Synthesis and characterization of alkylgermasesquioxanes

Article abstract of DOI:10.1016/S0022-328X(02)02157-5

Alkyl (chloro)ethoxygermanes, RGe(OEt)_nCl_3-n (R = i-Pr, n = 0; R = t-Bu, n =0-3; R = cyclo-C₆H₁₁, n = 0) were hydrolyzed with aqueous NaOH in xylene at 130-140 °C to give cage hexakis(alkylgermasesquioxane)s, (RGe)₆O₉. These structures of cage (RGe)₆O₉ were fully confirmed by spectroscopic and X-ray diffraction methods. t-Butyldichloro(ethoxy)germane, t-BuGe(OEt)Cl₂, was carefully treated with water at 5 °C for 3 h to afford cis, trans -1,3,5-tri-t -butyl-1,3,5-trichlorocyclotrigermoxane, (t-BuClGeO)₃. Hydrolysis of (t-BuClGeO)₃ at 5 °C for additional 33 h gave a tricyclic anti-form ladder prepared by hydrolysis of t-butyl(chloro)diethoxygermane, t-BuGe(OEt)₂Cl, at 5 °C for 6 h, and its structure was determined by spectroscopic and X-ray diffraction analysis. The tricyclic ladder germoxane reacted with aqueous NaOH in xylene at 1300-140 °C for 3 h to afford hexakis(t-butylgermasesquioxane), (t-BuGe)₆O₉. The formation mechanism of the germasesquioxane, (t-BuGe)₆O₉ from t-butyl(chloro)ethoxygermanes, t-BuGe(OEt)_nCl_3-n (n = 0-3) is also discussed.

Full text of DOI:10.1016/S0022-328X(02)02157-5

Journal of Organometallic Chemistry 667 (2003) 135Á142
/
www.elsevier.com/locate/jorganchem
Synthesis and characterization of alkylgermasesquioxanes
Masato Nanjo, Takaomi Sasage, Kunio Mochida *
Department of Chemistry, Faculty of Science, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo 171-8588, Japan
Received 7 October 2002; received in revised form 20 November 2002; accepted 25 November 2002
Abstract
Alkyl(chloro)ethoxygermanes, RGe(OEt)nCl3ꢀn (Rꢁ
/
i-Pr, nꢁ
/
0; Rꢁ
/
t-Bu, nꢁ
/
0Á
/
3; Rꢁ
/
cyclo-C6H11, nꢁ0) were hydrolyzed
/
with aqueous NaOH in xylene at 130Á140 8C to give cage hexakis(alkylgermasesquioxane)s, (RGe)6O9. These structures of cage
/
(RGe)6O9 were fully confirmed by spectroscopic and X-ray diffraction methods. t-Butyldichloro(ethoxy)germane, t-BuGe(OEt)Cl2,
was carefully treated with water at 5 8C for 3 h to afford cis, trans-1,3,5-tri-t-butyl-1,3,5-trichlorocyclotrigermoxane, (t-
BuClGeO)3. Hydrolysis of (t-BuClGeO)3 at 5 8C for additional 33 h gave a tricyclic anti-form ladder 5,7-dichloro-1,3,5,7,9,11-hexa-
t-butyltricyclo[7.3.1.13,7]hexagermoxanes, (t-BuGe)6O8Cl2. The tricyclic ladder (t-BuGe)6O8Cl2 was also prepared by hydrolysis of
t-butyl(chloro)diethoxygermane, t-BuGe(OEt)2Cl, at 5 8C for 6 h, and its structure was determined by spectroscopic and X-ray
diffraction analysis. The tricyclic ladder germoxane reacted with aqueous NaOH in xylene at 130Á
hexakis(t-butylgermasesquioxane), (t-BuGe)6O9. The formation mechanism of the germasesquioxane, (t-BuGe)6O9 from t-
butyl(chloro)ethoxygermanes, t-BuGe(OEt)nCl3ꢀn (nꢁ0Á3) is also discussed.
# 2002 Elsevier Science B.V. All rights reserved.
/
140 8C for 3 h to afford
/
/
Keywords: Germoxane; Germasesquioxane; Structures; X-ray diffraction; Cage compound
1. Introduction
and co-workers first reported the hexakis(t-butylgerma-
sesquioxane), (t-BuGe)6O9 by hydrolysis of t-BuGeCl3,
and its structure was confirmed by X-ray diffraction
analysis [14]. In this paper, we describe the synthesis and
characterization of hexakis(alkylgermasesquioxane)s
and their intermediates in hydrolysis of alkyl(chlor-
o)ethoxygermanes by utilization of the difference in
reactivity between the chlorine and alkoxy groups on the
germanium atom.
