donor-acceptor oligogermanes: Synthesis, structure, and electronic properties

Article abstract of DOI:10.1021/om4008218

A series of oligogermanes, (Me₃Si)₃GeGeCl ₃, (C₆F₅)₃GeGePh₃, (C₆F₅)₃GeGe(p-Tol)₃, and (C ₆F₅)₂Ge[Ge(p-Tol)₃]₂, containing substituents with different electronic properties at neighboring germanium atoms were synthesized. According to X-ray diffraction studies, UV/visible spectroscopy, and quantum chemical calculations, these donor-acceptor oligogermanes are characterized by energies of electronic transitions lower than those for other similar compounds.

Full text of DOI:10.1021/om4008218

Article
pubs.acs.org/Organometallics
“
Donor−Acceptor” Oligogermanes: Synthesis, Structure, and
Electronic Properties
Kirill V. Zaitsev,* Andrey A. Kapranov, Andrei V. Churakov, Oleg Kh. Poleshchuk,
Yuri F. Oprunenko, Boris N. Tarasevich, Galina S. Zaitseva, and Sergey S. Karlov
,
†
†
‡
§,∥
†
†
†
†
†
Department of Chemistry, Moscow State University, Leninskye Gory 1, Moscow 119991, Russia
‡
Russian Academy of Sciences, N.S. Kurnakov General and Inorganic Chemistry Institute, Leninskii pr., 31, Moscow, Russia
§National Research Tomsk Polytechnic University, Lenin Av., 30, Tomsk 634050, Russia
∥Tomsk State Pedagogical University, Kievskaya Str., 60, Tomsk 634061, Russia
*
S Supporting Information
ABSTRACT: A series of oligogermanes, (Me Si) GeGeCl , (C F ) GeGePh ,
3
3
3
6
5
3
3
(
C F ) GeGe(p-Tol) , and (C F ) Ge[Ge(p-Tol) ] , containing substituents with
6 5 3 3 6 5 2 3 2
different electronic properties at neighboring germanium atoms were synthesized.
According to X-ray diffraction studies, UV/visible spectroscopy, and quantum chemical
calculations, these “donor−acceptor” oligogermanes are characterized by energies of
electronic transitions lower than those for other similar compounds.
7
8
INTRODUCTION
At present, oligomeric and polymeric silanes and stannanes
are the most explored classes of heavy hydrocarbon analogues.
In contrast, germanium derivatives
■
The design of “molecular conductors” (molecular wires, or
9
,10
1
−4
are less known, partially
nanowires)
has attracted significant interest due to the
due to the absence of common synthetic approaches to these
compounds. Depending on the nature of substituents at
germanium atoms, the formation of Ge−Ge bonds has been
potential applications of these materials in molecular electronics
and nanotechnologies. The most common molecular con-
ductors are organic compounds with extended systems of
conjugate C−C bonds (linear oligo- or polyphenylenes,
oligothiophenes, etc.). At present, the primary focus of these
studies is gradually shifting toward molecules with noncarbon
backbones, which often contain nonclassical bonds and have
unusual electronic properties.
10
achieved by various methods, including hydrogermolysis,
1
1,12
germylene insertion into Ge−X bonds (X = N, O, Hal),
1
3,14
Wurtz reactions,
reactions of germyllithium compounds
15
with germanium halides, decomposition of germylmercuri-
1
6,17
als,
metals,
dehydrocoupling reactions catalyzed by transition
1
8−21
22
and reduction of halogermanes by SmI2. These
Compounds of group 14 elements (Si, Ge, and Sn) with
element−element bonds may be regarded as molecular
conductors. The distinctive feature of these heavy analogues
of saturated hydrocarbons is the delocalized nature of element−
element bonds (σ conjugation) (Chart 1). Such conjugation is
responsible for the conductivity, photoluminescence, thermo-
chromism, electrochemical, and nonlinear optical properties
of these compounds, which are typically observed for
unsaturated hydrocarbons.
methods often produce mixtures of compounds; thus, the yields
of target products are usually low. In addition, oligogermanes
with electron-withdrawing substituents are particularly unstable
and decompose even under mild conditions. As a result, nearly
all reported oligogermanes contain only electron donor groups
(
alkyl and/or aryl) at adjacent Ge atoms. Therefore, the
5
6
synthesis of unsymmetrical oligogermanes with electron-
withdrawing substituents still presents a significant challenge.
The optical and electronic properties of oligogermanes
strongly depend on the primary chain length and the nature of
substituents at Ge atoms. The presence of substituents with
different electronic effects in unsymmetrical oligogermanes
allows control of the strength and polarity of Ge−Ge bonds
and therefore the physical properties and chemical behavior of
these compounds.
Chart 1. Schematic Representation of Compounds of Group
1
4 Elements Containing Element−Element Bonds
In this paper, we report the synthesis, structures, and
properties of di- and trigermanes with strong electron acceptors
(
Cl and C F ) at one Ge atom and strong electron donors
6 5
(
Me Si, Ph, and p-Tol) at one or two adjacent Ge atoms (Chart
3
Received: August 22, 2013
Published: October 25, 2013
©
2013 American Chemical Society
6500
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Article
2
). These “donor−acceptor” oligogermanes were studied by
Scheme 2. Synthesis of Perfluorophenyl Germanium
Chlorides
1
13
19
multinuclear NMR ( H, C, F), UV/visible spectroscopy, X-
Chart 2. Types of “Donor−Acceptor” Oligogermanes
Investigated in This Work
ray analysis, and quantum chemical calculations in order to
determine the influence of substituents at Ge atoms on the
geometry and electronic structure of resulting molecules.
RESULTS AND DISCUSSION
■
Synthesis. In our work, two general synthetic approaches to
unsymmetrical donor−acceptor oligogermanes were used.
23
24
Oligogermanes 1 and 2 stabilized by bulky Me Si groups
3
were synthesized according to published procedures (Scheme
1). The unusual formation of 2 may be caused by the low
stability of (Me Si) GeGeCl Ge(SiMe ) due to the presence
3
3
2
3 3
of two sterically bulky groups at one Ge atom or the reducing
properties of the lithium reagent. The presence of Me Si groups
3
increases the stability of oligogermanes, preventing their
decomposition with the formation of germylenes and/or
germanium polymers. The phenyl analogue of compound 1,
the digermane Ph GeGeCl , is unstable and decomposes even
3
3
at room temperature, producing a mixture of Ph GeCl
3
(
according to NMR) and insoluble colored germanium
25
polymers, possibly [GeCl ] .
2
n
The presence of electron-donating and electron-withdrawing
substituents at adjacent Ge atoms in digermane 1 produces a
highly polar molecule with the properties of a Lewis acid.
However, charge-transfer complexes of 1 with triphenylphos-
phine, pyridine, 4-dimethylaminopyridine, and acetonitrile
could not be isolated, as the addition of bases led to
decomposition of digermane 1 with the formation of red or
yellow insoluble precipitates, which were probably polymers of
dichlorogermylene.
Figure 1. Molecular structure of (C F ) GeCl (3). Displacement
6
5 3
ellipsoids are shown at the 50% probability level. Selected bond
lengths (Å) and bond angles (deg): Ge(1)−Cl(1) = 2.1566(8),
Ge(1)−C = 1.9391(15); C−Ge(1)−C = 112.85(4), Cl(1)−Ge(1)−C
=
105.84(4).
26
triarylchlorogermanes. The aryl rings are arranged in a
propeller-like conformation (the torsion angle Cl−Ge−C(1)−
C(6) is 56.74(12)°).
The starting materials for other unsymmetrical donor−
acceptor oligogermanes, halides 3 and 4, were synthesized
according to modified procedures (Scheme 2).
Because of the presence of electron-withdrawing C6F5
substituents, in 3 the Ge−Cl distances are shorter and the
Ge−C distances are usually shorter than the average distances
The 19F NMR spectra of 3 and 4 contain three multiplets
corresponding to o-, p- and m-fluorine atoms of the aromatic
ring.
2
7
in other triarylgermanes: Ph GeCl (2.187(2) and 1.937(6) Å
3
28
The molecular structure of germane 3 was determined by X-
ray diffraction studies (Figure 1). In the solid state, molecule 3
or 2.161(2) and 1.933(5) Å, respectively), [o-(MeOCH )-
2
29
C H ] GeCl (2.213(1) and 1.951(2) Å, respectively), [o-
6
4 3
26
has C symmetry. The germanium atom in 3 has a slightly
EtOC H ] GeCl (2.2287(8) and 1.941(3) Å, respectively),
6 4 3
30
3
t
distorted tetrahedral geometry: all bond angles at Ge are close
[o-(Bu )C H ] GeCl (2.198(1) and 1.975(4) Å, respectively).
