Phenyltrichlorogermane synthesis by the reaction of chlorobenzene and the dichlorogermylene intermediate formed from elemental germanium and tetrachlorogermane

Article abstract of DOI:10.1021/om010761q

Phenyltrichlorogermane was synthesized with high selectivity, 96%, from elemental germanium, tetrachlorogermane, and chlorobenzene using no catalyst, almost all germanium and tetrachlorogermane being converted. Dichlorogermylene was formed as a reaction intermediate by the reaction of germanium with tetrachlorogermane and inserted into the C-Cl bond of chlorobenzene to yield phenyltrichlorogermane.

Full text of DOI:10.1021/om010761q

Organometallics 2001, 20, 5583-5585
5583
P h en yltr ich lor oger m a n e Syn th esis by th e Rea ction of
Ch lor oben zen e a n d th e Dich lor oger m ylen e In ter m ed ia te
F or m ed fr om Elem en ta l Ger m a n iu m a n d
Tetr a ch lor oger m a n e
Masaki Okamoto, Takuya Asano, and Eiichi Suzuki*
Department of Chemistry and Materials Science, Tokyo Institute of Technology,
Ookayama, Meguro-ku, Tokyo 152-8550, J apan
Received August 10, 2001
Phenyltrichlorogermane was synthesized with high selectivity, 96%, from elemental
germanium, tetrachlorogermane, and chlorobenzene using no catalyst, almost all germanium
and tetrachlorogermane being converted. Dichlorogermylene was formed as a reaction
intermediate by the reaction of germanium with tetrachlorogermane and inserted into the
C-Cl bond of chlorobenzene to yield phenyltrichlorogermane.
In tr od u ction
dichlorogermylene insertion into the carbon-chlorine
bond in chlorobenzene (eq 1).9 The drawbacks of this
In 1947, Rochow reported the direct synthesis of
dimethyldichlorogermane by the reaction of elemental
germanim with gaseous methyl chloride at 320-360 °C.1
Since that time, various organic halides,1-5 such as ethyl
chloride,1,3 propyl chloride,4,5 and chlorobenzene,1,5 also
have been reported to react with elemental germanium
in the presence of a copper or silver catalyst to afford
organohalogermanes. Furthermore, we have recently
found a new reaction for synthesizing alkyltrichloro-
germanes directly from elemental germanium, hydrogen
chloride, and an alkene using a copper catalyst.6 The
direct synthesis is a very simple method to synthesize
organogermanes, and elemental germanium as a ger-
manium source is readily available.
Organogermanes can be synthesized using a ger-
mylene intermediate.7-9 Chernyshev et al. have re-
ported the gas-phase synthesis of various organochloro-
germanes using dichlorogermylene formed in the gas-
phase reaction of tetrachlorogermane with dichloro-
silylene, which was obtained by the pyrolysis of hexa-
chlorodisilane or 1,1-dichlorosilacyclopent-3-ene.8,9 For
example, phenyltrichlorogermane was obtained by the
reaction are that the disilane and the silacyclopentene
are not easily obtainable and that stoichiometric amounts
of silicon-containing byproducts are formed.
Berliner et al. have reported that elemental germa-
nium reacts with tetrachlorogermane to afford dichloro-
germylene in the absence of a catalyst.10,11 The di-
chlorogermylene thus formed reacted with butadiene
under the vapor-phase flow conditions to form 1,1-
dichlorogermacyclopent-3-ene (eq 2), whose yield was,
however, only 15%.10 This reaction has the advantages
that elemental germanium and tetrachlorogermane as
sources of dichlorogermylene are more readily available
than hexachlorodisilane or the silacyclopent-3-ene and
(1) Rochow, E. G. J . Am. Chem. Soc. 1947, 69, 1729.
(2) (a) Gar, T. K.; Mironov, V. F. Metalloorg. Khim. 1993, 6, 285,
and references therein. (b) Petrov, A. D.; Mironov, V. F.; Golgy, I. E.
Bull. Akad. Sci. USSR, Div. Chem. Sci. 1956, 1169. (c) Moedritzer, K.
J . Organomet. Chem. 1966, 6, 282. (d) Belij, A. P.; Gorbunov, A. I.;
Golubtsov, S. A.; Feldshein, N. S. J . Organomet. Chem. 1969, 17, 485.
(e) Chong, T.; Skaates, J . M. J . Catal. 1973, 28, 20. (f) Gorbunov, A.
