Preparation and structural characterization of bis[tris(trimethylsilyl)-germyl]zinc, [(Me3Si)3Ge]2Zn

Article abstract of DOI:10.1246/bcsj.76.1261

Bis[tris(trimethylsilyl)germyl]zinc, [(Me₃Si)₃Ge]₂Zn, was prepared by the reaction of [tris(trimethylsilyl)germyl]lithium, (Me₃Si)₃GeLi(thf), with zinc chloride, ZnCl₂, and by the reaction of tris(trimethylsilyl)germane, (Me₃Si)₃GeH, with diethylzinc, Et₂Zn. The molecular structure of [(Me₃Si)₃Ge]₂Zn was determined by spectroscopic and X-ray diffraction methods. In [(Me₃Si)₃Ge]₂Zn, the two tris(trimethylsilyl)germyl ligands, (Me₃Si)₃Ge, are bonded in a linear fashion to the zinc atom and are staggered with respect to each other. The reactions of bis(germyl)zinc with substrates were also examined.

Full text of DOI:10.1246/bcsj.76.1261

Ó 2003 The Chemical Society of Japan
Bull. Chem. Soc. Jpn., 76, 1261–1264 (2003) 1261
Preparation and Structural Characterization of Bis[tris(trimethylsilyl)-
germyl]zinc, [(Me3Si)3Ge]2Zn
ꢀ
ꢀ
Masato Nanjo, Takashi Oda, and Kunio Mochida
Department of Chemistry, Faculty of Science, Gakushuin University,
1-5-1 Mejiro, Toshima-ku, Tokyo 171-8588
(Received December 26, 2002)
Bis[tris(trimethylsilyl)germyl]zinc, [(Me3Si)3Ge]2Zn, was prepared by the reaction of [tris(trimethylsilyl)germyl]-
lithium, (Me3Si)3GeLi(thf), with zinc chloride, ZnCl2, and by the reaction of tris(trimethylsilyl)germane, (Me3Si)3GeH,
with diethylzinc, Et2Zn. The molecular structure of [(Me3Si)3Ge]2Zn was determined by spectroscopic and X-ray dif-
fraction methods. In [(Me3Si)3Ge]2Zn, the two tris(trimethylsilyl)germyl ligands, (Me3Si)3Ge, are bonded in a linear
fashion to the zinc atom and are staggered with respect to each other. The reactions of bis(germyl)zinc with substrates
were also examined.
The chemistry of organozinc compounds has been a major
research theme in organic synthesis and organometallic
2(Me3Si)3GeLi(thf)3 þ ZnCl2
chemistry.1 Despite the large number of reports on organozinc
ꢁꢁꢁꢁꢁꢁ! [(Me3Si)3Ge]2Zn
diethyl ether
ð1Þ
r.t., 1 day
1
reagents, far less attention has been devoted to silyl- or ger-
myl-substituted zinc compounds. Up to now, four bis(silyl)-
zinc derivatives {(t-Bu3Si)2Zn,2a [(Me3Si)3Si]2Zn,2b (Me3-
Si)2Zn,2c and (Ph3Si)2Zn2dg have been prepared, and only
two X-ray crystal structures of (t-Bu3Si)2Zn and [(Me3-
Si)3Si]2Zn have been determined. Although a few examples
of bis(germyl)zinc, (Ph3Ge)2Zn and (Et3Ge)2Zn, are
known,3a{c no solid state structure, or few reactivities, of
bis(germyl)zinc derivatives have been reported.
In this report we describe the first successful isolation of
bis[tris(trimethylsilyl)germyl]zinc, [(Me3Si)3Ge]2Zn (1), pre-
pared by several methods, and its structural characterization
by X-ray diffraction analysis. Some reactions of the bis(ger-
myl)zinc 1 with substrates are also examined.
