Synthesis and characterization of Group 14 elements - Dithienylsulfur cycloadducts and oligomers

Article abstract of DOI:10.1016/S0020-1693(00)00111-0

T31he reactions of various organometallic dichlorides R₂MCl₂ (R = Bu, Ph; M = Si, Ge, Sn) with 2,2'-dilithio 3,3'-dithienylsulfur were described. They gave simultaneously cycloadducts and oligomers. The X-ray crystal structure of the heterocycle 3b shows a slightly distorted six-membered ring with the two heteroatoms (sulfur and germanium) in a boat conformation. The molecular weights of the oligomers were determined by size exclusion chromatography. Starting from metal divalent species, insoluble oligomers were obtained. The presence of bivalent metallic sites in these chains was verified by cycloaddition reaction with 3,5-di-t-butyl orthoquinone. Electrical studies show that these non-doped oligomers behave as semi-conductors. (C) 2000 Elsevier Science S.A.

Full text of DOI:10.1016/S0020-1693(00)00111-0

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Inorganica Chimica Acta 305 (2000) 46–52
Synthesis and characterization of Group 14
elements — dithienylsulfur cycloadducts and oligomers
Sandrine Faure´, Bruno Valentin, Jacques Rouzaud, Heinz Gornitzka, Annie Castel,
Pierre Rivie`re *
Laboratoire d’He´te´rochimie Fondamentale et Applique´e, UMR no. 5069, Uni6ersite´ Paul Sabatier, 118 Route de Narbonne,
F-31062 Toulouse Ce´dex 04, France
Received 20 January 2000; accepted 8 March 2000
Abstract
The reactions of various organometallic dichlorides R2MCl2 (R =Bu, Ph; M =Si, Ge, Sn) with 2,2%-dilithio 3,3%-dithienylsulfur
were described. They gave simultaneously cycloadducts and oligomers. The X-ray crystal structure of the heterocycle 3b shows a
slightly distorted six-membered ring with the two heteroatoms (sulfur and germanium) in a boat conformation. The molecular
weights of the oligomers were determined by size exclusion chromatography. Starting from metal divalent species, insoluble
oligomers were obtained. The presence of bivalent metallic sites in these chains was verified by cycloaddition reaction with
3,5-di-t-butyl orthoquinone. Electrical studies show that these non-doped oligomers behave as semi-conductors. © 2000 Elsevier
Science S.A. All rights reserved.
Keywords: Heterocycle; Organometallic polymers; Polygermylenes; Electrical conductivity
1. Introduction
2. Experimental
The role of organometallic polymers in material
chemistry has recently increased considerably [1]. The
presence of a Group 14 metal (M =Si or Ge) in poly-
meric chains introduces specific physical properties
(conductivity [1], electroluminescence [2]). The best
known are the polysilanes and polygermanes [3] in
which electron delocalization can occur through the s
electrons of metalꢀmetal bonds. On the other hand, for
polymers having one or two alternating Group 14 metal
atoms and a p-conjugated system (acetylene, phenyl,
thiophene, pyrrol, etc.) [1,4], s–p delocalization is con-
sidered. In this work, we are interested in polycon-
densed structures having the potential semi-conductors
properties. Towards this end, we have used a novel
ligand, 3,3%-dithienylsulfur, capable of giving cycloaddi-
tion or polymerization reactions.
All of the reactions were performed under a dry
nitrogen atmosphere using standard Schlenk techniques
and dry solvents. NMR spectra were recorded on
Bruker AC 80 (1H), AC 200 (13C, in the sequence
Jmod) and Bruker 300 (13C NMR in the solid state,
ENSCM, Montpellier). Mass spectra were measured
with a Hewlett –Packard HP 5989 in the electron im-
pact mode (70 eV) or a Rybermag R10-10 spectrometer
operating in the electron impact mode or by chemical
desorption (DCI, CH4). IR spectra with a Perkin –
Elmer 1600 FT spectrometer. SEC analysis was per-
formed using a Waters apparatus fitted with three
Styragel HR® columns (10 , 10 , and 10 A) and refrac-
tometry detection. Melting points were measured on a
Leitz microscope. Elemental analysis were performed
by the Centre de Microanalyse de l’Ecole Nationale
Supe´rieure de Chimie de Toulouse.