6 4 3
to tetrahedral values (106 and 112°), which is typical for
At the same time, a significant change in the structural
Scheme 1. Synthesis of Chlorine-Containing Germanes
6
501
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Scheme 3. Synthesis of Germanes 5 and 6 by the Action of Germyllithium Reagents on (C F ) GeCl (3)
6
5 3
3
1
parameters for (C F ) Ge and (C F ) GeCl (3) (d(Ge−C) =
6
5 4
6 5 3
1
1
.956(4) vs 1.9391(15) Å; ∠(C−Ge−C) = 105.0(2) vs
av
12.85(4)°, respectively) is due to a decrease of the steric
volume of chlorine. This fact becomes particularly noticeable if
the bond lengths of the germanium atom in (C F ) GeCl (3)
6
5 3
are compared with those in (C Cl ) GeCl: Ge(1)−Cl(1) =
6
5 3
2
1
.1566(8) vs. 2.159(5) Å; Ge(1)−C = 1.9391(15) vs.
av
32
.977(7) Å.
Germanium halide 3 was used in alkylations by germyl-
lithium reagents (Scheme 3). Compound 6 was obtained as the
major product (15%), and 5 was a minor product (8%). The
low yields of both compounds could be a result of the
competitive substitution of fluorine atoms in perfluorophenyl
fragments. The second Ge−Ge bond in 6 was formed by
nucleophilic substitution of a C F group, which was the first
6
5
example of such a substitution at germanium. In general, this
3
3,34
type of nucleophilic substitution is very rare.
Instead of nucleophilic substitution, an alternative approach
to unsymmetrical donor−acceptor oligogermanes involves the
use of more selective hydrogermolysis reactions. This method is
suitable for germanium monohydrides and monoamides. The
synthetic procedure, recently optimized by Weinert and co-
workers, allows to obtain various oligogermanes with high
yields.
Figure 2. Molecular structure of (C F ) GeH (7). Displacement
ellipsoids are shown at the 50% probability level. Selected bond
6
5 3
35,36
Hydrides 7 and 8 were synthesized
by the reduction of
lengths (Å) and bond angles (deg): Ge(1)−H(1) = 1.33(3), Ge(1)−
halides 3 and 4 with LiAlH (Scheme 4) and studied by
C
= 1.946(3); C−Ge(1)−C = 110.92(14), C−Ge(1)−H(1)
=
4
av
av
av
1
08.0(14).
Scheme 4. Synthesis of Perfluorophenylgermanes 7 and 8
electron-withdrawing substituents in triarylgermanes reduce
bond lengths at the Ge atom.
The optimal conditions of hydrogermolysis reactions
(
solvent and the reaction time) depend on the structures of
10,46
the starting materials.
Compounds 5, 6, and 9 were
obtained with good yields by quick heating in n-hexane
Scheme 5). However, our attempts to prepare germanes 5, 6,
(
and 9 in MeCN were not successful.
The rates of hydrogermolysis (2−3 h in hexane at 100 °C in
a sealed flask) for perfluorophenylgermanes 7 and 8 were
higher than those for other germanes (40−50 h reflux in
MeCN), where an intermediate with solvent was formed. This
fact can be explained by the increased Ge−H acidity of
multinuclear NMR spectroscopy. Because of the presence of
electron-withdrawing C6F groups, the signals of Ge−H
6
protons in 7 (δ 6.28 ppm, CDCl ) and 8 (δ 5.37 ppm,
3
CDCl ) are shifted strongly downfield in comparison with their
3
phenyl analogues or other similar compounds containing
3
7,38
electron-donating groups (δ 3.5−4.2 ppm).
Furthermore,
Scheme 5. Synthesis of Oligogermanes 5, 6, and 9 in
Hydrogermolysis Reactions
the signals of these protons in 7 and 8 appear as multiplets due
to coupling with neighboring F atoms (triplet with J
4
= 3.5
H−F
4
Hz and quintet with J
= 5.6 Hz, respectively).
H−F
The molecular structure of compound 7 was determined by
an X-ray diffraction study (Figure 2). Overall, the structure of
this molecule resembles that of chloride 3. The Ge−H bond
length in 7 (1.33(3) Å) is the shortest known for
3
9
triarylgermanes (1.71 Å in [o-MeC H ] GeH, 1.42(3) Å in
6
4 3
40
41
[
o-Me NC H ] GeH, 2.05 Å in Mes GeH, 1.48(3) Å in
2 6 4 3 3
42 30
t
Ph GeH, 1.37(2) Å in [o-(Bu )C H ] GeH ). In addition,
3
6
4 3
this bond length is one of the shortest for all germanes reported
43
to date (1.15(9) and 1.37(7) Å in PhGeH , 1.70(10) Å in
3
4
4
38
Mes GeGe(Mes)(SiEt )H, 1.45(3) Å in [Ph Ge] GeH,
1
2
3
3
3
45
.50(4) Å in Ph Ge(GePh ) GePh H ). Thus, in general,
3 2 2 2
6
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Article
compounds with electron-withdrawing substituents at the Ge
atom.
Table 2. Ge−Ge Bond Lengths in Trigermanes Determined
by X-ray Analysis
The 19F NMR spectra of 5, 6, and 9 contain three signals
with 2:2:1 integration ratio, which indicates the magnetic
equivalence of all C F groups and free rotation around the
compd
d(Ge−Ge), Å
2.429(1)
ref
Ph GeGeMe GePh
2
69
70
12
49
49
71
71
72
3
2
6
5
Ph GeGePh GePh
3
2.438(2), 2.441(2)
2.421(2), 2.425(2)
2.4318(5), 2.4338(4)
2.4450(4), 2.4359(5)
2.620(1)
Ge−Ge bonds.
3
2
Ph (Cl)GeGePh GePh Cl
Crystal Structures of Oligogermanes 1, 5, 6, and 9.
The influence of substituents on the strength and polarity of
Ge−Ge bonds in oligogermanes is the primary focus of all
structural studies of these compounds. An analysis of literature
data for di- and trigermanes shows that the majority of their
molecules either are symmetrical or contain substituents with
similar electronic properties. The average Ge−Ge distances
vary from 2.393 to 2.714 Å in digermanes (Table 1) and from
2
2
2
(
(
p-Tol) GeGePh Ge(p-Tol)
3 2 3
p-Tol) GeGe(p-Tol) Ge(p-Tol)
3
3
t
2
t
t
Me(Bu ) GeGe(Bu ) Ge(Bu ) Me
2
2
2
t
t
t
Br(Bu ) GeGe(Bu ) Ge(Bu ) Br
2.595(1), 2.623(1)
2.622(1), 2.660(1)
2
2
2
t
t
t
I(Bu ) GeGe(Bu ) Ge(Bu ) I
2
2
2
Table 3. Selected Bond Distances (Å) and Bond Angles
(
deg) in (Me Si) GeGeCl (1)
3
3
3
Table 1. Ge−Ge Bond Lengths in Digermanes Determined
Ge(1)−Ge(2)
2.4083(2)
2.3853(5)
2.3878(5)
2.3887(5)
Ge(2)−Cl(2)
Ge(2)−Cl(1)
Ge(2)−Cl(3)
2.1635(4)
2.1658(4)
2.1671(4)
by X-ray Analysis
Ge(1)−Si(2)
Ge(1)−Si(1)
Ge(1)−Si(3)
Si(2)−Ge(1)−Si(1)
Si(1)−Ge(1)−Si(3)
Si(2)−Ge(1)−Si(3)
compd
d(Ge−Ge), Å
2.393(2)
ref
[
[
{
(
Cl CCO GePh ]
47
21
48
49
50
51
52
53
54
55
55
15
56
57
11
58
59
3
2
2 2
114.495(16) Cl(2)−Ge(2)−
103.131(19)
102.287(19)
103.306(19)
115.559(14)
115.093(15)
115.643(14)
(C F )GeH ]
2.394(1)
2.402(1)
2.408(1)
2.413(1)
2.418(1)
2.419(1)
2.4216(4)
2.421(1)
2.421(8)
2.4253(7)
2.421(13)