Spherical organosilsesquioxanes with the formula
(RSiO1.5)n
and related compounds containing Siꢀ
/
O
bonds in a main chain have been a subject of consider-
able interest because of their unique structures, chemi-
cal, physical properties, and potential technological
utility [1]. Matsumoto and co-workers [2], and several
groups [3Á
sheet-like oligomers and polymers of (RSiO1.5 n
established their structures by X-ray analysis. They are
organometallic analogues of silicate anions,
(SinO2.5n
nꢀ. The modified silicate can be used as pre-
/7] reported the synthesis of cage, ladder, and
)
and
2. Results and discussion
)
ceramic building blocks [8], organolithic macromolecu-
lar materials [9], heterogeneous silica-supported metal
2.1. Preparation and structures of
hexakis(alkylgermasesquioxane)s (1)
catalyst [10] and potential photoresists [11Á13], and so
/
on. While the organosilsesquioxanes have been amply
investigated, there have been few reports on organoger-
masesquioxanes [14]. To the best of our knowledge, Puff
When a xylene solution of one mole equivalent of
alkyltrichlorogermane, RGeCl3 (Rꢁ
cyclo-C6H11 (c)) containing three mole equivalents of
NaOH in water was heated at 130Á140 8C for 3 h, the
/i-Pr (a), t-Bu (b),
/
corresponding hexakis(alkylgermasesuquioxane) ((R-
Ge)6O9, 1) were obtained as the sole products in isolated
* Corresponding author. Tel.: ꢂ
1029.
E-mail address: kunio.mochida@gakushuin.ac.jp (K. Mochida).
/
81-3-3986-0221; fax: ꢂ81-3-5992-
/
70Á98% yields.
/
0022-328X/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
doi:10.1016/S0022-328X(02)02157-5

136
M. Nanjo et al. / Journal of Organometallic Chemistry 667 (2003) 135Á142
/
hexakis(alkylgermasesquioxane)s, 1a and 1c, adopt
cage structures. Two six-membered Ge3O3 rings are
joined co-facially by Geꢀ
/
O bridges, generating three
further eight-membered Ge4O4 rings. The average Geꢀ
/
˚
O bond length in six-membered ring is 1.752 A, and that
˚
in eight-membered ring is 1.760 A. The average Oꢀ
/
Geꢀ
/
O bond angle in six- and eight-membered rings is 1088,
and that GeꢀOꢀGe bond angle is 1318 in six- and eight-
membered rings. The observed GeꢀO bond length, Oꢀ
GeꢀO and GeꢀOꢀGe bond angles for 1a and 1c are
consistent with those of 1b reported previously [14]. The
GeꢀO bond lengths of (Ph2GeO)3 and (t-Bu2GeO)3 are
1.77 and 1.78 A, respectively. The Oꢀ
OꢀGe bond angles of (Ph2GeO)3 and (t-Bu2GeO)3 are
107.4 and 128.6, and 107.0 and 133.08, respectively
[15,16]. The GeꢀO bond length of 1a and 1c is just a
little shorter than those of (Ph2GeO)3 and (t-Bu2GeO)3.
Ge bond angles of 1a and 1c
Concentration of the reaction mixture by evaporation
of xylene followed by recrystallization from diethyl ether
gave a colorless crystal with the composition of germox-
/
/
/
/
/
/
/
anes, (RGe)6O9 (1aÁc). These structures of germases-
/
quioxanes were fully established by spectroscopic (1H-,
13C-NMR, IR, and MS) and X-ray diffraction methods.
A xylene solution of one mole equivalent of t-butyl-
triethoxygermane, t-BuGe(OEt)3 containing three mole
/
˚
/
Geꢀ
/
O and Geꢀ
/
/
equivalents of NaOH in water at 130Á140 8C for 3 h
/
/
under similar reaction conditions also gave 1b in isolated
64% yield, together with small amounts of unidentified
products. The colorless crystal 1b was obtained by the
recrystallization from diethyl ether. The ORTEP drawings
of 1a and 1c are shown in Figs. 1 and 2. The crystal
structure of 1b, prepared by hydrolysis of t-BuGeCl3,
has been reported by Puff and co-workers [14].
The Oꢀ
/
Geꢀ
/
O and Geꢀ
/
Oꢀ
/
are somewhat wider, possibly due to distortion brought
about by the cage structures. In contrast to (R2GeO)3
(RꢁPh, t-Bu) where the Ge3O3 ring is invariably near-
/
planar, the two six-membered Ge3O3 rings in 1a and 1c
adopt a chair conformation. The bond angles about
germanium for 1a and 1c show some deviation from the
ideal tetrahedral value. The three eight-membered
Ge4O4 in 1a and 1c adopt a crown configuration with
the four oxygen atoms lying above the Ge4 plane.
In the hydrolysis reaction of RGeCl3 and RGe(OEt)3,
several germoxanes are postulated to be possible inter-
mediates for the formation of the cage germoxanes. To
obtain further information we attempted the spectro-
scopic detection of an intermediate species involved in
hydrolysis of RGeCl3 and RGe(OEt)3, but without
success. Therefore, we tried to isolate intermediates in
hydrolysis of t-butyl(chloro)ethoxygermane, t-BuGe-
H2O=NaOH
t-BuGe(OEt)3
1b
xylene; reflux; 3 h
Selected bond lengths, angles, and crystallographic
data are summarized in Tables 1, 2 and 4. The
(OEt)nCl3ꢀn (nꢁ
/
0Á3) by utilization of the difference
/
in reactivity between the chlorine and ethoxy groups on
the germanium atom.