2
3
4
,
* Corresponding author. Tel.: +33-561-558 348; fax: +33-561-
558 204.
E-mail address: riviere@ramses.ups-tlse.fr (P. Rivie`re)
The 3,3-dithienylsulfur was prepared as described in
[5].
0020-1693/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(00)00111-0

S. Faure´ et al. / Inorganica Chimica Acta 305 (2000) 46–52
47
2.1. Reaction of 2 with Bu2GeCl2
When more dilute solutions (2.29 mmol of 2 in 15 ml
of diethylether and Ph2GeCl2 (0.68 g, 2.29 mmol) in 25
ml of diethylether at −15°C) were used, small quanti-
ties of monomeric heterocycle 3b can be isolated from
the methanolic filtrate using the procedures described:
after concentration of MeOH, the extraction of the
residue using hot hexane gave a white powder 0.39 g
(40%) which was recrystallized from CHCl3. 3b: m.p.
112–116°C. H NMR (CDCl3): l 7.22 (d, J =5 Hz,
2H, H4), 7.72 (d, 3J =5 Hz, 2H, H5), 7.01–7.90 (m,
10H, C6H5). 13C{1H} NMR (CDCl3): l 128.70 (C8),
130.00 (C9), 134.65 (C7), 136.97 (C6) (C6H5); 120.78
(C2), 127.11 (C5), 131.61 (C4), 135.22 (C3) (C4H2S). MS:
m/z 424 ([M ]+, 78%), 347 ([M −Ph], 100%). Anal.
Calc. for C20H14GeS3: C, 56.77; H, 3.33. Found: C,
56.12; H, 3.29%.
A solution of Bu2GeCl2 (0.39 g, 1.5 mmol) in 3 ml of
diethylether was added dropwise to a solution of 2 [5,7]
(1.5 mmol) in 3 ml of diethylether at 0°C. After having
been stirred at 20°C for 15 h, the mixture was hy-
drolyzed. After extraction, drying under Na2SO4, the
1
solvents were evaporated. The H NMR analysis of the
1
3
crude mixture shows the formation of 3a (60%) and 4a
1
(40%). 4a: H NMR (CDCl3): l 0.70–1.79 (m, 18H,
Bu), 6.64–6.94 (m, 2H, H4), 7.27–7.56 (m, 2H, H5).
The mass spectrum (DCI, CH4) indicates the presence
of 5a: m/z 767 ([M +1], 2%), 709 ([M −Bu], 2%).
When the same reaction was performed in more
dilute solutions (2.8 mmol of Bu2GeCl2 in 17 ml of
diethylether and 2 (2.8 mmol) in 30 ml of diethylether
at −15°C), the distillation of the residue led to pure
2.3. Crystal and experimental data for 3b
3a: Eb: 110°C/5.10−3 mmHg), 0.21 g (20%). H NMR
1
3
(CDCl3): l 0.70–1.79 (m, 18H, Bu), 7.10 (d, J =5 Hz,
[C20H14GeS3], Mr =423.08, orthorhombic, Pbca, a =
3
2H, H4), 7.63 (d, J =5 Hz, 2H, H5). 13C{1H} NMR
,
13.544(2), b=15.115(2), c=17.544(2) A, V=3591.6(8)
(CDCl3): l 13.70 (CH3), 16.61, 26.07 and 27.15 (CH2);
122.75 (C2), 126.90 (C5), 130.33 (C4), 135.63 (C3)
(C4H2S). MS: m/z 384 ([M ]+, 23%), 327 ([M −Bu],
100%). Anal. Calc. for C16H22GeS3: C, 50.16; H, 5.79;
S, 25.11. Found: C, 50.81; H, 6.09; S, 24.75%.
