Vinylgallium and alkyllithium compounds: Transmetalation and generation of oligolithium cages

Article abstract of DOI:10.1002/chem.201102057

Vinylgallium compounds [C₆H_6-n{(H)C=C(SiR ₂R′)-GaR″₂}_n] (3, R=Ph, Me; R′=Ph, Me; R″=tBu, Et; n=1, 2) are easily accessible by hydrogallation of the corresponding alkynylbenzene derivatives with H-GaCl

Full text of DOI:10.1002/chem.201102057

FULL PAPER
DOI: 10.1002/chem.201102057
Vinylgallium and Alkyllithium Compounds: Transmetalation and Generation
of Oligolithium Cages
[
a]
Werner Uhl,* Dirk Kovert, Marcus Layh, and Alexander Hepp
Abstract: Vinylgallium compounds
C H {(H)C=C
R=Ph, Me; R’=Ph, Me; R’’=tBu, Et;
n=1, 2) are easily accessible by hydro-
gallation of the corresponding alkynyl-
ortho-deprotonation of the aromatic
rings the unprecedented solvent-free
and [{(C H Li) ACHUTNGTRENNU{GN HC=C ACHTNUGTRNENG(U SiMe )Li} } ] (6)
6 3 3 2 3
[
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(SiR R’)ꢀGaR’’ } ] (3,
in moderate yields. Their solid-state
structures revealed the presence of
unique molecular lithium clusters with
6, 8, or 9 lithium atoms that may be de-
6
6ꢀn
2
2 n
oligolithium
cluster compounds
(SiPh )Li} ACTHNGUETRNNU(G tBuLi) ]
[{(C H Li)HC=C
A
H
U
G
R
N
N
6
4
3
2
2
(4), [{(C H Li)HC=C ACHTUGNTRNEUNG( SiPh Me)Li} ] (5)
2 4
6
4
benzene derivatives with HꢀGaCl and
rived from two edge-sharing Li tetra-
2
4
subsequent reaction with alkyllithium
derivatives. Treatment of 3 with an
excess amount of tert-butyl- or ethyl-
lithium yielded by transmetalation and
hedra (4), three Li4 tetrahedra in a
chain joined by two common edges (5)
or a tricapped trigonal prism of lithium
atoms (6).
Keywords: cluster compounds · gal-
lium · lithium · metalation · trans-
metalation
Introduction
best of our knowledge not been reported thus far. Quantum
chemical calculations for simple alkyllithium compounds
(R=Me, Et, nPr, nBu, iPr, sBu, tBu) indicate the octahe-
dron to be the thermodynamically most stable constitutional
isomer relative to smaller or larger lithium clusters, although
Lithium is unique in its propensity to form oligonuclear or-
ganometallic clusters with carbon atoms of saturated or un-
saturated carbanionic ligands in the bridging positions.
[1,2]
This particular property is caused by the relatively large po-
larising effect of the small lithium cations through which
lithiumꢀcarbon bonding interactions are on the borderline
the difference to the square antiprismatic structure (Li ,
8
[7]
D ) is small for MeLi and EtLi. Transmetalation with an
4
d
exchange of a relatively electronegative metal such as mer-
cury or tin for lithium is an important method for the syn-
between merely ionic and covalent. The importance of lithi-
um compounds in preparative chemistry for the transfer of
organic groups, the application as strong bases or the activa-
tion of small molecules is well known and cannot be over-
emphasized. Alkyllithium derivatives, for instance, are rou-
tine reagents in chemistry. Their fascinating structural diver-
sity in solution and the solid state depends strongly on the
presence or absence of coordinating solvents and the Lewis
base strength of the latter. Of particular interest are the
structures of solvent-free compounds that are frequently de-
rived from regular metalpolyhedra with triangular faces that
are completely or partially capped by the respective alkyl
substituents and explain the solubility of these compounds
in non-coordinating solvents. The most common polyhedra
are the tetrahedron and octahedron that are found, for in-
[4,8]
thesis of a broad variety of organolithium derivatives.
Currently we are very interested in the generation and the
chemical properties of vinylgallium compounds that have a
[9–12]
relatively hard vinylic carbon atom bonded to gallium.