I.; Belyi, A. P.; Rybakov, N. N. Rus. J . Phys. Chem. 1978, 52, 1054. (g)
Lee, M. E.; Bobbitt, K. L.; Lei, D.; Gasper, P. P. Synth. React. Met.-
Org. Chem. 1990, 20, 77.
(3) (a) Rochow, E. G. J . Am. Chem. Soc. 1950, 72, 198. (b) Zueva, G.
Ya.; Luk’yankina, N. V.; Kechina, A. G.; Ponomarenko, V. A. Bull.
Acad. Sci. USSR, Div. Chem. Sci. 1966, 10, 1780.
(4) (a) Rochow, E. G.; Didtschenko R.; West, R. C., J r. J . Am. Chem.
Soc. 1951, 73, 5486. (b) Zueva, G. Ya.; Luk’yankina, N. V.; Ponomar-
enko, V. A. Bull. Acad. Sci. USSR, Div. Chem. Sci. 1967, 186.
(5) Zueva, G. Ya.; Khaustova, T. I.; Serezhkina, N. V.; Ponomarenko,
V. A. Izv. Akad. Nauk SSSR, Ser. Khim. 1979, 2792.
(8) (a) Chernyshev, E. A.; Komalenkova, N. G.; Yakovleva, G. N.;
Bykovchenko, V. G.; Khromykh, N. N.; Bykovchenko, V. G. Russ. J .
Gen. Chem. 1997, 67, 894. (b) Chernyshev, E. A.; Komalenkova, N.
G.; Yakovleva, G. N.; Bykovchenko, V. G.; Khromykh, N. N.; Boch-
karev, V. N.; Shcherbinin, V. V. Russ. J . Gen. Chem. 1997, 67, 1725.
(c) Chernyshev, E. A.; Komalenkova, N. G.; Bykovchenko, V. G. Russ.
Chem. Bull. 1998, 47, 1029. (d) Chernyshev, E. A.; Komalenkova, N.
G.; Yakovleva, G. N.; Bykovchenko, V. G.; Khromykh, N. N. Russ. J .
Gen. Chem. 1998, 68, 403. (e) Chernyshev, E. A.; Komalenkova, N.
G.; Yakovleva, G. N.; Bykovchenko, V. G.; Khromykh, N. N.; Boch-
karev, V. N.; Shcherbinin, V. V. Russ. J . Gen. Chem. 1999, 69, 90.
(9) (a) Chernyshev, E. A.; Komalenkova, N. G.; Yakovleva, G. N.;
Bykovchenko, V. G. Russ. J . Gen. Chem. 1995, 65, 1717. (b) Cherny-
shev, E. A.; Komalenkova, N. G.; Yakovleva, G. N.; Bykovchenko, V.
G.; Khomykh, N. N.; Bochkarev, V. N.; Shcherbinin, V. V. Russ. J .
Gen. Chem. 1997, 67, 1722.
(6) Okamoto, M.; Chikamori, T.; Asano, T.; Suzuki, E. Organome-
tallics, submitted.
(7) (a) Satge, J .; Massol, M.; Riviere, P. J . Organomet. Chem. 1973,
56, 1, and references therein. (b) Neumann, W. P. Chem. Rev. 1991,
91, 311, and references therein.
(10) Berliner, E. M.; Gar, T. K.; Mironov, V. F. J . Gen. Chem. USSR
1972, 42, 1165.
(11) Berliner, E. M.; Gar, T. K.; Mironov, V. F. J . Gen. Chem. USSR
1975, 45, 2637.
10.1021/om010761q CCC: $20.00 © 2001 American Chemical Society
Publication on Web 11/15/2001

5584 Organometallics, Vol. 20, No. 26, 2001
Okamoto et al.
that no byproducts are produced in the formation of the
germylene.
Here, we show that batch reaction of elemental
germanium, tetrachlorogermane, and chlorobenzene, in
which dichlorogermylene is an intermediate, gives
phenyltrichlorogermane as sole product in high conver-
sions.