2.4255(3)
2.4340(5)
2.4352(3)
2.436(7)
2.437(2)
6
5
2
2
Cl(1)
i
[2,6-(Pr ) C H ]GeH }
2
6
3
2
2
115.667(18) Cl(2)−Ge(2)−
p-Tol) GeGePh3
Cl(3)
3
(PhGeCl2)2
113.605(16) Cl(1)−Ge(2)−
Cl(3)
Ph GeGeMe3
3
Si(2)−Ge(1)−
102.926(14) Cl(2)−Ge(2)−
[(p-Tol) Ge]2
3
Ge(2)
Ge(1)
Ph GeGeMe Ph
3
2
Si(1)−Ge(1)−
104.061(13) Cl(1)−Ge(2)−
(
2
Me GeCl)2
Ge(2)
Ge(1)
n
Ph GeGe(Bu )
3
3
Si(3)−Ge(1)−
104.033(13) Cl(3)−Ge(2)−
Ph GeGeEt3
Ge(2)
Ge(1)
3
((Me Si) SiGeCl )
3 3 2 2
t
Bu Me GeGePh
Compound 1 is isostructural with Hal B*Sb(SiMe ) (Hal =
3 3 3
73 74
2
3
{
[(Me Si)NC(Ph)] Ge(SiMe )}
Cl, Br, I) and (Cl Si) Si(GeMe ) . Both Ge atoms in
3 2 3 2
3
2
3
2
[
(
(
3,5-(F C) C H GeH ]
molecule 1 have distorted-tetrahedral environments, while the
molecule as a whole adopts a gauche (staggered) conformation
with the torsion angles Si−Ge−Ge−Cl between 42.01 and
43.72° (Figure 3). At the same time the Ge−Ge bond length is
very short (2.4083 Å, Table 3; compare with Table 1). The
lengths of Ge−Cl bonds (average 2.1655 Å, Table 3) are also
shortened in comparison with [(Me Si) SiGeCl ] (2.288 and
3
2
6
3
2 2
C F ) GeGeEt
3
6
5
3
Ph Ge)
3
2
i
Bu GeGePh
2.4410(5), 2.4409(5) 56
3
3
(
Ph Ge) ·2C H
2.446(1)
2.448(2)
2.448(1)
2.456(2)
2.457(1)
2.4635(12)
2.4637(7)
2.4637(4)
60
61
62
62
20
63
64
65
3
2
6
6
t
[
{
{
(Bu ) MeSiGeCl ]
2 2 2
[(CO) Cr]I Ge}
5
2
2
3
3
2 2
15
t
61
[(CO) W]I Ge}
2.158 Å) or [(Bu ) MeSiGeCl ] (2.205 and 2.186 Å). The
5
2
2
2 2 2
(
(
(
Ph P) PtHGeHMesGeH Mes
Ge−Si distances in 1 (average 2.3873 Å) are within the typical
75,67
3
2
2
Ph GeOTf)
range of 2.38−2.41 Å
but still somewhat smaller than those
2
2
i
Pr ) GeGePh
3
3
i
[2,6-(Pr ) C H ] GeH−Ge(N )[2,6-
2
6
3
2
3
i
(
Pr ) C H ]
2 6 3 2
i
{
[(Et P) PtH][2,6-(Pr ) C H ] Ge}
2.466(1)
66
67
68
3
2
2
6
3
2
2
((Me Si) Ge)
2.4787(7)
3
3
2
t
[(Bu ) Ge]
2.714(1), 2.705(1)
3
2
2
.421 to 2.660 Å in trigermanes (Table 2). These bond lengths
depend not only on the steric volume of substituents at Ge
atoms (bulky substituents increase the Ge−Ge bond length)
but also on the electronic properties of these groups. Electron
donors, such as Alk, Ar, and Me Si groups, increase the distance
3
between adjacent germanium atoms, while electron-with-
drawing substituents, such as C F and (CF ) Ar, produce
6
5
3 2
the opposite effect.
All germanes synthesized in this work were isolated as
colorless crystalline solids. The general views and selected
structural parameters of molecules 1, 5, 6, and 9 are shown in
Figures 3−6 and Tables 3 and 5−7; the crystallographic data
are given in Table S-1 (see the Supporting Information).
Figure 3. Molecular structure of (Me Si) GeGeCl (1). Displacement
ellipsoids are shown at the 50% probability level. Hydrogen atoms are
omitted for clarity.
3
3
3
6
503
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in similar compounds, such as 2.421(13) Å in
Ge bond in 5 is also longer than that in another unsymmetrical
t
55
[
(Me Si) SiGeCl ] and 2.447 Å for [(Bu ) MeSiGeCl ] .
digermane, (C F ) GeGeEt (2.436 Å).
3
3
2 2
2
2 2
6
5 3
3
The observed shortening of bond lengths in 1 in comparison
with other germanes is probably the result of reduced steric
repulsion between the substituents.
The structural parameters of molecule 1 were also estimated
by DFT calculations (Table 4). It is evident that the calculated
bond lengths are overestimated while the calculated bond
angles are very close to their experimental values.
In the solid state, molecule 5 adopts a very unusual eclipsed
54
conformation with a torsion angle C(1)−Ge(1)−Ge(2)−
C(11) of −0.87(17)°. Similar to the case for molecule 9, the
eclipsed aryl rings in 5 have reciprocal orientations with the
shortest C
···C distance of 3.285(6) Å.
F
H
The molecular structure of [(p-Tol) Ge] Ge(C F ) (6) is
3
2
6 5 2
highly symmetric (Figure 5). The coordination environments
Table 4. Selected Bond Distances (Å) and Bond Angles
(
deg) for (Me Si) GeGeCl (1) According to DFT
3 3 3
Calculations
Ge−Ge
Ge−Si
2.491
2.447
Ge−Cl
2.217
Si−Ge−Ge
Si−Ge−Ge
114.2−114.6
103.9
Cl−Ge−Cl
Cl−Ge−Ge
103.4
114.4, 115.2, 115.3
The molecule of (p-Tol) GeGe(C F ) (5) lies on a
3
6 5 3
crystallographic 3-fold axis. Both germanium atoms have
distorted-tetrahedral geometry (Figure 4). The Ge−Ge bond
Figure 5. Molecular structure of [(p-Tol) Ge] Ge(C F ) (6).
3
2
6 5 2
Displacement ellipsoids are shown at the 50% probability level.
Hydrogen atoms are omitted for clarity.
of all Ge atoms in 6 are distorted tetrahedra. The value of the
Ge(2)−Ge(1)−Ge(2) angle (124.10°; Table 6) is close to
Table 6. Selected Bond Distances (Å) and Bond Angles
(
deg) in [(p-Tol) Ge] Ge(C F ) (6)
3
2
6 5 2
Ge(1)−Ge(2)
Ge(1)−C(11)
Ge(2)−C(31)
2.459(5)
1.992(4)
1.949(3)
Ge(2)−C(21)
Ge(2)−C(41)
Ge(1)−C(11A)
1.957(4)
1.961(3)
1.992(4)
110.58(14)
Ge(2)−Ge(1)−Ge(2)
124.10(3)
C(31)−Ge(2)−
C(41)
Figure 4. Molecular structure of (C F ) GeGe(p-Tol) (5). Displace-
ment ellipsoids are shown at the 50% probability level. Hydrogen
atoms and the solvate molecule of chloroform are omitted for clarity.
6
5
3
3
C(11)−Ge(1)−
108.0(2)
C(31)−Ge(2)−
108.17(15)
105.09(16)
112.19(11)
108.51(10)
111.96(10)
C(11A)
C(21)
C(11)−Ge(1)−
113.34(10) C(21)−Ge(2)−
Ge(2A)
C(41)
C(11)−Ge(1)−Ge(2)
98.91(10) C(31)−Ge(2)−
Ge(1)
C(11A)−Ge(1)−
98.91(10) C(21)−Ge(2)−
is significantly elongated (2.4652 Å; Table 5) in comparison
Ge(2)
Ge(1)
52
with that in (p-Tol) GeGe(p-Tol) (2.419 Å; Table 2),
3
3
C(11A)−Ge(1)−
113.34(10) C(41)−Ge(2)−
although the steric volumes of substituents in both compounds
are approximately the same. This fact can be explained by the
effect of strongly electron withdrawing C F groups. The Ge−
Ge(2A)
Ge(1)
6
5
1
20°, which reflects an effective σ delocalization between
germanium atoms. The difference in angles Ge(2)−Ge(1)−
Table 5. Selected Bond Distances (Å) and Bond Angles
Ge(2) (124.10(3)°) and C(11)−Ge(1)−C(11A) (108.0(2)°)
(
deg) in (C F ) GeGe(p-Tol) (5)
6
5 3
3
76
is explained by Bent’s rule.
The aromatic rings adopt staggered conformations with the
Ge(1)−Ge(2)
Ge(1)−C(1)
2.4652(11)
1.963(4)
Ge(2)−C(11)
1.944(4)
values of torsion angles C−Ge−Ge−C between 38.81 and
4
4.52°.