They are obtained by the reaction of alkynes with dialkyl-
gallium hydrides (hydrogallation). We were hoping to
employ these compounds in transmetalation reactions with
an exchange of gallium for lithium by the treatment with al-
kyllithium derivatives. The preferred hard–hard interaction
between the lithium atoms and vinylic carbon atoms is
thought to serve as a driving force for the suggested trans-
formations. We report our first experiments on this topic to
afford unprecedented solvent-free lithium cluster com-
pounds.
[3]
[3]
stance, in (tBuLi)4 and (nBuLi)6, respectively. Dimeric or
polymeric forms have been reported in few cases with bulky
[
4]
substituents, such as [LiC
A
H
U
G
R
N
U
G
and [LiCH-
Results and Discussion
3
[5]
ACHTUNGTRENNUNG( SiMe ) ] . Larger polyhedra, with the exception of the re-
3
2
1
ꢀ
[6]
cently published anion [Li1
A
H
U
G
R
N
U
G
Syntheses of the dichlorogallium and dialkylgallium starting
2
2 4 6
[13]
compounds: Dichlorogallium hydride, HꢀGaCl , is a ver-
2
satile reagent for the hydrogallation of alkenes and al-
[
10–13]
[
a] Prof. Dr. W. Uhl, Dipl.-Chem. D. Kovert, Dr. M. Layh, Dr. A. Hepp
Institut fꢀr Anorganische und Analytische Chemie
der Universitꢁt Mꢀnster, Corrensstrasse 30
kynes.
Interestingly, even dual hydrogallation of alkynes
[11]
was observed at low temperatures,
whereas the corre-
sponding dialkylgallium hydrides reacted in this manner
only in rare cases under relatively drastic reaction condi-
tions. Due to their specific functionalities, the obtained di-
4
8149 Mꢀnster (Germany)
Fax : (+49)251-8336660
E-mail: uhlw@uni-muenster.de
[
14]
Chem. Eur. J. 2011, 17, 13553 – 13561
ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
13553

chlorogallium compounds show an interesting structural
chemistry and are suitable precursors for the generation of a
broad variety of secondary products by means of salt elimi-
and 2c, the product 3c was identified by NMR spectroscopy,
which indicated a structure similar to the tBu analogues, but
analytically pure samples of 3c could not be isolated. The
product showed additional signals in the NMR spectra that
were consistent with the presence of products that resulted
from a dismutation reaction of 3c. This type of reaction has
been described in detail for the hydogallation of C H (1,3,5-
[12]
nation reactions.
Three of these dichlorogallium deriva-
tives [C H {CH=C
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
A
H
U
G
R
N
U
G
6
6ꢀn
2
2 n
Ph; 2b, n=1, R=Ph, R’=Me; 2c, n=2, R=R’=Me) have
been applied in the investigations reported in this article.
The syntheses and molecular structures of 2a and 2c have
6
3
n
CꢁCtBu) with HGaR2 (R=Et, Pr, iPr, CH tBu, tBu),
3
2
which led in high yields to GaR and [3,3,3]-cyclophanes
3
[18]
[{C H (1,3,5-C=C(H)tBu) }
A
H
U
G
R
N
U
G
or in the case of
6
3
3
2
3
[Ph(H)C=C
acterized trivinylgallium compound trans,trans,cis-[Ga{C-
ACHTUNGTREN(NUNG SiMe )GaMe ] to the crystallographically char-
6
5
3
2
[16]
(
Scheme 1). The products were isolated in moderate yields
A
H
U
G
R
N
N
(SiMe )=CH(Ph)} ].
The solution NMR spectra of 3a–c
3
3
are again indicative of the trans isomer as evident from the
3
small J
A
H
U
G
R
N
U
G
The solid-state structure of 3a (Figure 1) is similar to pre-
viously described compounds of that type.
[15–17]
The atom
Ga1 is essentially planar and only 0.3 pm above the plane of
Scheme 1.
of 40–66% (Scheme 1). Previous detailed investigations of
this type of reaction have shown the thermodynamically fa-
vored trans products (Ga trans to H) with the gallium atom
in the geminal position to the silyl substituent to be the ex-
clusive products. The specific regioselectivity may be ex-
plained by the larger negative partial charge of the silyl-sub-
stituted carbon atom as compared to the phenyl-substituted
carbon atom of the alkyne starting materials and the pre-
ferred interaction of the positively charged gallium atom
with this carbon atom in the first step of the reaction. The
preference of the trans geometry of such addition products
and a possible mechanism of cis/trans isomerization have
been discussed on the base of quantum chemical calcula-
Figure 1. Molecular structure and numbering scheme of 3a; displacement
ellipsoids are drawn at the 40% level. Selected bond lengths [pm] and
angles [8]: Ga1ꢀC1 200.0(2), Ga1ꢀC2 201.5(3), Ga1ꢀC3 200.9(3), C1ꢀ
C10 134.3(3), C10ꢀC101 147.8(3); Ga1-C1-Si1 117.89(13), Ga1-C1-C10
122.97(19), Si1-C1-C10 119.07(19).
