Reaction of germanes and digermanes with triflic acid: The route to novel organooligogermanes

Article abstract of DOI:10.1016/j.jorganchem.2011.11.021

Novel germanium containing triflates were prepared from the reactions of trifluoromethanesulfonic acid with tetraphenylgermane (1) and digermanes (Ph₃GeGeMe₃ (4), Ph₃GeGePh₃ (5)). The improved procedures for synthesis of known organogermanium compounds (Ph₄Ge (1), Ph₃GeCl (2), Ph₃GeGeMe₃ (4), Ph₃GeGePh₃ (5)) were also presented. The crystal structure of Ph₃GeOTf (6) and Ph₂Ge(OTf)Ge(OTf)Ph ₂ (7) was studied by X-ray analysis. In 7 each germanium atom is pentacoordinated due to intramolecular interaction with O atom of the neighboring triflate group.

Full text of DOI:10.1016/j.jorganchem.2011.11.021

Journal of Organometallic Chemistry 700 (2012) 207e213
Contents lists available at SciVerse ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Note
Reaction of germanes and digermanes with triflic acid: The route to novel
organooligogermanes
,
a
a
b
c
Kirill V. Zaitsev a , Andrey A. Kapranov , Yuri F. Oprunenko , Andrei V. Churakov , Judith A.K. Howard ,
*
Boris N. Tarasevich a, Sergey S. Karlov a , Galina S. Zaitseva
,
a
*
a Chemistry Department, Moscow State University, B-234 Leninskie Gory, 119991 Moscow, Russia
b Institute of General and Inorganic Chemistry, Russian Acad. Sci., Leninskii pr. 31, 119991 Moscow, Russia
c Department of Chemistry, University of Durham, South Road, DH1 3LE Durham, United Kingdom
a r t i c l e i n f o
a b s t r a c t
Article history:
Novel germanium containing triflates were prepared from the reactions of trifluoromethanesulfonic acid
with tetraphenylgermane (1) and digermanes (Ph3GeGeMe3 (4), Ph3GeGePh3 (5)). The improved
procedures for synthesis of known organogermanium compounds (Ph4Ge (1), Ph3GeCl (2), Ph3GeGeMe3
(4), Ph3GeGePh3 (5)) were also presented. The crystal structure of Ph3GeOTf (6) and Ph2Ge(OTf)Ge(OTf)
Ph2 (7) was studied by X-ray analysis. In 7 each germanium atom is pentacoordinated due to
intramolecular interaction with O atom of the neighboring triflate group.
Received 13 October 2011
Received in revised form
14 November 2011
Accepted 16 November 2011
Keywords:
Germanium
Ó 2011 Elsevier B.V. All rights reserved.
Triflate
Trifluoromethanesulfonic acid
X-ray analysis
Oligogermanes
UV/visible spectroscopy
1. Introduction
It is known that the action of trifluoromethanesulfonic acid
(HOTf) on organogermanium compounds containing aromatic
In the last few years chemistry of organogermanium compounds
attracts intent attention of researchers and especially interest is given
to oligogermanes [1,2]. This interest is based not only on academic
investigations [3e5] but also on a search of new unique properties of
these compounds such as thermochromism, absorption in UV/visible
spectral region [6e15], conductivity, luminescence [16]. Besides
organogermanium compounds may be used as precursors for
synthesisofnew materialsforexamplenanostructures [17]. The main
problem in chemistry of oligogermans consists in limitation of reli-
able synthetic methods for obtaining compounds with required
structure and properties. The reaction of hydrogermolysis developed
by Weinert et al. [15] and also application of alkaline organo-
germanium reagents investigated by Marschner, Baumgartner et al.
[14] partially solved this problem. Meanwhile, a search of new
techniques for modification of organogermanium compounds and
improvement of synthesis of knownwidely used compounds may be
regarded as a topic for investigation.
groups results to electrophilic substitution of one Ar group [6,18] but
commonly triflates obtained are used subsequently without isola-
tion in reactions occurring with nucleophilic substitution of OTf
group. The investigations of such intermediate triflate compounds
are very rare [6]. Meanwhile, triflate group is strong electron
acceptor and it’s introduction in organogermanium molecule,
especially in oligogermane substances, may result to substantial
changing of structural parameters of these molecules, for example of
GeeGe bond. In this work we used modified procedures for
synthesis of mono- and digermanes. The compounds obtained were
investigated in reaction with trifluoromethanesulfonic acid.
2. Results and discussion
Using modified procedures we synthesized several germanes
and digermanes (Scheme 1) which would be used than for inter-
action with triflic acid. All compounds were obtained in high yields
as analytically pure samples.
In the course of this work we interested in the investigation of
substitution of two aryl groups at one germanium atom in oligo-
germanes by action of HOTf. As a model compound for studying of
* Corresponding authors. Tel.: þ7 495 939 38 87; fax: þ7 495 932 88 46.
E-mail addresses: zaitsev@org.chem.msu.ru (K.V. Zaitsev), sergej@org.chem.
msu.ru (S.S. Karlov).
