Synthesis, structure, and photolysis of germatetrasilacyclopentanes

Article abstract of DOI:10.1021/om9804374

The five-membered-ring systems germatetrasilacyclopentanes [R₂Si]₄GeR′₂ (1) (1a, R = i-Pr, R′ = Me₃SiCH₂; 1b, R = i-Pr, R′ = Ph; 1c, R = t-BuCH₂, R′ = Ph) were synthesized and characterized. The structures of 1b,c have been determined by X-ray crystallography. The Si₄Ge rings of 1b,c form an envelope and a distorted half-chair conformation, respectively. The photolysis of 1 using two kinds of light sources (low- and high-pressure mercury lamps) was carried out. The photochemical decomposition of la afforded two types of four-membered-ring products, cyclotetrasilane (Si₄; main) and germatrisilacyclobutane (Si₃Ge; minor), with extrusion of germylene (Ge:) and silylene (Si:), respectively. Compounds 1b,c gave, besides the four-membered-ring products as in la, two types of three-membered products, cyclotrisilanes (Si₃) and disilagermiranes (Si₂Ge), with extrusion of silagermene (Si=Ge) and disilene (Si=Si), respectively. This is the first case in which the unusual decomposition of five-membered rings into three-membered rings and dimetallenes has been found.

Full text of DOI:10.1021/om9804374

Organometallics 1998, 17, 5091-5101
5091
Syn th esis, Str u ctu r e, a n d P h otolysis of
Ger m a tetr a sila cyclop en ta n es
Hideo Suzuki,† Ken Tanaka,† Bin Yoshizoe,† Tsuyoshi Yamamoto,†
Nozomu Kenmotsu,† Syu Matuura,† Tohru Akabane,† Hamao Watanabe,*,† and
Midori Goto*,‡
Department of Chemistry (Materials Science), Faculty of Engineering, Gunma University,
Kiryu, Gunma 376, J apan, and National Institute of Materials and Chemical Research,
Tsukuba, Ibaraki 305, J apan
Received May 26, 1998
The five-membered-ring systems germatetrasilacyclopentanes [R2Si]4GeR′2 (1) (1a , R )
i-Pr, R′ ) Me3SiCH2; 1b, R ) i-Pr, R′ ) Ph; 1c, R ) t-BuCH2, R′ ) Ph) were synthesized and
characterized. The structures of 1b,c have been determined by X-ray crystallography. The
Si4Ge rings of 1b,c form an envelope and a distorted half-chair conformation, respectively.
The photolysis of 1 using two kinds of light sources (low- and high-pressure mercury lamps)
was carried out. The photochemical decomposition of 1a afforded two types of four-
membered-ring products, cyclotetrasilane (Si4; main) and germatrisilacyclobutane (Si3Ge;
minor), with extrusion of germylene (Ge:) and silylene (Si:), respectively. Compounds 1b,c
gave, besides the four-membered-ring products as in 1a , two types of three-membered
products, cyclotrisilanes (Si3) and disilagermiranes (Si2Ge), with extrusion of silagermene
(SidGe) and disilene (SidSi), respectively. This is the first case in which the unusual
decomposition of five-membered rings into three-membered rings and dimetallenes has been
found.
In tr od u ction
The chemistry of silacycles containing a heteroatom
such as oxygen, nitrogen, etc. comprises intriguing
subjects to be studied with regard to their properties.
Although a large number of studies of homosilacycles,
Sin, have appeared, there are only limited reports
focused on the ring systems containing germanium, Sin-
Ge.1 We have previously studied some properties of
various peralkylated cyclosilanes, [R1R2Si]n (n ) 3-7)2
and [R2Si]3O.3 Recently, we reported the synthesis,
molecular structure, and photolysis of four-membered
[R2Si]3Ge(CH2SiMe3)2 (A, R ) i-Pr; B, R ) t-BuCH2),1b
three-membered [R2Si]2Ge(CH2SiMe3)2, and the four-
membered oxo compound [R2SiGe(CH2SiMe3)2SiR2]O (R
) t-BuCH2).4 Subsequently, we also reported the
structure and photolysis of five-membered-ring com-
pounds [R2Si]4GePh2 (R ) i-Pr, t-BuCH2) in a prelimi-
nary communication.5 This paper deals with the full
account of the germatetrasilacyclopentanes [R2Si]4GeR′2
(1a -c), including the molecular structures of the last
two compounds (1b,c) via X-ray crystal analysis and the
photochemical behavior of the three compounds.
† Gunma University.
‡ National Institute of Materials and Chemical Research.
(1) (a) n ) 2, [(Me3Si)2Si]2Ge(SiMe3)2: Heine, A.; Stalke, D. Angew.
Chem., Int. Ed. Engl. 1994, 33, 113. (b) n ) 3, [R2Si]3Ge(CH2SiMe3)2
(R ) i-Pr, t-BuCH2): Suzuki, H.; Okabe, K.; Kato, R.; Sato, N.; Fukuda,
Y.; Watanabe, H.; Goto, M. Organometallics 1993, 12, 4833. (c) n ) 4,
[Ph2Si]4GePh2: Hengge, E.; Brychy, U. Monatsh. Chem. 1966, 97, 1309.
(d) n ) 5, [Me2Si]5GeMe2: Carberry, E.; Dombek, B. D. J . Organomet.
Chem. 1970, 22, C43.
(2) (a) Watanabe, H.; Kato, M.; Okawa, T.; Nagai, Y.; Goto, M. J .
Organomet. Chem. 1984, 271, 225. (b) Watanabe, H.; Okawa, T.; Kato,
M.; Nagai, Y. J . Chem. Soc., Chem. Commun. 1983, 781. (c) Watanabe,
H.; Kougo, Y.; Nagai, Y. J . Chem. Soc., Chem. Commun. 1984, 66. (d)
Watanabe, H.; Muraoka, T.; Kageyama, M.; Yoshizumi, M.; Nagai, Y.
Organometallics 1984, 3, 141. (e) Watanabe, H.; Shimoyama, H.;
Muraoka, T.; Okawa, T.; Kato, M.; Nagai, Y. Chem. Lett. 1986, 1057.
(f) Watanabe, H.; Kato, M.; Okawa, O.; Kougo, Y.; Nagai, Y.; Goto, M.
Appl. Organomet. Chem. 1987, 1, 157. (g) Watanabe, H.; Kougo, Y.;
Kato, M.; Kuwabara, H.; Okawa, H.; Nagai, Y. Bull. Chem. Soc. J pn.
1984, 57, 3019.
Resu lts a n d Discu ssion
P r ep a r a tion s of 1a -c. Compound 1a was obtained
in moderate yield (56%) by the treatment of 1,4-
dichlorooctaisopropyltetrasilane with bis((trimethyl-
silyl)methyl)germylenedilithium, which was prepared
by the reaction of bis((trimethylsilyl)methyl)bis(trimethyl-
silyl)germane, (Me3SiCH2)2Ge(SiMe3)2, with lithium in
HMPA (see Experimental Section). The use of bis-
(trimethylsilyl)dialkylgermane as a starting material
may provide a new convenient method for the prepara-
(4) Suzuki, H.; Okabe, K.; Uchida, S.; Watanabe, H.; Goto, M. J .
Organomet. Chem. 1996, 509, 177.
(3) Watanabe, H.; Tabei, E.; Goto. M.; Nagai. Y. J . Chem. Soc.,
Chem. Commun. 1987, 522.
(5) Suzuki, H.; Kenmotu, N.; Tanaka, K.; Watanabe, H.; Goto, M.
Chem. Lett. 1995, 811.
10.1021/om9804374 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 10/24/1998

5092 Organometallics, Vol. 17, No. 23, 1998
Suzuki et al.
tion of dialkylgermylenedi(alkalimetal),6 because the
latter compound had been prepared by the reaction of
R2GeCl2 with potassium in low yield (Bu2GeK2, 22%)7
or via many steps from R2GeHLi and Me3SiLi (Et2GeLi2,
73%).8 Compounds 1b,c were synthesized by the reac-
tion of the corresponding 1,4-dichlorooctaalkyltetra-
silane with (diphenylgermylene)dipotassium9a in mod-
erate to good yields (46 and 61%, respectively).9b
The compounds 1a -c, which are indefinitely air-
stable, as are the four-membered germatrisilacyclo-
butanes A and B,1b were identified in the usual manner
(NMR, IR, and mass spectral data, as well as elemental
analysis).
F igu r e 1. Molecular structure of 1b.
Molecu la r Str u ctu r es of 1b,c.10 The molecular
structures of 1b,c, determined by X-ray crystal analysis,
are shown in Figures 1 and 2, respectively. The
crystallographic units of both compounds comprise four
molecules. The selected bond distances and bond and
torsion angles for 1b are listed in Tables 1 and 2 and
for 1c in Tables 3 and 4, respectively. Table 5 sum-
marizes the comparisons of bond distances and angles
and ring torsion angles for the two compounds together
with the related ones.
F igu r e 2. Molecular structure of 1c.
Å for 1c; the former is shorter than the distance (2.457
Å) for A, and the latter is nearly the same as that (2.444
Å) for B. The Si-Si and Si-Ge bond distances of 1b,c
are, however, considerably longer than the correspond-
ing normal ones, 2.34 Å for Si-Si and 2.39 Å for Si-Ge
bonds calculated using the covalent bond radii for Si
and Ge atoms. Interestingly, it should be noted that in
1b,c the longer Si-Si bond lengths in comparison to
those for the four-membered rings A and B are presum-
ably due to the greater steric repulsion between the
bulky substituents in the five-membered rings, because
the same substituents (i-Pr or t-BuCH2; steric substitu-
ent constants Es(i-Pr) ) -0.47; Es(t-BuCH2) ) -1.47)15
are attached to the four- (A and B) and five-membered-
ring silicons (1b,c).