[15]
tions only recently. In solution, the configuration was un-
the three adjacent carbon atoms (C1, C2, C3). There are ad-
ditional long-range contacts to the ipso- and one ortho-C
atom of two phenyl substituents (Ga1ꢀC101 337.1 pm, Ga1ꢀ
C106 307.0 pm, Ga1ꢀC121 341.3 pm, Ga1ꢀC122 356.0 pm),
3
ambiguously deduced from the small J
stants (2b, 10 Hz) between silicon and the vinylic hydrogen
atoms. The respective J
ACHTUNGTRENNUNG( Si,H) coupling con-
3
ACHTUNGTRENUNNG( Si,H) coupling constants of the cor-
responding cis isomers were typically found to be around
thereby resulting in a very distorted pentagonal bipyramidal
arrangement around gallium. In particular, the small dis-
tance to a CꢀH group of the phenyl group attached to the
[15–17]
20 Hz.
Solid-state structure determinations of 2a and 2c
revealed the presence of dimeric molecules with four-coordi-
nate gallium atoms and one terminal and two bridging chlor-
ine atoms and confirmed the trans configuration of the vinyl
C=C bond was calculated to contribute to the particular sta-
[15]
bility of the trans isomers. This phenyl group is twisted by
an angle of 23.58 against the plane defined by the vinyl
group (Ga1, Si1, C1, C10, H10, C101). GaꢀC and C=C dis-
[12]
substituent.
The alkylation of the GaꢀCl functionalities of 2a and 2b
with two equivalents of tert-butyl lithium proceeded smooth-
ly at ꢀ788C to give the alkyl derivatives 3a and 3b in mod-
erate yields of 52 and 61% (Scheme 1). In the case of EtLi
tances are unexceptional.
13554
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Chem. Eur. J. 2011, 17, 13553 – 13561

Oligolithium Cages
FULL PAPER
Treatment of the dialkylgallium compounds 3 with tert-
butyl- and ethyllithium: Three alternative reactions may be
expected upon treatment of compounds 3 with an excess
amount of alkyllithium: 1) formation of simple Lewis acid–
base adducts; 2) condensation reactions by the release of tri-
alkylgallium derivatives or their adducts, which in some
[19]
cases could be initiated by the addition of Lewis bases;
and 3) transmetalation as the most desirable reaction. The
latter was indeed observed upon treatment of the vinyldigal-
lium compounds with tert-butyl (3a, 3b) or ethyllithium (3c)
in benzene or n-hexane. Compound 3c was not isolated in a
pure form, but treated in situ with an excess amount of the
lithium compound. Interestingly, transmetalation is accom-
panied by o-lithiation of the aryl substituents. Di- or trime-
talated vinylbenzene derivatives were generated, and the
lithium clusters 4 to 6 were isolated in moderate yields after
relatively long reaction times of 16 h to 2 days at room tem-
perature (Schemes 2–4). Interestingly, an excess amount of
alkyllithium reagent was incorporated into the cluster in the
case of 4, but not in the case of 5 and 6, for which a lithium
gallanate LiGaR was formed as byproduct instead, which
4
Scheme 4.
was identified by its characteristic NMR spectroscopic data
1
[
LiGatBu4 (C D ):
H NMR: d=1.18 ppm (CMe );
6
6
3
7
1
Li NMR: d=ꢀ3.7 ppm; and LiGaEt (C D ): H NMR: d=
4
6
6
7
1
.29 (br, CH ), 0.01 ppm (br, CH ); Li NMR: d=
3 2
ꢀ
4.3 ppm]. The excess amount of alkyllithium (Schemes 3
and 4) was nevertheless found to increase the yield of 5 and
6
relative to a stoichiometric reaction (elimination of
GaR ). Transmetalation of a more electropositive metal (in
3
this case Li versus Ga) to the more electronegative organic
ligand (here vinyl versus tBu) is a useful synthetic tool in or-
[8]
ganometallic Li/Sn or Li/Hg systems, but has to the best of
our knowledge not been observed in gallium chemistry. The
clusters 4 to 6 represent each a novel type of solvent-free
lithium aggregate with an—in the case of 5 and 6—unprece-
dentedly high number of lithium atoms in a molecular spe-
cies (8 in the case of 5, 9 in the case of 6). Although exam-
ples of hexanuclear octahedral lithium clusters are well
known for simple alkyllithium compounds such as
Scheme 2.