3
A , Z =8, Dcalc=1.565 Mg m−3, F(000)=1712, u=
,
−1
,
0.71073 A, T =173(2) K, v(Mo Ka)=2.053 mm
,
crystal size 0.6×0.4×0.3 mm, 2.33°BqB22.59°,
29 369 reflections (2363 independent) collected on a
STOE-IPDS diffractometer. A semi-empirical absorp-
tion correction was performed (Tmax=0.7337 and
Tmin =0.5094). The structure was solved by direct
method using SHELXS-97 [8] and refined using the least-
squares method on F2 [9]. All non-hydrogen atoms
were refined anisotropically and all hydrogen atoms
were refined with a riding model. Maximum residual
2.2. Reaction of 2 with Ph2GeCl2
To a solution of 2 (2 mmol) in 3.5 ml of diethylether
was added (0.60 g, 2 mmol) of Ph2GeCl2 at 0°C. The
mixture was stirred for 12 h at 20°C. After hydrolysis,
extraction with a THF/Et2O mixture, concentration of
the solvents, the residue was extracted with 13 ml of
methanol leading to the formation of a white powder
which was isolated after decantation and drying: 4b,
electron density 0.239 e A−3, R1 [I \2|(I)]=0.0202
,
and wR2 (all data)=0.0436 with R1=SꢀꢀFoꢀ−ꢀFcꢀꢀ/SꢀFoꢀ
2
2 2
2 2 1/2
and wR2=[Sw(Fo −Fc ) /Sw(Fo ) ] . Selected bond
lengths and angles are displayed in Table 1.
1
0.77 g (90%); m.p. 96–100°C (dec.). H NMR (CDCl3):
l 7.14–7.65 (m, 14H, C6H5, C4H2S). 13C{1H} NMR
(CDCl3): l 128.58 (C8), 129.68 (C9), 134.55 (C7) (C6H5);
127.03 (C5), 131.46 (C4) (C4H2S). Anal. Calc. for
C20H14GeS3: C, 56.77; H, 3.33. Found: C, 56.20; H,
3.87%. The mass spectrum (DCI, CH4) shows the pres-
ence of 5b: m/z 846 ([M ]+, 3%), 769 ([M −Ph], 5%).
2.4. Reaction of 2 with Bu2SnCl2
Using the same procedure as described above, 1.49
mmol of 2 in 3.5 ml of diethylether and Bu2SnCl2 (0.45
g, 1.49 mmol) gave after concentration, a viscous oil.
1
The H NMR analysis of the crude mixture shows the
presence of 3c (39%) and 4c (37%). Treatment by a
Et2O/pentane mixture (1:4), and further decantation
gave a yellow oil containing principally the oligomer 4c,
while the pentanic solution indicates the major forma-
Table 1
,
Selected bond lengths (A) and bond angles (°) for 3b
Ge(1)ꢀC(1)
Ge(1)ꢀC(5)
Ge(1)ꢀC(15)
Ge(1)ꢀC(9)
S(1)ꢀC(2)
1.915(2)
1.926(3)
1.933(2)
1.939(2)
1.755(2)
S(1)ꢀC(6)
S(2)ꢀC(4)
S(2)ꢀC(1)
C(1)ꢀC(2)
C(3)ꢀC(4)
1.766(3)
1.704(3)
1.719(2)
1.370(3)
1.351(4)
1
tion of 3c. H NMR (CDCl3): l 0.70–1.85 (m, 18H,
3
3
