New arylchlorogermylenes stabilized by two ortho side-chain donor ligands

Article abstract of DOI:10.1016/S0277-5387(02)01279-2

Arylchlorogermylenes stabilized by two ortho side-chain donor ligands (aryl = 2,6-(CH₂NR₂)₂C₆H₃ with R = Et: 1 and R = i-Pr: 2) were synthesized; 1 was characterized by an x-ray analysis and intramolecular coordinations N → Ge were evidenced from the two side-chains. In this paper, all known stable and isolated halogermylenes are reviewed. Significant bond lengths of their X-ray structures are reported and compared. Surprisingly, attempts to obtain chlorogermylenes bearing a substituent with a strong electron-withdrawing effect such as 2,4,6-tris(trifluoromethyl)phenyl (Ar′) or 2,6-bis(trifluoromethyl)phenyl (Ar″) led us to new compounds, the diarylchlorogermanes Ar₂GeHCl or Ar₂^″GeHCl or Ar₂^″GeHCl.

Full text of DOI:10.1016/S0277-5387(02)01279-2

Polyhedron 21 (2002) 2827ꢂ2834
/
www.elsevier.com/locate/poly
New arylchlorogermylenes stabilized by two ortho side-chain donor
ligands
C. Bibal, S. Mazie`res, H. Gornitzka, C. Couret ꢀ
´ ´ ´ ´
Laboratoire Heterochimie Fondamentale et Appliquee, Universite Paul Sabatier, UMR-5069, 118 route de Narbonne, 31062 Toulouse Cedex, France
Received 23 July 2002; accepted 9 October 2002
Abstract
Arylchlorogermylenes stabilized by two ortho side-chain donor ligands (arylꢁ
/
2,6-(CH2NR2)2C6H3 with Rꢁ
/
Et: 1 and Rꢁ/i-Pr:
2) were synthesized; 1 was characterized by an X-ray analysis and intramolecular coordinations N0
/
Ge were evidenced from the
two side-chains. In this paper, all known stable and isolated halogermylenes are reviewed. Significant bond lengths of their X-ray
structures are reported and compared. Surprisingly, attempts to obtain chlorogermylenes bearing a substituent with a strong
electron-withdrawing effect such as 2,4,6-tris(trifluoromethyl)phenyl (Ar?) or 2,6-bis(trifluoromethyl)phenyl (Arƒ) led us to new
?
ƒ
compounds, the diarylchlorogermanes Ar2GeHCl or Ar2GeHCl.
# 2002 Elsevier Science Ltd. All rights reserved.
Keywords: Halogermylenes; Donor side-chain; Intramolecular coordination; Diarylchlorogermanes
1. Introduction
1. Data will be compared with those of other known
stable and isolated halogermylenes, which are reviewed.
Divalent compounds of the heavier Group 14 ele-
ments remain of intensive investigation for the last 20
years and their chemistry raised up a widespread
interest. If symmetrical disubstituted germanium, tin
and lead R2M derivatives are relatively numerous,
2. Experimental
2.1. Equipment
unsymmetrical compounds Rꢀ
/
MꢀR? have received less
/
All manipulations were carried out under an argon
atmosphere using Schlenk and vacuum line techniques
or a glove box. All the solvents were dried by appro-
attention [1]. Among this class of derivatives, mono-
halogermylenes RGeX present a particular interest as
efficient synthons in organometallic chemistry: thus they
permit very easy nucleophilic substitution reactions at
the metal leading to various unsymmetrical germylenes.
In order to access the side-chain donor stabilized
dicoordinated germanium compounds such as triple
1
priate procedures and freshly distilled before use. H,
13C and 19F NMR spectra were recorded on Bruker AC
spectrometers, chemical shifts (d, ppm) are relative to
SiMe4 (TMS) for 1H and 13C NMR, CF3COOH for 19
NMR. EI mass spectra were obtained at 70 eV on a
F
bonded species, germynes RGeꢁ
RGeꢁGeR, we have synthesized two new arylchloro-
germylenes ArGeCl (Arꢁ2,6-(CH2NR2)2C6H3 with
RꢁEt: 1 and Rꢁi-Pr: 2) stabilized by two side-chain
/
CR? and digermynes
HewlettꢂPackard 5989 instrument and samples were
/
/
contained in glass capillaries under argon. Melting
points were determined on a hot-plate microscope
apparatus Leitz Biomed in sealed capillary tubes under
/
/
/
donor ligands. Here, are described their synthesis, their
spectroscopic characterization and the X-ray analysis of
argon and are uncorrected. Complex GeCl2×
1-bromo-2,6-bis(bromomethyl)benzene [3] and 1-bro-
mo-2,6-bis[(dialkylamino)methyl]benzene, alkylꢁEt, i-
/dioxane [2],
/
Pr [4] were prepared accordingly to literature procedures
but for the three last known compounds missing
spectroscopic data were added.