C(11)−Ge(2)−
112.27(11) C(11)−Ge(2)−
106.50(12)
110.54(11)
C(11A)
Ge(1)
The Ge−Ge bond lengths in 6 (2.459 Å; Table 6) are
C(1)−Ge(1)−Ge(2)
108.38(12) C(1)−Ge(1)−
significantly elongated in comparison with p-tolyl oligoger-
manes [(p-Tol) Ge] GePh (2.4318 and 2.4338 Å) and [(p-
C(1A)
3
2
2
6
504
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Organometallics
Tol) Ge] Ge(p-Tol) (2.4450 and 2.4359 Å) (Table 3).
Article
49
the gap due to the interactions of Ge−Ge bond orbitals with
3
2
2
3
5,42,53,60,78,79
Similar to the case for compound 5, this elongation is probably
caused by the effects of electron-withdrawing C F groups.
molecular orbitals of aryl substituents.
Weinert and co-workers established earlier that the HOMO−
LUMO gap decreases upon the introduction of electron-
6
5
In compound 9, both germanium atoms have tetrahedral
geometries and adopt almost ideal eclipsed conformations with
the values of torsion angles C−Ge−Ge−C of less than 2°
3
8,79
donating groups to Ge atoms in oligogemanes.
In this
work, we calculated the energies of the frontier orbitals in a
series of model compounds (Table 8). Our results show that
the energy of the HOMO and LUMO in digermanes also
decreases upon the introduction of electron-withdrawing
substituents.
(
Figure 6 and Table 7). Such a conformation allows weak
interactions between acceptor and donor aromatic rings (C6F5
and Ph, respectively); the shortest C ···C distance is 3.246(3)
F
H
Å.
The lowest gaps were obtained for digermanes containing
only electron-withdrawing substituents at Ge atoms. This result
may be caused by HOMO destabilization (as observed for
56
electron-donating substituenes ) and LUMO stabilization. The
latter effect is more significant for oligogermanes with electron-
withdrawing groups. It is known that the synthesis of
oligogermanes with simple acceptors, such as halogens, is
often problematic (for example, Ge Cl could not be isolated in
3
8
80
pure form). Therefore, the successful introduction of C6F5
groups in oligogermanes is an important step in the chemistry
of these compounds.
According to molecular orbital analysis, the electron density
of the HOMO in symmetrical di- and trigermanes
Me GeGeMe , Ph GeGePh , Ph GeGePh GePh , and
3
3
3
3
3
2
3
(
C F ) GeGe(C F ) (Figure 9 and Supporting Information)
6 5 3 6 5 3
is localized across their Ge−Ge bonds. The LUMO in phenyl
derivatives and other oligogermanes with donor aryl groups is
in the aromatic groups; for the alkyl derivative Me GeGeMe
3
3
and digermanes with only electron-withdrawing aromatic
groups it is in the Ge−Ge bond.
The NBO analysis shows that germanium atoms in all our
3
compounds are sp hybridized, with a Wiberg index of 0.9 and a
population of the bonding Ge−Ge orbital of 1.85 e.
Figure 6. Molecular structure of (C F ) GeGePh (9). Displacement
ellipsoids are shown at the 50% probability level. Hydrogen atoms are
omitted for clarity.
6
5
3
3
UV/Visible spectroscopy. At present, only symmetric
oligogermanes or derivatives with donor substituents have been
studied by UV/visible spectroscopy. The distinctive feature in
all these compounds in comparison with their carbon analogues
is the presence of strong absorptions in their UV/visible spectra
Table 7. Selected Bond Distances (Å) and Bond Angles
(
deg) in (C F ) GeGePh (9)
6
5 3
3
4
−1
−1
Ge(1)−Ge(2)
Ge(1)−C(21)
Ge(1)−C(11)
Ge(1)−C(31)
C(21)−Ge(1)−C(11)
C(21)−Ge(1)−C(31)
C(11)−Ge(1)−C(31)
C(21)−Ge(1)−Ge(2)
C(11)−Ge(1)−Ge(2)
C(31)−Ge(1)−Ge(2)
2.4623(4)
1.9624(18)
1.9634(18)
1.9636(18)
111.40(8)
109.49(8)
109.30(8)
108.51(6)
109.15(5)
108.95(5)
Ge(2)−C(41)
Ge(2)−C(51)
Ge(2)−C(61)
1.9445(18)
1.9447(18)
1.9454(18)
(ε > 10 M cm ). The HOMO in oligogermanes is localized
along the Ge−Ge bond (σ-bonding orbital) and formed by
7
hybridized atomic orbitals of all Ge atoms. Since the LUMO in
many oligogermanes is also localized between the Ge atoms
(σ*-antibonding orbital), this absorption in UV/visible spectra
may be interpreted as a σ → σ* transition.
C(41)−Ge(2)−C(51)
C(41)−Ge(2)−C(61)
C(51)−Ge(2)−C(61)
C(41)−Ge(2)−Ge(1)
C(51)−Ge(2)−Ge(1)
C(61)−Ge(2)−Ge(1)
111.85(8)
112.19(8)
113.19(8)
106.44(6)
106.41(6)
106.17(6)
In aryl-substituted oligogermanes, the LUMO is localized on
the carbon atoms of aromatic rings (π*-antibonding orbital).
However, the σ → π* transitions are forbidden and have low
intensity in UV/visible spectra. Therefore, the UV/visible
absorptions of such molecules may be also regarded as σ → σ*
transitions. It should be noted that phenyl substituents at
germanium act as strong σ-donors and increase the energy of
the HOMO for systems of Ge−Ge bonds.
The UV spectra of unsymmetrical germanes 1, 2, 5, 6, 9 and
similar compounds are shown in Figures 10 and 11. The main
absorption bands are typical for Ge−Ge bonds. The bands of π
→ π* transitions in aryl substituents are relatively weak and
appear as shoulders of more intense absorptions.
The Ge···F distances in structures 5, 6, and 9 are greater than
3
.0 Å; therefore, the intermolecular interactions of this type are
11
very weak or absent.
DFT Calculations. The electronic and geometrical
structures of studied compounds have been analyzed by the
DFT method. According to our calculations and the earlier
results of Weinert et al., the size of the HOMO−LUMO gap in
oligogermanes depends on the type of substituents at
germanium (alkyl or aryl) and the primary chain length
According to Table 9, the introduction of electron-with-
drawing groups C F in digermanes 5 and 9 results in small
6
5
(
Figures 7 and 8). An increase in the number of Ge atoms in
hypsochromic shifts of absorptions (as compared to similar
compounds containing electron-donating phenyl or tolyl
groups). At the same time, the presence of C F groups in
the chain decreases of the gap, which leads to a red shift in the
UV/visible absorption. The presence of aromatic rings
instead of alkyl groups at germanium atoms also decreases
77
6
5
trigermane 6 leads to a bathochromic shift of the absorption.
6
505
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Organometallics
Article
Figure 7. Dependence between HOMO−LUMO gap and number of Ge atoms in Ge Ph2n+2: (a) at GAUSS; (b) at ADF.
n
Figure 8. Dependence between HOMO−LUMO gap and number of Ge atoms in Ge Me2n+2: (a) at GAUSS; (b) at ADF.
n
Table 8. UV/Visible Bands and the HOMO−LUMO Gaps in
time, it was demonstrated that a C F group at the Ge atom can
6 5
Selected Digermanes According to DFT Calculations
be substituted by germanium nucleophiles to produce a Ge−Ge
bond. The introduction of electron-withdrawing groups to
germanium atoms in donor−acceptor oligogermanes leads to a
small hypsochromic shift of absorptions in UV spectra of
digermanes (HOMO stabilization), which is in agreement with
earlier reports. In the case of trigermanes, the introduction of
electron-withdrawing groups produces a bathochromic shift of
UV absorptions (LUMO stabilization).
These results constitute a significant step forward in the
chemistry of oligogermanes. The synthetic approaches used in
this work, in particular, the hydrogermolysis reaction, extend
the range of available oligogermanes toward the derivatives with
electron-withdrawing substituents and unsymmetrical donor−
acceptor compounds.
