Synthesis of hexakis(alkylgermasesquioxane)s from alkyl(chloro)ethoxygermanes and their formation mechanism

Article abstract of DOI:10.1246/cl.2002.1124

Alkyl(chloro)ethoxygermanes were hydrolyzed with water to give 1,3,5-trialkyl-1,3,5-trichlorocyclotrigermoxanes. Hydrolysis of 1,3,5-trichlorocyclotrigermoxanes gave 5,7-dichloro-1,3,5,7,9,11-hexaalkyltricyclo[7.3.1.1^3,7 ]-hexagermoxanes. The t

Full text of DOI:10.1246/cl.2002.1124

1124
Chemistry Letters 2002
Synthesis of Hexakis(alkylgermasesquioxane)s from Alkyl(chloro)ethoxygermanes and Their
Formation Mechanism
Masato Nanjo, Takaomi Sasage, and Kunio Mochidaꢀ
Department of Chemistry, Faculty of Science, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo 171-8588
(Received August 8, 2002; CL-020669)
Alkyl(chloro)ethoxygermanes were hydrolyzed with
water to give 1,3,5-trialkyl-1,3,5-trichlorocyclotrigerm-
oxanes. Hydrolysis of 1,3,5-trichlorocyclotrigermoxanes
gave
5,7-dichloro-1,3,5,7,9,11-hexaalkyltricyclo[7.3.1.13;7]-
hexagermoxanes. The tricylic anti-form ladder hexagerm-
oxanes reacted with water to afford hexakis(alkylgermasesquiox-
ane)s. These cage and ladder germoxanes were identified by
spectrospcopic and X-ray diffraction methods.
Organosilsesquioxanes with the formula (RSiO1:5)n contain-
ing Si-O bonds as a main chain have been of considerable interest
because of their unusual structures and properties, and as new
materials.1 Matsumoto, Unno, and co-workers,2 and other
groups3{7 reported the synthesis of cage, ladder, and sheet-like
oligomers and polymers of (RSiO1:5 n
structures by X-ray analysis. They are found to be organo-
metallic analogues of silicate anions, (SinO2:5n
nꢁ. The modified
) and established their
)
silicate can be used as pre-ceramic building blocks,8 organolithic
macromolecular materials,9 heterogeneous silica-supported met-
al catalyst,10 potential photoresists,11{13 and so on. While the
organosilsesquioxanes have been amply investigated, there have
been few reports on organogermasesquioxanes.14 We describe
herein the synthesis of hexakis(alkylgermasesquioxane)s by
hydrolysis of alkyl(chloro)ethoxygermanes and cyclic germ-
oxanes as intermediates of the cage germoxanes, and determina-
tion of these structures by X-ray diffraction methods.
The alkyl(chloro)ethoxygermanes, RGe(OEt)nCl3-n (R =
i-Pr, n = 0; R = t-Bu, n = 0–3; R = c-C6H11, n = 0) reacted with
aqueous NaOH solution in xylene at 130–140 ꢂC for 3 h. The
concentration of the reaction mixture by evaporation of xylene
followed by crystallization from pentane gave colorless crystals
Figure 1. An ORTEP representation of the structure of 1a (hydrogꢂen
ꢀ
atoms are omitted for clarity). Selected bond length (A) and angles ( ):
Ge1–O4 1.746(4), Ge1–O3 1.758(4), Ge1–O1 1.763(4), Ge1–C1
1.916(5), O4–Ge1-O3 107.95(18), O4–Ge1–O1 108.27(17), O3–
Ge1–O1 107.26(17), O4–Ge1–C1 111.2(2).
showing that this molecule is strain-free.
The tert-butyl(chloro)diethoxygermane, t-BuGe(OEt)2Cl
prepared by tert-butyltrichlorogermane, t-BuGeCl3 and ethanol
in the presence of pyridine at room temperature for 2 weeks, was
carefully hydrolyzed with water in ethanol at 5 ꢂC for 6 h. The
reaction mixture was concentrated by evaporation of ethanol. The
residue was stirred in benzene at 5 ꢂC and the generated solids
were filtered off. The concentration of the organic layer by
evaporation of benzene followed by recrystallization from
hexane gave only 5,7-dichloro-1,3,5,7,9-hexa-tert-butyltricy-
with a composition of hexakis(alkylgermasesquioxane)s,
(RGe)6O9, 1a–c in 60–98% yields.
clo[7.3.1.13;7]octagermoxane, (t-BuGe)6O8Cl2
2
in 29%
isolated yield.
The germasesquioxane 1a–c was fully established by
spectroscopic and X-ray diffraction methods. As a typical
example, a molecular structure of hexakis(isopropylgermases-
quioxane), (i-PrGe)6O9, 1a is shown in Figure 1.15 The average
The 1H NMR spectrum of 2 displayed two tert-butyl signals
at 1.29 and 1.32 ppm in 1 : 2 ratio. The 13C NMR showed four
signals at 25.9, 26.5, 30.5, and 34.7 ppm. These NMR data
ꢀ
Ge–O bond length is 1.755 A in six-and eight-membered rings.
The average O–Ge–O and Ge–O–Ge bond angles are 108ꢂ and
130.5ꢂ, respectively. All these values are within the normal range,
Copyright Ó 2002 The Chemical Society of Japan