The five-membered Si4Ge rings of 1b,c form an
envelope and a distorted half-chair conformation, as
shown in Figures 1 and 2, respectively.
The Si-Si bond distances of 1b,c are the same value,
2.414 Å (average), which is considerably longer than the
reported values for cyclopentasilanes of 2.342 Å ([H2-
Si]5)14 to 2.395 Å ([Ph2Si]5)11 (Table 5) by 0.019-0.072
Å, and those (average, 2.390 Å) for the related four-
membered compounds [i-Pr2Si]3Ge(CH2SiMe3)2 (A) and
[(t-BuCH2)2Si]3Ge(CH2SiMe3)2 (B) by 0.02-0.03 Å.1b
The Si-Ge bond distances are 2.434 Å for 1b and 2.449
(6) The preparation of (Me3Si)3GeLi by the reaction of (Me3Si)4Ge
with MeLi has been reported; see: (a) Brook, A. G.; Abdesaken, F.;
Sollradl, H. J . Organomet. Chem. 1986, 299, 9. (b) Freitag, S.; Herbst-
Irmer, R.; Lameyer, L.; Stalke, D. Organometallics 1996, 15, 2839.
(7) Bulten, E. J .; Noltes, J . G. Tetrahedron Lett. 1967, 4125.
(8) Bravo-Zhivotovskii, D. A.; Pigarev, S. D.; Vyazankina, O. A.;
Vyazankin, N. S. Zh. Obshch. Khim. 1987, 57, 2644 and references
therein.
(9) (a) Mochida, K.; Tatsushige, N.; Hamashima, M. Bull. Chem.
Soc. J pn. 1985, 58, 1443. (b; †) Interestingly enough, the corresponding
five-membered compound bearing neopentyl groups on silicons and
trimethylsilylmethyls on germanium, [R2Si]4GeR′2 (1d : R ) t-BuCH2;
R′ ) Me3SiCH2), could not be obtained by the present method under
the various reaction conditions attempted. Therefore, it is likely that
the combination of two kinds of the bulky substituents creates steric
repulsions between them too large to allow the compound to be
formed: Cl[(t-BuCH2)2Si]4Cl + (Me3SiCH2)2GeLi2 (or K2) f [(t-BuCH2)2-
Si]4Ge(CH2SiMe3)2 (1d ).
The five inner angles of the two Si4Ge rings range
from 100.9 to 110.5° (average 105.5°) in 1b and from
99.6 to 109.7° (average 103.0°) in 1c. Comparisons of
the five angles between the two rings exhibit some
interesting features. The magnitude of the correspond-
ing angles, which are very close to each other, falls in
the following order: Si-Ge-Si (110.5°, 1b; 109.7°, 1c)
>
Si-Si-Si (106.0°, 1b; 102.3°, 1c) > Si-Si-Ge
(102.5°, 1b; 100.3°, 1c). As described above, both
compounds have smaller angles of Si-Si-Ge and
Si-Si-Si than of Si-Ge-Si and longer Si-Si bonds
than the normal ones, reflecting that the spaces around
the silicon atoms of the compounds are significantly
crowded with fairly large angular strain energies. This
leads to the possibility of ring cleavage at the Si-Si
(10) An X-ray crystal analysis of 1a is underway.
(11) Parkanyi, L.; Sasvari, K.; Declercq, J . P.; Germain, G. Acta
Crystallogr. 1978, B34, 3678.
(12) Carlson, C. W.; Haller, K. J .; Zhang, X.-H.; West, R. J . Am.
Chem. Soc. 1984, 106, 5521.
(13) Poschl, U.; Siegl, H.; Hassler, K. J . Organomet. Chem. 1996,
506, 93.
(14) Smith, Z.; Seip, H. M.; Hengge, E.; Bauer, G. Acta Chem. Scand.
1976, A30, 697.
(15) In Steric Effects in Organic Chemistry; Newman, M. S., Ed.;
New York, 1956; p 598.

Germatetrasilacyclopentanes
Organometallics, Vol. 17, No. 23, 1998 5093
Ta ble 1. Selected Bon d Dista n ces (Å) for 1b
Ge(1)-Si(1)
Si(2)-Si(3)
Ge(1)-C(7)
Si(2)-C(19)
Si(3)-C(28)
2.436(1)
Ge(1)-Si(4)
Si(3)-Si(4)
Si(1)-C(13)
Si(2)-C(22)
Si(4)-C(31)
2.432(1)
2.417(1)
1.914(3)
1.920(3)
1.918(3)
Si(1)-Si(2)
Ge(1)-C(1)
Si(1)-C(16)
Si(3)-C(25)
Si(4)-C(34)
2.399(1)
1.988(3)
1.923(3)
1.933(3)
1.927(3)
2.427(1)
1.981(3)
1.931(3)
1.935(3)
Ta ble 2. Selected Bon d An gles a n d Tor sion An gles (d eg) for 1b
Ge(1)-Si(1)-Si(2)
104.0(1)
105.9(1)
110.5(1)
112.3(1)
107.3(1)
107.5(1)
115.5(1)
107.1(1)
110.7(1)
109.8(1)
114.0(1)
112.3(1)
109.5(1)
108.8(1)
113.8(1)
Si(1)-Si(2)-Si(3)
Si(3)-Si(4)-Ge(1)
Si(1)-Ge(1)-C(1)
Si(4)-Ge(1)-C(1)
Ge(1)-Si(1)-C(13)
Si(2)-Si(1)-C(13)
Si(1)-Si(2)-C(19)
Si(3)-Si(2)-C(19)
Si(2)-Si(3)-C(25)
Si(4)-Si(3)-C(25)
Si(3)-Si(4)-C(31)
Ge(1)-Si(4)-C(31)
C(1)-Ge(1)-C(7)
C(19)-Si(2)-C(22)
C(31)-Si(4)-C(34)
106.1(1)
Si(2)-Si(3)-Si(4)
Si(4)-Ge(1)-Si(1)
Si(1)-Ge(1)-C(7)
Si(4)-Ge(1)-C(7)
Ge(1)-Si(1)-(16)
Si(2)-Si(1)-C(16)
Si(1)-Si(2)-C(22)
Si(3)-Si(2)-C(22)
Si(2)-Si(3)-C(28)
Si(4)-Si(3)-C(28)
Si(3)-Si(4)-C(34)
Ge(1)-Si(4)-C(34)
C(13)-Si(1)-C(16)
C(25)-Si(3)-C(28)
100.9(1)
106.4(1)
115.5(1)
106.2(1)
114.3(1)
107.4(1)
117.6(1)
110.0(1)
102.8(1)
116.0(1)
106.2(1)
104.9(1)
107.4(1)
111.1(1)
Si(2)-Si(1)-Ge(1)-Si(4)
Ge(1)-Si(1)-Si(2)-Si(3)
Si(3)-Si(4)-Ge(1)-Si(1)
-2.9(1)
-18.8(1)
23.1(1)
Si(1)-Si(2)-Si(3)-Si(4)
Si(2)-Si(3)-Si(4)-Ge(1)
C(7)-Ge(1)-Si(1)-C(16)
34.5(1)
-34.3(1)
0.2(1)
Ta ble 3. Selected Bon d Dista n ces (Å) for 1c
Ge(1)-Si(1)
Si(3)-Si(4)
Ge(1)-C(7)
Si(2)-C(23)
Si(3)-C(38)
2.443(3)
Si(1)-Si(2)
Si(4)-Ge(1)
Si(1)-C(13)
Si(2)-C(28)
Si(4)-C(43)
2.402(3)
2.455(3)
1.890(10)
1.913(10)
1.907(10)
Si(2)-Si(3)
Ge(1)-C(1)
Si(1)-C(18)
Si(3)-C(33)
Si(4)-C(48)
2.416(3)
2.424(4)
1.980(9)
1.887(10)
1.933(10)
1.964(8)
1.910(9)
1.904(9)
1.908(9)
Ta ble 4. Selected Bon d An gles a n d Tor sion An gles (d eg) for 1c
Ge(1)-Si(1)-Si(2)
101.0(1)
103.1(1)
109.7(1)
113.2(2)
105.7(3)
115.3(4)
107.4(3)
106.7(3)
121.6(3)
112.2(3)
122.4(4)
105.2(4)
114.4(3)
112.7(4)
108.3(5)
Si(1)-Si(2)-Si(3)
Si(3)-Si(4)-Ge(1)
Si(1)-Ge(1)-C(1)
Si(4)-Ge(1)-C(1)
Ge(1)-Si(1)-C(13)
Si(2)-Si(1)-C(13)
Si(1)-Si(2)-C(23)
Si(3)-Si(2)-C(23)
Si(2)-Si(3)-C(33)
Si(4)-Si(3)-C(33)
Si(3)-Si(4)-C(43)
Ge(1)-Si(4)-C(43)
C(1)-Ge(1)-C(7)
C(23)-Si(2)-C(28)
C(43)-Si(4)-C(48)
101.4(1)
Si(2)-Si(3)-Si(4)
Si(4)-Ge(1)-Si(1)
Si(1)-Ge(1)-C(7)
Si(4)-Ge(1)-C(7)
Ge(1)-Si(1)-C(18)
Si(2)-Si(1)-C(18)
Si(1)-Si(2)-C(28)
Si(3)-Si(2)-C(28)
Si(2)-Si(3)-C(38)
Si(4)-Si(3)-C(38)
Si(3)-Si(4)-C(48)
Ge(1)-Si(4)-C(48)
C(13)-Si(1)-C(18)
C(33)-Si(3)-C(38)
99.6(1)
103.3(3)
116.4(3)
101.3(3)
118.7(3)
109.4(4)
102.7(3)
104.1(3)
105.3(3)
107.8(3)
104.8(3)
108.8(4)
114.1(4)
122.6(5)
Si(2)-Si(1)-Ge(1)-Si(4)
Ge(1)-Si(1)-Si(2)-Si(3)
Si(3)-Si(4)-Ge(1)-Si(1)
16.2(1)
-40.2(1)
14.1(1)
Si(1)-Si(2)-Si(3)-Si(4)
Si(2)-Si(3)-Si(4)-Ge(1)
C(7)-Ge(1)-Si(1)-C(18)
51.7(1)
-39.3(1)
13.9(4)
bonds to form products such as germatrisilacyclobutane,
cyclotrisilane, and disilene. Indeed, the ring cleavage
occurred at this bond in the photolysis as described
below. In contrast, the four-membered Si3Ge (A and
B) afforded only the products due to Si-Ge bond
cleavage: that is, cyclotrisilane and germylene.1b The
angle difference (12.6°) between the sums of the five
inner angles of 1b (527.4°) and 1c (514.8°) is fairly large
and can be correlated well to the difference between the
torsion angles in the two rings 1b (Table 2) and 1c
(Table 4).