The treatment of [tris(trimethylsilyl)germyl]zinc chloride
solvated by THF, (Me3Si)3GeZnCl(thf),5 which was prepared
by the reaction of ZnCl2 with one molar amount of
(Me3Si)3GeLi(thf), with additional (Me3Si)3GeLi(thf)3 in di-
ethyl ether at room temperature for 1 h, also gave bis(germyl)-
zinc 1 in 93% isolated yield. This result suggests that (Me3-
Si)3GeZnCl(thf) is an intermediate in the formation of the
bis(germyl)zinc 1 by the reaction of ZnCl2 with two molar
amounts of (Me3Si)3GeLi(thf):
(Me3Si)3GeZnCl(thf) þ (Me3Si)3GeLi(thf)3 ꢁꢁꢁꢁꢁꢁ! 1
diethyl ether
r.t., 1 day
ð2Þ
Results and Discussion
Two molar amounts of tris(trimethylsilyl)germane,
(Me3Si)3GeH, reacted with diethylzinc, Et2Zn, in diethyl ether
(or THF) at room temperature for 1 day to give bis(germyl)-
zinc 1 quntitatively:
Preparation of Bis[tris(trimethylsilyl)germyl]zinc,
[(Me3Si)3Ge]2Zn. Bis[tris(trimethylsilyl)germyl]zinc, [(Me3-
Si)3Ge]2Zn, 1 was prepared by several methods. The treat-
ment of zinc chloride (ZnCl2) with two molar amounts of
[tris(trimethylsilyl)germyl]lithium solvated by tetrahydrofuran
(THF), (Me3Si)3GeLi(thf)3,4 prepared by the reaction of tetra-
kis(trimethylsilyl)germane, (Me3Si)4Ge, with THF solution of
MeLi, in diethyl ether at room temperature for 1 day afforded
colorless crystals with a composition of [(Me3Si)3Ge]2Zn (1)
in 83% isolated yield. 1H, 13C, and 29Si NMR examinations
of a C6D6 solution of the colorless crystals 1 revealed a single
assigned to the trimethylsilyl group (Me3Si). No coordinating
THF in 1 was observed. The symmetrical bis(germyl)zinc 1
2(Me3Si)3GeH þ Et2Zn ꢁꢁꢁꢁꢁꢁ! 1
diethyl ether
ð3Þ
r.t., 1 day
This method is experimentally easier and gives higher yields
of 1 than the ZnCl2–(Me3Si)3GeLi(thf) methods. Attempts
to prepare ethyltris(trimethylsilyl)germylzinc, (Me3Si)3GeZn-
Et, as an intermediate in the formation of the bis(germyl)zinc
1 have failed, probably due to its thermodynamically instabil-
ity.
ꢂ
could be recrystallized from pentane at ꢁ20 C as colorless
needles that are very flammable in air. The bis(germyl)zinc
1 are thermally stable for prolonged periods in the absence
of air at room temperature.
The formation and the mechanism of bis(triphenylgermyl)-
zinc, (Ph3Ge)2Zn, by a treatment of Et2Zn with triphenylger-
ꢂ
mane, Ph3GeH, in diglyme at 150 C for 1.5 h were reported

1262 Bull. Chem. Soc. Jpn., 76, No. 6 (2003)
Preparation and Reactions of Bis(germyl)zinc
ꢀ
Table 1. The Selected Bond Lengths (A) and Bond Angles
(ꢂ) of [(Me3Si)3Ge]2Zn (1)
Ge1–Si1
Ge1–Zn1
Zn1–Ge1
Si1–C2
Si2–C6
Si2–C5
Si3–C9
2.3788(6)
2.3818(2)
2.3818(3)
1.876(3)
1.867(3)
1.880(3)
1.879(3)
Ge1–Si3
Ge1–Si2
Si1–C3
Si1–C1
Si2–C4
Si3–C8
Si3–C7
2.3761(7)
2.3863(6)
1.875(3)
1.879(3)
1.869(3)
1.869(3)
1.879(3)
ꢀ
Si3–Ge1–Si1
Si1–Ge1–Zn1
Si1–Ge1–Si2
Ge1–Zn1–Ge1
C3–Si1–C1
C3–Si1–Ge1
C1–Si1–Ge1
C6–Si2–C5
C6–Si2–Ge1
C5–Si2–Ge1
C8–Si3–C7
C8–Si3–Ge1
C7–Si3–Ge1
112.55(2)
107.842(17) Si3–Ge1–Si2
Si3–Ge1–Zn1 107.599(18)
110.29(2)
Zn1–Ge1–Si2 104.495(17)
113.54(2)
179.999(2)
109.18(15)
109.09(9)
112.22(9)
108.11(16)
111.23(9)
112.25(9)
108.52(13)
109.93(10)
111.30(9)
ꢀ
C3–Si1–C2
C2–Si1–C1
C2–Si1–Ge1
C6–Si2–C4
C4–Si2–C5
C4–Si2–Ge1
C8–Si3–C9
C9–Si3–C7
C9–Si3–Ge1
108.07(13)
108.54(12)
109.66(9)
108.91(18)
107.78(19)
108.47(10)
108.01(15)
108.11(13)
110.88(9)
the experimental section.
