New method of synthesis of 1,1-bis(trialkylsilyl)- and bis(trialkylgermyl) germacyclopenta-2,4-dienes

Article abstract of DOI:10.1007/s11172-005-0124-8

The reactions of 1,1-dichloro-2,3,4,5-tetraphenyl-1-germacyclopenta-2,4- diene (1), magnesium, and R₃ECl (E = Si, Ge) under mild conditions (20°C, THF) gave 1,1-bis(trimethylsilyl)-2,3,4,5-tetraphenyl-1- germacyclopenta-2,-4-diene (2a) and 1,1-

Full text of DOI:10.1007/s11172-005-0124-8

2334
Russian Chemical Bulletin, International Edition, Vol. 53, No. 10, pp. 2334—2335, October, 2004
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New method of synthesis of 1,1ꢀbis(trialkylsilyl)ꢀ and
bis(trialkylgermyl)germacyclopentaꢀ2,4ꢀdienes
A. V. Lalov, K. S. Nosov, M. P. Egorov,ꢀ and O. M. Nefedovꢀ
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
47 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: (095) 135 5328. Eꢀmail: mpe@ioc.ac.ru
The reactions of 1,1ꢀdichloroꢀ2,3,4,5ꢀtetraphenylꢀ1ꢀgermacyclopentaꢀ2,4ꢀdiene (1), magꢀ
nesium, and R3ECl (E = Si, Ge) under mild conditions (20 °C, THF) gave 1,1ꢀbis(triꢀ
methylsilyl)ꢀ2,3,4,5ꢀtetraphenylꢀ1ꢀgermacyclopentaꢀ2,4ꢀdiene (2а) and 1,1ꢀbis(triethylꢀ
germyl)ꢀ2,3,4,5ꢀtetraphenylꢀ1ꢀgermacyclopentaꢀ2,4ꢀdiene (2b) respectively. The reacꢀ
tion is versatile and applies to the compounds R3ECl (E = Si, Ge) that do not react with
magnesium.
Key words: germoles, Grignard reagents, organohalosilanes, organohalogermanes.
The reactions of organohalosilanes (ꢀgermanes, ꢀ
nylꢀ1ꢀgermacyclopentaꢀ2,4ꢀdienes (2b) (yield 80%—90%)
stannanes) with alkali metals have been studied fairly comꢀ
prehensively as a method of construction of an E—E´
bond.1 The use of magnesium instead of alkali metals has
some advantages related to the lower reactivity and, hence,
higher selectivity of magnesium. In addition, magnesium
does not cleave the E—E´ bonds (E, E´ = Si, Ge, Sn).
However, no data on the use of magnesium in these reacꢀ
tions have been reported as yet.
(Scheme 1).
Scheme 1
In the last two decades, special interest has been atꢀ
tracted by organoelement compounds in which a Group 14
element is incorporated in an unsaturated fiveꢀmembered
heterocycle, namely, silacyclopentaꢀ2,4ꢀdienes (siloles),
germacyclopentaꢀ2,4ꢀdienes (germoles), and stannacycloꢀ
pentaꢀ2,4ꢀdienes (stannoles). These are of interest both
for considering the conjugation and aromaticity effects
and in view of their unusual reactivity. Several methods
for the synthesis of 1,1ꢀbisꢀsubstituted germoles containꢀ
ing E—E bonds (E = Si, Ge, Sn) are known, namely,
metallation of 1,1ꢀdichlorogermoles with alkali metals
followed by treatment with alkylating agents,2 treatment
of 1,1ꢀdichlorogermoles with organolithium reagents,3 the
2a: E = Si; R = Me
2b: E = Ge; R = Et
The reaction mechanism may include the intermediꢀ
ate formation of germyl Grignard reagents from diꢀ and
monochlorogermoles (Scheme 2).
When the reaction was carried out in the presence of a
five or sixꢀfold excess of 2,3ꢀdimethylbutaꢀ1,3ꢀdiene
(2,3ꢀDMB), which is an efficient trap for germylenes, no
adduct resulting from [4+2]ꢀcycloaddition of germylene
4 to 2,3ꢀDMB was detected. Thus, no αꢀelimination of
MgCl2 from the germyl Grignard reagent 3 takes place
during the reaction.
The reaction is general for the compounds R3ECl
(E = Si, Ge; R = Alk, Aryl) that do not react with magneꢀ
sium. On attempted use of Me3SnCl, only Me3SnSnMe3
resulting from the reaction of Me3SnCl with Mg, was
isolated in a high yield. The replacement of magnesium
by an alkali metal (Li or Na) under the same conditions
resulted only in a germaniumꢀcontaining polymer.
4
reaction of 1ꢀunsubstituted germole Me3SnNEt2 and
the in situ reaction of germole unsubstituted at germaꢀ
nium with lithium and Me3SiCl.5 This study describes a
new general method for the synthesis of 1,1ꢀbisꢀsubstiꢀ
tuted germoles with Ge—Si and Ge—Ge bonds.
We found that the reaction of 1,1ꢀdichloroꢀ2,3,4,5ꢀ
tetraphenylꢀ1ꢀgermacyclopentaꢀ2,4ꢀdiene (1) with magꢀ
nesium and R3ECl (E = Si, Ge) carried out under
mild conditions (20 °C, THF) affords 1,1ꢀbis(trimethylꢀ
silyl)ꢀ (2a) and 1,1ꢀbis(triethylgermyl)ꢀ2,3,4,5ꢀtetrapheꢀ
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2234—2236, October, 2004.
1066ꢀ5285/04/5310ꢀ2334 © 2004 Springer Science+Business Media, Inc.