Generally, the absolute values of the ring torsion
angles have been recognized to be a measure of the
degree of planarity in cyclic molecules.16 For 1b,c, the
average torsion angles were 22.7 and 32.3°, respectively;
the former is the smallest among the related cyclopen-
tasilanes (26.7° for [H2Si]5 to 33.4° for [(CH2)5Si]5)12-14
(Tables 2, 4, and 5)). It is reasonable to consider that
the greater steric repulsions between bulkier neopentyl
groups as compared to those between isopropyls cause
larger torsion angles, forming a less planar ring for 1c
than for 1b. When we compare the torsion angles and
bond distances of 1b with those of 1c, interesting
features can be seen: (a) the torsion angles M-M-M-
M, 1b (22.7°) < 1c (32.3°), and (b) the bond distances,
1b (Ge-C, 1.985 Å; Si-C, 1.925 Å) > 1c (Ge-C, 1.972
Å; Si-C, 1.907 Å). Consequently, these results probably
reflect the fact that 1b releases the steric repulsions
between the substituents by elongation of the bond
distances, whereas 1c retains a more distorted config-
uration than 1b. The results are in harmony with those
observed for the Si3Ge rings of A and B.1b
(16) Bucont, R. In Topics in Stereochemistry; Wiley: New York, 1974;
p 163.

5094 Organometallics, Vol. 17, No. 23, 1998
Suzuki et al.
Ta ble 5. Com p a r ison of Bon d Dista n ces, Bon d An gles, a n d Tor sion An gles of 1b,c a n d Rela ted Com p ou n d s
bond dist (Å)
bond angle (deg) torsion angle (deg)
entry no.
1
compd
Si-Si
2.414
(2.399-2.427) (2.432-2.436) (1.914-1.935) (100.9-110.5)
[(t-BuCH2)2Si]4GePh2 (1c) 2.414 2.449 1.907 103.0
(2.402-2.424) (2.443-2.455) (1.887-1.933) (99.6-109.7)
Si-Ge
Si-C
M-M-M
M-M-M-M
ref
[i-Pr2Si]4GePh2 (1b)
2.434
1.925
105.5
22.7
(2.9-34.5)
32.3
this work
2
this work
(14.1-51.7)
3
4
5
6
7
[Ph2Si]5
2.395
(2.371-2.413)
2.347
(2.343-2.350)
2.359
(2.350-2.366)
2.375
1.895
(1.869-1.917) (102.7-106.7)
1.906 104.5
(1.900-1.912) (101.3-106.3)
1.894 102.5
(1.890-1.897) (99.0-105.7)
1.880 102.6
104.5
27.0
(7.3-37.0)
27.2
(9.7-41.7)
33.4
(10.0-51.7)
31.8
(0.7-49.4)
26.7 (Cs)
27.9 (C2)
11
12
12
13
14
[(CH2)4Si]5
[(CH2)5Si]5
trans-1,3-Si5Ph8F2
[H2Si]5
(2.363-2.386)
2.342
(1.870-1.886) (98.5-106.5)
104.3
[H2Si]523 and [CH2]5,23 respectively, and also that (6 kcal/
mol) experimentally determined previously for [R2Si]5.2e
Further, with the longest absorption bands (280 nm) for
1b,c and that (255 nm) for a linear diphenyldecaalkyl-
pentasilane, Ph(Me2Si)5Ph,24 because the two rings have
two phenyl groups as the substituents in the molecules,
the ring strain energies for 1b,c could be estimated to
be ca. 10 kcal/mol. If the six-membered ring in this
series can also be regarded as approximately strain-free
for the same reason mentioned before,2e the magnitude
of the ring strain energies thus obtained in the SinGe
ring series for n ) 5, 4, 3, and 2 is 0, 10-12, 25-27,
and 36-38 kcal/mol, respectively. It should be noted,
however, that the six-membered-ring system containing
one germanium (Si5Ge) still might have some ring strain
energy, because a germanium atom, having a larger
diameter than that of silicon, has been incorporated in
the ring system. Thus, this point remains to be clari-
fied.
P h otolysis of 1a -c Usin g Low -P r essu r e Mer cu r y
La m p (λ 254 n m Ligh t). Generally, the photolysis of
cyclosilanes25 and -germanes26 is well-known to bring
about ring contraction, giving the corresponding smaller
rings with extrusion of silylene (R2Si:) and germylene
(R2Ge:), respectively. Previously, we reported that the
photolysis of three- and four-membered rings [R2Si]nGe-
(CH2SiMe3)2 (n ) 24 and 31b (A, B)) causes ring contrac-
tion with extrusion of germylene ((Me3SiCH2)2Ge:) by
the preferential cleavage of the two Si-Ge bonds. In
the present study, the photolysis of 1a -c was carried
out using a low-pressure lamp (λ ) 254 nm) by
irradiating a cyclohexane or 3-methylpentane solution
of the compounds placed in a sealed tube connected with
a UV-monitoring cell, and the progress of the reaction
F igu r e 3. UV spectra for 1a (s), 1b (- -), and 1c (‚‚‚).
UV Sp ectr a a n d Rin g Str a in En er gies of 1a -c.
The three compounds 1a -c have the same longest
wavelength absorption maxima at λ 280 nm (sh), with
varying extinction coefficients (ꢀ 1100, 5700, and 7600
for 1a -c, respectively), as has been shown in Figure 3.
The absorption maximum at λ 280 nm is slightly longer
than those (λ 260 ([Pr2Si]5),2c 266 ([Et2Si]5),17 and 272
nm ([Me2Si]5)18) reported for the peralkylcyclopentasi-
lanes and is different from those (251 ([Ph2Si]5)19 and
294 nm ([(p-MeC6H4)2Si]5)20) for the perarylcyclopenta-
silanes. Interestingly, this absorption maximum (λ 280
nm) of 1a -c is almost the same as those (λ 280 ([Me2-
Si]4SiMePh21) and 284 nm ([Me2Si]4SiPh221)) reported
for the partially arylated cyclopentasilanes. Previously,
we found that the ring strain energies of peralkylcy-
closilanes can be estimated as the differences in the
transition energies between the two series (linear and
cyclic) of polysilanes of the same silicon numbers (∆∆E
) ∆E(linear) - ∆E(cyclic)), using their longest absorp-
tion bands of [R2Si]n and Me(Me2Si)nMe, where n ) 3-6,
respectively.2e Similarly, with the aid of the longest
absorption bands of 1a (λmax 280 nm) and the corre-
sponding linear compound Me(Me2Si)5Me (λmax 250
nm),22 the ring strain energy of 1a could be equally
evaluated to be 12 kcal/mol. Thus, this value for 1a
determined experimentally is larger than those (6 and
5.8-8.3 kcal/mol) calculated for the model compounds
(23) Zhao, M.; Gimarc, B. M. Inorg. Chem. 1996, 35, 5378.
(24) Ruehl, K. E.; Matyjaszewskii, K. J . Organomet. Chem. 1991,
410, 1.
(25) For reviews and references therein see: (a) Tsumuraya, T.;
Batcheller, S. A.; Masamune, S. Angew. Chem., Int. Ed. Engl. 1991,
30, 902. (b) Weidenbruch, M. Chem. Rev. 1995, 95, 1479. (c) Steinmetz,
M. G. Chem. Rev. 1995, 95, 1527.
(26) (a) Carberry, E.; Dombek, B. D.; Cohen, S. C. J . Organomet.
Chem. 1972, 36, 61. (b) Masamune, S.; Hanzawa, Y. J . Am. Chem.
Soc. 1982, 104, 6136. (c) Collins, S.; Murakami, S.; Snow, J . T.;
Masamune, S. Tetrahedron Lett. 1985, 26, 1281. (d) Rivier, P.; Castel,
A.; Satge, J .; Giyot, D. J . Organomet. Chem. 1984, 264, 193. (e) Ando,
W.; Tsumuraya, T. Tetrahedron Lett. 1986, 27, 3251. (f) Ando, W.;
Tsumuraya, T. Organometallics 1988, 7, 1882. (g) Tsumuraya, T.; Sato,
S.; Ando, W. Organometallics 1990, 9, 2061. (h) Mochida, K.: Kanno,
N.; Kato, R.; Kotani, M.; Yamauchi, S.; Wakasa, M.; Hayashi, H. J .
Organomet. Chem. 1991, 415, 191. (i) Mochida, K.; Tokura, S. Bull.
Chem. Soc. J pn. 1992, 65, 1642. (j) Mochida, K.; Tokura, S. Organo-
metallics 1992, 11, 2752.