2.2. Preparation and structures of tricyclic anti-form
ladder hexagermoxanes (2)
The tert-butyl(chloro)diethoxygermane, t-BuGe(O-
Et)2Cl, prepared by treatment of tert-butyltrichloroger-
mane, t-BuGeCl3 with ethanol in the presence of
stoichiometric amounts of pyridine at room temperature
for 2 weeks, was carefully hydrolyzed in ethanol at 5 8C
for 6 h. After GC examination of the disappearance of t-
BuGe(OEt)2Cl, the reaction mixture was concentrated
by evaporation of ethanol. The residue was dissolved in
benzene at 5 8C and the generated solids were filtered
off. Concentration of the organic layer by evaporation
of benzene followed by recrystallization from hexane
gave 5,7-dichloro-1,3,5,7,9-hexa-tert-butyltricyclo[7.3.
1.13,7]octagermoxane ((t-BuGe)6O8Cl2 2) in 29% iso-
Fig. 1. ORTEP drawing of 1a. Thermal ellipsoids are drawn at the 30%
probability level.
1
lated yield. The H-NMR spectrum of 2 displayed two

M. Nanjo et al. / Journal of Organometallic Chemistry 667 (2003) 135Á
/142
137
Table 1
˚
Selected bond lengths (A) and angles (8) of 1a
Bond lengths
Ge1ꢀ
Ge1ꢀ
Ge2ꢀ
Ge2ꢀ
Ge3ꢀ
Ge3ꢀ
/
O4
O1
O1
O2
O6
O2
1.746(4)
1.763(4)
1.751(3)
1.755(3)
1.750(3)
1.763(4)
Ge1ꢀ
Ge1ꢀ
Ge2ꢀ
Ge2ꢀ
Ge3ꢀ
Ge3ꢀ
/
O3
C1
O5
C4
O3
C7
1.758(4)
1.916(5)
1.751(3)
1.941(5)
1.760(4)
1.926(5)
/
/
/
/
/
/
/
/
/
/
Bond angles
O4ꢀ
O4ꢀ
O1ꢀ
O1ꢀ
O6ꢀ
O6ꢀ
/
Ge1ꢀ
Ge1ꢀ
Ge2ꢀ
Ge2ꢀ
Ge3ꢀ
Ge3ꢀ
/
O3
C1
O5
C4
O3
C7
107.95(18)
111.2(2)
O4ꢀ
O3ꢀ
O1ꢀ
O5ꢀ
O6ꢀ
O3ꢀ
/
Ge1ꢀ
Ge1ꢀ
Ge2ꢀ
Ge2ꢀ
Ge3ꢀ
Ge3ꢀ
/
O1
C1
O2
C4
O2
C7
108.27(17)
111.9(2)
O3ꢀ
O1ꢀ
O5ꢀ
O2ꢀ
O3ꢀ
O3ꢀ
/
Ge1ꢀ
Ge1ꢀ
Ge2ꢀ
Ge2ꢀ
Ge3ꢀ
Ge3ꢀ
/
O1
C1
O2
C4
O2
C7
107.26(17)
110.0(2)
/
/
/
/
/
/
/
/
109.68(17)
110.5(2)
/
/
107.65(17)
109.81(19)
109.00(18)
110.5(2)
/
/
108.72(17)
110.4(2)
/
/
/
/
/
/
/
/
108.47(18)
110.5(2)
/
/
/
/
107.68(17)
110.6(2)
/
/
/
/
/
/
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 indicated that germoxane 2
was a symmetrical structure. The structure of 2 had
determined unequivocally by X-ray crystallography.
Fig. 2. ORTEP drawing of 1c. Thermal ellipsoids are drawn at the 30% probability level.