The crystal structure of bis(germyl)zinc 1 is differrent from
that of (Me3Si)3GeZnCl(thf). The germylzinc chloride has di-
meric structures consisiting of two ꢀ-chlorine atoms.5
Reactivity. The reactions of bis(germyl)zinc 1 with some
electrophiles in diethyl ether under an argon atmosphere in a
Schlenk tube were examined at room temperature. All of
the products were identified by GC, GC-MS, and NMR spectra
compared with those of authentic samples. The yields of the
products were determined by GC with internal-standard meth-
ods.
Fig. 1. An ORTEP representation of bis[(tris(trimethylsi-
lyl)germyl]zinc 1 (hydrogen atoms are omitted for clarity).
The bis(germyl)zinc 1 could be preserved under an argon at-
mosphere at room temperature. The hydrolysis of bis(germyl)-
zinc 1 in diethyl ether with deoxygenated water proceeded ex-
tremely slowly to give tris(trimethylsilyl)germane, (Me3Si)3-
GeH, in only 38% yield after 7 days of stirring under an argon
atmosphere at room temperature. Unreacted 1 still remained.
The addition of hydrochloric acid of 1 under an argon atmo-
sphere for 2 h completely promoted the hydrolysis reaction
to give (Me3Si)3GeH. This reactivity contrasts with that of
the analogous silyl derivatives, [(Me3Si)3Si]2Zn,2b which ap-
pear to be more reactive. The bis(germyl)zinc 1 did not react
with an excess amount of Me3SiCl at all for 2 days. Unreacted
1 was completely recovered. On the other hand, the bis(ger-
myl)zinc 1 reacted easily with I2 to afford iodotris(trimethylsi-
lyl)germane, (Me3Si)3GeI in 91% yield after 3 h of stirring un-
der an argon atmosphere at room temperature. In 4 h of
stirring under an argon atmosphere, the reaction of bis(ger-
myl)zinc 1 with MeI proceeded to form (Me3Si)3GeI in 93%
yield. The reaction took place even in a dark condition.
The presence of (Me3Si)3GeI suggests that Me2Zn is simulta-
neously formed as a reactive species. Further stirring for 3
days led to the final formation of methyltris(trimethylsi-
lyl)germane, (Me3Si)3GeMe (50% yield), with the precipita-
tion of ZnI2 salt:
by Bychkov and co-workers.3b
Several studies on the preparation of a binary group 12-ele-
ment germyl derivatives by reactions of organogermanium hy-
drides with diorganometals have been reported.6{8 The easi-
ness of the reaction is in the order Zn < Cd < Hg.
Crystal Structure. The molecular structure of 1 was un-
equivocally confirmed by an X-ray diffraction analysis. The
molecular structure of 1 is shown in Fig. 1. The bis(germyl)-
zinc 1 has a crystallographic inversion center on the zinc atom.
The two tris(trimethylsilyl)germyl, (Me3Si)3Ge, ligands are
bonded in a linear fashion to the zinc atom, and are staggered
with respect to each other, as shown in Fig. 1. The structual
features are similar to that found in [(Me3Si)3Si]2Zn.2b The
ꢀ
bond angle of Ge1–Zn–Ge1 is 180ꢂ. No solvent coordinating
to the zinc metal of 1 was observed due to the steric hindrance
of the (Me3Si)Ge ligand. The Ge–Zn bond length of 2.3818(3)
ꢀ
A is somewhat longer than that found in (Me3Si)3Ge-
ZnCl(thf).5 The average Si–Ge–Zn angle of 106.65(1) A is
ꢀ
smaller than that found in Si–Ge–Si angles (av 112.13(2)ꢂ).