(17) Carlson, C. W.; West, R. Organometallics 1983, 2, 1792.
(18) Carberry, E.; West, R.; Glass, G. E. J . Am. Chem. Soc. 1969,
91, 5446.
(19) Gilman, H.; Atwell, W. H. J . Organomet. Chem. 1965, 4, 176.
(20) Nakano, T.; Ochi-ai, Y.; Nagai, Y. Chem. Express 1990, 5, 857.
(21) Helmer, B. J .; West, R. J . Organomet. Chem. 1982, 236, 21.
(22) Gilman, H.; Atwell, W. H.; Schwebke, G. L. J . Organomet.
Chem. 1964, 2, 369.

Germatetrasilacyclopentanes
Organometallics, Vol. 17, No. 23, 1998 5095
F igu r e 4. Reaction profile for the photolysis of 1a in
cyclohexane at room temperature: (s) before irradiation;
(- -) after irradiation for 30 min; (- - -) after irradiation
for 60 min; (- - -) after irradiation for 120 min.
F igu r e 5. Reaction profile for the photolysis of 1b in
cyclohexane at room temperature: (s) before irradiation;
(- -) after irradiation for 30 min; (- - -) after irradiation
for 60 min; (- - -) after irradiation for 120 min.
was monitored by the spectral changes during the
irradiation.
First, the photolysis of 1a at room temperature was
investigated. As seen in Figure 4, a solution of 1a (14
mg, 2.0 × 10-5 mol) in cyclohexane (3 mL) showed
spectral changes during the irradiation. Thus, the
solution became pale yellow after ca. 80 min, and a new
weak and broad band at λ 420 nm began to appear. On
further irradiation, the band at λ 420 nm grew, attained
maximum intensity after 6 h, and began to decrease.
In separate experiments, the band at 420 nm disap-
peared rapidly when air (O2) was introduced into the
system. From the above results and the analogous
observations of the photolysis of germatrisilacyclo-
butanes A and B,1b the band at 420 nm27 is attributable
to tetrakis((trimethylsilyl)methyl)digermene, (Me3Si-
CH2)2GedGe(CH2SiMe3)2, which was formed via dimer-
ization of bis((trimethylsilyl)methyl)germylene, (Me3-
SiCH2)2Ge:.1b On the other hand, in the experiments
using 1b,c, no distinct absorption band was observed
and Figure 5 shows the reaction profile for 1b.
F igu r e 6. Reaction profile for the photolysis of 1a in 3-MP
at 77 K: (s) before irradiation; (- -) after irradiation for
2 h; (- - -) after irradiation for 4 h; (- - -) after irradiation
for 6 h.
Second, to confirm the formation of unstable and
reactive species in the reactions, the photolysis of the
compounds at 77 K was carried out. Irradiations of
1a -c (2.0 × 10-5 mol) in 3-methylpentane (3 mL) for 6
h at 77 K produced yellow glasses along with absorption
bands at λmax 465 nm for 1a (Figure 6) and λmax 400 nm
for 1b (Figure 7) and 1c. When the temperature was
raised, the bands disappeared. The band at λ 465 nm
arising from 1a at low temperature is likely to be the
germylene (Me3SiCH2)2Ge:.1b The 400 nm band at 77
K produced from 1b (Figure 7) and 1c is attributed to
F igu r e 7. Reaction profile for the photolysis of 1b in 3-MP
at 77 K: (s) before irradiation; (- -) after irradiation for
2 h; (- - -) after irradiation for 4 h; (- - -) after irradiation
for 6 h.
2g
the corresponding tetraalkyldisilene R2SidSiR2 and/
27f
or germasilene R2SidGePh2
BuCH2.
with R ) i-Pr and t-
To obtain further insight into the photochemical
processes actually occurring, the products were isolated
by preparative GLC and identified by comparison of the
GLC retention times and MS fragmentation patterns
with those of the authentic samples prepared by alter-
native methods. Thus, the photolysis of 1a -c at room
temperature in cyclohexane was carried out at varying
irradiation times. Table 6 summarizes the results,
containing products and yields based on the starting
1a -c employed. Irradiation (15 min) of 1a (14.0 mg)
in cyclohexane (3 mL) afforded the cyclotetrasilane
[i-Pr2Si]4 (2a)2d and germatrisilacyclobutane [i-Pr2Si]3Ge-
(CH2SiMe3)2 (A) in 20 and 1% yields, respectively,
(27) From the results in Table 6 (vide infra), however, the band
occurring from 1a (Figure 4) may be due to a mixture of the digermene
and a small amount of tetraisopropyldisilene, i-Pr2SidSi-i-Pr2 (λmax 400
nm),2g formed via dimerization of diisopropylsilylene (i-Pr2Si:), although
the two bands due to digermene and disilylene could not be distin-
gushed from each other because the absorption bands for R2MdMR2
(M ) Si and Ge) bondings are generally recognized to appear in the
region λ 378-460 nm;27a-e for example, Mes2GedGeMes2 (410 nm),26b
Mes2SidGeMes2 (414 nm),27f and Mes2SidSiMes2 (420 nm).27g (a) See
ref 25a. (b) Baines, K. M.; Stibbs, W. G. Adv. Organomet. Chem. 1996,
39, 275. (c) Okazaki, R.; West, R. Adv. Organomet. Chem. 1996, 39,
231. (d) Weidenbruch, M.; Sturmann, M.; Kilian, H.; Pohl, S.; Saak,
W. Chem. Ber. 1997, 130, 735. (e) Kishikawa, K.; Tokitoh, N.; Okazaki,
R. Chem. Lett. 1998, 239. (f) Baines, K. M.; Cooke, J . A. Organome-
tallics 1992, 11, 3487. (g) Fink, M. J .; Michalczyk, M. J .; Michl, J .;
West, R. J . Organomet. Chem. 1984, 3, 793.

5096 Organometallics, Vol. 17, No. 23, 1998
Suzuki et al.
Ta ble 6. P r od u cts a n d Yield s in th e P h otolysisa of 1a -c in th e P r esen ce (or Absen ce) of
2,3-Dim eth yl-1,3-bu ta d ien e (DMB)
product yields (%)b,c
trapping
agent
time
conversn
compd [R2Si]4GeR′2
(min) of 1a -c (%) 2a
2c
A
3b
3c
7b
8b
8c
9c
10a
10b
11c
R ) i-Pr, R′ ) Me3SiCH2 (1a ) none
15
30
60
15
30
60
49
86
94
43
80
93
20
36
54
27
44
33
1
2
2
3
3
2
DMB
29
56
39
R ) i-Pr, R′ ) Ph (1b)
none
30
60
90
30
60
90
44
65
81
41
69
85
10
17
14
9
15
16
7
9
8
5
6
6
3
7
7
1
1
1
2
6
6
∼1
∼1
1
DMB
12
23
17
R ) t-BuCH2, R′ ) Ph (1c)
none
20
40
60
20
40
60
39
55
74
38
58
74
∼1
∼1
∼1
2
1
∼1
5
10
8
6
8
1
3
4
1
4
3
DMB
∼1 ∼1
∼1 ∼1
∼1 ∼1
4
6
10
4
9
16
8
a
b
Samples were irradiated with a low-pressure Hg lamp (30 W) at room temperature. In all experiments, the presence of unidentified
polymeric compounds (Mw ≈ 3500; polystyrene as the standard) was detected by GPC analysis. c GLC yields based on 1a -c employed;
thermal conductivity corrections have been made.
Sch em e 1. P ossible P a th w a ys fr om 1a -c to th e P r od u cts
accompanied by 51% unreacted 1a .28 The formation of
2a and compound A thus obtained proves that the Si4-
Ge ring of 1a decomposed into the smaller Si4 and Si3-
Ge rings with the extrusion of germylene and silylene
along the paths a and b (a . b), respectively, in Scheme
1. Similarly, the experiment (1 h) using 1b afforded
trisilane H(i-Pr2Si)3H (7b) (7%)29 and disilane H(i-Pr2-
Si)2H (8b) (6%),30 together with 2a (17%), germatrisi-
lacyclobutane [i-Pr2Si]3GePh2 (3b) (9%), and unreacted
1b (35%).28 The trisilane 7b and disilane 8b was
probably formed from 1b via paths c and d, respectively
(Scheme 1), not from the cyclotetrasilane 2a produced
from 1b by path a, because the photolysis of 1a , which
produced the same cyclotetrasilane 2a as described
above, did not give the compounds 7b and 8b under the
present reaction conditions. On the other hand, the
experiment using 1c afforded on irradiation for 40 min
the germatrisilacyclobutane [(t-BuCH2)2Si]3GePh2 (3c)
(10%) together with the disilane H((t-BuCH2)2Si)2H (8c)
(3%), the disilanol H((t-BuCH2)2Si)2OH (9c) (4%), un-
reacted 1c (45%), and trace amounts of many products
containing the cyclotetrasilane [(t-BuCH2)2Si]4 (2c).28,31
The compounds 8b,c and 9c are presumably produced
2c
via the tetraalkyldisilenes R2SidSiR2 (R ) i-Pr and
t-BuCH2) by way of path d (Scheme 1). The formation
of the disilenes 6b,c from 1b,c is evidenced by the
observations of the bands at λ 400 nm due to the
(28) In the photolysate, the presence of unidentified polymeric
compounds (Mw ≈ 3500) was also detected by GPC analysis using
polystyrene as the standard.
(29) Masamune, S.; Tobita, H.; Murakami, S. J . Am. Chem. Soc.
1983, 105, 6524.
(31) Matsumoto, H.; Minemura, M.; Takatsuna, K.; Nagai, Y.; Goto,
(30) Weidenbruch, M.; Peter, W. J . Organomet. Chem. 1975, 84, 151.