Bu), 7.20 (d, J =5 Hz, 2H, H4), 7.66 (d, J =5 Hz, 2H,
H5). 13C{1H} NMR (CDCl3): l 13.71 (CH3); 13.55,
27.19 and 28.46 (CH2); 125.31 (C2), 127.88 (C5), 131.32
(C4), 137.53 (C3) (C4H2S). MS: m/z 430 ([M ]+, 21%),
C(1)ꢀGe(1)ꢀC(5)
C(1)ꢀGe(1)ꢀC(15) 112.41(10)
C(5)ꢀGe(1)ꢀC(15) 114.75(11)
C(1)ꢀGe(1)ꢀC(9)
C(5)ꢀGe(1)ꢀC(9)
C(15)ꢀGe(1)ꢀC(9) 110.67(10)
99.60(11)
C(2)ꢀS(1)ꢀC(6)
C(4)ꢀS(2)ꢀC(1)
C(2)ꢀC(1)ꢀGe(1) 125.97(18)
C(1)ꢀC(2)ꢀS(1) 127.2(2)
C(6)ꢀC(5)ꢀGe(1) 125.0(2)
C(5)ꢀC(6)ꢀS(1) 127.9(2)
105.77(12)
92.83(12)
1
373 ([M −Bu], 93%). 4c: H NMR (CDCl3): l 0.70–
3
1.85 (m, 18H, Bu), 6.87 (d, J =5 Hz, 2H, H4), 7.50 (d,
110.33(11)
108.55(11)
3J =5 Hz, 2H, H5). The mass spectrum indicates the
presence of 5c. m/z 859 ([M +1], 100%), 801 ([M −Bu],
91%).

48
S. Faure´ et al. / Inorganica Chimica Acta 305 (2000) 46–52
2.5. Reaction of 2 with Ph2SiCl2
2.8. Reaction of 2 with Cl2M
A solution of 2 (1.5 mmol) in 3.5 ml of diethylether
was added to a solution of Ph2SiCl2 (0.38 g, 1.5 mmol)
in 3 ml of diethylether at −15°C. The mixture was
stirred for 12 h at 20°C, then refluxed for 1 h. After
hydrolysis, extraction with a mixture Et2O/THF, drying
on Na2SO4 and concentration of the solvents, a brown
oil was obtained. This oil was dissolved in 1 ml of
diethylether and added to 15 ml of MeOH. After
decantation, a new brown oil was dried under vacuo
and identified to be oligomeric form 4d: 1H NMR
A 1.49 mmol sample of 2 in 15 ml of Et2O was added
to a suspension of Cl2M (Cl2Ge, dioxane or Cl2Sn)
(1.50 mmol) in 8 ml of diethylether at −15°C. The
mixture was stirred for 12 h at 20°C, yielding a precip-
itate. After decantation and drying, yellow powder very
sensitive to hydrolysis was obtained. 7a: m.p. \300°C.
1H NMR (CDCl3, DMSO-d6): l 6.50–7.40 (m, 4H,
C4H2S). IR (Nujol): l(CH): 720 and 865 cm−1, we also
observed the presence of H2O: w(OH): 3391 cm−1 and
l(HOH): 1633 cm−1. 7b: m.p. \300°C. 1H NMR
(CDCl3, DMSO-d6): l 6.50–7.20 (m, 4H, C4H2S). IR
(Nujol) l(CH): 716 and 865 cm−1, w(OH): 3391 and
3
(CDCl3): l 7.19 (d, J =5 Hz, 2H, H4), 7.36–7.45 (m,
5H, C6H5), 7.64–7.76 (m, 7H, C6H5, H5). The filtrate
was concentrated, the residue extracted with hot hex-
ane. After cooling at −30°C for 12 h, a white powder
was isolated after decantation and drying: 3d: 0.16 g
(33%). 1H NMR (CDCl3): l 7.20 (d, 3J =5 Hz, 2H,
l(HOH): 1633 cm−1
.