ΔEHOMO−LUMO (eV)
a
digermane
λmax(calcd) (nm)
GAUSS
ADF
Cl GeGeCl3
184
5.12
8.13
7.84
6.00
7.68
5.90
7.49
5.72
5.19
5.65
4.94
3.74
6.19
6.18
4.58
6.25
4.48
5.45
4.36
3.88
4.18
3.47
3
H GeGeH3
3
146, 125
152, 134
171, 146, 129
132
(
F C) GeGe(CF )
3 3 3 3
H GeGeCl3
3
Me GeGe(CF )
3
3
3
Me GeGeCl3
174, 150
137, 158
204, 165
210, 206
3
Me GeGeMe3
3
Me GeGePh3
3
Ph GeGePh3
3
Me GeGe(C F )
6 5 3
3
(
C F ) GeGe(C F )
6 5 3 6 5 3
a
These data show good correlation: ΔE = −0.6 + 0.85[ΔEGAUSS], r
EXPERIMENTAL SECTION
General Remarks. All reactions were carried out under a
protective atmosphere using standard Schlenk techniques. GeCl and
ADF
■
=
0.987; sd = 0.17; n = 11.
4
Similar behavior is shown by (Me Si) GeGe(SiMe ) and
C F Br (Aldrich) were distilled prior to use. Me SiCl (Aldrich) was
distilled over aluminum dust. Bu Li and Li powder (Aldrich) were
3
3
3 3
6
5
3
n
(
Me Si) GeGeCl . A bathochromic shift of UV absorptions is
also observed for oligogermanes with longer primary chains.
3
3
3
used as supplied. Solvents were dried using standard procedures.
1
H NMR (400.130 MHz), C NMR (100.613 MHz), and 19F
13
NMR spectra (376.498 MHz) were recorded on Bruker 400 and
CONCLUSIONS
In the course of our work, a series of mono-, di-, and
trigermanes with electron-withdrawing C F substituents were
■
Agilent 400MR spectrometers at 298 K. Chemical shifts are given in
1
13
ppm relative to the internal reference Me Si ( H and C NMR
4
19
6
5
spectra) or the external reference CFCl3 ( F spectra). Elemental
synthesized. Oligogermanes 5 and 9 are characterized by
unusual eclipsed conformations in the solid state. For the first
analyses were carried out by the Microanalytical Laboratory of the
Chemistry Department of Moscow State University using a Heraeus
6
506
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Article
Figure 9. Calculated molecular orbitals for (C F ) GeGe(C F ) : (left) HOMO; (middle) HOMO-1; (right) LUMO.
6
5
3
6 5 3
Table 9. Comparison of Absorption Maxima in UV/Visible
Spectra for 1, 2, 5, 6, 9, and Related Compounds
compd
λmax (nm)
240 (σ → σ*)
ref
Ph GeGePh3
49
3
(
p-Tol) GeGe(p-Tol)3
241 (σ → σ*)
226 (σ → σ*)
234 (σ → σ*)
this work, 49
this work
3
Ph GeGe(C F ) (9)
3
6 5 3
(p-Tol) GeGe(C F ) (5)
this work
3
6 5 3
(
(
Me Si) GeGe(SiMe )
3 3
209 (σ → σ*)
231 (σ → σ*)
67
3
3
Me Si) GeGeCl (1)
this work
3
3
3
[
[
[
(p-Tol) Ge] GePh
2
251 (σ → σ*)
253 (σ → σ*)
258 (σ → σ*)
49
3
2
(p-Tol) Ge] Ge(p-Tol)
2
49
3
2
Figure 10. UV/visible absorption spectra of 1 and 2 in n-hexane.
(p-Tol) Ge] Ge(C F )
6 5 2
this work
3
2
(6)
(
(Me Si) GeGeCl ) (2)
265 (σ → σ*), 297 (σ → σ*) this work
3
3
2 2
Synthesis of Starting Materials. Chloro[tris(perfluorophenyl)]-
82
germane (3). A solution of C F Br (5.00 mL, 40.10 mmol) in
6
5
diethyl ether (15 mL) was added dropwise at −78 °C to a vigorously
n
stirred solution of Bu Li (2.5 M solution in hexane, 16 mL, 40.10
mmol) in hexane (25 mL). The stirring was continued at the same
temperature for 5 min. GeCl (1.48 mL, 12.94 mmol) was added at
4
−
78 °C to the slurry of C F Li obtained; the reaction mixture was
6 5
stirred at the same temperature for 2 h and then warmed to ambient
temperature overnight. The volatiles were removed under reduced
pressure, the residue was extracted with hexane (3 × 40 mL), and the
solution obtained was concentrated in vacuo. The residue was cooled
to −30 °C, and the colorless crystals of 3 were isolated by filtration
82
and dried in vacuo. Yield: 3.33 g (82%). Mp: 110−111 °C (lit mp
Figure 11. UV/visible absorption spectra of 5, 6, 9 and (p-
Tol) GeGe(p-Tol) in CH Cl .
19
1
06−110 °C). F NMR (δ, ppm, CDCl ): −127.22 (m, 2F), −145.19
3
3
3
2
2
13
(
m, 1F), −158.13 (m, 2F). The signals of C F in C NMR spectra
6
5
could not be obtained due to insufficient intensity of signals and
Vario Elementar instrument. UV/visible spectra were recorded using a
double-beam spectrophotometer Evolution 300 “Thermo Scientific”
using a 0.10 cm cuvette. Mass spectra (EI-MS, 70 eV) were recorded
on a Finnigan MAT INCOS 50 quadrupole mass spectrometer with
direct injection; all assignments were made with reference to the most
abundant isotopes.
nuclear coupling.
Crystals for X-ray analysis were obtained from n-hexane at −30 °C.
8
2
Dibromo[bis(perfluorophenyl)]germane (4). A solution of
C
F
5
Br (2.53 mL, 20.25 mmol) in diethyl ether (50 mL) was added
dropwise to a slurry of Mg (0.50 g, 20.58 mmol) in diethyl ether (50
mL). The reaction mixture was refluxed for 1 h, and then GeCl (1.20
6
4
5
5
49
61
Ph GeNMe ,
(p-Tol) GeNMe ,
(p-Tol) GeH,
[(p-
g, 5.60 mmol) was added and the mixture was stirred at ambient
temperature overnight. The solution was filtered, the volatiles were
removed in vacuo, and residue was fractionated to afford 4 as a
3
2
3
2
3
81
23
24
Tol) Ge] , (Me Si) GeCeCl (1), and [(Me Si) GeCl ] (2)
3
2
3
3
3
3
3
2 2
were prepared according to published procedures. Improved protocols
82
82
82
were used for the synthesis of (C F ) GeCl, (C F ) GeBr ,
colorless liquid with bp 120−125 °C/0.7 mmHg) (lit. bp 180−185
6
5
3
6
5
2
2
35
36
83
(
C F ) GeH, and (C F ) GeH .
°C/12 mmHg or lit. bp 120 °C/0.6 mmHg). Yield: 1.03 g (18%).
6
5
3
6
5
2
2
19
Warning! C F Li generated for synthesis and also appearing as a side
F NMR (δ, ppm, CDCl
3
): −127.02 (m, 2F), −145.77 (m, 1F),
6
5
13
product is potentially explosive.
−158.52 (m, 2F). The signals of C F in C NMR spectra could not
6
5
6
507
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Organometallics
Article
be obtained due to insufficient intensity of signals and nuclear
volatiles were removed in vacuo, and the residue was dissolved in
dichloromethane. The solution was filtered, the volatiles were
evaporated, and the remaining solid was washed with n-hexane (5
mL) and recrystallized from a mixture of dichloromethane and n-
coupling.
3
5
Tris(perfluorophenyl)germane (7). LiAlH (0.11 g, 2.90 mmol)
4
was added at 0 °C to a solution of compound 3 (1.36 g, 2.23 mmol) in
toluene (20 mL). Diethyl ether (20 mL) was added dropwise to the
reaction mixture, the resulting slurry was stirred for 1 h at ambient
temperature, and then EtOAc (3 mL) and a 10% solution of HCl were
added. The aqueous phase was extracted with diethyl ether (3 × 20
mL), and the combined organic phases were dried over Na SO . The
1
hexane to afford 5 as a white solid. Yield 0.59 g, 66%. H NMR (δ,
3
3
ppm, CDCl ): 7.18 (d, 6H, J
= 7.6 Hz, Ar), 7.06 (d, 6H, J
=
3
H−H
H−H
13
7.6 Hz, Ar), 2.33 (s, 9H, 3CH3). C NMR (δ, ppm, CDCl ): 139.80,
3
134.75, 129.48, 129.08 (Ar), 21.35 (CH ). The signals of C F groups
3
6 5
1
9
could not be detected due to low intensity and nuclear coupling.
F
2
4
solvent was removed in vacuo, and the residue was recrystallized from
NMR (δ, ppm, CDCl ): −124.53 (2F), −150.07 (1F), −160.35 (2F).