M. Chem. Lett. 1985, 1005.

Germatetrasilacyclopentanes
Organometallics, Vol. 17, No. 23, 1998 5097
disilenes2g in the experiments at 77 K (Figure 7)
described above.
From the above observations and the results in Table
6, it was found that the germatetrasilacyclopentane 1a
photochemically decomposes mainly into cyclotetrasi-
lane 2a and germylene ((Me3SiCH2)2Ge:) via path a, 1b
via paths a-d, and 1c via paths b and d. Thus, the
compounds 1b,c are apparently subject to not only the
Si-Ge bond cleavages (path a) but also to the Si-Si
bond cleavages (paths b-d) simultaneously, resulting
in the formation of various products (Table 6 and
Scheme 1). The complicated reactions forming the
various products arising from the two kinds of bond
cleavages can probably be attributed to the ring strain
energies, the steric repulsions between bulky substitu-
ents on ring silicons, the existence of the light-absorbing
phenyl groups on germanium, and/or the ring size. In
any event, it should be emphasized that, in the pho-
tolysis of the Si4Ge rings, the Si-Si bond cleavages
leading to the smaller rings (Si3Ge, Si3, and Si2Ge),
dimetallenes (SidSi and SidGe), and silylene (Si:)
derivatives were first found by the present study, while
via the photolysis of the four-membered Si3Ge rings A
and B, the same type of cleavage reaction has not been
observed.
P h otolysis of 1a -c Usin g High -P r essu r e Mer -
cu r y La m p (λ >310 n m Ligh t). To investigate the
effect of the light-sensitive phenyl substituents on the
product formation, photolysis of 1b,c in cyclohexane
solution using a high-pressure mercury lamp (λ > 310
nm) was carried out (see Experimental Section).
Photolysis of 1b gave 2a (15%), 3b (4%), and the
trisilaoxetane [i-Pr2Si]3O29 (7%), which was formed by
the oxidation of cyclotrisilane 4b [i-Pr2Si]3, 7b (2%), and
8b (2%),28 as shown in Scheme 1. A similar experiment
with 1c gave 2c (2%), 3c (4%), 8c (∼1%), and 9c (3%).28
These results were similar to those obtained via the
former light source. Thus, the difference between the
reactions via the two types of light sources could not be
clarified, except for the isolation of the trisilaoxetane
generated from 1b using the high-pressure lamp (lower
energy). Although the isolation of this compound might
suggest a certain effect by the use of the latter, the effect
of the phenyl substituents on the product formation
could not be clarified. However, the latter effect seems
not to be very significant, because the large steric
repulsions between the bulky substituents on the ring
silicons have been shown to affect mainly the direction
of the decomposition reactions, as described below.
Subsequently, to obtain further information via ir-
radiation using the high-pressure lamp, compounds
1a -c were photolyzed in the presence of an excess
amount of carbon tetrachloride33 as a trapping agent,
and all the results are summarized in Table 7. Irradia-
tion of 1a gave the 1,4-dichlorotetrasilane Cl(i-Pr2Si)4Cl
(82%) and dichlorogermane (Me3SiCH2)2GeCl2 (68%).1b
Interestingly, 1b afforded various products, such as
dichlorogermane Ph2GeCl2 (22%)34 and the series of
dichlorosilanes Cl(i-Pr2Si)nCl (n ) 2,30 3,29 and 4) with
varying yields of 18-25%. A similar experiment using
1c gave the dichlorosilane (t-BuCH2)2SiCl2 (20%)2b and
a trace amount of 1,4-dichlorotetrasilane Cl((t-BuCH2)2-
Si)4Cl, along with other dichlorosilanes Cl((t-BuCH2)2-
Next, trapping experiments of the reactive intermedi-
ates with 2,3-dimethyl-1,3-butadiene (DMB, a well-
known trapping agent for germylenes and silylenes)
were performed at room temperature, and Table 6
summarizes the results of the experiments. Irradiation
of 1a in the presence of DMB afforded the expected
germylene trapping product 1,1-bis((trimethylsilyl)-
methyl)-3,4-dimethyl-1-germacyclopent-3-ene (10a) (29-
56%),1b together with 2a , A, and unreacted 1a . Simi-
larly, irradiation of 1b afforded the corresponding
germylene trapping product 1,1-diphenyl-3,4-dimethyl-
1-germacyclopent-3-ene (10b) (∼23%),32 together with
2a (∼16%), 3b (∼6%), 7b (1%), and unreacted 1b.28 The
experiments using 1c afforded the silylene trapping
product 1,1-dineopentyl-3,4-dimethyl-1-silacyclopent-3-
ene (11c) (∼16%),1b along with the germylene trapping
product 10b (∼10%), 3c (∼8%), and unreacted 1c.28
With regard to dimetallene trapping, previously it was
shown that, in the photolysis of the three-membered-
ring analogue [R2Si]2Ge(CH2SiMe3)2 (R ) t-BuCH2),
DMB fairly well trapped the corresponding intermediate
disilene as well as silylene.4 However, in the present
experiments using DMB for the reactions of 1a -c, none
of the corresponding dimetallene R2MdSiR2 (M ) Si or
Ge) trapping products could be detected by the GLC
method from the resulting product mixtures. Thus, the
reason DMB did not trap the dimetallenes, even the
disilene coming from 1c, may be due to the fact that
their concentrations are too low and/or lifetimes too
short to form the corresponding products in the present
systems.
(33) Absorption band λ 280 nm: Saha, N. K. Bull. Acad. Sci. United
Provinces Agra Oudh, India 1933, 2, 233; Chem. Abstr. 1933, 27, 4733.
(34) Kraus, C. A.; Brown, C. L. J . Am. Chem. Soc. 1930, 52, 3690.
(32) Bobbitt, K. L.; Maloney, V. M.; Gaspar, P. P. Organometallics
1991, 10, 2772.

5098 Organometallics, Vol. 17, No. 23, 1998
Suzuki et al.
Ta ble 7. P r od u cts a n d Yield s in th e P h otolysisa of 1a -c a n d Rela ted Com p ou n d s in th e P r esen ce of
Ca r bon Tetr a ch lor id e
product yields (%)b
Cl(R2Si)nCl
amt of
C2Cl6
R′ (R′2GeCl2)
R (n ) 4)
R (n ) 3)
R (n ) 2)
entry
no.
time conversn
R (n ) 1)c
compd
(min) of 1-4 (%) Me3SiCH2 Ph i-Pr t-BuCH2 i-Pr t-BuCH2 i-Pr t-BuCH2 t-BuCH2 (10-2 mmol)
1
2
3
[i-Pr2Si]4Ge(CH2SiMe3)2 (1a ) 150
96
100
75
68
82
25
2.9
2.7
1.5
[i-Pr2Si]4GePh2 (1b)
[(t-BuCH2)2Si]4GePh2 (1c)
150
150
22
9
18
19
∼1
7
3
20
9
20
8
4
5
6
7
8
[i-Pr2Si]4 (2a )
40
150
150
150
150
100
67
100
100
100
90d
nil
10
nil
1.8
0.7
1.5
2.5
2.0
[(t-BuCH2)2Si]4 (2c)
[i-Pr2Si]3GePh2 (3b)
[(t-BuCH2)2Si]3GePh2 (3c)
[(t-BuCH2)2Si]3 (4c)
14
25
16
∼1
11
60
7
10
2
10
a
b
Samples were irradiated with a high-pressure Hg lamp (100 W) at room temperature. GLC yields based on 1-4 (ca. 0.02 mmol)
employed; thermal conductivity corrections have been made. c The yields of i-Pr2SiCl2 could not be determined because of overlapping
with unknown product (tetrachloroethylene?) in GLC. No change in the yield was observed even after prolonged irradiation (∼120 min).
d
Si)nCl (n ) 231 and 31b) and Ph2GeCl2. Previously, the
reactions of germylenes,26j,35 dimethylsilylene,36 and
disilenes37 with carbon tetrachloride have been reported
to give the corresponding dichlorogermanes, -silane, and
-disilanes, respectively. Therefore, in the present reac-
tions, the formation of products R′2GeCl2 (R′ ) Me3-
SiCH2, Ph), (t-BuCH2)2SiCl2, and Cl(R2Si)2Cl (R ) i-Pr,
t-BuCH2) indicates the intermediacies of the corre-
sponding germylenes (R′2Ge:), silylene ((t-BuCH2)2Si:),
and disilenes (R2SidSiR2), respectively.
amounts in all cases (see also the Experimental Section).
Thus, carbon tetrachloride itself did not undergo the
photochemical scission to form the byproduct under the
reaction conditions employed.
From the above results and observations, the pho-
tolyses of five-membered rings 1a -c using the two kinds
of light sources (low- and high-pressure mercury lamps)
disclosed the following. (1) Compound 1a decomposes
to form two kinds of four-membered products, cyclotet-
rasilane 2a (main) and germatrisilacyclobutane 3a
(minor), with extrusion of germylene and silylene,
respectively (paths a and b (a . b)) (Scheme 1). (2)
Compounds 1b,c decompose into two kinds of three-
membered-ring products, cyclotrisilanes 4b,c and disi-
lagermiranes 5b,c, with extrusion of germasilenes and
disilenes (paths c and d), together with two kinds of
four-membered products described above (paths a and
b). This is the first case in which the five-membered
rings partially cleaved into dimetallenes and three-
membered rings. (3) Among the four paths, for 1b path
a was the main route but for 1c path a was the minor
route.
To clarify the origins of the three types of dichlorosi-
lanes Cl(R2Si)nCl (n ) 2-4) from 1b,c, photolyses using
the intermediates 2-4 as the starting materials in place
of 1b,c were carried out (entries 4-8 in Table 7), and
the results were compared with those obtained from
1b,c. The results thus obtained are as follows. (1) 1,4-
Dichlorotetrasilanes Cl(R2Si)4Cl (R ) i-Pr, t-BuCH2)
come from cyclotetrasilanes 2a ,c (entries 4,5) and/or
their precursor 1,4-biradical species (•SiR2(R2Si)2R2Si•).