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.11.021

208
K.V. Zaitsev et al. / Journal of Organometallic Chemistry 700 (2012) 207e213
PhMgBr
GeCl4
Ph4Ge
THF, reflux
1 57%
AlCl3
Ph4Ge + GeCl4
Ph3GeCl
heating
2 82 %
Me3GeBr
THF, -78oC
-LiBr
Li
Ph3GeCl
Ph3GeLi
Ph3Ge GeMe3
THF
-LiCl
3
2
4 82%
PhMgBr
GeCl4
Ph3Ge GePh3
69%
Mg (excess)
Et2O, reflux
5
Scheme 1.
this process we used tetraphenylgermane Ph4Ge (1). The possibility
of substitution of two phenyl groups in tetraphenylgermane was
shown earlier [19], but methods of structure establishing were not
reliable. It is significant that in such reaction the mild conditions
(room temperature, short time) are necessary especially in the case
of oligogermanes due to lability of GeeGe bond.
We established that action of two equivalents of HOTf on Ph4Ge
(1) results exclusively to formation of Ph3GeOTf (6) (Scheme 2).
The increase of the time of the reaction to several days did not
result to changing the product nature. According to NMR the
byproducts formed in the course of this reaction represent
a mixture of unidentified compounds. In the control experiment
with one equivalent of HOTf the triphenylgermaniumtriflate (6)
was also obtained but with greater yield.
Fig. 1. Molecular structure of compound Ph3GeOTf (6). Selected bond length (Å) and
angles (ꢀ): Ge(1)eO(11) 1.9225(17) Å, Ge(1)eC(21) 1.919(2) Å, Ge(1)eC(11) 1.921(2) Å,
Ge(1)eC(31) 1.931(2) Å, O(11)eGe(1)eC(11) 96.99(9)ꢀ, O(11)eGe(1)eC(21) 102.73(9)ꢀ,
O(11)eGe(1)eC(31) 107.21(9)ꢀ, C(21)eGe(1)eC(11) 116.98(10)ꢀ, C(21)eGe(1)eC(31)
116.38(10)ꢀ, C(11)eGe(1)eC(31) 113.31(10)ꢀ. There are two independent molecules in
crystal. Only one independent molecule is presented in Figure.
intramolecular interactions. It should be noted that this reaction is
occurred under more mild conditions (room temperature) than the
synthesis of related derivative of the trichloroacetic acid 8 (pro-
longed reflux in toluene; see Scheme 4) [24].
The structure of the compound 7 was established by X-ray
analysis (Figs. 2 and 3, Table 2).
Evidently, introduction of two triflate groups to one Ge atoms is
impossible in the course of this method due to the electron
acceptor ability of OTf that complicate sequential electrophilic
substitution at C atom.
In the centrosymmetric structure of 7, both germanium atoms
possess trigonal bipyramidal coordination environment. The
triflate oxygen atoms occupy axial positions, while phenyl groups
and neighboring germanium atom lie in equatorial sites. The GeeO
bond lengths in almost linear OeGeeO fragment are significantly
different (2.065(3) and 2.344(4) Å). This fragment may be consid-
ered as 3ce4e bond. As expected, both the GeeO bonds are longer
than ordinary germanium-triflate 2ce2e bond in the complex 6
(1.9225(17) Å).
The GeeGe distance in 7 (2.4635(12) Å) is somewhat longer
than in parent compound Ph3GeGePh3 (1) (Ph3GeGePh3
(2.437(2) Å) [25], Ph3GeGePh3*2C6H6 (2.446(1) Å) [26]). The latter
may be caused by sterical requirements of the bridging triflate
ligands.
The crystal structure of the compound (6) was investigated by
X-ray analysis (Fig. 1, Table 2).
The germanium atom in Ph3GeOTf (6) has a slightly distorted
tetrahedral coordination. The GeeO bond length is sufficiently
increased in comparison with related compounds containing GeeO
bond (1.9225(17) vs. 1.86(1) Å in Ph3GeO2CCF3 [20], 1.767(2) Å in
(Ph3Ge)2O [21]) what denotes the significant ionic character of this
bond in 6. Similar increasing the length of the covalent GeeO bond
was found in pentacoordinated germanium compounds (for
example, in C10H6(OMe)(Ge(H)(OTf)(NpOMe)), 1.988(3) Å [22])
where weakening covalent bonds are admitted.
At the action of two equivalents of HOTf on the hex-
aphenyldigermane (5) the new complex (OTf)Ph2GeGePh2(OTf) (7)
was obtained with high yield (Scheme 3).
In this case it is interesting to note the retention of GeeGe bond
and the rupture of two GeeC6H5 bonds at the neighboring
germanium atoms (compare bond energy GeeC (255 kJ/mol) and
GeeGe (163 kJ/mol)) [23]. We believed that the main reasons of
predominant rupture of GeeC bonds consist in steric hindrances for
attack on the GeeGe bond and the formation of the thermodi-
namically advantageous product which contained two strong
CF3
O
S
O
Ph2Ge
O
O
2 eq. HOTf
GePh2
Ph3Ge GePh3
CH2Cl2
-PhH
6
O
S
2 eq. HOTf
1 eq. HOTf
Ph3GeOTf
66%
Ph4Ge
Ph3GeOTf
91%
O
CF3
CH2Cl2
-PhH
CH2Cl2
-PhH
6
1
6
7
54%
Scheme 2.