138
M. Nanjo et al. / Journal of Organometallic Chemistry 667 (2003) 135Á142
/
Table 2
˚
Selected bond lengths (A) and angles (8) of 1c
Bond lengths
Ge1ꢀ
Ge1ꢀ
Ge2ꢀ
Ge2ꢀ
Ge3ꢀ
Ge3ꢀ
/
O7
O1
O8
O1
O2
O9
1.753(7)
1.768(6)
1.745(6)
1.761(7)
1.756(7)
1.765(7)
Ge1ꢀ
Ge1ꢀ
Ge2ꢀ
Ge2ꢀ
Ge3ꢀ
Ge3ꢀ
/
O3
C1
O2
C7
O3
C13
1.765(6)
1.920(9)
1.757(7)
1.942(9)
1.760(6)
1.936(9)
/
/
/
/
/
/
/
/
/
/
Bond angles
O7ꢀ
O7ꢀ
O8ꢀ
O8ꢀ
O2ꢀ
O2ꢀ
/
Ge1ꢀ
Ge1ꢀ
Ge2ꢀ
Ge2ꢀ
Ge3ꢀ
Ge3ꢀ
/
O3
C1
O2
C7
O3
C13
109.8(3)
107.2(3)
109.8(4)
106.4(3)
107.3(3)
111.1(4)
O7ꢀ
O3ꢀ
O8ꢀ
O2ꢀ
O2ꢀ
O3ꢀ
/
Ge1ꢀ
Ge1ꢀ
Ge2ꢀ
Ge2ꢀ
Ge3ꢀ
Ge3ꢀ
/
O1
C1
O1
C7
O9
C13
109.1(3)
113.3(3)
108.8(3)
111.1(4)
109.1(4)
112.5(4)
O3ꢀ
O1ꢀ
O2ꢀ
O1ꢀ
O3ꢀ
O9ꢀ
/
Ge1ꢀ
Ge1ꢀ
Ge2ꢀ
Ge2ꢀ
Ge3ꢀ
Ge3ꢀ
/
O1
C1
O1
C7
O9
C13
107.5(3)
109.9(3)
106.4(3)
114.3(4)
109.7(3)
107.1(4)
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
The ORTEP drawing is shown in Fig. 3 as an anti-form
ladder germoxane. Selected bond lengths, angles, and
crystallographic data are summarized in Tables 3 and 4.
structural parameters of 2 (e.g. Geꢀ
GeꢀOꢀGe angles, OꢀGeꢀ
those for 1. All these values are within the normal range,
showing that this molecule is strain-free.
A xylene solution of one mole equivalent of 2
containing 10 mol equivalents of NaOH in water was
/
O bond lengths,
/
/
/
/
O angels) are similar with
The average Geꢀ
membered rings is same (1.76 A). The average Oꢀ
is 1078; the average GeꢀOꢀGe bond angle is 126.58. The
/O bond length in the six- and eight-
˚
/
Geꢀ/O
/
/
Fig. 3. ORTEP drawing of 2. Thermal ellipsoids are drawn at the 30% probability level.

M. Nanjo et al. / Journal of Organometallic Chemistry 667 (2003) 135Á
/142
139
Table 3
˚
Selected bond length (A) and angles (8) of 2
Bond lengths
Ge1ꢀ
Ge1ꢀ
Ge2ꢀ
Ge2ꢀ
Ge3ꢀ
Ge3ꢀ
/
O4*
O1
O1
C5
1.751(3)
1.780(3)
1.746(3)
1.946(4)
1.768(3)
1.776(3)
Ge1ꢀ
Ge1ꢀ
Ge2ꢀ
Ge2ꢀ
Ge3ꢀ
Ge3ꢀ
/
O3
C1
O2
C1
O3
C9
1.765(3)
1.947(4)
1.755(3)
2.1739(12)
1.759(3)
1.939(4)
/
/
/
/
/
/
/O4
/
/O2
/
Bond angles
O4*ꢀ
O4*ꢀ
O1ꢀGe2ꢀ
O1ꢀGe2ꢀ
O4ꢀGe3ꢀ
O4ꢀGe3ꢀ
Ge2ꢀO1ꢀ
/
Ge1ꢀ
/
O3
107.39(13)
109.80(15)
108.32(13)
106.12(10)
108.59(13)
110.95(16)
128.13(16)
O4*ꢀ
O3ꢀGe1ꢀ
O1ꢀGe2ꢀ
O2ꢀGe2ꢀ
O4ꢀGe3ꢀ
O3ꢀGe3ꢀ
Ge2ꢀO2ꢀ
/
Ge1ꢀ
/
O1
106.43(13)
112.05(16)
114.97(17)
105.68(10)
106.90(14)
111.75(16)
125.70(16)
O3ꢀ
O1ꢀ
O2ꢀ
C5ꢀ
O3ꢀ
O2ꢀ
Ge1ꢀ
/
Ge1ꢀ
Ge1ꢀ
Ge2ꢀ
Ge2ꢀ
Ge3ꢀ
Ge3ꢀ
O3ꢀ
/
O1
C1
C5
107.68(13)
113.18(16)
113.14(17)
109.97(14)
107.13(13)
111.30(16)
127.80(15)
/
Ge1ꢀ
/C1
/
/
C1
C5
/
/
/
/O2
/
/
/
/
/
/Cl1
/
/
Cl1
O2
C9
/
/
Cl1
O2
/
/O3
/
/
/
/
/
/C9
/
/
/
/C9
/
/Ge1
/
/
Ge3
/
/Ge3
Table 4
Crystallographic data for 1a, 1c, and 2
1a
1c
2
Formula
Molecular
weight
C18H42Ge6O9
838.06
C36H66Ge6O9
1078.43
C24H54Cl2Ge6O8
977.11
Crystal
Colorless prism Colorless prism Colorless prism
description
Crystal size
(mm)
0.40ꢃ
0.20
/
0.20ꢃ
/
0.20ꢃ
0.20
/
0.20ꢃ
/
0.40ꢃ
0.30
Triclinic
/
0.30ꢃ
/
Crystal system Triclinic
¯
Orthorhombic
P212121
11.6520(4)
17.6130(6)
21.2470(9)
90
2.3. Preparation of cyclic germoxanes (3)
The tert-butyldichloro(ethoxy)germane,
¯
Space group
˚
P/
1/
P/
1
/
a (A)
˚
11.9140(11)
12.5490(11)
13.2720(15)
64.205(5)
1559.9(3)
2
10.2730(10)
10.8580(10)
10.9450(10)
71.909(5)
986.84(16)
1
t-Bu-
b (A)
˚
c (A)
Ge(OEt)Cl2, prepared by treatment of t-BuGeCl3 with
ethanol at room temperature for 2 weeks, was in control
of hydrolysis at 5 8C for 3 h to give a new cyclic
germoxane, (t-BuGeOCl)3 (3). The cyclic germoxane 3
b (8)
3
V (A )
˚
4360.5(3)