(2) The 1,3-dichlorotrisilane Cl((t-BuCH2)2Si)3Cl occurs
mainly from cyclotrisilane 4c2b (entry 8) and/or its
precursor 1,3-biradical species (•SiR2(R2Si)R2Si•, R )
t-BuCH2), because the starting 4c, in contrast to the
starting intermediates 2c and 3c (entries 5,7), gave the
corresponding 1,3-dichlorosilane in high yield. Cyclo-
trisilane [i-Pr2Si]3 4b (and/or its precursor biradical)
would form a similar product, but this experiment could
not be carried out because of the difficulty of obtaining
4b due to its remarkably high air sensitivity.29 (3)
Dichlorodisilanes Cl(R2Si)2Cl (R ) i-Pr, t-BuCH2) prob-
ably are derived mainly via disilenes 6b,c generated
directly from 1b,c and also from disilagermiranes [R2-
Si]2GePh2 (5b,c) (path d in Scheme 1),38 but not from
the intermediates 2-4 arising from 1b,c, because the
starting 2-4 produced the dichlorodisilanes in only
small amounts or did not form them at all (entries 4-8).
(4) In the last column in Table 7, the formation of
byproduct, hexachloroethane, produced from the pho-
tolysis of 1a -c and 2-4 did not exceed the calculated
Consequently, it can be concluded that the difference
between the decomposition reactions of 1b,c is probably
due to the larger steric repulsions between the bulkier
neopentyl groups in 1c in comparison to those between
the isopropyls in 1b on silicons, because the ring strain
energies of both compounds were estimated to be almost
the same.
Exp er im en ta l Section
Gen er a l P r oced u r e. All the reactions were carried out
using a dry flask under an atmosphere of inert gas (N2 or Ar).
IR spectra were recorded with a Hitachi EPI-G3 spectrometer.
1H and 13C NMR spectra were recorded using a Varian Gemini-
200M spectrometer in CDCl3 with Me4Si as an internal
standard. 29Si NMR spectra were recorded in C6D6 with a
J EOL ALPHA 500 spectrometer. Mass spectra were recorded
by using a J EOL DX-302 spectrometer (Ip ) 70 eV). UV
spectra were obtained by using a Hitachi 200-10 spectrometer.
GLC analysis was performed by using an Ohkura GC-103 gas
chromatograph equipped with a glass column (1 m) packed
with SE-30 (2-10%) on Celite 545-AW (60-80 mesh). Prod-
uct yields from the photolysis of 1a -c were determined by the
GLC method in which thermal conductivity corrections have
been made by using an external standard (paraffin, C17H36 or
(35) (a) Neumann, W. P.; Schriewer, M. Tetrahedron Lett. 1980, 21,
3273. (b) Tomoda, S.; Simoda, M.; Takeuchi, Y.; Kajii, Y.; Obi, K.;
Tanaka, I.; Honda, K. J . Chem. Soc., Chem. Commun. 1988, 910.
(36) Nakao, R.; Oka, K.; Dohmaru, T.; Nagata, Y.; Fukumoto, T. J .
Chem. Soc., Chem. Commun. 1985, 766.
(37) Kira, M.; Iwamoto, T.; Kabuto, C.; Sakurai, H. Presented at
the 8th International Conference on the Organometallic Chemistry of
Germanium, Tin, and Lead, Sendai, J apan, 1995; Abstr. 34.
(38) Its analogue, [(t-BuCH2)2Si]2Ge(CH2SiMe3)2, has been observed
to decompose into disilene and germylene.4
C
19H40) in the experiments with a low-pressure mercury lamp
and an internal standard (paraffin, C17H36 or C19H40 or C22H46
with a high-pressure one.
)

Germatetrasilacyclopentanes
Organometallics, Vol. 17, No. 23, 1998 5099
Ma ter ia ls. Tetrahydrofuran and benzene used in the
synthesis were dried over sodium wire and freshly distilled in
the flask containing benzophenone-ketyl radical before use.
Hexane, cyclohexane, and pentanes were dried over lithium
aluminum hydride and freshly distilled before use. Carbon
tetrachloride and hexamethylphosphoric triamide (HMPA)
were dried over calcium hydride and distilled at atmospheric
and reduced pressure, respectively, before use. Other solvents
and materials were commercially available.
-13.76 (Si2,3), -12.13 (Si1,4); UV (cyclohexane) λmax 280 nm
(sh) (ꢀ 5700 mol-1 dm3 cm-1); IR (KBr pellet; cm-1) 3060 (w),
2976 (s), 2952 (s), 2860 (vs), 1580 (w), 1464 (m), 1428 (m), 1002
(w), 990 (w), 916 (w), 878 (s), 730 (s), 698 (vs), 624 (m), 464
(m), 448 (m), 360 (w), 298 (w); MS m/e (relative intensity) 684
(10, M+), 642 (8, [M - C3H6]+), 484 (50), 121 (100). Anal.
Calcd for C36H66Si4Ge: C, 63.27; H, 9.73. Found: C, 63.65;
H, 10.04.
Syn th esis of 1,1-Dip h en ylocta n eop en tyl-1-ger m a tet-
r a sila cyclop en ta n e (1c). 1,4-Dichlorooctaneopentyltetrasi-
lane powder (D) (0.34 g, 0.45 mmol) was added at 0 °C to a
solution of diphenylgermylenedipotassium9 in HMPA/THF,
prepared by the reaction of diphenylgermane (0.16 g, 0.70
mmol) with potassium (0.21 g, 5.4 mmol) in a mixture of
HMPA (1.0 mL) and THF (2.0 mL) (see above), and the mixture
was then diluted with THF (5.5 mL). After 1 h of stirring at
0 °C, hexane was added to the resulting reaction mixture. In
a manner similar to that for 1b described above, the mixture
was then treated to give a solid product, which was recrystal-
lized from ethanol, affording colorless crystals of 1c (0.25 g,
61% based on the 1,4-dichlorotetrasilane used; mp 390-406
P r ep a r a t ion of 1,1-Bis((t r im et h ylsilyl)m et h yl)oct a -
isop r op yl-1-ger m a cyclop en ta sila n e (1a ). A solution of bis-
((trimethylsilyl)methyl)bis(trimethylsilyl)germane,1b (Me3-
SiCH2)2Ge(SiMe3)2 (0.49 g, 1.3 mmol), in hexane (0.5 mL) was
slowly added to a blue suspension of lithium (39 mg, 5.62
mmol) in HMPA (2.4 mL) via serum cap by use of a hypodermic
syringe at room temperature. After 2 h of stirring, the
resulting greenish yellow reaction mixture containing (Me3-
SiCH2)2GeLi2 was cooled to 0 °C, followed by addition of
benzene (5.5 mL). A solution of 1,4-dichlorooctaisopropyltet-
rasilane (C), Cl(i-Pr2Si)4Cl (0.46 g, 0.87 mmol), in benzene (5.5
mL) was added to the above reaction mixture. After 3 h of
stirring and addition of hexane, the resulting mixture was
washed with water, dried over calcium chloride, and then
filtered. The filtrate was condensed below 150 °C in vacuo to
give a semisolid which was recrystallized from ethanol to afford
colorless crystals of 1a (0.34 g, 56% based on the 1,4-
dichlorotetrasilane used; mp 206-209 °C (sealed capillary)):
1H NMR (δ, CDCl3) 0.10 (s, 18H, SiCH3), 0.37 (s, 4H, CH2-
SiMe3), 1.2-1.4 (m, 48H, CH(CH3)2), 1.40-1.55 (m, 8H,
CHMe2); 13C NMR (δ, CDCl3) 1.60 (CH2SiMe3), 2.67 (SiCH3),
15.72 (Si1-4CHMe2), 22.49 and 22.69 (Si1,4CH(CH3)2), 23.53 and
23.87 (Si2,3CH(CH3)2; 29Si NMR (δ, C6D6) -12.51 (Si2,3), -10.70
(Si1,4), 2.39 (SiMe3); UV (cyclohexane) λmax 280 nm (sh) (ꢀ 1100
mol-1 dm3 cm-1); IR (KBr pellet; cm-1) 2948 (s), 2916 (s), 2860
(s), 2708 (vs), 1464 (m), 1386 (w), 1362 (w), 1262 (m), 1246 (s),
1056 (m), 1046 (w), 1018 (s), 984 (w), 916 (w), 878 (s), 850 (vs),
832 (vs), 754 (m), 736 (m), 682 (w), 628 (m), 596 (w), 522 (w),
492 (w), 446 (w), 358 (w); MS m/e (relative intensity) 704 (40,
M+), 689 (10, [M - Me]+), 662 (25, [M - C3H6]+), 619 (45, [M
- C3H6 - C3H7]+), 201 (100). Anal. Calcd for C32H78Si6Ge:
C, 54.59; H, 11.17. Found: C, 53.96; H, 11.22.