3
+
+
hexane to afford 7 as a white solid. Yield: 0.93 g (72%). Mp: 130−131
EI-MS: m/z (%): 575 (4) [(C F ) Ge] , 347 (100) [(p-Tol) Ge] ,
6 5 3 3
3
5
1
4
+
+
+
°
=
−
C (lit. mp 130−132 °C). H NMR (δ, ppm, CDCl ): 6.28 (t, J
167 (4) [C
absorption (CH , λmax in nm (ε in M cm )): 234 (4.6 × 10 ).
Anal. Calcd for C39H F15Ge : C, 50.93; H, 2.30. Found: C, 50.95; H,
21 2
6 5
F ] , 164 (14) [(p-Tol)Ge] , 91 (9) [p-Tol] . UV/visible
3
H−F
1
9
−1
−1
4
3.5 Hz, GeH). F NMR (δ, ppm, CDCl ): −126.55 (m, 2F),
147.46 (m, 1F), −158.96 (m, 2F). The signals of C F in C NMR
2
Cl
2
3
13
6
5
spectra could not be obtained due to insufficient intensity of signals
and nuclear coupling. Crystals for X-ray analysis were obtained from n-
hexane at −30 °C.
2.26. Crystals for X-ray analysis were obtained from n-hexane at −30
°C.
1,1,1,3,3,3-Hexakis(p-tolyl)-2,2-bis(perfluorophenyl)trigermane
(6). A solution of compound 8 (0.52 g, 1.27 mmol) in n-hexane (8
3
6
Bis(perfluorophenyl)germane (8). LiAlH (0.50 g, 13.40 mmol)
4
mL) was added to a solution of (p-Tol) GeNMe (0.99 g, 2.54 mmol)
was added at 0 °C to a solution of compound 4 (3.45 g, 6.10 mmol) in
toluene (8 mL). Diethyl ether (7 mL) was added dropwise over 10
min, the resulting slurry was stirred for 1 h at ambient temperature,
and then EtOAc (3 mL) and a 10% solution of HCl were added. The
aqueous phase was extracted with diethyl ether (3 × 20 mL), and
combined organic phases were dried over Na SO . The solvent was
3
2
in n-hexane (15 mL). The resulting solution was stirred in a sealed
flask at 100 °C for 3 h. The reaction mixture was cooled to ambient
temperature, the volatiles were removed in vacuo, and the residue was
dissolved in dichloromethane. The solution was filtered, the volatiles
were evaporated, and the remaining solid was washed with n-hexane (5
mL) and dried in vacuo to afford 6 as a white solid. Yield: 0.56 g
2
4
removed in vacuo, and the residue was fractionated to afford 8 as a
36
1
3
(
7
51%). H NMR (δ, ppm, CDCl ): 7.10 (d, 12H, J
= 7.6 Hz, Ar),
colorless oil with bp 125 °C/15 mmHg (lit. bp 103 °C/5 mmHg or
3
H−H
3
13
.03 (d, 12H, J
= 7.6 Hz, Ar), 2.35 (s, 18H, 6CH3). C NMR (δ,
5
0−60 °C/1 mmHg). The oil solidified after standing at ambient
H−H
1
ppm, CDCl ): 139.00, 135.04, 131.96, 128.91 (Ar), 21.37 (CH ). The
temperature. Yield: 1.86 g (75%). H NMR (δ, ppm, CDCl ): 5.37
3
3
3
4
19
signals of C F groups could not be detected due to low intensity and
(
quint, J
= 5.6 Hz, GeH). F NMR (δ, ppm, CDCl ): −125.42 m
6 5
H−F
3
19
13
nuclear coupling. F NMR (δ, ppm, CDCl ): −119.33 (m, 2F),
(
2F), −149.03 m (2F), −159.56 m (2F). The signals of C F in
C
3
6
5
−
153.08 (m, 1F), −161.21 (m, 2F). EI-MS: m/z (%): 347 (100) [(p-
NMR spectra could not be obtained due to insufficient intensity of
+ + +
Tol) Ge] , 167 (9) [C F ] , 91 (4) [p-Tol] . UV/visible absorption
signals and nuclear coupling.
3
6 5
8
1
1
−1
−1
4
(CH Cl , λ in nm (ε in M cm )): 258 (1.4 × 10 ). Anal. Calcd
Hexakis(p-tolyl)digermane. H NMR (δ, ppm, CDCl ): 7.20 (d,
2 2 max
3
3
3
for C H F Ge : C, 59.03; H, 3.85. Found: C, 58.90; H, 3.93.
1
2H, J
= 7.8 Hz, Ar), 7.06 (d, 12H, J
=7.8 Hz, Ar), 2.32 (s,
54 42 10
3
H−H
H−H
+
Crystals for X-ray analysis were obtained from n-hexane at −30 °C.
,1,1-Triphenyl-2,2,2-tris(perfluorophenyl)digermane (9). Solid
compound 7 (0.53 g, 0.92 mmol) was added to a solution of
Ph GeNMe (0.32 g, 0.92 mmol) in n-hexane (10 mL). The reaction
1
8H, CH ). EI-MS m/z (%): 694 (6) [M] , 347 (100) [M − (p-
3
+
+
1
Tol) Ge] , 165 (19) [Ge(p-Tol)] . UV/visible absorption (CH Cl ,
λmax in nm (ε in M cm )): 241 (1.8 × 10 ). The C NMR
3
2
2
−1
−1
4
13
84
spectrum was consistent with literature data.
Synthesis of “Donor−Acceptor” Oligogermanes. [Tris-
3
2
mixture was stirred in a sealed flask at 100 °C for 2 h. The reaction
mixture was cooled to ambient temperature, the volatiles were
removed in vacuo, and the residue was dissolved in dichloromethane.
The solution was filtered, the volatiles were evaporated, and the
remaining solid was washed with n-hexane (5 mL) and recrystallized
2
3
(
trimethylsilyl)germyl]trichlorogermane (1). The product was
purified by sublimation (0.4 mmHg, external heating at 340 °C).
−
1
−1
UV/visible absorption (n-hexane, λ in nm (ε in M cm )): 231
max
4
(
−
1.4 × 10 ). Crystals for X-ray analysis were obtained from n-hexane at
30 °C. The H and C NMR spectra were consistent with literature
1
13
from a mixture of chloroform and n-hexane to afford 9 as a white solid.
23
1
data.
Yield: 0.70 g (86%). H NMR (δ, ppm, CDCl
3
): 7.38−7.32 (m, 4H,
): 134.80,
F groups could not be
6 5
13
1
,1,1,4,4,4-Hexakis(trimethylsilyl)-2,2,3,3-tetrachlorotetrager-
Ar), 7.30−7.20 (m, 11H, Ar). C NMR (δ, ppm, CDCl
132.86, 129.82, 128.40 (Ar). The signals of C
detected due to low intensity and nuclear coupling. F NMR (δ, ppm,
CDCl ): −124.59 (m, 2F), −149.40 (m, 1F), −159.95 (m, 2F). UV/
visible absorption (CH , λmax in nm (ε in M cm )): 226 (3.7 ×
2
3
24
−1
mane (2). UV/visible absorption (n-hexane, λ in nm (ε in M
max
−
1
4
4
1
13
19
cm )): 297 (4.8 × 10 ), 265 sh (1.6 × 10 ). The H and C NMR
24
spectra were consistent with literature data.
3
−1
−1
1
,1,1-Tris(p-tolyl)-2,2,2-tris(perfluorophenyl)digermane (5).
2
Cl
10 ). Anal. Calcd for C H F Ge : C, 49.26; H, 1.72. Found: C,
n
4
Method 1. A solution of Bu Li in n-hexane (2.5 M, 0.40 mL, 1.00
36
15 15
2
mmol) was added to a solution of (p-Tol) GeH (0.35 g, 1.00 mmol)
48.96; H, 1.64. Crystals for X-ray analysis were obtained from a
mixture of chloroform with n-hexane at −30 °C.
3
in diethyl ether (20 mL). The reaction mixture was stirred at ambient
temperature for 1 h. The resulting solution of (p-Tol) GeLi was added
X-ray Study. The intensities of reflections for 1, 3, 5−7, and 9
were measured on a Bruker SMART APEX II diffractometer with a
graphite monochromator: λ(Mo Kα) = 0.71073 Å, ω-scanning mode.