Scheme 3.

K.V. Zaitsev et al. / Journal of Organometallic Chemistry 700 (2012) 207e213
209
in contrast to the interaction of GePh4 (1) with HOTf (2 equivalents)
which gives the isolated monotriflate product 6. We believed that
in the case of the compound 4 there are several reaction pathways
including simultaneous substitution phenyl- and methyl groups.
The substitution of methyl groups in the presence of geometrically
strained aryl groups was published for related Sn compounds [27].
Under prolonged storage of sample of Ph2(TfO)GeGeMe3 (9) it’s
transformation to trigermane Me3GeGePh2GePh2(OTf) (9a) was
occurred with very low yield (Scheme 6). It should be noted that in
this case the reaction was attended by precipitation of colored
insoluble solids which may present side polymeric products.
Appears that 9 decomposes with the liberation of diphenylgermy-
lene which inserts into the GeeGe bond or into the GeeO bond of
the initial compound 9. The second way looks more reliable due to
more ionic character of this bond.
CCl3
C
O
O
Ph2Ge
O
CCl3COOH
Ph3Ge
GePh2
GePh3
toluene, 110oC
-PhH
14
O
C
CCl3
19 45%
Scheme 4.
It should be noted that the similar results were found for
decomposition of oligogermanes by Satge et al. (for EtGeCl2GeCl3,
(PhCl2Ge)3GePh or (C6F5)3GeGe(F)ClGe(C6F5)3) and others (for
MesGeCl2GeCl2Mes) but no structural characterization of the
products was presented [28]. The poor quality of the crystals 9a was
unsatisfactory to establish the exact geometrical parameters of the
structure. However, the composition and molecular connectivity
were determined unambiguously (Fig. 4).
It is well known that the triflate group at Ge atom is readily
substituted by nucleophiles for example by chloride. We estab-
lished that the action of excess of ammonium chloride on 9 results
to the novel compound 10 with high yield (Scheme 7). Unfortu-
nately, the further substitution with the action of O-nucleophile
(N,N-dimethylethanolamine) in presence of Et3N failed due to the
formation of mixture of unidentified compounds. The formation of
hypothetical Me3GeePh2GeeOCH2CH2NMe2 with possible inter-
molecular GeeN interaction may facilitate the liberation of
germylene.
Both phenyl and trifluoromethyl groups were found to be
rotationally disordered over two positions with equal occupancies
(Fig. 2). In crystal, the same disorder components of Ph-rings
belonging to adjacent molecules form short intermolecular C/C
contacts (C(15A)/C(16A) e 3.156 Å, C(12B)/C(13B) e 3.319 Å).
Thus, different orientations of phenyl groups are mutually alter-
nating along the crystal and the occupancies of both disordered
sites are equal. The latter was independently confirmed by struc-
ture refinement.
The related derivative of trichloroacetic acid (Cl3CCO2)Ph2Ge-
GePh2(O2CCCl3) (8) was obtained using published procedure
(Scheme 4) [10,24] for investigation of it’s UV/visible properties
(see below).
In this work we investigated reactivity of Ph3GeGeMe3 (4) with
triflic acid under similar conditions (Scheme 5).
The substitution of one phenyl group results to desired
compound under mild conditions, but the reaction of 4 with two
equivalents of HOTf results to a mixture of unidentified compounds
Fig. 2. Molecular structure of complex Ph2(OTf)GeGe(OTf)Ph2 (7). Selected bond length (Å) and angles (ꢀ): Ge(1)eGe(1A) 2.4635(12) Å, Ge(1)eC(11) 1.934(5) Å, Ge(1)eC(21)
1.934(5) Å, Ge(1)eO(1) 2.065(3) Å, Ge(1)eO(2A) 2.344(4) Å; O(1)eGe(1)eO(2A) 177.89(13)ꢀ, Ge(1A)eGe(1)eC(21) 120.29(15)ꢀ, Ge(1A)eGe(1)eC(11) 121.68(15)ꢀ,
C(11)eGe(1)eC(21) 117.20(20)ꢀ. Hydrogen atoms are omitted for clarity.

210
K.V. Zaitsev et al. / Journal of Organometallic Chemistry 700 (2012) 207e213
Fig. 3. Intermolecular contacts in complex Ph2(OTf)GeGe(OTf)Ph2 (7).
The high intensive (ε > 104 Mꢁ1$cmꢁ1) electronic absorption in
UV/visible region is unique speciality of oligogermanes ( -delo-
were distilled prior to use. HOSO2CF3 (Aldrich), HO2CCCl3 (Aldrich)
and powdered Li (Aldrich) were used as supplied. Me3GeBr was
obtained using published procedure [30]. 1H NMR (400 MHz), 13
s
calization like in oligosilanes and oligostannanes) in comparison
with similar carbon derivatives [1,29]. In Table 1 there are values of
absorption bands of several oligogermanes. UV/visible spectra of
the compounds obtained in the course of this work are presented in
Fig. 5. It is interesting to note that additional bands corresponding
C
NMR (100 MHz) and 19F (376.4 MHz) spectra were recorded with
a Bruker 400 spectrometer (in CDCl3 at 295 K). Chemical shifts are
given in ppm relative to internal Me4Si (1H and 13C NMR spectra) or
internal CFCl3 (19F spectra). Elemental analyses were carried out by
the Microanalytical Laboratory of the Chemistry Department of the
Moscow State University. UV/visible spectra were obtained using
two ray spectrophotometer Evolution 300 «Thermo Scientific» with
cuvette of 0.10 cm long. Mass spectra (EI-MS, 70 eV) were recorded
on a quadropoule mass spectrometer FINNIGAN MAT INCOS 50
with direct insertion; all assignments were made with reference to
the most abundant isotopes.