2.9. Preparation of 9
3
H4), 7.74 (d, J =5 Hz, 2H, H5), 7.37–7.78 (m, 10H,
To a solution of 2,5-dilithiothiophene [10] (1.0 mmol)
in 2 ml of THF was added Cl2Ge·dioxane (0.21 g, 0.9
mmol) at −40°C. The mixture was stirred for 3 h at
this temperature and then slowly warmed to room
temperature (r.t.). After decantation and washing with
THF, a yellow powder was obtained. 13C NMR (solid
state): l 125–140 (large signal, C4H2S). IR (Nujol):
C6H5). 13C{1H} NMR (CDCl3): l 128.36 (C8), 130.52
(C9), 135.82 (C7), 139.73 (C6) (C6H5); 120.20 (C2),
127.14 (C5), 133.95 (C3), 135.05 (C4) (C4H2S). MS: m/z
378 ([M ]+, 78%), 301 ([M −Ph], 100%). We could also
detect traces of oxidized compound: m/z 576 ([M ]+,
30%), 499 ([M −Ph], 25%).
l(CH): 808 cm−1
.
2.10. Reaction of 7a and 9 with 3,5-di-t-butyl
ortho-quinone
A mixture of polymer 7a or 9 (0.67 mmol) and (0.11
g, 0.50 mmol) of quinone in 2 ml of THF was heated in
a sealed tube at 100°C for 2 days. After concentration,
the residue was extracted with a mixture of 2 ml of
Et2O and 3 ml of pentane giving a white powder,
identified to be the spirocompound 8 [11] (20–30%).
2.6. Reaction of 2 with MesGeCl3
To a solution of 2 (2 mmol) in 3.5 ml of diethylether
was added (0.60 g, 2 mmol) of MesGeCl3 in 3 ml of
diethylether at −10°C. The mixture was stirred at 20°C
for 3 h. After hydrolysis (3 N HCl), extraction and
2.11. Preparation of 10
1
drying, the solution was concentrated. The H NMR
analysis shows the formation of 3e (20%) and
polygermylenes (MesClGe)n. 3e: H NMR (CDCl3): l
Triethylamine (0.16 g, 1.55 mmol) was added drop-
wise to a solution of catechol (0.18 g, 0.79 mmol) and
dithienyldichlorogermane (0.23 g, 0.75 mmol) in 2 ml of
benzene. The mixture was refluxed for 4 h. Benzene (9
ml) was then added and the mixture filtered (elimina-
tion of Et3N·HCl). The filtrate was concentrated and
the residue extracted with 5 ml of pentane. The white
solid, obtained after decantation and drying, was re-
crystallized from 2 ml of toluene. 10: m=0.20 g (59%);
1
2.26 (s, 6H, o-CH3), 2.43 (s, 3H, p-CH3), 6.86 (sl, 2H,
3
3
C6H2), 7.12 (d, J =5 Hz, 2H, H4), 7.72 (d, J =5 Hz,
2H, H5). MS: m/z 424 ([M ]+, 17%), 389 ([M −Cl], 4%),
305 ([M −Mes], 23%).
2.7. Reaction of 2 with Mes2GeCl2
1
Using the same procedure as described above, 2 (0.9
mmol) in 2 ml of diethylether and Mes2GeCl2 (0.35 g,
0.9 mmol) in 1.5 ml of diethylether at 0°C gave an
m.p. 175°C. H NMR (CDCl3): l 1.30 (s, 9H, t-Bu),
1.40 (s, 9H, t-Bu), 7.36 (dd, J3–4=3.5, J4–5=4.8 Hz,
2H, H4), 7.71 (d, J3–4=3.5 Hz, 2H, H3), 7.87 (d,
J4–5=4.8 Hz, 2H, H5), 6.86 (d, J =2.2 Hz, 1H, H5%),
6.99 (d, J =2.2 Hz, 1H, H3%). 13C{1H} NMR (CDCl3):
l 29.58 and 31.78 (CH3); 34.90 (Cquat, t-Bu); 109.38
(C3%), 114.62 (C%), 134.56 (C%, C%), 142.43 (C%); 148.88
1
orange solid. The H NMR analysis shows the major
formation of (Mes2Ge)n: 2.25 (sl, 18H, o-CH3 and
p-CH3), 6.79 (sl, 4H, C6H2). The mass spectrum indi-
cates the formation of 3f: m/z 508 ([M ]+, 3%), 389
([M −Mes], 19%).