[3]
[20]
(
nBuLi)6 or (LiCH SiMe ) ,
larger aggregates are un-
2
3 6
known for neutral molecular compounds, but an icosahedral
Li12 cluster has recently been reported for the ionic species
+
ꢀ
[Li
A
H
U
G
R
N
N
(tmta) ]
A
H
U
G
R
N
U
G
A
H
U
G
R
N
N
{(CH ) } @-Cl]
(tmta=trimethylhexahy-
2
12
2 4 6
[6]
drotriazine). The yellow (4, 5) or pale green (6) air-sensi-
tive compounds are soluble in n-hexane (4, 5) or benzene
(
6) and the spectroscopic and spectrometric characterization
was consistent with the proposed constitution. In the cases
of 4 and 5, it was impossible to determine exact figures of
3
the J
A
H
U
G
E
N
N
(Si,H) coupling constants. For 6, a value of 16 Hz was
detected, which is not fully conclusive about the existence of
cis or trans isomers in solution. The solid-state structures
(
see below) reveal the exclusive presence of formal “trans
isomers” with lithium and hydrogen atoms on opposite sides
Scheme 3.
of the C=C double bonds in accordance with the configura-
Chem. Eur. J. 2011, 17, 13553 – 13561
ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
13555

W. Uhl et al.
Figure 2. a) Molecular structure of compound 4; ellipsoids are drawn at the 40% level. Selected bond lengths [pm]: C
(1, 2, 3) 222.6(4) (av), C
11)ꢀLi (101, 103)ꢀLi(1, 2’, 3) 234.2(4)–273.6(4), C10ꢀLi1 238.4(4), C10ꢀLi2’ 258.1(4), C136ꢀLi1’ 258.0(4). Symmetry transforma-
tions: ꢀx, y, ꢀz+0.5. b) Li skeleton of 4; ellip-
A
H
U
G
R
N
U
(ipso)ꢀLi2 241.4(4) (av); C(1, 102,
2
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
A
H
U
G
R
N
N
ACHTUNGTRENNUNG
6
C
6
skeleton of 4; ellipsoids are drawn at the 40% level. Symmetry transformations: ꢀx, y, ꢀz+0.5. c) Li
6
soids are drawn at the 40% level. Connecting lines between Li atoms are drawn to show the geometry, not to imply LiꢀLi interactions. Symmetry trans-
formations: ꢀx, y, ꢀz+0.5.
tion of the starting compounds. But the situation is compli-
cated by the formation of oligomers and the resulting multi-
ple LiꢀC interactions.
atoms varies from trigonal pyramidal (Li3), distorted square
pyramidal (Li1) to seesaw (Li2). A crystallographic C axis
2
passes through the centre of the three stacked heterocycles
Compound 4 is the 1:1 adduct of the dilithiated vinylben-
and relates the peripheral substituents SiPh , phenyl and
3
7
zene [(C H Li)HC=C
A
H
U
G
R
N
U
G
tert-butyl to each other. The Li NMR spectrum showed two
6
4
3
the solid state (Figure 2a) and its structure may be visual-
ized as a strongly distorted octahedron of four lithium
atoms that form a central lithium rectangle (Li1ꢀLi1 243.4;
Li1ꢀLi3 402.4; Li3ꢀLi3 239.7 pm) and two further lithium
atoms in an “axial” position (Li2ꢀLi1 av 287; Li2ꢀLi3 av
signals with an relative intensity of 2:1 that could be as-
7
1
signed by Li NMR/ H-HOESY spectroscopy to three mag-
netically inequivalent lithium environments (C=CLi and
PhLi have the same chemical shift) found in the solid state.