The structures were solved by direct methods and refined by full
3
dropwise at −78 °C to a solution of compound 3 (0.61 g, 1.00 mmol)
in diethyl ether (20 mL). The reaction mixture was warmed slowly to
ambient temperature and stirred overnight. Water (20 mL) was added,
the aqueous phase was extracted with diethyl ether (3 × 20 mL), and
the combined organic phases were washed with brine and dried over
Na SO . The solvent was removed in vacuo. According to NMR data,
2
85
matrix least squares on F (SHELXTL) with anisotropic thermal
parameters for all non-hydrogen atoms (except the CHCl molecule in
3
5). The positions of hydrogen atoms were calculated and refined using
2
4
the residue was a mixture of (C F ) GeGe(p-Tol) (5), (C F ) Ge-
a rigid model. In 5, the solvent molecule (CHCl ) is positioned on a 3-
6
5
3
3
6
5
2
3
[
Ge(p-Tol) ] (6), and unidentified compounds. The mixture was
fold crystallographic axis and disordered over the inversion center.
Crystallographic data for compounds 1, 3, 5−7, and 9 are given in
Table S-1 (Supporting Information).
3
2
purified by column chromatography (silica, petroleum ether/dichloro-
methane 40/3 then 2/1) to afford (p-Tol) GeGe(C F ) (5; 0.07 g,
3
6 5 3
8
%) and [(p-Tol) Ge] Ge(C F ) (6; 0.16 g, 15%). The purity of each
The crystallographic data for compounds 1, 3, 5−7, and 9 have
been deposited with the Cambridge Crystallographic Data Centre as
Supplementary Publications under the CCDC numbers 952348−
952353, respectively. They can be obtained free of charge from the
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
3
2
6 5 2
product was better than 95%.
Method 2. Solid (C F ) GeH (7; 0.56 g, 0.97 mmol) was added to
a solution of (p-Tol) GeNMe (0.38 g, 0.97 mmol) in n-hexane (10
mL). The resulting solution was stirred in a sealed flask at 100 °C for 2
h. The reaction mixture was cooled to ambient temperature, the
6
5 3
3
2
6
508
dx.doi.org/10.1021/om4008218 | Organometallics 2013, 32, 6500−6510

Organometallics
Article
(
23) Mallela, S. P.; Saar, Y.; Hill, S.; Geanangel, R. A. Inorg. Chem.
ASSOCIATED CONTENT
■
1
(
1
999, 38, 2957−2960.
24) Mallela, S. P.; Geanangel, R. A. Inorg. Chem. 1994, 33, 1115−
120.
(25) (a) du Mont, W. W.; Gust, T.; Seppala, E.; Wismach, C.; Jones,
*
S
Supporting Information
Text, figures, tables, and CIF files giving crystallographic data
for 1, 3, 5−7, and 9, computational details, calculated HOMO/
LUMO energy levels, and frontier orbitals. This material is
available free of charge via the Internet at http://pubs.acs.org.
P. G.; Ernst, L.; Grunenberg, J.; Marsmann, H. C. Angew. Chem., Int.
Ed. 2002, 41, 3829−3832. (b) Al-Rafia, S. M. I.; Momeni, M. R.;
McDonald, R.; Ferguson, M. J.; Brown, A.; Rivard, E. Angew. Chem.,
Int. Ed. 2013, 52, 6390−6395.
AUTHOR INFORMATION
■
*
(26) Yoder, C. H.; Agee, T. M.; Griffith, A. K.; Schaeffer, C. D.;
Corresponding Author
E-mail for K.V.Z.: zaitsev@org.chem.msu.ru.
Carroll, M. J.; De Toma, A. S.; Fleisher, A. J.; Gettel, C. J.; Rheingold,
A. L. Organometallics 2010, 29, 582−590.
(27) Dakternieks, D.; Lim, A. E. K.; Zobel, B.; Tiekink, E. R. T. Main
Author Contributions
All authors have contributed equally and given approval to the
final version of the manuscript.
Group Met. Chem. 2000, 23, 789−790.
(28) Prince, P. D.; McGrady, G. S.; Steed, J. W. New J. Chem. 2002,
2
6, 457−461.
Notes
(29) Sugiyama, Y.; Matsumoto, T.; Yamamoto, H.; Nishikawa, M.;
Kinoshita, M.; Takei, T.; Mori, W.; Takeuchi, Y. Tetrahedron 2003, 59,
689−8696.
30) Samanamu, C. R.; Anderson, C. R.; Golen, J. A.; Moore, C. E.;
The authors declare no competing financial interest.
8
(
ACKNOWLEDGMENTS
■
Rheingold, A. L.; Weinert, C. S. J. Organomet. Chem. 2011, 696, 2993−
2999.
We thank the RFBR (project 12-03-31153) for financial
support. This work was supported in part by the M. V.
Lomonosov Moscow State University Program of Develop-
ment. We thank the Hochschulrechenzentrum of the Philipps-
Universitat Marburg for their excellent service. We sincerely
̈
thank Dr. S. Y. Bylikin, Open University Milton Keynes, for
fruitful discussions.
(
31) Karipide, A.; Forman, C.; Thomas, R. H. P.; Reed, A. T. Inorg.
Chem. 1974, 13, 811−815.
32) Fajarí, L.; Julia, L.; Riera, J.; Molins, E.; Miravitlles, C. J.
(
́
Organomet. Chem. 1989, 363, 31−37.
(
(
(
33) Lepore, S. D.; Mondal, D. Tetrahedron 2007, 63, 5103−5122.
34) Chambers, R. D.; Chivers, T. J. Chem. Soc. 1964, 4782−4790.
35) Bochkarev, M. N.; Maiorova, L. P.; Vyazankin, N. S. J.
Organomet. Chem. 1973, 55, 89−96.
REFERENCES
(36) Bochkarev, M. N.; Maiorova, L. P.; Korneva, S. P.; Bochkarev, L.
N.; Vyazankin, N. S. J. Organomet. Chem. 1974, 73, 229−236.
■
(
(
1) James, D. K.; Tour, J. M. Chem. Mater. 2004, 16, 4423−4435.
2) Kobayashi, H.; Kobayashi, A.; Tajima, H. Chem. Asian J. 2011, 6,
(37) Riedmiller, F.; Wegner, G. L.; Jockisch, A.; Schmidbaur, H.
Organometallics 1999, 18, 4317−4324.
1
(
(
(
688−1704.
(38) Samanamu, C. R.; Amadoruge, M. L.; Yoder, C. H.; Golen, J. A.;
3) Avarvari, N.; Wallis, J. D. J. Mater. Chem. 2009, 19, 4061−4076.
4) McCreery, R. L. Chem. Mater. 2004, 16, 4477−4496.
Moore, C. E.; Rheingold, A. L.; Materer, N. F.; Weinert, C. S.
Organometallics 2011, 30, 1046−1058.
5) Bukalov, S. S.; Leites, L. A.; Krylova, I. V.; Egorov, M. P. J.
(39) Cameron, T. S.; Mannan, K. M.; Stobart, S. R. Cryst. Struct.
Organomet. Chem. 2001, 636, 164−171.
6) Kodaira, T.; Watanabe, A.; Ito, O.; Matsuda, M.; Tokura, S.; Kira,
M.; Nagano, S.; Mochida, K. Adv. Mater. 1995, 7, 917−919.
Commun. 1975, 4, 601−604.
40) Kawachi, A.; Tanaka, Y.; Tamao, K. Organometallics 1997, 16,
102−5107.
41) Lambert, J. B.; Stern, C. L.; Zhao, Y.; Tse, W. C.; Shawl, C. E.;
Lentz, K. T.; Kania, L. J. Organomet. Chem. 1998, 568, 21−31.
42) McGrady, G. S.; Odlyha, M.; Prince, P. D.; Steed, J. W.
CrystEngComm 2002, 4, 271−276.
43) Barrow, M. J.; Ebsworth, E. A. V.; Harding, M. M.; Rankin, D.
W. H. J. Chem. Soc., Dalton Trans. 1980, 603−606.
44) Baines, K. M.; Cooke, J. A.; Vittal, J. J. J. Chem. Soc., Chem.
Commun. 1992, 1484−1485.
45) Samanamu, C. R.; Amadoruge, M. L.; Schrick, A. C.; Chen, C.;
(
(
5
(
(
(
(
4
(
7) Miller, R. D.; Michl, J. Chem. Rev. 1989, 89, 1359−1410.
8) Sita, L. R. Adv. Organomet. Chem. 1995, 38, 189−243.
9) Amadoruge, M. L.; Weinert, C. S. Chem. Rev. 2008, 108, 4253−
(
294.
10) Weinert, C. S. Dalton Trans. 2009, 1691−1699.