to
p
/
p* transition in phenyl groups are less intensive and are
s* band or appeared as
overlapped with more intensive
s
/
shoulders to corresponding bands [8]. It is evident that reported
earlier UV/visible absorption for Ph3GeGePh3 (240 nm) [10,26] was
not correctly referred to
s /
s* band typical for GeeGe bond but
corresponds to absorption of phenyl group.
So the introduction of electron acceptor or electron acceptor
groups forming hypervalent interaction with Ge atom in molecule
of oligogermanes does not render significant influence on value of
UV/visible absorption.
In summary, germane and digermanes containing triflate group
at Ge atom were obtained. The compound Ph2(OTf)GeGe(OTf)Ph2
(7) in solid state is characterized by pentacoordinated germanium
atom. These compounds are perspective precursors for synthesis of
more complex organogermanium structures.
All solvents were purified using standard procedures. Tetrahy-
drofuran, diethyl ether, triethylamine were stored under solid KOH
and than distilled under sodium/benzophenone. Toluene was
refluxed and distilled under sodium. Dichloromethane was distilled
under CaH2.
3.1.1. Synthesis of Ph4Ge (1) [31]
The solution of GeCl4 (6.43 g, 29.0 mmol) in THF (40 ml) was
added over 10 min to the solution of PhMgBr (prepared from PhBr
(56.47 g, 360.0 mmol) and Mg (10.00 g, 420.0 mmol) in THF
(115 ml)) in THF. The reaction mixture was heating under reflux for
18 h. Raw product was filtered off, washed carefully with diluted
acetic acid and recrystallized from toluene. Tetraphenylgermane (1)
was isolated as a white solid. Yield 10.20 g (57%). Analytically pure
samples for subsequent experiments were obtained by sublimation
(0.4 mm Hg, external bath 310 ꢀC). 1H NMR (400 MHz, CDCl3, ppm):
3. Experimental
3.1. General methods and remarks
All manipulations were performed under a dry, oxygen-free
argon atmosphere using standard Schlenk techniques. GeCl4
(Aldrich), PhBr (Aldrich), N,N-dimethylethanolamine (Aldrich)
d
¼ 7.55e7.52, 7.47e7.41 (2m, 20O, aromatic hydrogens). 13C NMR
(100 MHz, CDCl3, ppm):
carbons).
d
¼ 136.06,135.37, 129.08, 128.24 (aromatic
HOTf
Ph3Ge GeMe3
Ph2Ge GeMe3
OTf
CHCl3
-PhH
4
3.1.2. Synthesis of Ph3GeCl (2) [32]
The mixture of Ph4Ge (1) (2.00 g, 5.35 mmol), AlCl3 (0.07 g,
0.49 mmol) and GeCl4 (0.35 g, 1.60 mmol) was heated at 120ꢀS for
4 h. The reaction melt was cooled to room temperature and the
9
39%
Scheme 5.

K.V. Zaitsev et al. / Journal of Organometallic Chemistry 700 (2012) 207e213
211
OTf
9
Me3GeGePh2
[GePh2]
Me3GeGePh2
Me3GeGePh2GePh2OTf
- Me3GeOTf
OTf
9a
9
Scheme 6.
solid formed was twice recrystallized from hexane. Triphenyl-
ether (35 ml). After violent reaction the mixture was heated under
reflux for 1 h. At room temperature the solution of GeCl4 (5.32 g,
24.80 mmol) in toluene (60 ml) was added dropwise to the solution
of Grignard reagent. The reaction mixture was heated under reflux
for 4 h, then cooled to room temperature and toluene (50 ml), 10%
HCl were added. The white solid was filtered off, washed with hot
toluene and water. The purification was performed by extraction
with CHCl3 in Soxlett apparatus for 40 h. Hexaphenyldigermane (5)
was isolated as a white powder. Yield 5.20 g (69%). 1H NMR
chlorogermane (2) was isolated as a white solid. Yield 1.95 g (81%).
1H NMR (400 MHz, CDCl3, ppm):
d
¼ 7.67e7.65, 7.49e7.43 (2m,15H,
aromatic hydrogens). 13C NMR (100 MHz, CDCl3, ppm):
134.04, 130.48, 128.63 (aromatic carbons).
d
¼ 134.70,
3.1.3. Synthesis of Ph3GeLi (3) [33]
The solution of Ph3GeCl (2) (0.37 g, 1.10 mmol) in THF (20 ml)
was added dropwise to suspension of powdered Li (0.05 g,
5.40 mmol) in THF (20 ml) at room temperature. The reaction
mixture was stirred overnight and then was filtered yielding a dark
brown solution used consequently as obtained.