ꢀ
The mean Ge–Si bond length of 2.3804 A is quite normal.
The selected bond lengths and bond angles of 1 are summa-
rized in Table 1. Crystallographic data of 1 are summarized in

M. Nanjo et al.
Bull. Chem. Soc. Jpn., 76, No. 6 (2003) 1263
Table 2. Reactions of Bis[tris(trimethylsilyl)germyl]zinc
(1) with Substrates in Diethyl Ether
ness-of-fit indicator were 0.0399 (Rw ¼ 0:1255 for all data,
3506 reflections) and 1.141, respectively, for 3357 reflcetion with
I > 2ꢆðIÞ.
Substrate
Reaction conditions
Products (Yield/%)
Preparation of Bis[tris(trimethylsilyl)germyl]zinc (1) by
Treatment of [Tris(trimethylsilyl)germyl]lithium with Zinc
Chloride. Zinc chloride, ZnCl2, (0.13 g, 0.95 mmol) reacted with
two molar amounts of [tris(trimethylsilyl)germyl]lithium solvated
by THF, (Me3Si)3GeLi(thf)3 (0.88 g, 1.70 mmol) containing di-
ethyl ether (10 mL) in a Schlenk tube at room temperature for 1
day under an argon atmosphere. The concentration of the reaction
mixture by the removal of diethyl ether, followed by recrystalliza-
tion from pentane at ꢁ20 ꢂC, gave colorless crystals flammable in
air with a composition of bis[tris(trimethylsilyl)germyl]zinc,
[(Me3Si)3Ge]2Zn (1) (0.52 g, 0.80 mmol) in 83% yield. 1H NMR
(C6D6) ꢁ 0.39 (s, 54 H); 13C {1Hg NMR (C6D6) ꢁ 5.2;
29Si {1Hg NMR (C6D6) ꢁ ꢁ2:3.
H2O
HCl
I2
Me3SiCl
MeI
r.t., 7 d
r.t., 2 h
r.t., 3 h
r.t., 2 d
r.t., 1 h
r.t., 3 d
(Me3Si)3GeH (38)
(Me3Si)3GeH (100)
(Me3Si)3GeI (91)
No reaction
(Me3Si)3GeI (93)
(Me3Si)3GeMe (50)
1 þ MeI ꢁꢁꢁ! (Me3Si)3GeI þ Me2Zn
r.t., 4 h
ꢁꢁꢁ! (Me3Si)3GeMe þ ZnI2
ð4Þ
r.t., 3 d
The formation of Me2Zn was confirmed by the 1H NMR spec-
tra (ꢁ ¼ ꢁ1:44 in THF-d8) and a chemical trapping experiment
with chlorotriphenylgermane, Ph3GeCl. The Me2Zn was
quenched with Ph3GeCl to yield methyltriphenylgermane,
Ph3GeMe, in 59% yield. The formation of (Me3Si)3GeI and
Me2Zn may be explained by electron-transfer processes as
one possible reaction mechanism. Since bis(germyl)zinc 1
with low ionization oxidative potentials is an excellent elec-
tron donor, electron-transfer from 1 to MeI with high reductive
potentials generates geminate radical anions composed of the
radical cation of 1 and the radical anion of MeI. The radical
cation of 1 possibly reacts with the radical anion of MeI to af-
ford (Me3Si)3GeI and Me2Zn.9 The reaction mechanism for
the formation of (Me3Si)3GeMe and ZnI2 is unclear.
Preparation of Bis[tris(trimethylsilyl)germyl]zinc (1) by the
Treatment of [Tris(trimethylsilyl)germyl]zinc Chloride with
[Tris(trimethylsilyl)germyl]lithium. To a THF solution (10
mL) of [tris(trimethylsilyl)germyl]zinc chloride, (Me3Si)3GeZnCl
(0.10 g, 0.21 mmol), in a Schlenk tube (Me3Si)3GeLi(thf)3 (0.11
g, 0.21 mmol) in diethyl ether (10 mL) was added under an argon
atmosphere. The reaction mixture was stirred at room temperature
for 1 h. After the removal of diethyl ether, [(Me3Si)3Ge]2Zn (1)
(0.13 g, 0.20 mmol) was formed quantitatively. [(Me3Si)3Ge]2Zn:
1H NMR (C6D6) ꢁ 0.39 (s, 54 H); 13C {1Hg NMR (C6D6) ꢁ 5.2;
29Si {1Hg NMR ꢁ ꢁ2:3.