Synthesis of substituted germacyclopentaꢀ2,4ꢀdienes Russ.Chem.Bull., Int.Ed., Vol. 53, No. 10, October, 2004
2335
Scheme 2
Experimental
This study was financially supported by the Russian
Foundation for Basic Research (Project No. 02ꢀ03ꢀ
33148).
All experiments were carried out under dry argon. Commerꢀ
cial samples of Me3SiCl and Et3GeCl were additionally purified
by distillation. Germole 1 was synthesized by a reported proceꢀ
dure;6 THF was refluxed over sodium benzophenone ketyl and
distilled under argon prior to use. 1H NMR spectra were reꢀ
corded in CDCl3 on a Bruker AMꢀ200 NMR spectrometer.
Mass spectra (EI, 70 eV) were recorded on a Finnigan MAT
INCOS instrument.
References
1. M. P. Egorov and P. P. Gaspar, Germanium: Organogermanium
Chemistry, Encyclopedia of Inorganic Chemistry, Ed. R. B. King,
Wiley and Sons, Chichester, 1994, 3, 1292; K. A. Kocheshkov,
N. N. Zemlyanskii, N. I. Sheverdina, and E. M. Panov,
Metody elementoorganicheskoi khimii. Germanii, olovo, svinets
[Methods of Organoelement Chemistry. Germanium, Tin, Lead]
Nauka, Moscow, 1968, 358 (in Russian).
2. W. P. Freeman, T. Don Tilley, F. P. Arnold, A. L. Rheingold,
and P. K. Gantzel, Angew. Chem., Int. Ed. Engl., 1995,
34, 1887.
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O. M. Nefedov, G. G. Aleksandrov, I. L. Eremenko, and
S. E. Nefedov, Izv. Akad. Nauk. Ser. Khim., 2000, 1278 [Russ.
Chem. Bull., Int. Ed., 2000, 49, 1275].
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Egorov, and O. M. Nefedov, Izv. Akad. Nauk. Ser. Khim.,
1996, 2764 [Russ. Chem. Bull., 1996, 45, 2623 (Engl. Transl.)].
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General procedure. 1,1ꢀDichloroꢀ2,3,4,5ꢀtetraphenylꢀ1ꢀ
germacyclopentaꢀ2,4ꢀdiene (10.2 g, 0.4 mmol) in 2 mL of anꢀ
hydrous THF and chlorotrimethylsilane (0.26 g, 2.4 mmol) or
chlorotriethylgermane (0.47 g, 2.4 mmol) were added under
argon to iodineꢀactivated magnesium (0.020 g, 0.8 mmol). The
reaction mixture was stirred until the newly appeared orange
color disappeared again (1 h). THF was removed in vacuo and
the residue was dissolved in benzene and filtered. Benzene was
evaporated and the residue was recrystallized from hexane.
1,1ꢀBis(trimethylsilyl)ꢀ2,3,4,5ꢀtetraphenylꢀ1ꢀgermacycloꢀ
pentaꢀ2,4ꢀdiene (2a). Yield 0.2 g (87%), m.p. 114—115 °C
(Ref. 7: 114 °C). 1H NMR (CDCl3), δ: 0.20 (s, 18 H,
2 (CH3)3Si); 6.80—7.10 (m, 20 H, Ph). MS, m/z: 576 [M]+.
1,1ꢀBis(triethylgermyl)ꢀ2,3,4,5ꢀtetraphenylꢀ1ꢀgermacycloꢀ
pentaꢀ2,4ꢀdiene (2b). Yield 0.26 g (85%). 1H NMR (CDCl3), δ:
0.60 (t, 18 H, 2 (CH3CH2)3Ge); 1.10 (q, 12 H, 2 (CH3CH2)3Ge);
6.80—7.10 (m, 20 H, Ph). Found (%): C, 63.63; H, 6.96;
Ge, 28.17. C40H50Ge3. Calculated (%): C, 64.18; H, 6.73;
Ge, 29.09. MS, m/z: 691 [M+ – Et – C2H2], 588 [M+ – Et3Ge],
559 [M+ – Et3Ge – Et], 531 [M+ – Et3Ge – Et – C2H4], 501
[M+ – Et3Ge – 2 Et – C2H4], 427 [M+ – 2 Et3Ge].
6. H. D. Curtis, J. Am. Chem. Soc., 1969, 91, 6011.
7. P. Jutzi and A. Karl, J. Organomet. Chem., 1981, 215, 19.
Received September 14, 2004