°C (sealed capillary)): 1H NMR (δ, CDCl3) 0.81 (s, 36H, Si1,4
-
CH2C(CH3)3, 1.17 (s, 36H, Si2,3CH2C(CH3)3, 0.9-1.6 (m, 16H,
Si1-4CH2Bu-t), 7.2-7.7 (m, 10H, C6H5); 13C NMR (δ, CDCl3)
30.10 (Si2,3CH2CMe3), 31.08 (Si1,4CH2Bu-t), 31.61 (Si1,4CH2CMe3),
32.02 (Si2,3CH2Bu-t), 33.60 (Si1,4CH2C(CH3)3), 34.18 (Si2,3CH2C-
(CH3)3), 127.39 (Ph C4), 127.49 (Ph C3,5), 137.57 (Ph C2,6),
142.13 (Ph C1); 29Si NMR (δ, C6D6) -29.01 (Si2,3), -23.98 (Si1,4);
UV (cyclohexane) λmax 280 nm (sh) (ꢀ 7600 mol-1 dm3 cm-1);
IR (KBr pellet; cm-1) 3064 (w), 2948 (vs), 2900 (s), 2864 (s),
1658 (w), 1580 (w), 1476 (m), 1464 (m), 1430 (w), 1386 (w),
1362 (s), 1256 (w), 1224 (m), 1158 (w), 1126 (w), 1078 (w), 1016
(w), 762 (w), 730 (m), 700 (m), 672 (w), 664 (w), 466 (w); MS
m/e (relative intensity) 908 (7, M+), 837 (3, [M - (CH2Bu-t)]+),
667 (4, [M - (CH2Bu-t) - Si(CH2Bu-t)2]+), 136 (100). Anal.
Calcd for C52H98Si4Ge: C, 68.76; H, 10.88. Found: C, 67.93;
H, 10.98.
The 1,4-dichlorotetrasilane (D) mentioned above was pre-
pared in 89% yield by the reaction of octaneopentylcyclotet-
rasilane31 with phosphorus pentachloride (mp 221-223 °C):
IR (KBr pellet; cm-1) 500 (νSi-Cl); MS m/e (relative intensity)
679 (3, [M - (CH2Bu-t)]+), 545 (5, [M - ClSi(CH2Bu-t)2]+), 375
(12, [M - ClSi(CH2Bu-t)2-Si(CH2Bu-t)2]+), 340 (35, [M - 2(ClSi-
(CH2Bu-t)2)]+), 73 (100). Anal. Calcd for C40H88Si4Cl2: C,
63.86; H, 11.79. Found: C, 64.21; H, 11.90.
P r ep a r a tion of Au th en tic Sa m p les of th e P r od u cts
F or m ed in th e P h otolysis Usin g 1b,c. 1,1-Dip h en yl-
h exa isop r op yl-1-ger m a t r isila cyclob u t a n e (3b ). By a
method similar to that for 1b, this compound was prepared
by the reaction of diphenylgermylenedipotassium9 with 1,3-
dichlorohexaisopropyltrisilane29 (26%; mp 258-260 °C (sealed
capillary)): 1H NMR (δ, CDCl3) 1.1-1.4 (m, 36H, CH(CH3)2),
1.5-1.8 (m, 6H, CHMe2), 7.2-7.6 (m, 10H, C6H5); 13C NMR
(δ, CDCl3) 14.58 (Si1,3CHMe2), 14.83 (Si2CHMe2), 21.58, 21.89,
and 22.31 (Si1-3CH(CH3)2), 127.36 (Ph C4), 127.92 (Ph C3,5),
136.44 (Ph C2,6), 141.70 (Ph C1); UV (cyclohexane) λmax 305 nm
(ꢀ 1010 mol-1 dm3 cm-1); MS m/e (relative intensity) 570 (55,
M+), 528 (25, [M - C3H6]+), 486 (20, [M - 2(C3H6)]+), 121 (100).
Anal. Calcd for C30H52Si3Ge: C, 63.26; H, 9.20. Found: C,
62.59; H, 9.23.
1,1-D ip h e n y lh e x a n e o p e n t y l-1-g e r m a t r is ila c y c lo -
bu ta n e (3c). This compound was prepared by using 1,3-
dichlorohexaneopentyltrisilane in a fashion similar to that for
1c mentioned above (33%; mp 350-360 °C (sealed capillary)):
1H NMR (δ, CDCl3) 0.92 (s, 36H, Si1,3CH2C(CH3)3), 1.14 (s, 18H,
Si2CH2C(CH3)3), 1.3-1.6 (m, 12H, SiCH2Bu-t), 7.2-7.6 (m,
10H, C6H5); 13C NMR (δ, CDCl3) 29.70 (Si2CH2CMe3), 31.07
(Si1,3CH2Bu-t), 31.48 (Si1,3CH2CMe3), 31.60 (Si2CH2Bu-t), 33.31
(Si1,3CH2C(CH3)3), 33.81 (Si2CH2C(CH3)3), 127.38 (Ph C4),
127.71 (Ph C3,5), 137.02 (Ph C2,6), 142.24 (Ph C1); UV (cyclo-
hexane) λmax 300 nm (sh) (ꢀ 1470 mol-1 dm3 cm-1); MS m/e
The 1,4-dichlorotetrasilane (C) mentioned above was pre-
pared in 95% yield by the reaction of octaisopropylcyclotet-
rasilane [i-Pr2Si]42d with phosphorus pentachloride in benzene
at room temperature (mp 49-51 °C, (sealed capillary)): IR
(KBr pellet; cm-1) 514 (νSi-Cl); MS m/e (relative intensity) 483
(5, [M - (i-Pr)]+), 377 (35, [M - (i-Pr2SiCl)]+), 228 (80, [M -
2(i-Pr2SiCl)]+), 58 (100). Anal. Calcd for C24H56Cl2Si4: C,
54.60; H, 10.69. Found: C, 54.96; H, 10.38.
Syn th esis of 1,1-Dip h en ylocta isop r op yl-1-ger m a cyclo-
p en ta sila n e (1b). A solution of diphenylgermane9 Ph2GeH2
(0.16 g, 0.70 mmol) in THF (0.5 mL) was slowly added to a
blue suspension of potassium (0.25 g, 6.4 mmol) in HMPA (1.2
mL) and THF (1.5 mL) via serum cap by use of a hypodermic
syringe at room temperature. After 2 h of stirring, the
resulting red reaction mixture containing (diphenylgermylene)-
dipotassium9 was diluted with THF (2.8 mL) and benzene (3.5
mL), and then unreacted potassium was removed with twee-
zers. A solution of 1,4-dichlorooctaisopropyltetrasilane (C)
(0.33 g, 0.63 mmol) in benzene (1.4 mL) was slowly added to
the above reaction mixture at 0 °C. After 1 h of stirring and
addition of hexane, the resulting mixture was washed with
water and dried over calcium chloride. After filtration,
evaporation of the filtrate afforded a solid product which was
recrystallized from ethanol to give colorless crystals of 1b (0.20
g, 46% based on the 1,4-dichlorosilane used; mp 370-378 °C
(sealed capillary)): 1H NMR (δ, CDCl3) 0.7-1.7 (m, 56H,
CH(CH3)2), 7.2-7.6 (m, 10H, C6H5); 13C NMR (δ, CDCl3) 16.12
(Si1,4CHMe2), 16.17 (Si2,3CHMe2), 21.72 and 23.13 (Si1,4CH-
(CH3)2), 23.65 and 23.83 (Si2,3CH(CH3)2), 127.09 (Ph C4), 127.88
(Ph C3,5), 136.24 (Ph C2,6), 141.53 (Ph C1); 29Si NMR (δ, C6D6)

5100 Organometallics, Vol. 17, No. 23, 1998
Suzuki et al.
Ta ble 8. Cr ysta llogr a p h ic Da ta for [i-P r 2Si]4GeP h 2
(1b) a n d [(t-Bu CH2)2Si]4GeP h 2 (1c)
mercury lamp (30 W) at room temperature, and the electronic
spectra were observed at periodic intervals during the irradia-
tion (Figure 4). After irradiation for 1 h (pale yellow), the seal
of the reaction cell was opened; thus, a colorless solution was
obtained. After evaporation of the solvent, the products
formed were isolated by preparative GLC and subjected to GC-
MS analysis. Thus, by a comparison with the authentic
samples in their GLC retention times and MS fragmentation
patterns, the main products were identified to be 2a and A.
The yields of 2a and A were determined, by the GLC
techniques mentioned above, to be 20 and 1% (C17H36 as an
external standard being used), respectively.28 Similarly, the
experiments using 1b,c were carried out and the resulting
products were analyzed. All the results have been summarized
in Table 6. In the photolysis of 1a -c, polymeric products
having molecular weights higher than those listed in Table 6
were detected by GPC analysis.28 Generally, polysilane (R1R2-
Si)n41 and polygermane (R1R2Ge)n42 have been known to exhibit
UV absorption maxima in the region of ca. 300-350 nm.
However, no distinct absorption band in the above region could
be recognized for the photolyzates of 1a -c, suggesting that a
polymer such as (R2M)n (M ) Si or Ge) did not form in amounts
detectable by UV spectroscopy. Accordingly, from the photo-
poduct mixture the polymeric products detected by the GPC
method have not been isolated because of an insufficient
amount of the mixture due to a very small scale reaction.
1b
1c
Crystal Data
36H66Si4Ge
683.861
formula
fw
C
C52H98Si4Ge
908.259
cryst size (mm)
cryst syst
space group
unit cell dimens
a (Å)
0.8 × 0.2 × 0.2
monoclinic
P21/n
0.1 × 0.4 × 0.5
monoclinic
P21/a
11.595(5)
20.013(5)
17.386(5)
101.06(2)
3960(2)
4
19.943(4)
15.428(1)
21.543(4)
105.59(1)
6384(5)
4
b (Å)
c (Å)
â (deg)
V (Å3)
Z
Dcalcd (g cm-3
)
1.147
0.9447
Data Collection
diffractometer
µ(Cu KR) (cm-1
temp (°C)
Enraf-Nonius C4D4 Enraf-Nonius C4D4
)
24.0
15.8
23
23
scan mode
scan range
no. of rflns
collecd
ω-2θ
ω-2θ
4-120
7-120
6330
9485
used (|Fo| g 3σ|Fo|) 5459
7668
ψ scan method
0.834/1.000
abs cor
ψ scan method
transmissn factor
(min/max)
0.762/0.996
Ir r a d ia tion of 1a -c in 3-Meth ylp en ta n e a t 77 K. Typi-
cally, 1a (14.0 mg, 2.0 × 10-5 mol) and 3-methylpentane (3
mL) were placed in a quartz cell. After the solution was
degassed by freeze-pump-thaw cycles, the cell, which was
sealed in vacuo, was placed into a quartz Dewar filled with
liquid nitrogen. The resulting matrix was similarly irradiated
through the quartz window, and the electronic spectra were
taken at periodic intervals. Irradiation of the matrix for 2 h
at 77 K produced a pale yellow glass with an absorption band
at 465 nm, as shown in Figure 6. In the experiments using
1b,c, the same absorption band at 400 nm was observed and
the reaction profile for 1b is shown in Figure 7.
