂC(CH )ꢁ). MS: m/z 242 (M , 18), 199 (M ꢂ Pr,
3
i
ꢆ
i
64), 157 (M ꢂ 2 Pr, 100). Anal. Calcd for C H Ge:
2
3
12 24
duction of the chlorogermane by LiAlH in ether, fol-
C, 59.83; H, 10.04. Found: C, 59.77; H, 10.17.
4
lowed by preparative GLC, afforded pure
i
H Pr GeSiEt in 14% overall yield (0.141 g, 0.514
2
3
ACKNOWLEDGMENTS
i
mmol) based on the starting Ph Pr GeCl.
2
i
1
H Pr GeSiEt : H NMR (CDCl , 299.9 MHz): d 0.74
2
3
3
3
3
(
q, J ꢁ 7.8 Hz, ꢂCH CH , 6H), 1.00 (t, J ꢁ 7.8
Hz, ꢂCH CH , 9H), 1.167 (d, JHH ꢁ 7.5 Hz,
ꢂCH(CH ) , 6H), 1.173 (d, JHH
We are grateful to Prof. Y. Takeuchi, Kanagawa
HH
2
3
HH
3
73
University, Japan, for the Ge NMR measurements
2
3
3
ꢁ
7.2 Hz,
and his helpful discussion.
3
2

Synthesis, Characterization, and Photoreactions of 1,2-Disiladigermacyclobutane 405
ida, K.; Tokura, S. Organometallics 1992, 11, 2752–
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9
14] In general, the Si NMR signal of a silicon attached
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shift to the higher magnetic field. For example, c-
i
i
4
1,4
Si Pr : d ꢂ6.63; c-OSi Pr : d 15.66 (Si ); d ꢂ20.87
(
4
8
8
2,3
Si ).
[
15] The structure of 7 was determined on the basis of its
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64, 193–206; (d) Caderry, E.; Dombek, B. D.; Cohen,
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Si NMR signal (d 2.4) which shifted to the higher
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field rather than that of 1 (d 9.3). If the chlorination
29
occurs at the Ge–Si or Si–Si bond of 1, the Si NMR
6
247–6250.
signal should appear in much lower field than that of
[
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i
i
Cl Pr GeSi Pr Cl (d 33.2).
2
2
[
[
[
16] These compounds were only identified by GC-MS
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