ꢀ Corresponding author. Fax: ꢃ
E-mail address: couret@chimie.ups-tlse.fr (C. Couret).
/
33-5-6155-8204
0277-5387/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved.
PII: S 0 2 7 7 - 5 3 8 7 ( 0 2 ) 0 1 2 7 9 - 2

2828
C. Bibal et al. / Polyhedron 21 (2002) 2827ꢂ2834
/
1
2.2. Preparations
tals. Yield: 22.70 g, 96%. M.p.: 76 8C. H NMR (C6D6,
3
250.1 MHz, d ppm): 0.95 (d, JH/H
ꢁ
/
6.5 Hz, 24H,
6.5 Hz, 4H, CH(i-Pr)),
3.88 (s, 4H, CH2N), 7.28 (t, JH/H 7.6 Hz, 1H, 4-aryl-
7.6 Hz, 2H, 3,5-aryl-H); 13C NMR
3
2.2.1. Preparation of 1-bromo-2,6-
bis(bromomethyl)benzene
CH3(i-Pr)), 2.95 (sept, JH/H
ꢁ
/
3
ꢁ
/
3
To a stirred solution of 2-bromometaxylene (24.95 g,
0.135 mol) in CCl4 (150 ml) were added 2 equiv. of N-
bromosuccinimide (NBS) (48.01 g, 0.270 mol) and a
catalytic amount of 2,2?-azobis-(2-methylpropionitrile)
(AIBN). The reaction mixture was heated to reflux and
stirred for 6 h. The succinimide formed was then filtered
off and the orange filtrate evaporated to dryness. A solid
was obtained and recrystallized in hexane (150 ml)
affording white needles. Yield: 21.11 g (46%). M.p.:
H), 7.77 (d, JH/H
ꢁ
/
(C6D6, 50.3 MHz, d ppm): 20.91 (CH3(i-Pr)), 49.00
(CH(i-Pr)), 50.17 (CH2N), 124.80 (1-aryl-C), 126.96 (4-
aryl-C), 128.59 (3,5-aryl-C), 142.12 (2,6-aryl-C); EI MS
(70 eV, m/z %): 382 (Mꢃ, 18), 367 (Mꢃꢄ
/Me, 100), 282
(MꢃꢄNi-Pr2, 26), 182 (Mꢃꢄ
/
/
2(Ni-Pr2), 56).
2.2.4. Preparation of chloro[2,6-
bis[(diethylamino)methyl]phenyl]germylene (1)
95 8C (literature: 97ꢂ
/
98 8C [3a]); 1H NMR (CDCl3,
A
solution
of
1-bromo-2,6-bis[(diethylami-
250.1 MHz, d ppm): 4.65 (s, 4H, CH2), 7.29 (t, 3JH/H
ꢁ
/
no)methyl]benzene (2.0 g, 6.1 mmol) in Et2O (15 ml)
was treated by a stoichiometric amount of n-butyl-
lithium (4.2 ml, 1.6 M in hexane) at 0 8C, and the
mixture was stirred for 30 min. After removal of the
solvents in vacuum, 15 ml of THF was added. The 1-
lithio-2,6-bis[(diethylamino)methyl])benzene was then
3
6.7 Hz, 1H, 4-aryl-H), 7.42 (d, JH/H
ꢁ6.7 Hz, 2H, 3,5-
/
aryl-H); 13C NMR (CDCl3, 50.3 MHz, d ppm): 33.92
(CH2Br), 126.69 (1-aryl-C), 128.08 (4-aryl-C), 131.45
(3,5-aryl-C), 138.52 (2,6-aryl-C). EI MS (70 eV, m/z %):
342 (Mꢃ, 11); 263 (Mꢃꢄ
/
Br, 100), 182 (Mꢃꢄ
Br2, 35),
/
103 (Mꢃꢄ
/
Br3, 32).