Exp er im en ta l Section
Germanium grains (purity: 99.99%, size: <45 µm)
were washed with stirring in a 46% HF aqueous solution
for 1 h at room temperature, rinsed with deionized
water, and dried using a rotary evaporator. The ger-
manium grains (6.9 mmol), tetrachlorogermane (0.87-
4.4 mmol), and chlorobenzene (200 mmol) were charged
into a 120 mL stainless steel (SUS 316) autoclave, and
then nitrogen, 30 atm pressure, was added. The auto-
clave was heated at 300 and 350 °C while stirring the
reaction mixture. The pressure finally reached 67 and
75 atm, respectively. The reaction was stopped at 4, 8,
15, or 40 h, and the reaction mixture was cooled and
filtered. Toluene (1 mL) was added to the reaction liquid
as an internal standard. The products were analyzed
quantitatively by gas chromatography and identified by
GC-MS. Tetrachlorogermane and germanium conver-
sions are defined by the following equations.
tetrachlorogermane conversion (%) )
amount of tetrachlorogermane
F igu r e 1. Time courses of the amounts of germanes in
the reaction at 300 °C (a) and 350 °C (b): Phenyltrichlo-
rogermane (0), diphenyldichlorogermane (O), triphenyl-
chlorogermane (3), tetrachlorogermane (4), and the sum
of germanes (b). The amounts of elemental germanium,
tetrachlorogermane, and chlorobenzene charged in the
autoclave were 6.9, 4.4, and 200 mmol, respectively.
Dashed and dotted lines represent the amount of tetra-
chlorogermane charged and the sum of amounts of elemen-
tal germanium and tetrachlorogermane charged, respec-
tively.
remaining after the reaction (mmol)
100 -
× 100
× 100
amount of tetrachlorogermane
charged (mmol)
germanium conversion (%) )
[sum of amounts of germanes (mmol)] -
[amount of tetrachlorogermane charged (mmol)]
amount of germanium charged (mmol)
Resu lts a n d Discu ssion
emental germanium with chlorobenzene was carried out
in the absence of copper, the germanium was hardly
converted (0.7% conversion) and no diphenyldichloro-
germane, which is one of the main products of the direct
synthesis, was formed.12 According to eq 3, the reaction
of germanium and tetrachlorogermane leads to the
formation of 2 equiv of dichlorogermylene.6,10,11 Dichloro-
germylene can easily react with chlorobenzene to give
phenyltrichlorogermane9 as shown in eq 4. Thus, the
conversion of 1 mol of tetrachlorogermane should result
in the formation of 2 mol of phenyltrichlorogermane (eq
5). As shown in Figure 1a, at the initial stages of the
The reaction of germanium, tetrachlorogermane, and
chlorobenzene at 300 °C gave phenytrichlorogermane
selectively. Figure 1a shows the changes of germane
product amounts as a function of reaction time. All data
were obtained from individual runs. The amount of
tetrachlorogermane decreased with reaction time, and
almost all tetrachlorogermane was consumed after 8 h.
The phenyltrichlorogermane amount increased at twice
the rate of tetrachlorogermane consumption. At 8 h, 98%
of the total amount of all organogermanes was phenyl-
trichlorogermane. In the direct synthesis from elemental
germanium and chlorobenzene using a copper catalyst,
diphenyldichlorogermane and phenyltrichlorogermane
were formed both with ca. 50% selectivity.12 This
product distribution is quite different from that obtained
in the present study. Additionally, a catalyst such as
copper is not prerequisite for our phenyltrichloroger-
mane synthesis. This suggests that a direct synthesis
was not involved. Actually, when the reaction of el-
reaction, the rate of phenyltrichlorogermane formation
was almost twice as great as that of tetrachlorogermane
consumption. This result is consistent with eq 5, indi-
cating the intermediacy of dichlorogermylene. At 15 and
40 h, the formation of a very small amount of diphenyl-
dichlorogermane was observed. This probably is caused
by the disproportionation of phenyltrichlorogermane (eq
(12) The reaction of elemental germanium (6.88 mmol) and chlo-
robenzene (200 mmol) with copper(I) chloride catalyst (2.27 mmol) was
carried out in a 120 mL autoclave at 350 °C for 60 h. The germanium
conversion was 76%, and the selectivities for phenyltrichlorogermane,
diphenyldichlorogermane, and triphenylchlorogermane were 53%, 45%,
and 2%, respectively.