4
Z
Radiation (l
˚
(A))
MoÁ
(0.71070)
295
/
Ka
MoÁ
(0.71070)
200
/
Ka
MoÁKa
(0.71070)
200
/
1
was isolated by distillation in 31% yield. The H-, 13C-
NMR examination of 3 showed a single isomer; 1H-
NMR (CDCl3) 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. A
Temperature
(K)
Dcalc (g cmꢀ3
Unique
reflections
Goodness-of-
fit
)
1.784
4280
1.643
3511
1.644
2604
fragment peak (Mꢂꢀ
/
t-Bu) with m/z 487 was observed.
1.048
1.041
1.113
The NMR (1H and 13C{1H}) and GCÁ
/MS spectra
R
0.0479
0.0388
0.0443
0.0377
0.0371
0.0354
indicate that 3 exists as a single isomer. The geometry is
cis,trans-1,3,5-tri-tert-butyl-1,3,5-trichlorocyclotriger-
moxane.
Rw
heated at 130Á
reaction mixture by evaporation of xylene, the crude
products were identified by NMR, GC, and GCÁMS
/
140 8C for 3 h. After concentration of the
/
spectra. The cage germoxane 1b was formed in 18%
isolated yield together with oligogermoxanes. The
structure of the oligogermoxanes may suppose to be
After careful control of hydrolysis of 3 at 5 8C for an
additional 33 h, the anti-form ladder germoxane 2 was
formed in 45% GC yield. A small amount of the cage
oligomers of 2 from NMR, GCÁMS, and GPC data.
/
The presence of 1b suggests that the anti-form ladder
germoxane 2 is clearly an intermediate for the formation
of cage germoxanes, (t-BuGe)6O9.
germoxane 1b was also detected by GCÁMS.
/

140
M. Nanjo et al. / Journal of Organometallic Chemistry 667 (2003) 135Á142
/
H2O=EtOH
3. Experimental
3
2
5
ꢀC; 33 h
3.1. General methods
The formation of 1b was identified with NMR, GC,
and GCÁMS spectra in comparison with those of
authentic sample. The presence of 2 suggests that the
germoxane 3 is clearly an intermediate for the formation
of tricyclic anti-form ladder germoxanes, (t-Bu-
Ge)6O8Cl2.
/
The NMR spectra were obtained on a Varian Unity
Inova 400 MHz NMR spectrometer. The GCÁMS
spectra were measured on a JEOL JMS-DX 303 mass
spectrometer. Gas chromatography was performed on a
Shimadzu GC 8A with 1 m 20% SE30 column. Liquid
chromatography was performed on a Twincle with an
Asahipak GS 310 column. X-ray crystallographic data
/
and diffraction intensities were collected on
MacScience DIP2030 diffractometer utilizing graphite-
a
2.4. Reaction mechanism
˚
Ka (lꢁ0.71073 A) radiation. The
monochromated MoÁ
/
/
The simplest rationalization of the above results is
shown below. At first, t-butyldichloro(ethoxy)germane,
t-BuGe(OEt)Cl2, may be hydrolyzed to give t-butyldi-
chloro(hydroxyl)germane, t-BuGe(OH)Cl2, by the dif-
ference in reactivity between the chlorine and ethoxy
groups on the germanium atom and then, cyclic
trigermoxane, (t-BuGeOCl)3, 3 is formed by the dehy-
drative condensation of t-BuGe(OH)Cl2. The cycliza-
tion product 3 exists as cis,trans geometry. No all-cis
isomer is formed probably due to the steric hindrance of
t-butyl groups. Subsequently, two 3 easily couple co-
facially to give a tricyclic anti-form ladder 5,7-dichloro-
1,3,5,7,9,11-hexa-t-butyltricyclo[7.3.1.13,7]hexagermox-
ane 2, which undergoes isomerization under these
experimental conditions to give a syn-isomer after the
structures were solved by direct methods using the
program system SIR-92. A refinement was performed
by full-matrix least-square using program a SILICON
Graphics O2 with maXus.
3.2. Materials
i-PrGeCl3 [17] and cyclo-C6H12GeCl3 [18], were
prepared as reported in the literature.