added dropwise to a solution of GeCl2×
g, 6.1 mmol) in THF (15 ml) at ꢄ78 8C. The solution
/dioxane (1.41
/
2.2.2. Preparation of 1-bromo-2,6-
bis[(diethylamino)methyl]benzene
was allowed to warm to room temperature (r.t.) and
stirred for 30 min. Volatile materials were removed in
vacuum and the residue was treated in pentane. The
mixture was filtered to remove LiCl and concentrated
under reduced pressure. After several hours in pentane
at r.t., X-ray quality crystals of 1 were obtained. Yield:
To a stirred solution of 1-bromo-2,6-bis(bromo-
methyl)benzene (21.11 g, 0.062 mol) dissolved in 150
ml of toluene was added dropwise a solution of
diethylamine (21.67 g, 0.296 mol, 31 ml) in 50 ml of
toluene for 1 h. After 10 min a white precipitate of
diethylammonium bromide was formed. The reaction
mixture was stirred for 18 h and the solid filtered off.
The filtrate was evaporated to dryness to lead to a
yellow oil, which was purified by distillation affording a
colorless oil (132 8C/0.25 mmHg (literature: 150 8C/0.5
1
1.84 g, 85%. M.p.: 70 8C. H NMR (C7D8, 400.1 MHz,
3
d ppm): 1.18 (t, JH/H
ꢁ7.1 Hz, 12H, CH3(Et)), 2.85,
/
3
2.86 (2q, JH/H
system, 2JH/H
ꢁ
/
7.1 Hz, 8H, CH2(Et)), 3.62, 3.91 (AB
ꢁ
/
14.3 Hz, 4H, CH2N), 7.25ꢂ
/7.46 (m, 3H,
3,4,5-aryl-H); 13C NMR (C7D8, 100.6 MHz, d ppm):
9.72 (CH3(Et)), 44.94 (CH2(Et)), 58.68 (CH2N), 123.93
(3,5-aryl-C), 127.60 (4-aryl-C), 145.04 (2,6-aryl-C),
157.48 (1-aryl-C); EI MS (70 eV, m/z %):356 (Mꢃ,
1
mmHg [4b]b)). Yield: 12.95 g (64%). H NMR (CDCl3,
3
80.1 MHz, d ppm): 1.07 (t, JH/H
ꢁ7.0 Hz, 12H,
/
3
CH3(Et)), 2.61 (q, JH/H
ꢁ
/
7.0 Hz, 8H, CH2(Et)), 3.69
24), 327 (Mꢃꢄ
/
Et, 22), 291 (Mꢃꢄ
/
2MeꢄCl, 18), 217
/
(s, 4H, CH2N); 7.16ꢂ
/
7.52 (m, 3H, 3,4,5-aryl-H); 13C
(Arꢀ2Me, 100).
/
NMR (CDCl3, 50.3 MHz, d ppm): 12.07 (CH3(Et)),
47.30 (CH2(Et)), 57.90 (CH2N), 125.92 (1-aryl-C),
126.66 (4-aryl-C), 128.66 (3,5-aryl-C), 139.71 (2,6-aryl-
Anal. Found: C, 54.19; H, 7.76. Calc. for
C16H27N2GeCl: C, 54.07; H, 7.66%.
C); EI MS (70 eV, m/z %): 326 (Mꢃ, 19), 311 (Mꢃꢄ
/
2.2.5. Preparation of chloro[2,6-
bis[(diisopropylamino)methyl]phenyl]germylene (2)
Me, 100), 254 (Mꢃꢄ
/
NEt2, 29), 240 (Mꢃꢄ
/
CH2NEt2,
28).
Anal. Found: C, 58.84; H, 8.42. Calc. for
C16H27N2Br: C, 58.71; H, 8.31%.
A solution of 1-bromo-2,6-bis[(diisopropylami-
no)methyl]benzene (1.30 g, 3.4 mmol) in THF (15 ml)
was treated with a stoichiometric amount of n-butyl-
lithium (2.3 ml, 1.6 M in hexane) at ꢄ
mixture was stirred for 20 min at ꢄ78 8C and slowly
added to a solution of GeCl2×dioxane (0.79 g, 3.4 mmol)
in THF (15 ml) at the same temperature. The solution
was then allowed to warm up to r.t. and stirred for 30
min. Solvents were evaporated in vacuum and the
residue was treated with pentane. The mixture was
filtered to remove LiCl and a yellow solid was obtained
after evaporation to dryness. Yield: 1.26 g, 90%. M.p.