(400 MHz, CDCl3, ppm):
d
¼ 7.32e7.21 (m, 30H, aromatic hydro-
gens). 13C NMR (100 MHz, CDCl3, ppm):
d
¼ 137.31, 135.53, 128.74,
128.25 (aromatic carbons). UV/visible (CH2Cl2): lmax 222 nm (ε
2.8 ꢂ 104 Nꢁ1 smꢁ1), 238 nm (ε 1.9 ꢂ 104
N
ꢁ1 smꢁ1).
3.1.4. Synthesis of Ph3GeGeMe3 (4)
At ꢁ78ꢀS the solution of Me3GeBr (0.22 g, 1.10 mmol) in ether
(20 ml) was added dropwise to the solution of Ph3GeCl (3) in THF
(20 ml) prepared as described above. The reaction mixture was
slowly heated to room temperature and was stirred overnight. Then
water (20 ml) was added, the water phase was extracted with ether
(3 ꢂ 20 ml), dried over Na2SO4 and evaporated at reduced pressure.
The residue was recrystallized from hexane/CH2Cl2 mixture. The
Ph3GeGeMe3 (4) was isolated as a white solid. Yield 0.38 g (82%). 1H
3.1.6. Reaction of Ph4Ge (1) with one equivalent of
trifluoromethanesulfonic acid. Synthesis of Ph3GeOTf (6) [18]
Trifluoromethanesulfonic acid (0.04 ml, 0.47 mmol) was added
at 0ꢀS to the solution of Ph4Ge (1) (0.18 g, 0.47 mmol) in CH2Cl2
(10 ml). The reaction mixture was heated to room temperature and
stirred overnight. The volatiles were removed under vacuum,
hexane (5 ml) and trace amounts of CH2Cl2 were added and the
solution was stored at ꢁ30ꢀS overnight. The crystals formed were
isolated and dried under reduced pressure. Triphenylgermyltriflate
(6) was isolated as a white solid. Yield 0.20 g (91%). 1H NMR
NMR (400 MHz, CDCl3, ppm):
hydrogens), 7.38e7.33 (m, 9O, aromatic hydrogens), 0.45 (s, 9O,
Ge(SO3)3). 13C NMR (100 MHz, CDCl3, ppm):
d
¼ 7.48e7.42 (m, 6O, aromatic
d
¼ 138.16, 135.21,
(400 MHz, CDCl3, ppm):
d
¼ 7.76e7.66 (m, 6O, aromatic hydro-
128.43, 128.19 (aromatic carbons), ꢁ0.84 (CO3).
gens), 7.58e7.48 (m, 9O, aromatic hydrogens). 13C NMR (100 MHz,
CDCl3, ppm):
d
¼ 134.68, 131.94, 130.46, 129.10 (aromatic carbons),
3.1.5. Synthesis of Ph3GeGePh3 (5) [31]
The solution of PhBr (54.60 g, 348.00 mmol) in ether (110 ml)
was added dropwise to suspension of Mg (10.00 g, 417.00 mmol) in
118.58 (q, J ¼ 318.0 Hz, CF3). 19F NMR (376.4 MHz, CDCl3, ppm):
d
¼ ꢁ77.03 (s, CF3).
Crystals suitable for X-ray analysis were obtained at storage of
the solution of Ph3GeOTf (6) in CH2Cl2 at ꢁ30ꢀS.
3.1.7. Reaction of Ph4Ge (1) with two equivalents of
trifluoromethanesulfonic acid. Synthesis of Ph3GeOTf (6)
Trifluoromethanesulfonic acid (0.07 ml, 0.84 mmol) was added
at 0ꢀS to the solution of Ph4Ge (1) (0.16 g, 0.42 mmol) in CH2Cl2
(10 ml). The reaction mixture was heated to room temperature and
stirred overnight. The colorless solution was carefully separated
from a brown oil, the volatiles were removed under vacuum.
Hexane (5 ml) and trace amounts of CH2Cl2 were added to the
residue and the solution was stored at ꢁ30ꢀS overnight. The
crystals formed were isolated and dried under reduced pressure.
Triphenylgermyltriflate (6) was isolated as a white solid. Yield
0.15 g (66%). 1H, 13S and 19F NMR spectra were correspond to
mentioned above.
3.1.8. Synthesis of Ph2Ge(OTf)Ge(OTf)Ph2 (7)
Trifluoromethanesulfonic acid (0.87 g, 5.90 mmol) was added at
0ꢀS to the solution of Ph3GeGePh3 (1) (1.20 g, 1.97 mmol) in CH2Cl2
(30 ml). The reaction mixture was heated to room temperature and
stirred for 48 h. The volatiles were removed under vacuum, the
residue was washed with hexane. Hexane (5 ml) and CH2Cl2 were
added to the solid obtained up to dissolving. After storage at ꢁ30ꢀS
the crystals formed were isolated by filtration and dried under
vacuum. Ph2Ge(OTf)Ge(OTf)Ph2 (7) was isolated as a pale yellow
Fig. 4. Molecular structure of compound Me3GeGe(Ph)2Ge(Ph)2OTf (9a). Hydrogen
atoms are omitted for clarity.