11) Bender, J. E.; Holl, M. M. B.; Mitchell, A.; Wells, N. J.; Kampf, J.
(
(
W. Organometallics 1998, 17, 5166−5171.
12) Haberle, K.; Drager, M. J. Organomet. Chem. 1986, 312, 155−
65.
13) Komoriya, H.; Kako, M.; Nakadaira, Y. Organometallics 1996,
5, 2014−2018.
14) Hlina, J.; Baumgartner, J.; Marschner, C. Organometallics 2010,
9, 5289−5295.
15) Mallela, S. P.; Geanangel, R. A. Inorg. Chem. 1991, 30, 1480−
482.
(
(
1
(
1
(
2
(
1
(
Golen, J. A.; Rheingold, A. L.; Materer, N. F.; Weinert, C. S.
Organometallics 2012, 31, 4374−4385.
(46) Bochkarev, M. N.; Vyazankin, N. S.; Bochkarev, L. N.; Razuvaev,
G. A. J. Organomet. Chem. 1976, 110, 149−157.
(47) Simon, D.; Hab
267, 133−142.
(48) Spikes, G. H.; Fettinger, J. C.; Power, P. P. J. Am. Chem. Soc.
2005, 127, 12232−12233.
̈ ̈
erle, K.; Drager, M. J. Organomet. Chem. 1984,
(
(
16) Razuvaev, G. A. J. Organomet. Chem. 1980, 200, 243−259.
17) Castel, A.; Riviere, P.; Saintroch, B.; Satge, J.; Malrieu, J. P. J.
Organomet. Chem. 1983, 247, 149−160.
18) Tanabe, M.; Hanzawa, M.; Osakada, K. Phosphorus, Sulfur,
Silicon Relat. Elem. 2011, 186, 1384−1388.
19) Braddock-Wilking, J.; Bandrowsky, T.; Praingam, N.; Rath, N. P.
Organometallics 2009, 28, 4098−4105.
20) Arii, H.; Nanjo, M.; Mochida, K. Organometallics 2008, 27,
147−4151.
21) Pankratov, L. V.; Nevodchikov, V. I.; Zakharov, L. N.; Fukin, G.
(
(49) Amadoruge, M. L.; Short, E. K.; Moore, C.; Rheingold, A. L.;
Weinert, C. S. J. Organomet. Chem. 2010, 695, 1813−1823.
(50) Haberle, K.; Drager, M. Z. Naturforsch., B: Chem. Sci. 1987, 42,
323−329.
(
(
4
(
(51) Parkanyi, L.; Kalman, A.; Sharma, S.; Nolen, D. M.; Pannell, K.
H. Inorg. Chem. 1994, 33, 180−182.
(52) Ng, M. C. C.; Craig, D. J.; Harper, J. B.; van Eijck, L.; Stride, J.
A. Chem. Eur. J. 2009, 15, 6569−6572.
K.; Khorshev, S. Y.; Bochkarev, M. N.; Struchkov, Y. T. Russ. Chem.
Bull. 1994, 43, 295−298.
22) Azemi, T.; Yokoyama, Y.; Mochida, K. J. Organomet. Chem.
(53) Amadoruge, M. L.; Yoder, C. H.; Conneywerdy, J. H.; Heroux,
K.; Rheingold, A. L.; Weinert, C. S. Organometallics 2009, 28, 3067−
3073.
(
2
005, 690, 1588−1593.
6
509
dx.doi.org/10.1021/om4008218 | Organometallics 2013, 32, 6500−6510

Organometallics
Article
(
54) Holbling, M.; Masters, S. L.; Flock, M.; Baumgartner, J.; Hassler,
K.; Robertson, H. E.; Wann, D. A. Inorg. Chem. 2008, 47, 3023−3033.
55) Subashi, E.; Rheingold, A. L.; Weinert, C. S. Organometallics
006, 25, 3211−3219.
56) Schrick, E. K.; aForget, T. J.; Roewe, K. D.; Schrick, A. C.;
(
2
(
Moore, C. E.; Golen, J. A.; Rheingold, A. L.; Materer, N. F.; Weinert,
C. S. Organometallics 2013, 32, 2245−2256.
(
57) Farwell, J. D.; Fernandes, M. A.; Hitchcock, P. B.; Lappert, M.
F.; Layh, M.; Omondi, B. Dalton Trans. 2003, 1719−1729.
(
58) Bochkova, R. I.; Drozdov, Y. N.; Kuzmin, E. A.; Bochkarev, L.
N.; Bochkarev, M. N. Russ. J. Coord. Chem. 1987, 13, 1126−1129.
(59) Drager, M.; Ross, L. Z. Anorg. Allg. Chem. 1980, 460, 207−216.
(60) Drager, M.; Ross, L. Z. Anorg. Allg. Chem. 1980, 469, 115−122.
(61) Lee, V. Y.; Yasuda, H.; Ichinohe, M.; Sekiguchi, A. J. Organomet.
Chem. 2007, 692, 10−19.
62) Renner, G.; Kircher, P.; Huttner, G.; Rutsch, P.; Heinze, K. Eur.
J. Inorg. Chem. 2000, 879−887.
63) Zaitsev, K. V.; Kapranov, A. A.; Oprunenko, Y. F.; Churakov, A.
(
(
V.; Howard, J. A. K.; Tarasevich, B. N.; Karlov, S. S.; Zaitseva, G. S. J.
Organomet. Chem. 2012, 700, 207−213.
(
64) Amadoruge, M. L.; Di Pasquale, A. G.; Rheingold, A. L.;
Weinert, C. S. J. Organomet. Chem. 2008, 693, 1771−1778.
65) Schafer, H.; Saak, W.; Weidenbruch, M. J. Organomet. Chem.
000, 604, 211−213.
66) Bender, J. E.; Litz, K. E.; Giarikos, D.; Wells, N. J.; Holl, M. M.
B.; Kampf, J. W. Chem. Eur. J. 1997, 3, 1793−1796.
67) Baumgartner, J.; Fischer, R.; Fischer, J.; Wallner, A.; Marschner,
C.; Florke, U. Organometallics 2005, 24, 6450−6457.
68) Weidenbruch, M.; Grimm, F. T.; Herrndorf, M.; Schafer, A.;
Peters, K.; Vonschnering, H. G. J. Organomet. Chem. 1988, 341, 335−
43.
(
2
(
(
̈
(
3
(
(
69) Drager, M.; Simon, D. J. Organomet. Chem. 1986, 306, 183−192.
70) Roller, S.; Simon, D.; Drager, M. J. Organomet. Chem. 1986, 301,
2
7−40.
71) Weidenbruch, M.; Hagedorn, A.; Peters, K.; von Schnering, H.
G. Chem. Ber. 1996, 129, 401−404.
72) Weidenbruch, M.; Hagedorn, A.; Peters, K.; von Schnering, H.
G. Angew. Chem., Int. Ed. Engl. 1995, 34, 1085−1086.
73) Lube, M. S.; Wells, R. L.; White, P. S. J. Chem. Soc., Dalton
Trans. 1997, 285−286.
74) Muller, L.; du Mont, W. W.; Ruthe, F.; Jones, P. G.; Marsmann,
(
(
(
(
H. C. J. Organomet. Chem. 1999, 579, 156−163.
(
(
(
(
75) Nanjo, M.; Sekiguchi, A. Organometallics 1998, 17, 492−494.
76) Bent, H. A. Chem. Rev. 1961, 61, 275−311.
77) Okano, M.; Mochida, K. Chem. Lett. 1990, 19, 701−704.
78) Amadoruge, M. L.; Golen, J. A.; Rheingold, A. L.; Weinert, C. S.
Organometallics 2008, 27, 1979−1984.
79) Amadoruge, M. L.; Gardinier, J. R.; Weinert, C. S. Organo-
metallics 2008, 27, 3753−3760.
80) Mochida, K.; Nakai, Y.; Shiota, S. Bull. Chem. Soc. Jpn. 1988, 61,
(
(
3
(
(
002−3004.
81) Bauer, H.; Burschkies, K. Chem. Ber. 1933, 66, 1041−1046.
82) Fenton, D. E.; Massey, A. G.; Urch, D. S. J. Organomet. Chem.
1
966, 6, 352−358.
83) Weidenbruch, M.; Wessal, N. Chem. Ber. 1972, 105, 173−187.
84) Schneider-Koglin, C.; Mathiasch, B.; Drager, M. J. Organomet.
Chem. 1993, 448, 39−46.
85) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112−122.
(
(
̈
(
6
510
dx.doi.org/10.1021/om4008218 | Organometallics 2013, 32, 6500−6510