Solution and Refinement
full-matrix
refinement method
block-diagonal
least squares
0.0887 (0.0897)
2.2308
least squares
0.0434 (0.0563)
0.9414
R (Rw)
S
(∆σ)max
0.79
0.66
peaks in diff Fourier max 0.25, min -0.7 max 0.8, min -0.4
map (e/Å3)
(relative intensity) 738 (25, M+), 682 (2, [M - C4H8]+), 667 (2,
[M - (CH2Bu-t)]+), 490 (15), 135 (100). Anal. Calcd for C42H76
Si3Ge: C, 68.36; H,10.38. Found: C, 68.02; H, 10.43.
-
P h otolysis of 1a -c in th e P r esen ce of 2,3-Dim eth yl-
1,3-bu ta d ien e. Typically, a mixture of 1a (14.0 mg. 2.0 ×
10-5 mol), 2,3-dimethyl-1,3-butadiene (70 µL, 6.2 × 10-4 mol),
and cyclohexane (3 mL) was placed in a quartz reaction cell
and degassed by freeze-pump-thaw cycles, and then the cell
was sealed in vacuo. The solution was irradiated for 1 h at
room temperature. The resulting colorless solution was
concentrated and analyzed as shown above. The main prod-
ucts were found to be the germylene trapping product 10a
(39%), 2a (33%), and A (2%).28 Similarly, the experiments
using 1b,c were carried out. The silylene trapping product
11c was produced along with the germylene trapping product
10b from 1c. All the results have also been summarized in
Table 6.
X-r a y Cr ysta l An a lysis of 1b,c. Crystals, obtained from
ethanol, were used for the X-ray analysis. Intensity data were
obtained on a Enraf-Nonius CAD-4 diffractometer equipped
with graphite-monochromated Cu KR radiation (λ ) 1.5418
Å) using the ω-2θ scan technique (2θ < 120° for 1b,c).
Structures of both 1b and 1c were solved by direct methods
using the MULTAN 78 program39 and refined by full-matrix
least-squares (1b) and block-diagonal least-squares methods
(1c). Thirty hydrogen atoms for 1c were found in the differ-
ence Fourier maps, and the other hydrogens of 1c and all
hydrogens for 1b were located in their calculated positions.
The final refinements with anisotropic temperature factors for
the non-hydrogen atoms had lowered the R values to 0.0434
2
(Rw ) 0.0563) (w ) 1/0.00887|Fo| - 0.35703|Fo| + 4.30635)
P h otolysis of 1b,c in Cycloh exa n e a t Room Tem p er -
a tu r e Usin g a High -P r essu r e Mer cu r y La m p . Typically,
a mixture of 1b (13.7 mg, 2.0 × 10-5 mol) and nonadecane
(5.4 mg, 2.0 × 10-5 mol) as an internal standard in cyclohexane
(3 mL) in a Pyrex tube was degassed by freeze-pump-thaw
cycles and then filled with Ar. The sample was irradiated with
a 100 W high-pressure Hg lamp at room temperature for 5 h
to give 2a (15%), 3b (4%), 7b (2%), 8b (2%), [i-Pr2Si]3O (7%),
and unreacted 1b (15%).28 Similar irradiation of 1c for 3.5 h
using docosane as an internal standard gave 2c (2%), 3c (4%),
8c (∼1%), 9c (3%), and unreacted 1c (24%).28
2
for 1b and 0.0887 (Rw ) 0.0897) (w ) 1/|Fo| ) for 1c. All the
calculations were performed with the UNICS III system.40 The
molecular structures, selected bond distances, and bond and
torsion angles are given in Figure 1 and Tables 1 and 2 for 1b
and in Figure 2 and Tables 3 and 4 for 1c, respectively. The
crystallographic data for 1b,c are summarized in Table 8.
P h otolysis of 1a -c in Cycloh exa n e a t Room Tem p er -
a tu r e. In a typical experiment, 1a (14.0 mg, 2.0 × 10-5 mol)
and cyclohexane (3 mL) was placed in a quartz tube fitted with
a UV-monitoring cell. After the solution was degassed by
freeze-pump-thaw cycles, the reaction tube was sealed in
P h otolysis of 1-4 in th e P r esen ce of Ca r bon Tetr a -
ch lor id e Usin g a High -P r essu r e Mer cu r y La m p . Typi-
cally, a mixture of 1b (13.7 mg, 2.0 × 10-5 mol), carbon
vacuo. The solution was irradiated with
a low-pressure
(39) Main, P.; Hull, S. E.; Lessinger, L.; Germain, G.; Declercq, J .;
Woolfson, M. M. MULTAN 78, A System of Computer Programs for
the Automatic Solution of Crystal Structures for the X-ray Diffraction
Data; University of York, England, and Louvain, Belgium, 1978.
(40) Sakurai, T.; Kobayashi, K. Rikagakukenkyujyo Houkoku 1978,
55, 69.
(41) West, R. In The Chemistry of Organic Silicon Compounds;
Patai, S., Rappoport, Z., Eds.; Wiley: New York, 1989; Chapter 19 and
references therein.
(42) Mochida, K.; Chiba, H. J . Organomet. Chem. 1994, 473, 45.

Germatetrasilacyclopentanes
Organometallics, Vol. 17, No. 23, 1998 5101
tetrachloride (174 µL, 1.8 × 10-3 mol), and nonadecane (5.4
mg, 2.0 × 10-5 mol) as an internal standard in cyclohexane (3
mL) was similarly irradiated for 150 min to give dichloroger-
mane Ph2GeCl2 (22%) and the series of dichlorosilanes Cl(i-
Pr2Si)nCl (n ) 2-4) in 18-25% yields, together with hexachlo-
roethane Cl3CCCl3, in 2.7 mmol yield (67.5%), as shown in
Table 7. Similar experiments using 1a ,c, 2a ,c, 3b,c, and 4c
(0.02 mmol of each) were carried out, and the results have
been also summarized in Table 7, in which the yields of
hexachloroethane were determined to be 2.9 mmol (72.5%),
1.5 (37.5), 1.8 (90), 0.7 (35), 1.5 (37.5), 2.5 (62.5), and 2.0 (100),
respectively. Further experiments of 1a -c using smaller
amounts (0.6 × 10-3 mol) of carbon tetrachloride resulted in
the formation of the same products in similar yields, as has
been shown in Table 7.
8H, CH2Bu-t), 1.01 and 1.06 (36H, CH2C(CH3)3), 3.89 (quintet,
J ) 3.6 Hz, 1H, SiH); IR (Nujol mull; cm-1) 3688 (ν(Si)O-H), 2108
(νSi-H); MS m/e (relative intensity) 358 (25, M+), 343 (15, [M
- CH3]+), 287 (100, [M - (CH2Bu-t)]+), 231 (66, [M - (CH2-
Bu-t) - C4H8]+), 187 (50). Anal. Calcd for C20H46SiO: C,
66.96; H, 12.92. Found: C, 66.84; H, 13.09.
Ack n ow led gm en t . We are grateful to Toshiba
Silicone Co., Ltd., and Shin-Etsu Chemical Co., Ltd., for
a generous gift of chlorosilanes. We are also grateful to
ASAI Germanium Research Institute for a gift of
tetrachlorogermane. This work was partially supported
(for H.S.) by the Gunma University Foundation for
Science and Technology.
Ch a r a cter iza tion s of th e P r od u cts F or m ed in th e
P h otolysis of 1c. 1,1,2,2-Tetr a n eop en tyld isila n e (8c): mp
1
57-59 °C (sealed capillary); H NMR (δ, CDCl3) 0.81 (AB q,
J AB ) 14.6 Hz, ∆νAB ) 19.8 Hz, 4H, SiCH2Bu-t), 0.83 (AB q,
J AB ) 14.6 Hz, ∆νAB ) 21.1 Hz, 4H, CH2Bu-t), 1.00 (s, 36H,
CH2C(CH3)3), 3.88 (quintet, J ) 3.9 Hz, 2H, SiH); MS m/e
(relative intensity) 342 (40, M+), 327 (3, [M - CH3]+), 271 (15,
[M - (CH2Bu-t)]+), 171 (65, [HSi(CH2Bu-t)2]+), 73 (100); IR
(KBr pellet; cm-1) 2116 (νSi-H). Anal. Calcd for C20H46Si2: C,
47.21; H, 11.39. Found: C, 47.18; H, 11.36.
Su p p or tin g In for m a tion Ava ila ble: Figures depicting
the crystal structures and tables of atomic parameters, aniso-
tropic temperature factors, bond distances and angles, and
torsion angles for 1b,c (32 pages). Ordering information is
given on any current masthead page.
1-Hydr oxy-1,1,2,2-tetr an eopen tyldisilan e (9c): mp 66.0-
1
66.5 °C (sealed capillary); H NMR (δ, CDCl3) 0.69-1.17 (m,
OM9804374