Chemistry Letters 2002
1125
indicated that germoxane 2 was a symmetrical structure. The
structure was established by X-ray crystallography.16 The
molecular structure is shown in Figure 2 as an anti-form ladder
ladder germoxane 2, which undergoes isomerization to give the
syn-type isomer. Dehydration of the syn-form germoxane gives
the cage germoxane 1.
ꢀ
germoxane. The average Ge–O bond length is 1.76 A in six-and
In summary, we synthesized cage hexakis(alkylgermasesqui-
oxane), (RGe)6O9, (R = i-Pr, t-Bu. c-C6H11) from hydrolysis of
RGe(OEt)nCl3-n (n = 0–3), and determined its crystal structure.
Cyclic and anti-form ladder germoxanes as intermediates of the
cage germoxanes by careful hydrolysis of RGe(OEt)nCl3-n were
examined.
eight-membered rings. The average O–Ge–O bond angle is 107ꢂ;
the average Ge–O–Ge is 126.5ꢂ. The structural parameters of 2
(e.g., Ge–O bond lengths, Ge–O–Ge angles, O–Ge–O angels) are
similar to those for 1.14;15
The authors thank Asai Germanium Research Institute Co.,
Ltd., for providing us trichlorogermane.
References and Notes
1
a) R. H. Baney, M. Itoh, A. Sakakibara, and T. Suzuki, Chem. Rev., 95,
1409 (1995). b) F. Feher, in ‘‘Silicon, Germanium, Tin, and Lead
Compounds. Metal Alkoxides, Diketonates and Carboxylates,’’ ed. by
B. Arkles, Gelest, Tullytown (1998), pp 43–59 and references cited
therein.
2
a) M. Unno, B. A. Shamsul, H. Saito, and H. Matsumoto, Organome-
tallics, 15, 2413 (1996). b) M. Unno, K. Takada, and H. Matsumoto,
Chem. Lett., 1998, 489. c) M. Unno, B. A. Shamsul, M. Arai, K. Takada,
and H. Matsumoto, Appl. Organomet. Chem., 13, 1 (1991). d) M. Unno,
A. Suto, K. Takada, and H. Matsumoto, Bull. Chem. Soc. Jpn., 73, 215
(2000). e) M. Unno, A, Suto, and H. Matsumoto, J. Am. Chem. Soc., 124,
1574 (2002).
3
4
U. Dittmar, B. J. Hendan, U. Floerke, and H. C. Marsmann, J.
Organomet. Chem., 489, 185 (1995) and references cited therein.
a) F. J. Feher, K. Rahimian, T. A. Budzichowski, and Z. W. Ziller,
Organometallics, 14, 3920 (1995) and references cited therein. b) F. J.
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(1989).
a) Y. I. Smolin, Kristallografiya, 15, 31 (1970). b) Y. I. Smolin, Y. F.
Shepelev, A. S. Ershov, D. Hoebbel, and W. Wieker, Kristallografiya,
29, 712 (1984). c) D. Hoebbel, A. Engelhardt, A. Samoson, K. Ujszaszy,
and Y. I. Smolin, Z. Anorg. Allg. Chem., 552, 236 (1987).
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H. Behbehani, B. J. Brisdon, M. F. Mahon, and K. Molloy, J.
Organomet. Chem., 469, 19 (1994).
Figure 2. An ORTEP representation of the structure of 2 (hydrogꢂen
ꢀ
atoms are omitted for clarity). Selected bond length (A) and angles ( ):
Ge1–O4#1 1.751(3), Ge1–O3 1.765(3), Ge1–O1 1.780(3), Ge1–C1
1.947(4), Ge2–O1 1.746(3), Ge2–O2 1.755(3), Ge2–C5 1.946(4), Ge2–
Cl1 2.1739(12), O4#1–Gel–O3 107.39(13), O4#1–Ge1–O1 106.43(13),