212
K.V. Zaitsev et al. / Journal of Organometallic Chemistry 700 (2012) 207e213
Table 2
NH4Cl
Ph2Ge GeMe3
OTf
Ph2Ge GeMe3
Cl
Details of crystallographic experiments for 6 and 7.
CH2Cl2
-NH4OTf
6
7
Formula
Fw
C19H15F3GeO3S
452.96
C26H20F6Ge2O6S2
751.72
10 94%
9
T, K
120(2)
Triclinic
Pꢁ1,4
150(2)
Triclinic
Pꢁ1,1
Scheme 7.
Crystal system
Space group, Z
a (Å)
b (Å)
c (Å)
9.7725(7)
13.1335(10)
14.8693(11)
93.571(1)
102.525(1)
92.339(1)
1856.5(2)
1.621
9.389(3)
9.839(3)
10.062(3)
110.792(4)
95.733(5)
117.674(4)
729.1(4)
1.712
crystals. Yield 1.48 g (54%). 1H NMR (400 MHz, CDCl3, ppm):
¼ 7.78e7.71 (m, 8O, aromatic hydrogens), 7.63e7.54 (m, 4O,
aromatic hydrogens), 7.54e7.47 (m, 8O, aromatic hydrogens). 13C
NMR (100 MHz, CDCl3, ppm):
¼ 134.50, 133.56, 131.69, 129.05
(aromatic carbons), 118.15 (q,
318.4 Hz, CF3). 19F NMR
(376.4 MHz, CDCl3, ppm):
d
a
b
g
(ꢀ)
(ꢀ)
(ꢀ)
d
V (Å3)
J
¼
dcalc (g cmꢁ3
)
d
¼ ꢁ76.53 (s, CF3). UV/visible (CH2Cl2):
Abs. coeff. (mmꢁ1
)
1.808
912
2.282
374
lmax 224 nm (ε 5.0 ꢂ 104 Nꢁ1 smꢁ1). Anal. Calc. for C26H20F6Ge2O6S2
(751.776): C 41.54, H 2.68, S 8.53. Found: C 41.37, H 2.60, S 8.49. EI-
MS m/z (%): 616 (1) [M ꢁ 2CF3]þ, 454 (3) [M ꢁ 2Oe2CF3SO3]þ, 377
(3) [Ph2Ge(O3SCF3)]þ, 306 (100) B ¼ [M ꢁ 2HePh2Ge(CF3SO3)e
CF3]þ, 77 (75) [Ph].
F(000)
q
Range (ꢀ)
1.41e26.00
16 112
7257 (0.0200)
7257/0/487
0.0287
0.0702
1.039
0.605/ꢁ0.340
2.29e25.50
5587
2674 (0.0294)
2674/12/173
0.0545
0.1496
1.079
1.402/ꢁ1.022
Reflections collected
Unique reflections (Rint
Data/restraints/parameters
R1 [I > 2 (I)]
wR2 (all data)
)
s
Crystals suitable for X-ray analysis were obtained at storage of
concentrated solution of Ph2Ge(OTf)Ge(OTf)Ph2 (7) in CH2Cl2 at
room temperature.
Goof
Largest difference in peak/hole (e Åꢁ3
)
3.1.9. Synthesis of Ph2Ge(O2CCCl3)Ge(O2CCCl3)Ph2 (8) [10,24]
Trichloroacetic acid (1.17 g, 7.16 mmol) was added to the
suspension of Ph3GeGePh3 (5) (1.00 g, 1.65 mmol) in toluene (4 ml).
The reaction mixture was heated at 110ꢀS in closed bulb over 72 h
and then cooled to room temperature. Hexane (15 ml) was added to
the mixture, the solid formed was filtered off. Ph2Ge(O2CCCl3)
Ge(O2CCCl3)Ph2 (8) was isolated as a white solid. Yield 0.57 g (45%).
3.1.11. Reaction of Ph3GeGeMe3 (4) with two equivalents of
trifluoromethanesulfonic acid
Trifluoromethanesulfonic acid (0.11 ml, 1.19 mmol) was added
at ꢁ70ꢀS to the solution of Ph3GeGeMe3 (4) (0.24 g, 0.59 mmol) in
CH2Cl2 (10 ml). The reaction mixture was stirred for 2 h and heated
to room temperature. The volatiles were removed under vacuum.
According to NMR analysis the mixture of unidentified compounds
was obtained.
1H NMR (400 MHz, CDCl3, ppm):
hydrogens), 7.58e7.48 (m, 12O, aromatic hydrogens). 13C NMR
d
¼ 7.76e7.66 (m, 8O, aromatic
(100 MHz, CDCl3, ppm):
d
¼ 166.36 (O2CCCl3), 134.25, 133.93,
130.81, 128.82 (aromatic carbons), 90.73 (O2CCCl3). 1H and 13C NMR
spectra correspond to mentioned in literature [10]. UV/visible
(CH2Cl2): lmax 224 nm (ε 3.9 ꢂ 104 Nꢁ1 smꢁ1).