(dec.): 77 8C. 1H NMR (C6D6, 250.1 MHz, d ppm): 1.03
/
78 8C. The
2.2.3. Preparation of 1-bromo-2,6-
/
bis[(diisopropylamino)methyl]benzene
/
A solution of diisopropylamine (29.98 g, 0.296 mol,
42 ml) and 1-bromo-2,6-bis(bromomethyl)benzene
(21.11 g, 0.062 mol) in toluene (250 ml) was heated to
reflux for 48 h. The white diisopropylamine bromide
solid was then removed by filtration; the filtrate was
concentrated in vacuum and the crude product recrys-
tallized from pentane at ꢄ20 8C affording white crys-
/

C. Bibal et al. / Polyhedron 21 (2002) 2827ꢂ
/
2834
2829
(d, 3JH/H
ꢁ
/
6.7 Hz, 12H, CH3(i-Pr)), 1.08 (d, 3JH/H
ꢁ
/
6.7
3. Results and discussion
3
Hz, 12H, CH3(i-Pr)), 3.42 (sept, JH/H
ꢁ
/
6.7 Hz, 4H,
15.0 Hz, 4H,
7.4 Hz, 2H, 3,5-aryl-H), 7.15 (t,
7.4 Hz, 1H, 4-aryl-H); 13C NMR (C6D6, 50.3
2
CH(i-Pr)), 3.70, 3.99 (AB system, JH/H
CH2N), 6.96 (d, 3JH/H
3JH/H
ꢁ
/
3.1. The arylchlorogermylenes 1 and 2
ꢁ
/
ꢁ
/
The reaction of ArLi with GeCl2×
/dioxane in THF in
MHz, d ppm): 20.33, 21.00 (CH3(i-Pr)), 51.25 (CH(i-
Pr)), 53.64 (CH2N), 123.15 (3,5-aryl-C), 128.19 (4-aryl-
C), 147.70 (2,6-aryl-C), 158.86 (1-aryl-C); IE MS (70 eV,
m/z %): 412 (Mꢃ, 26), 377 (Mꢃꢄ
Pr, 100).
Anal. Found: C, 58.51; H, 8.69. Calc. for
C16H27N2GeCl: C, 58.37; H, 8.57%.
1:1 molar ratio at ꢄ78 8C affords germylenes ArGeCl in
/
good yield (Eq. (1)). Single crystals of 1, suitable for an
X-ray structure determination were grown from pentane
at room temperature. The structure determination and
refinement [7] show a monomeric structure in the solid
state (Fig. 1). Significant bond lengths and angles are
presented in Table 1.
/
Cl, 26), 369 (Mꢃꢄ
i-
/
2.2.6. Preparation of chlorobis[2,4,6-
?
tris(trifluoromethyl)phenyl]germane Ar2GeHCl
diethyl ether solution of [2,4,6-tris(trifluoro-
methyl)phenyl]lithium [5] (2.14 mmol) was added drop-
wise to a 0 8C diethyl ether solution of GeCl2×dioxane
(196 mg, 0.85 mmol). The mixture was allowed to warm
to r.t. and stirred for 2 h. All volatiles were removed in
vacuum, 10 ml of pentane was added to filter the
insoluble salts. A yellow powder precipitated after 24
A
/
ð1Þ
In this complex, the Ar ligand is tridentate to
germanium: s-bonded through ipso-carbon C(1) and
also bis-orthochelated by intramolecular N0
/
Ge coor-
N distances
are quite different, 2.337(11) A for the coordinated bond
h at ꢄ20 8C in pentane. Yield: 0.11 g, 8%. M.p. (dec.):
/
dinations. In solid state, the observed Geꢀ
/
1
160 8C. H NMR (C6D6, 250.1 MHz, d ppm): 7.16 (13
˚
peaks, 5JH/F
ꢁ
/
4.5 Hz, 1H, Geꢀ
/
H), 7.75 (s, 4H, 3,5-aryl-
˚