O3–Ge1–O1 107.68(13), O4#1–Ge1–C1 109.80(15), O3–Ge1–C1
112.05(16), O1–Ge1–C1 113.18(16).
5
6
7
After hydrolysis of 2 with aqueous NaOH in xylene at 140 ꢂC
for 3 h, the cage germasesquioxane 1 was formed in 18% isolated
yield together with polygermoxane. The formation of 1 suggests
that the germoxane 2 is clearly an intermediate for the formation
of 1.
The tert-butyl(dichloro)ethoxygermane, t-BuGe(OEt)Cl2,
prepared by t-BuGeCl3 and ethanol at room temperature for 2
weeks, was treated with water at 5 ꢂC for 3 h to give 3 as a sole
product. The product 3 was isolated by distillation in 31% yield.
1H NMR spectrum of 3 displayed two tert-butyl signals at 1.29
and 1.33 ppm in 1 : 2 ratio. 13C NMR of 3 showed four signals at
25.2, 25.5, 35.4, and 39.6 ppm. The fragment peak (Mþ-t-Bu)
with m=z 487 was observed. The NMR (1H and 13C{1Hg) and GC-
MS spectra of 3 disclosed it to be 1,3,5-tri-tert-butyl-1,3,5-
trichlorotrigermoxane. After hydrolysis of 3 for an additional
33 h, the anti-form ladder germoxane 2 was formed.
8
V. W. Day, W. G. Klemperer, V. V. Mainz, and M. Miller, J. Am. Chem.
Soc., 107, 8262 (1985).
P. A. Agaskar, J. Am. Chem. Soc., 111, 6858 (1989).
9
10 F. J. Feher, T. A. Budzichowski, K. Rahimian, and J. W. Ziller, J. Am.
Chem. Soc., 144, 3859 (1992) and references cited therein.
11 H. Tosaka, K. Yamaguchi, M. Orihara, N. Ide, and K. Otaki, Jpn. Kokai
Tokkyo Koho 87-24268 (1987); Chem Abstr., 107, 124570 (1987).
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107, 124563 (1987).
13 R. Beer, H. Burgy, G. Calzaferri, and I. Kamber, J. Electron Spectrosc.
Relat. Phenom., 44, 121 (1987).
14 H. Puff, S. Franken, and W. Schuh, J. Organomet. Chem., 256, 23
(1983).
15 Crystal data for 1a: C18H42Ge6O9; fw = 838.06; crystal size
3
ꢁ
0:40 Â 0:20 Â 0:20 mm ; triclinic, space group P1, Z = 2, a =
ꢀ
11.9140(11) A,
ꢀ
12.5490(11) A,
ꢀ
b
=
c
=
13.2720(15) A, ꢀ
=
ꢂ
ꢂ
ꢂ
ꢀ 3
63.855(4) , ꢁ = 64.205(5) , ꢂ = 89.764(5) ; V ¼ 1559:3ð3Þ A ,
Dcalcd = 1.784 g/cm3; Goodness of fit = 1.048, R = 0.0388 (Rall
=
0.0479 for 4280 reflections), Rw = 0.1243 for 3522 reflections with
I > 2ꢃðIÞ. Crystallographic data for 1a have been deposited with the
Cambridge Crystallographic Data Centre as supplementary publication
no. CCDC-192754.
16 Crystal data for 2: C24H54Cl2Ge6O8; fw = 977.11; crystal size
3
ꢁ
0:40 Â 0:30 Â 0:30 mm ; triclinic, space group P1, Z = 1, a =
ꢀ
10.2730(10) A,
ꢀ
ꢀ
b
=
10.8ꢂ580(10) A,
c
=
ꢂ 10.9450(10) A, ꢀ
=
ꢀ 3
ꢂ
65.663(5) , ꢁ = 71.909(5) , ꢂ = 63.960(5) ; V = 986.84(16) A ,
Dcalcd = 1.644 g/cm3; Goodness of fit = 1.133, R = 0.0354 (Rall = 0.031
for 2604 reflections), Rw = 0.1188 for 2469 reflections with I > 2ꢃðIÞ.
CCDC-192755.
A reasonable mechanism is that two cyclic germoxanes 3
having probably cis,trans-1,3,5-tri-tert-butyl-1,3,5-trichlorocy-
clotrigermoxane geometry join co-facially to form the anti-form