3.1.12. Synthesis of Ph2(Cl)GeGeMe3 (10)
Solid NH4Cl (1.00 g, 18.70 mmol) was added to the solution of
Ph2(OTf)GeGeMe3 (9) (0.40 g, 0.81 mmol) in CH2Cl2 (10 ml). The
reaction mixture was stirred for 2 days, then filtered and all vola-
tiles were removed under vacuum. The residue was washed with
hexane and dried under reduced pressure. Ph2(Cl)GeGeMe3 (10)
was isolated as a white solid. Yield 0.29 g (94%). 1H NMR (400 MHz,
3.1.10. Reaction of Ph3GeGeMe3 (4) with one equivalent of
trifluoromethanesulfonic acid. Synthesis of Ph2(OTf)GeGeMe3 (9)
Trifluoromethanesulfonic acid (0.11 ml, 1.19 mmol) was added at
0ꢀS to the solution of Ph3GeGeMe3 (4) (0.50 g, 1.19 mmol) in CH2Cl2
(10 ml). The reaction mixture was heated to room temperature and
for 2 h. The volatiles were removed under vacuum, hexane and
CH2Cl2 were added to residue up to dissolving and solution was
stored at ꢁ30 S. The crystals formed were isolated and dried under
reduced pressure. Ph2(OTf)GeGeMe3 (9) was isolated as a beige
powder. Yield 0.23 g (39%). 1H NMR (400 MHz, CDCl3, ppm):
CDCl3, ppm):
d
¼ 7.61e7.55 (m, 4O, aromatic hydrogens), 7.45e7.37
(6O, aromatic hydrogens), 0.54 (s, 9O, SO3). 1H NMR spectrum
corresponds to mentioned in literature [19]. 13C NMR (100 MHz,
d
¼ 7.60e7.53 (m, 4O, aromatic hydrogens), 7.52e7.44 (m, 6O,
aromatic hydrogens), 0.68 (s, 9O, SO3). 13C NMR (100 MHz, CDCl3,
ppm):
d
¼ 135.53, 133.88, 131.10, 128.97 (aromatic carbons), 118.59
(q, J ¼ 318.4 Hz, CF3), ꢁ0.76 (CO3). Anal. Calc. for C16H19F3Ge2O3S
(493.601): C 38.93, H 3.88. Found: C 38.06, H 4.15.
Under prolonged storage of the concentrated solution of
Ph2(OTf)GeGeMe3 (9) in CH2Cl2 the crystals of Ph2(OTf)GeGePh2
-
GeMe3 (9a) suitable for X-ray analysis were obtained.
Table 1
The values of UV/visible absorption for several oligogermanes.
Compound
lmax, nm
Reference
Ph3GeGePh3 (5)
(F3CSO3)Ph2GeGePh2(O3SCF3) (7)
(Cl3CCO2)Ph2GeGePh2(O2CCCl3) (8) 224
ClPh2GeGePh2Cl 225
222 (
224
s
/
s*), 238 (
p
/
p*
)
This work
This work
This work
[29a]
Fig. 5. UV/visible spectra of 5, 7, 8 in CH2Cl2 solution.

K.V. Zaitsev et al. / Journal of Organometallic Chemistry 700 (2012) 207e213
213
[5] M. Hölbling, S.L. Masters, M. Flock, J. Baumgartner, K. Hassler, H.E. Robertson,
D.A. Wann, Inorg. Chem. 47 (2008) 3023.
[6] V.Y. Lee, H. Yasuda, M. Ichinohe, A. Sekiguchi, J. Organomet. Chem. 692 (2007)
10.
CDCl3, ppm):
carbons), ꢁ1.42 (CO3).
d
¼
138.24, 133.48, 129.72, 128.53 (aromatic
[7] M.L. Amadoruge, A.G. DiPasquale, A.L. Rheingold, C.S. Weinert, J. Organomet.
Chem. 693 (2008) 1771.
[8] M.L. Amadoruge, J.R. Gardinier, C.S. Weinert, Organometallics 27 (2008) 3753.
[9] M.L. Amadoruge, J.A. Golen, A.L. Rheingold, C.S. Weinert, Organometallics 27
(2008) 1979.
[10] M.L. Amadoruge, E.K. Short, C. Moore, A.L. Rheingold, C.S. Weinert,
J. Organomet. Chem. 695 (2010) 1813.
[11] E. Subashi, A.L. Rheingold, C.S. Weinert, Organometallics 25 (2006) 3211.
[12] J. Baumgartner, R. Fischer, J. Fischer, A. Wallner, C. Marschner, U. Flörke,
Organometallics 24 (2005) 6450.
3.1.13. Reaction of Ph2(Cl)GeGeMe3 (10) with N,N-
dimethylethanolamine
The solution of N,N-dimethylethanolamine (0.10 g, 1.16 mmol)
and Et3N (0.16 ml, 1.16 ml) in CH2Cl2 (20 ml) was added dropwise to
the solution of Ph2ClGeGeMe3 (10) in CH2Cl2 (20 ml) at ꢁ78 S. The
reaction mixture was heated slowly to room temperature and
stirred overnight. All volatiles were removed under reduced pres-
sure and residue was extracted with benzene (2y20 ml), the solvent
was removed in vacuo. According to NMR analysis the mixture of
unidentified compounds was obtained.
[13] M.L. Amadoruge, C.H. Yoder, J.H. Conneywerdy, K. Heroux, A.L. Rheingold,
C.S. Weinert, Organometallics 28 (2009) 3067.