N(2)0
/
Ge and 2.570(10) A for the other distance Geꢀ
/
H); 13C NMR (C6D6, 62.9 MHz, d ppm): 122.48 (q,
N(1). This latter is the longest coordination bond of all
known chlorogermylenes with substituents bearing ni-
1JC/F
o-CF3), 127.32 (s, 3,5-aryl-C), 133.57 (q, JC/F
ꢁ
/
273.7 Hz, p-CF3), 123.27 (q, J C/Fꢁ
/
275.7 Hz,
1
2
ꢁ
/
34.8
34.1 Hz, 4-aryl-C),
trogen donors in a side-chain. At the opposite, the Geꢀ
/
1
Hz, 2,6-aryl-C), 136.87 (q, JC/F
ꢁ
/
˚
Cl bond (2.309(4) A), oriented almost orthogonal to the
165.41 (s, 1-aryl-C); 19F NMR (C6D6, 188.3 MHz, d
ppm): 11.96 (s, 6F, p-CF3), 20.15 (s, 12F, o-CF3); IE MS
plane of the aryl ligand, lies in the range of chloroger-
mylenes coordinated by a side-chain nitrogen atom (see
Table 2). The geometry at the germanium center may
show us that the degree of hybridization of the metal is
(70 eV, m/z %): 671 (Mꢃꢄ
/
Hꢃ, 1), 653 (Mꢃꢄ
/
F, 2), 637
Ar, 100), 355 (ArGe, 5); IR
(Mꢃꢄ
/
Cl, 2), 391 (Mꢃꢄ
/
(C6D6, cmꢄ1): 2187.0 (n(GeH)).
quite low. Indeed, the angles (Table 1) C(1)ꢀ
Cl(1), C(1)ꢀGe(1)ꢀN(2), N(2)ꢀGe(1)ꢀCl(1), C(1)ꢀ
Ge(1)ꢀN(1) are in the range of 908 (74.2(4)8ꢂ97.2(4)8).
/
Ge(1)ꢀ
/
/
/
/
/
/
/
/
2.2.7. Preparation of chlorobis[2,6-
bis(trifluoromethyl)phenyl]germane Ar2GeHCl
ƒ
This seems indicate that the bonds to the ligands are
involving p-orbitals at the germanium atom. So, the
nitrogen atoms of the side-chains can interact easily with
the vacant p-orbital on the germanium; the lone pair is
A solution of [2,6-bis(trifluoromethyl)phenyl]lithium
[6] (50.61 mmol) in THF (100 ml) was added dropwise to
a solution of GeCl2×
/
dioxane (2.34 g, 10.11 mmol) in
THF (100 ml) at ꢄ78 8C during a period of 1 h. The
/
mixture was allowed to warm up to r.t. and stirred for 8
h. All volatiles were removed in vacuum, 100 ml of
pentane was added to filter the insoluble salts. A orange
powder precipitated at ꢄ20 8C in pentane. Yield: 0.54 g,
/
10%. M.p.: 132 8C. 1H NMR (C6D6, 250.1 MHz, d
3
ppm): 6.64 (t, JH/H
ꢁ7.9 Hz, 2H, 4-aryl-H), 7.27 (d,
/
3JH/H
ꢁ
/
7.9 Hz, 2H, 3,5-aryl-H), 7.38 (13 peaks, 5JH/F
H). 13C NMR (C6D6, 62.9 MHz, d
ꢁ
/
4.2 Hz, 1H, Geꢀ
/
1
ppm): 124.33 (q, JC/F
ꢁ274.9 Hz, o-CF3), 130.50 (s, 4-
/
2
aryl-C), 130.73 (s, 3,5-aryl-C), 135.51 (q, JC/F
ꢁ33.1
/
Hz, 2,6-aryl-C), 169.02 (s, 1-aryl-C); 19F NMR (C6D6,
188.3 MHz, d ppm): 20.54 (s); IE MS (70 eV, m/z %):
535 (Mꢃꢄ
/
Hꢃ, 3), 501 (Mꢃꢄ
/
Cl, 7), 323 (Mꢃꢄ
Ar,
/
Fig. 1. Thermal ellipsoid plot (30%) of 1. Hydrogen atoms are not
shown. Important structural data are given in Table 1.
100); IR (C6D6, cmꢄ1): 2167.9 (n(GeH)).