Preparation of Bis[tris(trimethylsilyl)germyl]zinc (1) by
Treatment of Tris(trimethylsilyl)germane with Diethylzinc.
To a diethyl ether (3 mL) solution of (Me3Si)3GeH (0.30 g, 1.0
mmol) in a Schlenk tube, Et2Zn in hexane (0.5 mL, 0.5 mmol)
was added under an argon atmosphere. The reaction mixture
was stirred at room temperature for 1 day. After removal of di-
ethyl ether, [(Me3Si)3Ge]2Zn (1) (0.32 g, 0.5 mmol) was formed
quantitatively.
Taking these results of reaction of 1 with H2O and Me3SiCl
into consideration, bis(germyl)zinc 1 is not only a very weak
base, but also a weak nucleophile. These results are summa-
rized in Table 2.
Hydrolysis of Bis[tris(trimethylsilyl)germyl]zinc (1) with
Water. A diethyl ether solution (10 mL) of 1 (1.00 mmol), an
excess amount of deoxygenated H2O, and nonadecane as internal
standard in a Schlenk tube was stirred under an argon atmosphere
at room temperature for 7 days. Tris(trimethylsilyl)germane,
(Me3Si)3GeH (0.38 mmol) was formed in 38% GC yield.
(Me3Si)3GeH: 1H NMR (C6D6) ꢁ 0.28 (s, 27 H), 2.16 (s, 1 H);
13C {1Hg NMR (C6D6) ꢁ 3.4. GC-MS m=z 294 (Mþ, 20), 278
(5), 220 (40), 146 (35), 131 (40), 73 (100).
Experimental
General Methods. The NMR spectra were obtained on a Var-
ian Unity Inova 400 MHz spectrometer. The GC-MS spectra were
measured on a JEOL JMS-DX 303 mass spectrometer. Gas chro-
matography was performed on a Shimadzu GC 8A with a 1 m
20% SE30 column. X-ray crystallographic data and diffraction in-
tensities were collected on a MacScience DIP2030 diffraction uti-
ꢀ
lizing graphite-monochromated Mo Kꢂ (ꢃ ¼ 0:71073 A) radia-
tion. The structures were solved by direct methods using the
program system SIR-92. A refinement was performed by a
SILICON Graphics O2 with maXus. THF, diethyl ether, and other
solvents were purified and dried as reported in the literature.
Materials. (Me3Si)3GeLi(thf)3,4 (Me3Si)3GeH,4 (Me3Si)3-
GeI,4 (Me3Si)3GeMe,4 Ph3GeCl,10 and Ph3GeMe11 were prepared
as reported in the literature. Me2Zn, Et2Zn, ZnCl2, Me3SiCl, and
MeI were commercially available.
Hydrolysis of Bis[tris(trimethylsilyl)germyl]zinc (1) with
Hydrochloric Acid.
A diethyl ether solution (10 mL) of 1
(1.00 mmol), an excess amount of conc. HCl, and nonadecane
as internal standard in a Schlenk tube was stirred under argon at-
mosphere at room temperature for 2 h. Tris(trimethylsilyl)ger-
mane, (Me3Si)3GeH (2.00 mmol) was formed quantitatively.
Reaction of Bis[tris(trimethylsilyl)germyl]zinc (1) with
Iodine. A diethyl ether solution of 1 (1.00 mmol), an excess
amount of I2, and nonadecane as an internal standard in a Schlenk
tube was stirred under an argon atmosphere at room temperature
for 3 h. Iodotris(trimethylsilyl)germane, (Me3Si)3GeI (1.82
mmol) was formed in 91% GC yield. (Me3Si)3GeI: 1H NMR
(C6D6) ꢁ 0.29 (s, 27 H); 13C {1Hg NMR (C6D6) ꢁ 0.81. GC-MS
m=z 420 (Mþ, 5), 220 (10), 146 (10), 73 (100).