3.3. Preparation of tert-butyltrichlorogermane (t-
BuGeCl3)
To a solution of trichlorogermane (46.0 g, 0.25 mol)
in Et2O (125 ml) was added a Et2O solution (25 ml) of
tert-butyl chloride (23.4 g, 0.25 mol) at 0 8C. The
mixture was stirred at 0 8C for 1 day and the solution
was concentrated to ca. 10 ml. After pentane (50 ml) was
slowly added, colorless solid was formed. Recrystalliza-
tion from Et2O formed pure t-BuGeCl3 (38.0 g, 0.15
mol, 60%) [17].
cleavage of Geꢀ/O bond in the eight-membered ring.
Further condensation occurs to give a most stable cage
germoxane 1b after several steps (Scheme 1).
In summary, we have synthesized cage hexakis(alk-
ylgermasesquioxane)s, (RGe)6O9, (Rꢁ
clo-C6H11), from hydrolysis of RGe(OEt)nCl3ꢀn (Rꢁ
i-Pr, nꢁ0; Rꢁt-Bu, nꢁ0Á3; Rꢁcyclo-C6H11, nꢁ0),
/i-Pr, t-Bu. cy-
/
/
/
/
/
/
/
and these structures were determined by spectroscopic
and X-ray diffraction methods. Cyclic germoxanes are
hydrolyzed to form tricyclic anti-form ladder germox-
anes, and additional hydrolysis of tricyclic germoxanes
afford cage germoxanes.
3.4. Preparation of tert-butyldichloro(ethoxy)germane,
t-BuGe(OEt)Cl2
t-BuGeCl3 (0.1 g, 0.4 mmol) and dry EtOH (20 ml)
were placed in two-necked 100 ml flask. The mixture
was stirred at room temperature (r.t.) for 2 weeks. Crude
t-BuGe(OEt)Cl (ꢀ
/
70%) was obtained by distillation.
7.0 Hz, 3 H), 1.05 (s, 9
1H-NMR (d, C6H6) 0.85 (t, Jꢁ
/
H), 3.94 (q, Jꢁ
/
7.0 Hz, 2 H). GCÁMS (70 eV) m/z
/
(relative intensity) 246 (Mꢂ, 13), 231 (34), 211 (13), 201
(56), 189 (24), 157 (100).
3.5. Preparation of tert-butyl(chloro)diethoxygermane,
t-BuGe(OEt)2Cl
To a solution of t-BuGeCl3 (7.08 g, 0.03 mol) in dry
EtOH (10 ml) was added pyridine (2.40 g, 0.03 mol) at
r.t. The mixture was stirred at r.t. for 1 week. Pure t-
BuGe(OEt)2Cl (1.09 g, 4.3 mmol, 14% yield) was
obtained by distillation, b.p. 50 8C/50 mmHg. 1H-
Scheme 1.

M. Nanjo et al. / Journal of Organometallic Chemistry 667 (2003) 135Á
/142
141
NMR (d, C6H6) 0.93 (t, Jꢁ
3.94 (q, Jꢁ
7.0 Hz, 4 H); 13C-NMR (d, C6H6) 18.8,
25.9, 26.7, 61.3. GCÁMS (70 eV) m/z (relative intensity)
/
7.0 Hz, 6 H), 1.12 (s, 9 H),
3.9. Hydrolysis of tert-butyltriethoxygermane
/
/
Aqueous NaOH (NaOH, 0.24 g, H2O, 30 ml) was
added to a stirred solution of t-BuGe(OEt)3 (0.62 g, 2.26
mmol) in xylene (15 ml). The mixture was heated to
reflux for 3 h. The organic layer was washed with water.
The aqueous phase was extracted with xylene. The
combined organic phase was dried over anhydrous
magnesium sulfate and evaporated. The residue was
recrystallized from Et2O to give hexakis(t-butylgerma-
sesquioxane) 1b (0.22 g, 0.24 mmol, 64%). 1H-NMR (d,
CDCl3) 1.22 (s); 13C-NMR (d, CDCl3) 26.5, 30.2.
256 (Mꢂ, 4), 231 (34), 211 (53), 199 (64), 164 (25), 154
(100). Found: C, 37.90; H, 7.25. Calc. for C8H19ClGeO2:
C, 37.64; H, 7.50%.