[14] J. Hlina, J. Baumgartner, C. Marschner, Organometallics 29 (2010) 5289.
[15] C.R. Samanamu, M.L. Amadoruge, C.H. Yoder, J.A. Golen, C.E. Moore,
A.L. Rheingold, N.F. Materer, C.S. Weinert, Organometallics 30 (2011) 1046.
[16] T.L. Bandrowsky, J.B. Carroll, J. Braddock-Wilking, Organometallics 30 (2011)
3559.
3.1.14. X-ray crystallographic study
Experimental details for the structures 6 and 7 are given in
[17] (a) R.G. Hobbs, S. Barth, N. Petkov, M. Zirngast, C. Marschner, M.A. Morris,
J.D. Holmes, J. Am. Chem. Soc. 132 (2010) 13742;
(b) D.C. Arnold, R.G. Hobbs, M. Zirngast, C. Marschner, J.J. Hill, K.J. Ziegler,
M.A. Morris, J.D. Holmes, J. Mater. Chem. 19 (2009) 954.
[18] W. Uhlig, J. Organomet. Chem. 409 (1991) 377.
[19] K. Mochida, I. Yoneda, M. Wakasa, J. Organomet. Chem. 399 (1990) 53.
[20] C. Glidewell, D.C. Liles, J. Organomet. Chem. 243 (1983) 291.
[21] C. Glidewell, D.C. Liles, Acta Cryst. B. 34 (1978) 119.
[22] F. Cosledan, A. Castel, P. Rivière, J. Satgé, M. Veith, V. Huch, Organometallics 17
(1998) 2222.
Table 2. Data were collected on
diffractometer (graphite monochromatized MoK
a
Bruker SMART APEX II
radiation,
a
l
¼ 0.71073 Å). The structures 6 and 7 was solved by direct methods
and refined by full matrix least-squares on F2 [34] with anisotropic
thermal parameters for all non-hydrogen atoms. As for 7, disordered
atoms of Ph-rings and CF3 groups were refined isotropically. In both
cases, all hydrogen atoms were placed in calculated positions and
refined using a riding model. In 7, phenyl and trifluoromethyl groups
were found to be rotationally disordered over two positions with
equal occupancies.
[23] C. Elschenbroich, Organometallics third, completely revised and enlarged
edition, Wiley-VCH, Weinheim, 2006.
[24] D. Simon, K. Haeberle, M. Draeger, J. Organomet. Chem. 267 (1984) 133.
[25] M. Dräger, L.Z. Ross, Z. Anorg. Allg. Chem. 460 (1980) 207.
[26] M. Dräger, L.Z. Ross, Z. Anorg. Allg. Chem. 469 (1980) 115.
[27] M. Mehring, C. Nolde, M. Schuermann, Inorg. Chim. Acta 362 (2009) 745.
[28] (a) M. Massol, J. Barrau, J. Satge, Inorg. Nucl. Chem. Lett. 7 (1971) 895;
(b) P. Riviere, M. Riviere-Baudet, C. Couret, J. Satge, Syn. React. Inorg. Metalorg.
Chem. 4 (1974) 295;
Appendix A. Supplementary material
The crystallographic data for 6, 7 have been deposited with the
Cambridge Crystallographic Data Centre as supplementary publi-
cation under the CCDC numbers 847597 and 847598. They can be
obtained free of charge from the Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
(c) A. Castel, J. Escudie, P. Riviere, J. Satge, M.N. Bochkarev, L.P. Maiorova,
G.A. Razuvaev, J. Organomet. Chem. 210 (1981) 37;
(d) M.A. Chaubon-Deredempt, J. Escudie, C. Couret, J. Organomet. Chem. 467
(1994) 37.
[29] (a) A. Castel, P. Riviere, B. Saint-Roch, J. Satge, J. Organomet. Chem. 247 (1983)
149;
(b) R.D. Miller, J. Michl, Chem. Rev. 89 (1989) 1359.
[30] V.F. Mironov, A.L. Kravchenko, Bull. Acad. Sci. USSR.. (Chem. Sci. (Izv. Akad.
Nauk SSSR, Ser. Khim.)) (1965) 1026 Engl.Transl.
References
[31] F. Glockling, K.A. Hooton, J. Chem. Soc. (1962) 3509.
[32] F. Rijkens, G.J.M. van der Kerk, Rec. Trav. Chim. 83 (1964) 723.
[33] C. Tamborski, F.E. Ford, W.L. Lehn, G.J. Moore, E.J. Soloski, J. Org. Chem. 27
(1962) 619.
[1] M.L. Amadoruge, C.S. Weinert, Chem. Rev. 108 (2008) 4253.
[2] C.S. Weinert, Dalton Trans. (2009) 1691.
[3] J.E. Bender, M.M. Banaszak Holl, A. Mitchell, N.J. Wells, J.W. Kampf, Organo-
metallics 17 (1998) 5166.
[34] G.M. Sheldrick, Acta Crystallogr. A64 (2008) 112.
[4] S.P. Mallela, Y. Saar, S. Hill, R.A. Geanangel, Inorg. Chem. 38 (1999) 2957.