Structural Studies. Bis(germyl)zinc 1 could be obtained in
the form of crystals suitable for X-ray diffraction studies. A single
crystal was sealed in a capillary glass tube for collection. Diffrac-
tion data were collected at 293 K on a MacScience DIP2030 im-
age plate diffraction employing graphite-monochromated Mo Kꢂ
ꢀ
radiation (ꢃ ¼ 0:71073 A). MF = C18H54Ge2Si6Zn, MW =
649.70, cryst size = 0.30 ꢃ 0.30 ꢃ 0.30 mm, triclinic,
Reaction of Dimethylzinc with Chlorotriphenylgermane.
To a diethyl ether solution (10 mL) of 1 (0.26 g, 0.40 mmol) in
a Schlenk tube, MeI (0.62 g, 4.3 mmol) was added under an argon
atmosphere. The reaction mixture was stirred at room temperature
ꢀ
P1, a ¼ 9:3840ð7Þ, b ¼ 9:4960ð6Þ, c ¼ 12:2610ð6Þ A, ꢄ ¼
ꢂ
ꢀ 3
70:174ð5Þ, ꢅ ¼ 62:489ð4Þ , V ¼ 882:80ð10Þ A , Z ¼ 1, Dcalcd
¼
1:222 g cmꢁ3, Temp/K = 293. The final R factor and the good-

1264 Bull. Chem. Soc. Jpn., 76, No. 6 (2003)
Preparation and Reactions of Bis(germyl)zinc
for 4 h. Then, chlorotriphenylgermane, Ph3GeCl (0.27 g, 0.80
mmol) was added to this solution. The reaction mixture was stir-
red at room temperature for 1 day. Methyltriphenylgermane,
Ph3GeMe, was formed in 59% yield.
J. Geib, Inorg. Chem., 26, 2106 (1987). c) L. Rosch and G. Altnau,
Angew. Chem., Int. Ed. Engl., 18, 60 (1979). d) E. Wiberg, O.
Stecher, H.-J. Andrasscheck, L. Kreuzbichler, and E. Staude, An-
gew. Chem., Int. Ed. Engl., 2, 507 (1963).
X-ray Crystallographic Data. Crystallographic data have
been deposited at the CCDC, 12 Union Road, Cambridge CB2
1EZ, UK and copies can be obtained on request, free of charge,
by quoting the publication citation and the deposition number
205945.
3
a) E. Amberger and W. Stoeger, Angew. Chem., Int. Ed.
Engl., 5, 522 (1966). b) V. T. Bychkov, N. S. Vyazankin, and
G. A. Razuvaev, Zh. Obshch. Khim., 43, 793 (1973). c) N. S.
Vyazankin, G. A. Razuvaev, and O. A. Kruglaya, Organomet.
Chem. Rev. A, 3, 323 (1968).
4
a) S. Freitag, R. Nerbst-Irmer, L. Lameyer, and D. Stalke,
Organometallics, 15, 2839 (1996). b) A. G. Brook, F. Abdessaken,
and H. Sollradl, J. Organomet. Chem., 299, 9 (1986).
This work was supported by a Grant-in-Aid for Scentific
Research (No. 11740344) from the Ministry of Education,
5
108.
6
M. Nanjo, T. Oda, and K. Mochida, Chem. Lett., 2002,
Culture, Sports, Science and Technology.
Mitsubishi Material Co., Ltd., for providing us with tetra-
chlorogermane.
We thank
N. S. Vyazankin, E. N. Gladyshev, and S. P. Korneva, Zh.
Obshch. Khim., 37, 1736 (1967).
N. S. Vyazankin, G. A. Razuvaev, and Z. N. Gladyshev,
Dokl. Akad. Nauk SSSR, 155, 830 (1964).
N. S. Vyazankin, G. A. Razuvaev, Z. N. Gladyshev, and S.
P. Korneva, J. Organomet. Chem., 7, 353 (1967).
J. K. Kochi, in ‘‘Organometallic Mechanism and Cataly-
sis,’’ Academic Press, New York (1978), Chapt. 17.
10 A. G. Brook and G. J. D. Peddle, J. Chem. Soc., A, 1966,
1241.
7
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