3.6. Preparation of tert-butyltriethoxygermane, t-
BuGe(OEt)3
To a solution of t-BuGeCl3 (7.12 g, 0.03 mol) in dry
EtOH (100 ml) was added pyridine (7.22 g, 0.10 mol) at
r.t. The mixture was stirred at r.t. for 5 days. Pure t-
BuGe(OEt)3 (3.28 g, 12.4 mmol, 41% yield) was
obtained by distillation, b.p. 70 8C/24 mmHg. 1H-
3.10. Hydrolysis of t-butyl(ethoxy)dichlorogermane
NMR (d, C6H6) 1.24 (s, 9 H), 1.25 (t, Jꢁ
H), 3.94 (q, Jꢁ
7.0 Hz, 6 H); 13C-NMR (d, C6H6) 18.5,
25.9, 33.4, 61.1. GCÁMS (70 eV) m/z (relative intensity)
/
7.0 Hz, 9
Water (3.0 mg, 0.17 mmol) was added to a stirred
solution of t-BuGe(OEt)Cl2 (0.03 g, 0.13 mol) in EtOH
at 5 8C for 3 h. A pure cis,trans-1,2,3-tri-t-butyl-1,2,3-
trichlorocyclotrigermoxane, (t-BuGeOCl)3, (3) was ob-
/
/
266 (Mꢂ, 2), 251 (4), 221 (14), 209 (28), 164 (100), 119
(60). Found: C, 45.70; H, 8.95. Calc. for C10H24GeO3:
C, 45.35; H, 9.13%.
1
tained. H-NMR (d, CDCl3) 1.29 (s, 9 H), 1.33 (s, 18
H); 13C-NMR (d, CDCl3) 25.2, 25.5, 35.4, 39.6. GCÁ
/
MS (70 eV) m/z (relative intensity) 487 (Mꢂꢀ
Bu, 100),
430 (80), 415 (20), 395 (14), 372 (11), 338 (8), 268 (5)709
(9), 660 (9).
/
3.7. Hydrolysis of iso-propyltrichlorogermane
Aqueous NaOH (NaOH, 3.62 g, H2O, 80 ml) was
added to a stirred solution of i-PrGeCl3 (7.11 g, 0.03
mol) in xylene (200 ml). The mixture was heated to
reflux for 3 h. The organic layer was washed with water.
The aqueous phase was extracted with xylene. The
combined organic phase was dried over anhydrous
magnesium sulfate and evaporated. The residue was
recrystallized from Et2O to give hexakis(i-propylgerma-
sesquioxane) 1a (3.90 g, 4.65 mmol, 93%). 1H-NMR (d,
3.11. Hydrolysis of t-butyldiethoxy(chloro)germane
Water (0.14 g, 7.6 mmol) was added to a stirred
solution of t-BuGe(OEt)2Cl (0.97 g, 3.5 mmol) in EtOH
(20 ml) at 5 8C for 6 h. After the solvent was evaporated,
the residue was dissolved in C6H6. The generated solids
were filtered off. Concentration of the organic layer by
evaporation of C6H6 followed by recrystallization from
hexane gave a pure 5,7-dichloro-1,3,5,7,9-hexa-tert-
butyltricyclo[7.3.1.13,7]octagermoxane, (t-BuGe)6O8Cl2
CDCl3) 1.25 (d, Jꢁ
/
7.5 Hz, 36 H), 1.73 (sept, Jꢁ7.5 Hz,
/
6 H); 13C-NMR (d, CDCl3) 17.4, 21.6; IR (KBr, cmꢀ1
)
499.5, 794.6, 875.6, 1465.8, 2869.9. GCÁMS (70 eV) m/z
/
(relative intensity) 795 (Mꢂ, 100), 752 (4), 709 (9), 660
(9); Found: C, 25.67; H, 5.23. Calc. for C18H42Ge6O9: C,
25.79; H, 5.05%.
1
(2), in 29.1% yield (0.18 g, 0.18 mmol). H-NMR (d,
C6D6) 1.29 (s, 18 H), 1.32 (s, 36 H); 13C-NMR (d, C6D6)
25.9, 26.5, 30.5, 34.7. m.p. 233Á
/
234 8C. GCÁ
/
MS (70 eV)
m/z (relative intensity) 921 (Mꢂꢀ
/Bu, 77), 827 (15), 57
3.8. Hydrolysis of cyclo-hexyltrichlorogermane
(100). Found: C, 29.75; H, 5.43. Calc. for
C24H54Cl2Ge6O8: C, 29.50; H, 5.57%.
Aqueous NaOH (NaOH, 3.70 g, H2O, 80 ml) was
added to a stirred solution of cyclo-HexGeCl3 (7.99 g,
0.03 mol) in xylene (200 ml). The mixture was heated to
reflux for 3 h. The organic layer was washed with water.
The aqueous phase was extracted with xylene. The
combined organic phase was dried over anhydrous
magnesium sulfate and evaporated. The residue was
recrystallized from Et2O to give hexakis(cyclo-hexylger-
3.12. Hydrolysis of 5,7-dichloro-1,3,5,7,9-hexa-tert-
butyltricyclo[7.3.1.13,7]octagermoxane
Aqueous NaOH (NaOH, 4 mg, H2O, 1 ml) was added
to a stirred solution of (t-BuGe)6O8Cl2 (0.01 g, 0.01
mmol) in xylene (10 ml). The mixture was heated to
reflux for 3 h. After the solvent was evaporated, the
residue was obtained. A pure (t-BuGe)6O9 (1.8 mg, 18%
yield) was isolated by preparative GPC. Polygermoxane,
1
masesquioxane) 1c (3.77 g, 3.50 mmol, 70%). H-NMR
(d, CDCl3) 1.3Á
1.9 (m); 13C-NMR (d, CDCl3) 26.3,
/
26.9, 27.2, 32.4; IR (KBr, cmꢀ1) 489.9, 796.5, 1448.4,
2850.6, 2925.8. Found: C, 40.49; H, 6.53. Calc. for
C36H66Ge6O9: C, 40.09; H, 6.17%.