Phenyltrichlorogermane Synthesis
Ta ble 1. Effect of th e Am ou n t of
Tetr a ch lor oger m a n e Ch a r ged on th e Tota l Am ou n t
of All Ger m a n es a n d th e Con ver sion of Elem en ta l
Ger m a n iu m in th e 15 h Rea ction a
Organometallics, Vol. 20, No. 26, 2001 5585
The conversion of tetrachlorogermane was 55%, and
phenyltrichlorogermane and diphenyldichlorogermane
were obtained in 52% and 3% yields, respectively. This
indicates that the phenylation occurred at the beginning
of the reaction of elemental germanium, tetrachloro-
germane, and chlorobenzene. At 4 h in Figure 1b, 5.8
mmol of dichlorobenzene was also formed, and chlorine
was not detected. Apparently, the chlorine formed as a
byproduct of the substitution is completely consumed
in forming dichlorobenzenes and hydrogen chloride (eq
8). Actually, hydrogen chloride was detected by GC-
MS.13 After 4 h, diphenyldichlorogermane and tri-
phenylchlorogermane were formed together with phenyl-
trichlorogermane. The total amount of all germanes was
larger than double the amount of tetrachlorogermane
charged, indicating that elemental germanium was still
consumed even after the consumption of all tetrachloro-
germane. This suggests that tetrachlorogermane is
formed by the disproportionation of phenyltrichloro-
germane (eq 6) and/or that phenylchlorogermylene,
which reacts with chlorobenzene to give diphenyldi-
chlorogermane, is formed as an intermediate in the
reaction of elemental germanium with phenyltrichloro-
germane (eq 9). Triphenylchlorogermane most likely
was formed by the disproportionation of diphenyldi-
chlorogermane (eq 10).
reaction
temp
elemental
germanium
amount of GeCl4 total amount of all
(°C)
charged/mmol
germanes/mmol
conversion (%)
300
0.88
2.2
1.7
4.5
12
48
64
4.4
8.8
8.8*
17*
100*
350
1.8
0.88
4.4
4.1
3.5
9.3
33
38
71
a
The amounts of elemental germanium and chlorobenzene
charged in the autoclave were 6.9 (* 8.8) and 200 mmol, respec-
tively.
6). In fact, when 3.1 mmol of phenyltrichlorogermane
in 20 mL of n-decane solvent was heated at 300 °C for
15 h, 0.24 mmol of diphenyldichlorogermane was formed
together with tetrachlorogermane.
The effect of the amount of tetrachlorogermane charged
was examined. Table 1 includes the results at 300 °C
for 15 h. The sum of tetrachlorogermane, phenyltri-
chlorogermane, and diphenyldichlorogermane amounts
was twice as great as that of tetrachlorogermane
charged, and phenyltrichlorogermane was almost the
sole germanium compound formed. This strongly sup-
ports the intermediacy of dichlorogermylene, formed by
the reaction of germanium with tetrachlorogermane. On
increasing the tetrachlorogermane amount to 4.4 mmol,
the conversion of elemental germanium increased to
64%. When equal molar amounts of elemental germa-
nium (8.8 mmol) and tetrachlorogermane (8.8 mmol)
were used, the conversions of germanium and tetra-
chlorogermane were 100% and 97%, respectively, and
the selectivity for phenyltrichlorogermane among
organochlorogermanes was 96%.
On raising the reaction temperature to 350 °C, the
time course of the reaction changed greatly. The result
is shown in Figure 1b. At the beginning of the reaction,
the amount of phenyltrichlorogermane formed was
almost the same as that of tetrachlorogermane con-
sumed; that is, elemental germanium hardly reacted.
This strongly suggests that the substitution of chlorine
in tetrachlorogermane for a phenyl group (eq 7) is the
Table 1 includes the effect of the amount of tetra-
chlorogermane charged in the autoclave. Under all
conditions, the total amount of all germanium com-
pounds was larger than twice the amount of tetrachloro-
germane, also suggesting that the reactions shown by
eqs 6 and 9 are operative.
Con clu sion s
Phenyltrichlorogermane was synthesized selectively
from elemental germanium, tetrachlorogermane, and
chlorobenzene without using a catalyst. The reaction
intermediate is dichlorogermylene, which is formed by
the reaction of germanium with tetrachlorogermane.
The reaction and the procedure used in this work are
very simple, and the starting materials are readily
obtainable.
OM010761Q
(13) Probably the hydrogen chloride reacted partly with elemental
germanium to give tetrachlorogermane (Ge + 4 HCl f GeCl4 + 2 H2),
whose reaction with chlorobenzene afforded dichlorobenzenes and
chlorine again (eq 8). The effect of the chain of these reactions on the
germanium conversion is small because the reaction of 4 mol of
hydrogen chloride gives 1 mol of germanium consumed and a part of
hydrogen chloride remained in the reaction mixture.
dominant process occurring. The reaction of tetra-
chlorogermane (4.4 mmol) and chlorobenzene (200
mmol) in the absence of elemental germanium at 350
°C for 8 h in the autoclave was carried out as a control.