2830
C. Bibal et al. / Polyhedron 21 (2002) 2827ꢂ2834
/
Table 1
Known so far stable and isolated halogermylenes are
chronologically reported in Table 2. We can distinguish
˚
Selected bond length (A) and angles (8) for 1
alkyl or arylhalogermylenes with Cꢀ
(compounds 1ꢂ2, 9ꢂ11, 13, 16ꢂ19, 23, 25ꢂ
heterohalogermylenes with YꢀGeꢀX (Yꢁ
moieties (compounds 3ꢂ8, 12, 14ꢂ15, 20ꢂ22, 24, 27ꢂ
34). As expected, a comparison of different coordinated
and non coordinated derivatives shows that intramole-
cular coordination of the amino functionality in the
side-chain makes longer and so weakens drastically the
/
Geꢀ
26, 35) and
N, O, P)
/
X linkage
Bond lengths
/
/
/
/
Ge(1)ꢀN(2)
Ge(1)ꢀCl(1)
2.337(11) Ge(1)ꢀN(1)
2.570(10)
1.941(11)
2.309(4)
Ge(1)ꢀC(1)
/
/
/
/
/
/
/
Bond angles
C(1)ꢀGe(1)ꢀCl(1)
C(1)ꢀGe(1)ꢀN(2)
97.2(4)
76.9(4)
N(2)ꢀGe(1)ꢀCl(1)
C(1)ꢀGe(1)ꢀN(1)
89.2(3)
74.2(4)
Geꢀ
/
Cl bond. Accordingly, such derivatives are suitable
localized in an orbital with high s character. On the
other hand, 1 exhibits a surprisingly short GeꢀC(1)
bond length (1.941(11) A) appreciably shorter than in
synthons for easy nucleophilic substitutions at the
divalent metal to access to many heteroleptic germy-
lenes. In our group, a recent example showed that
diazogermylenes RGeC(N2)R?, precursors of germynes
/
˚
˚
the other halogermylenes (1.989(5)ꢂ
2). This value seems to indicate a back bonding
donation of the germanium to the ipso-carbon
arising from consequent electronic effects of the two
side-chain ligands: donation N0Ge and withdrawing
/2.402(3) A) (Table
RGeꢁCR?, have been obtained from correspondent
chlorogermylenes 1 or 2 and a lithiodiazo compound
[12].
/
/
If many halogermylenes are stabilized by donor
ligands (cf. Table 2), none monohalogermylene bearing
strong electron-withdrawing effect substituent is known
yet. In this area, only the symmetric diarylgermylene
?
Ar2Ge: [Ar?ꢁ2,4,6-tris(trifluoromethyl)phenyl] has
been described [13]. In order to have suitable synthons
to access to electron poor low coordinated species of
germanium, we attempted to synthesize the two chlor-
inductive effect of the two ortho CH2NEt2 moieties,
increasing the electrophilic character of the ipso-carbon.
Removal of the back bonding by complexation of the
germanium atom, for example in the recently described
/
complex ArGeOH×
/
W(CO)5, leads as expected to a
˚
lengthening of the Geꢀ
/
C(1) bond (1.975(3) A) [8]. This
explanation can also be supported regarding the 13C
NMR chemical shift of the ipso-carbons C(1). Indeed, in
the above complex, the C(1) appears at 153.44 ppm [8],
much more shielded than in 1 (157.48 ppm) or in 2
(158.86 ppm). The 1H NMR spectra (80 MHz) of 1 and
2 at room temperature show that, in solution, the
chelate side-chains are equivalent due to a rapid
exchange of the coordination sites. The signal of the
two inequivalent benzyl hydrogen atoms appears as an
AB pattern; moreover, in the case of 1, we can also
observe two resonances for the methylenic protons of
the ethyl groups due to the chirality of the germanium
atom and for 2, two resonances for the methyl protons
of the isopropyl groups.
ogermylenes Ar?GeCl and ArƒGeCl (Arƒꢁ
fluoromethyl)phenyl).
/2,6-bis(tri-
3.3. New chlorodiarylgermanes
Surprisingly, the classic reaction using stoichiometric
amounts of lithio-derivatives Ar?Li [5] or ArƒLi [6] with
complex GeCl2×
chlorogermylenes but beside unidentified products to
/dioxane, did not lead to the expected
?