1
[(t-BuGe)6O9]n (4.6 mg) was also obtained. H-NMR
(d, C6D6) 1.25 (s); 13C-NMR (d, C6D6) 2.6, 29.6.

142
M. Nanjo et al. / Journal of Organometallic Chemistry 667 (2003) 135Á142
/
(e) M. Unno, A. Suto, H. Matsumoto, J. Am. Chem. Soc. 124
(2002) 1574.
3.13. X-ray crystallography
[3] U. Dittmar, B.J. Hendan, U. Floerke, H.C. Marsmann, J.
Organomet. Chem. 489 (1995) 185 (and references cited therein).
[4] (a) F.J. Feher, K. Rahimian, T.A. Budzichowski, Z.W. Ziller,
Organometallics 14 (1995) 3920 (and references cited therein);
(b) F.J. Feher, D.A. Newman, J.F. Walzer, J. Am. Chem. Soc.
111 (1989) 1741.
Crystallographic data for 1a, 1c, and 2 are summar-
ized in Table 4. Crystallographic data for 1a, 1b, and 2
have been deposited with the Cambridge Crystallo-
graphic Data Centre as supplementary publication no.
CCDC-192754, 193021, and 192755, respectively.
[5] (a) Y.I. Smolin, Kristallografiya 15 (1970) 31;
(b) Y.I. Smolin, Y.F. Shepelev, A.S. Ershov, D. Hoebbel, W.
Wieker, Kristallografiya 29 (1984) 712;
Acknowledgements
(c) D. Hoebbel, A. Engelhardt, A. Samoson, K. Ujszaszy, Y.I.
Smolin, Z. Anorg. Allg. Chem. 552 (1987) 236.
[6] J.F. Brown, L.H. Vogt, J. Am. Chem. Soc. 87 (1965) 4313.
[7] H. Behbehani, B.J. Brisdon, M.F. Mahon, K. Molloy, J.
Organomet. Chem. 469 (1994) 19.
The authors thank Mitsubishi Material Co., Ltd., and
Asai Germanium Research Institute Co., Ltd., for
providing us tetrachlorogermane (GeCl4) and trichlor-
ogermane (HGeCl3), respectively.
[8] V.W. Day, W.G. Klemperer, V.V. Mainz, M. Miller, J. Am.
Chem. Soc. 107 (1985) 8262.
[9] P.A. Agaskar, J. Am. Chem. Soc. 111 (1989) 6858.
[10] F.J. Feher, T.A. Budzichowski, K. Rahimian, J.W. Ziller, J. Am.
Chem. Soc. 144 (1992) 3859 (and references cited therein).
[11] H. Tosaka, K. Yamaguchi, M. Orihara, N. Ide, K. Otaki,
Japanese Patent 87, 24268 (1987); Chem Abstr. 107 (1987) 124570.
[12] M. Uchida, Japanese Patent 87, 15560 (1987); Chem. Abstr. 107
(1987) 124563.
References
[1] (a) R.H. Baney, M. Itoh, A. Sakakibara, T. Suzuki, Chem. Rev.
95 (1995) 1409;
(b) F. Feher, in: B. Arkles (Ed.), Silicon, Germanium, Tin, and
Lead Compounds. Metal Alkoxides, Diketonates and Carbox-
ylates (and references cited therein), Gelest, Tullytown, 1998, pp.
[13] R. Beer, H. Burgy, G. Calzaferri, I. Kamber, J. Electron
Spectrosc. Relat. Phenom. 44 (1987) 121.
[14] H. Puff, S. Franken, W. Schuh, J. Organomet. Chem. 256 (1983)
23.
43Á59.
/
[2] (a) M. Unno, B.A. Shamsul, H. Saito, H. Matsumoto, Organo-
metallics 15 (1996) 2413;
[15] L. Roß, M. Drager, Chem. Ber. 115 (1982) 615.
[16] H. Puff, S. Franken, W. Schuh, W. Schwab, J. Organomet. Chem.
254 (1989) 33.
(b) M. Unno, K. Takada, H. Matsumoto, Chem. Lett. (1998)
489.;
(c) M. Unno, B.A. Shamsul, M. Arai, K. Takada, H. Matsumoto,
Appl. Organomet. Chem. 13 (1991) 1;
[17] P.S. Ponomarenko, J. Organomet. Chem. 12 (1968) 115.
[18] R. Reimschneider, K. Menge, P. Klang, Z. Naturforsch. Teil B 11
(1956) 115.
(d) M. Unno, A. Suto, K. Takada, H. Matsumoto, Bull. Chem.
Soc. Jpn. 73 (2000) 215;