5
4
6
1
(C2%) (C6H2); 127.31 (C2), 128.68 (C4), 134.56 (C5),

S. Faure´ et al. / Inorganica Chimica Acta 305 (2000) 46–52
49
(2)
Regardless of the experimental conditions used (reac-
tion temperature, mode of addition of reagents, dilu-
tion, etc.) it was not possible to favor monomeric
heterocycles. All these heterocycles are sensitive to hy-
drolysis and oxidation. They decomposed rapidly dur-
ing attempts at recrystallization or during separation of
the reaction mixture. Nevertheless, they were perfectly
characterized by physical and chemical measurements
(1H and 13C NMR and mass spectrometry). Com-
pounds 3a and 3b could be isolated in pure form after
distillation or recrystallization. An X-ray crystal-struc-
ture study of compound 3b confirmed its monomeric
form as shown in Fig. 1. It also shows a slightly
distorted six-membered ring with the two heteroatoms
(sulfur and germanium) in a boat conformation. The
Fig. 1. Molecular structure of 3b in the solid state.
138.46 (C3) (C4H2S). MS: m/z 460 ([M ]+, 51%), 445
([M −CH3], 66%). Anal. Calc. for C22H26GeO2S2: C,
57.55; H, 5.70. Found: C, 57.80; H, 5.88%.
,
Ge(1) and S(1) atoms are 0.37 and 0.33 A out of the
A solution of 10 (0.05 g, 0.11 mmol) in 1 ml of
benzene was heated to 100°C for 12 h. The decomposi-
best plane formed by C(1), C(2)ꢀC(5) and C(6). The
1
,
bond distances C(1)ꢀC(2), 1.370(3) A and C(5)ꢀC(6),
tion was followed by H NMR spectroscopy showing
,
1.368(4) A are very close to that of the standard double
the formation of 8 (90%) and the presence of 10 (10%)
unchanged.
bond indicating that they are localized double bonds.
The corresponding angles C(1)ꢀC(2)ꢀS(1), 127.2(2)°,
C(2)ꢀC(1)ꢀGe(1),
125.97(18)°,
C(5)ꢀC(6)ꢀS(1),
127.9(2)° and C(6)ꢀC(5)ꢀGe(1), 125.0(2) deviate slightly
from the values expected for an sp2-hybridized C atom,
as it was often observed in heterocyclic structure con-
taining a germanium element [12,13]. The thiophene
rings are almost planar, with maximum deviation from
3. Results and discussion
The ligand 3,3%-dithienylsulfur was prepared in 35%
yield by the reaction of 3-thienyllithium with di(phenyl-
sulfonyl)sulfur (Eq. (1)) [5]. This low yield can be
explained by the low thermal stability of 3-thienyl-
lithium, which decomposes at −70°C [6] to give the
dithiophene. By contrast, 3,3%-dithienylsulfur is very
stable and was isolated in pure form after distillation.
,
the mean plane of the thiophene ring of 0.009 A for
C(1). The thiophene planes formed an angle of 155.5°
preventing any planarity of the tricyclic system in con-
trast to the structure of dithienosilole [14]. The germa-
nium atom retains its tetrahedral geometry though it is
slightly deformed. The C(1)ꢀGe(1)ꢀC(5) angle is de-
creased to 99.60(11)°, whereas the C(1)ꢀGe(1)ꢀC(15)
and C(5)ꢀGe(1)ꢀC(15) are increased to 112.41(10) and
114.75(11), respectively, probably due to the six-mem-
bered ring strain [13]. The GeꢀC distances are consis-
tent with literature data [13].