ƒ
chlorodiarylgermanes Ar2GeHCl and Ar2GeHCl in low
yields. In these compounds, the hydrogen atom bonded
to germanium exhibits an exceptional acidic character
because of the strong withdrawing effects of two aryl
3.2. Comparison of 1 and 2 with reviewed halogermylenes
1
groups 14 and of the chlorine atom. Thus, in the H
Fruitful comments can be made from a study of
known stable and isolated halogermylenes (Table 2).
Non hindered halogermylenes such as ethylchloroger-
mylene EtGeCl and phenylchlorogermylene PhGeCl
were the first representatives of halogermylenes [9,10].
These chlorogermylenes are ‘associated’ by intermole-
NMR spectra, the deshielded Geꢀ
?
7.16 ppm for Ar2GeHCl and at 7.38 ppm for Ar2GeHCl
/H signal appears at
ƒ
and in the Infra-Red spectra, we can observe character-
istic nGeꢀH at 2187.0 cmꢄ1 for Ar2GeHCl and at 2167.9
cmꢄ1 for Ar2GeHCl. These results evidenced the
?
ƒ
instability of these chlorogermylenes in our experimen-
tal conditions. Formation of chlorodiarylgermanes re-
mains difficult to explain; we can postulate that creation
cular germaniumꢀ
/
chlorine bonds but without Geꢀ
/
Ge
F, Cl,
bonds. All phenylhalogermylenes PhGeX (Xꢁ
/
Br, I) have been synthesized [11]. Later, were described
the most interesting halogermylenes stabilized as mono-
meric species by hindered substituents or by donor
ligands. Chlorogermylenes RGeCl are the most numer-
ous owing to the easy available and most often used
of a Geꢀ/H linkage probably arises from a radical
process. Is this result in relation with a triplet structure
of germylenes bearing strong electron-withdrawing
groups such as Ar? or Arƒ and Cl? This question is
now in study.
dichlorogermylene GeCl2×
/
C4H8O2 complex precursor.

C. Bibal et al. / Polyhedron 21 (2002) 2827ꢂ
/
2834
2831
Table 2
Stable and isolated halogermylenes (chronological order)

2832
C. Bibal et al. / Polyhedron 21 (2002) 2827ꢂ2834
/
Table 2 (continued)

C. Bibal et al. / Polyhedron 21 (2002) 2827ꢂ
/
2834
2833
Table 2 (continued)
ꢀ dimeric structure.
ꢀꢀ no structure.
[4] (a) H. Schumann, W. Wassermann, A. Dietrich, J. Organomet.
Chem. 365 (1989) 11;
4. Supplementary material
(b) J.A.M. van Beek, G. van Koten, G.P.C.M. Dekker, E.
Wissing, M.C. Zoutberg, C.H. Stam, J. Organomet. Chem. 394
(1990) 659;
Crystallographic data for the structural analysis of 1
have been deposited with the Cambridge Crystallo-
graphic Data Centre, CCDC No. 189943. Copies of
this information may be obtained free of charge from
The Director, CCDC, 12 Union Road, Cambridge, CB2
(c) H. Schumann, U. Hartmann, W. Wassermann, Chem. Ber. 124
(1991) 1567.
[5] G.E. Carr, R.D. Chambers, T.F. Holmes, D.G. Parker, J.
Organomet. Chem. 325 (1987) 13.
1EZ, UK (fax:
it@ccdc.cam.ac.uk or www: http://www.ccdc.cam.a-
ꢃ44-1223-336033; e-mail: depos-
/
[6] M.P. Bigwood, P.J. Corvan, J.J. Zuckermann, J. Am. Chem. Soc.
103 (1981) 7643.
c.uk).
[7] Crystal data for 1: C16H27ClGeN2, Mrꢁ
space group P21/c, aꢁ7.342(1), bꢁ
bꢁ92.42(2)8, Vꢁ3558.2(10) A , Zꢁ
F(000)ꢁ1488, lꢁ
mmꢄ1
crystal dimensions 0.6ꢅ
21.498, 27 345 reflections (Rint 0.1339) were collected on a
/
355.44, monoclinic,
˚
/
/
19.215(4), cꢁ25.244(4) A,
/
3
1.327 Mg mꢄ3
1.866
U 5
,
˚
/
/
/
8, rcalcd
293(2) K, m (Mo Ka)ꢁ
0.2ꢅ0.1 mm, 1.9385
ꢁ/
˚
/
/
0.71073 A, Tꢁ
/
/
,
/
/
/
/
ꢁ
/
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