(1)
Interest in this species rests in achieving selective
metallation reactions at positions 2 and 2% [5,7]. The
dilithio reagent, 2,2%-dilithio 3,3%-dithienylsulfur 2, ob-
tained by the reaction of 1 with nBuLi at 0°C, reacts
easily with organometallic dichlorides to give heterocy-
cles 3 and oligomers 4 simultaneously, which are very
difficult to separate (Eq. (2)).
Molecular weights of the oligomers 4 were deter-
mined by SEC (size exclusion chromatography), by
comparison with polystyrene references using THF as
the eluent. Due to this determination, only the compari-
son between the masses of the different samples from
one series is significant. This method cannot give exact
molecular weights. To test its range of validity, we

50
S. Faure´ et al. / Inorganica Chimica Acta 305 (2000) 46–52
analyzed reaction mixtures containing mixtures of
monomers 3a (Mw 384), 3b (424), and 3c (430). The
molecular weights obtained were 450, 470, and 490,
respectively. Agreement with exact values is not very
high. We conclude that the derivatives in Table 2 are
oligomers having four to eight units.
In the polymeric portion, we were also able to detect
cyclic dimers of calixarene type [15,16] (Eq. (3)), which
could be identified only by mass spectrometry.
These compounds do not melt and are practically
insoluble in common organic solvents (ethers, chlori-
nated solvents, DMSO, DMF). They could be charac-
terized by their IR spectra. The bands observed at 720
and 820 cm−1 seem to correspond to deformation
vibrations l(CH) out of the plane of the 2,3-disubsti-
tuted species. Indeed, all of the l(CH) bands of the di-
and tri-substituted thiophenes are found in this region
[17]: 788 cm−1 corresponding to 2,5-disubstituted, 730
and 820 cm−1 for the 2,4-disubstituted, and 810 cm−1
for the 2,3,5-trisubstituted. These oligomers readily re-
act water as evident from IR bands at 3400 cm−1
w(OH) and 1636 cm−1 l(OH) which are observed
regardless of the method used (KBr disk or Nujol mull
under nitrogen).
To verify the presence of bivalent metallic sites in
these chains, we tried cycloaddition reactions with 3,5-
di-tert-butyl orthoquinone; quinones being excellent
reagents in the characterization of bivalent species [11].
The reaction of oligomers with 3,5-di-tert-butyl ortho-
quinone, when carried out in sealed tubes at 100°C,
gave mainly the spiro compound 8 (Eq. (6)).
(3)
By contrast, when steric hindrance of the
organometallic group increases (R2M =MesClGe,
Mes2Ge), the nucleophilic substitution reaction be-
comes more difficult and heterocycle 3 could be de-
tected only in low yield (R2M =MesClGe 3e, 25%;
R2M =Mes2Ge 3f, traces in mass spectra).
In the case of MesGeCl3, a competitive halogen/
lithium exchange reaction occurred because we were
able to identify 3,3%-dithienylsulfur monochloride [M+]
232 and dichloride ([M+] 266) (Eq. (4)) by mass
spectrometry.
(6)
Compound 8 probably resulted by thermal redistri-
bution of the intermediate cycloadduct. We tried to
confirm the intermediate beginning with a simpler spe-
cies: a thiophene. The 2,5-dilithiothiophene was pre-
n
pared by the reaction of the BuLi with the dibromo
(4)
derivative [10] (Eq. (7)). Its reaction with dichloro-
germylene gave oligomer 9 which, as before, does not
melt and is only slightly soluble in common organic
solvents. It was characterized by IR and 13C NMR
measurements in the solid state. We observed a large
signal (125–140 ppm) which corresponds to carbon
atoms of the cyclic thiophene. The strong widening of
this signal is due in part to the presence of reticular
polymers.
The weakly stable organochlorogermyllithium 6 de-
composes to give mesitylchlorogermylene, which poly-
merizes rapidly.
The reaction of 2,2%-dilithio 3,3%-dithienylsulfur with
dichlorogermylene and stannylene results in oligomers 7
(Eq. (5)).
(5)
Table 2
Molecular weights of oligomers 4
(7)
The reaction with 3,5-di-tert-butyl orthoquinone
causes a change in colour of the reaction mixture, an
indication of a monoelectronic transfer [18], and there-
fore the presence of germylenes. After heating the mix-
Compound
Mn
Mw
3280
3500
1740
1100
I
4a
4b
4c
4d
2330
1.4
1.8
1.2
1.1
1910
1440
1010
1
ture at 100°C in a sealed tube, H NMR measurements
showed the spiroderivative as the main product, proba-

S. Faure´ et al. / Inorganica Chimica Acta 305 (2000) 46–52
51
Table 3
the conjugation of the thiophenic cycles. Since this
effect has already been observed in the literature [20],
the nature of the substituent on the germanium atom
(butyl or phenyl) or the nature of the Group 14 metal
(Ge or Sn) have little effect on the wavelengths. How-
ever, note the large band-widening when the Group 14
metal is in the bivalent form (7a and 7b).
Electrical conductivities for compounds 4b, 7a, 7b,
and 9 have also been examined. Measurements were
made with the aid of an ohm meter on disks of press
powder (10 min under 10 ton cm−2) (Table 4).
Characteristic UV band of some compounds
Compound
u (nm) (THF)
1
268
289
292
283
290 a
286 a
4a
4b
4c
7a
7b
a Wide band.
Oligomer 4b, which contains only tetravalent germa-
nium atoms does not show any conductivity. This
agrees with results known up to the present time [1]
which show that polymers having alternatively
organometallic and p-conjugated units are insulators in
a non-doped state. On the other hand, polymeric chains
having divalent metals, 7a, 7b, and 9 have a surface
Table 4
Conductivity data
Compound
Conductivity (S cm−1
)
4b
7a
7b
9
B10−14
3×10−7
10−7
conductivity which is not negligible (10−7–10−6
S
10−6
cm−1) due probably to electronic mobility arising from
the electron gaps introduced by the divalent metal. A
measure of the volume conductivity1 gave a value of
2.10−4 S cm−1 for compound 9, confirming the semi-
conductor character of this undoped oligomer.
bly by decomposition of the germadioxolane. In order
to test this proposal, we prepared dithienylgermadiox-
olane by a dehydrohalogenation reaction in the pres-
ence of an excess of an amine (Eq. (8)).
4. Supplementary material
Crystallographic data have been deposited with the
Cambridge Crystallographic Data Centre, as supple-
mentary publication No. 138867. Copies of the data
can be obtained free of charge on application to
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK
(fax:
cam.ac.uk).
+44-1223-336033:
e-mail:
deposit@ccdc.
(8)
Compound 10 is stable at r.t. and it can be isolated in
good yield. However, it decomposes rapidly upon heat-
ing (100°C) with formation of the spiro derivative 8
(90%). The same type of redistribution was observed in
the halogenated series [11].
References
[1] M. Ishikawa, J. Ohshita, in: H.S. Nalwa (Ed.), Handbook of
Organic Conductive Molecules and Polymers, vol. 2, Wiley, New
York, 1997, p. 685 and references therein.
Knowing that the bivalent germanium centers of
oligomers 7 and 9 react with the quinone at 100°C, the
formation of the spiro 8 in the two case can be ex-
plained by the low stability of germadioxolane interme-
diates having the thiophenic substituents. Moreover, we
had confirmed that the starting dichlorogermylene had
reacted completely. In addition, treatment of the reac-
tion mixture with THF at 50°C caused complete re-
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[2] A. Kraft, A.C. Grimsdale, A.B. Holmes, Angew. Chem., Int. Ed.
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1 The volume conductivity measures were performed by the Labo-
ratoire de Ge´nie Electrique de l’Universite´ Paul Sabatier, Toulouse,
France.

52
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