This may indicate that the cluster is retained in solution. Oc-
tahedral clusters of lithium atoms with substituents above
six of the eight trigonal faces of the octahedron are common
for simple solvent-free alkyllithium compounds such as
2
85 pm). Two adjacent triangular faces of the octahedron
are capped by tert-butyl- (faces Li2, Li3, Li3’; Li2, Li3, Li3’)
or C(H)SiPh groups (faces Li2, Li1, L1’; Li2’, Li1’, Li1), re-
3
[
20]
[21]
[22]
[3]
spectively. The ipso-carbon atoms of the phenyl group
(LiCH SiMe ) , (Lic-C H ) , (LiCHMe ) , (LinBu)6
2
3
6
6
11
6
2 6
[23]
(
C102; from here onwards the ipso-C is defined as that
or [LiC H
A
H
U
G
R
N
U
G
Tetrahedral or square-planar clus-
6
3
6
atom of the phenyl substituent connected to Li, ortho-C
atoms are then in 2,6-position to this atom) are located
above the long edges (Li1ꢀLi3) of the octahedron and have
ters are found in (MeLi) (short intermolecular LiꢀC inter-
4
[24]
actions give a three-dimensional polymeric structure),
[
25]
[2]
[26]
(LiEt)4
and (LitBu)
or (LiMes*·LinBu)2
respectively. Only the most bulky
substituents show isolated dimers as represented by [LiC-
and
4
[26]
short contacts (218.0(4)–248.0(4) pm) to the four lithium
atoms that represent the remaining two unoccupied faces of
the octahedron. Alternatively, the molecule can be viewed
as two edge-sharing (Li2ꢀLi2’) tetrahedra (Figure 2c), an ag-
[LiC H (2,4,6-iPr) ] ,
6
2
3 4
[
4]
[26]
A
H
U
G
R
N
U
G
[LiC H
A
H
U
G
R
N
N
(2,6-Mes) ] ,
and LiC H ACHNUTGTREUNNNG{ 2,6-(2,4,6-iPr C H )} ·tBuLi.
6 3 3 6 2 2
[LiC H3 ACHTUNGTRENNUNG{ 2,6-(2,6-
6
3
3
2
6
3
2
2
[27]
[28]
2
6
3
2
2
[5]
gregate of two LiC hetero-cubanes that share a common
[LiCH
A
H
U
G
R
N
U
G
crystallizes as a linear polymer, whereas
is found to be linked in a three-dimensional fash-
3
2
[29]
1
face (Li2, C102) or of three slightly puckered Li C hetero-
(LiPh)
2
2
cycles (Li1, C1 (vinyl-carbon atom); Li2, C102 (ipso-C
atom); Li3, C211 (tert-butyl)) that are stacked in an approxi-
mate AB pattern with the central ring being rotated by
around 908 relative to the two other rings (Figure 2b). This
leads to close LiꢀC contacts within and between the hetero-
cycles that range from 218.0(4) (Li1ꢀC1’) to 248.0(4) pm
ion by additional Li–p interactions to the aromatic rings.
The LiꢀC distances in these compounds vary significantly
depending on the nature of the ligand and the coordination
number of the lithium atom. The shortest contacts are found
in monomeric low coordinate compounds such as [LiC H -
6
3
[27]
A
H
U
G
R
N
N
{2,6-(2,4,6-iPr C H )} ]·C H
(203(2) pm),
[LiC H ACHTUNGTRENNUNG{ 2,6-
6 3
3
6
2
2
6
6
[27]
(
Li2ꢀC102). There are additional interactions to the ortho-C
(2,6-iPr C H )} ] (av 206.8(6) pm)
(203(6) pm) and LiMe (196.1(5) pm)
or LiCH ACHTUNGTRENNUNG( SiMe )
3 2
2
6
3
5]
2
2
[
[30]
atoms, the double bond and one ortho-C atom of the
in the gas phase.
SiPh Me group. The coordination sphere of the lithium
Larger distances in the range of 213–230 pm are found in
2
13556
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Chem. Eur. J. 2011, 17, 13553 – 13561

Oligolithium Cages
FULL PAPER
Figure 3. a) Molecular structure of compound 5; ellipsoids are drawn at the 40% level. Selected bond lengths [pm]: C
A
H
U
G
R
N
U
(1–4)ꢀLi
A
H
U
G
R
N
U
(1–8), C
A
H
U
G
R
N
U
(102–402)ꢀLi(3, 4,
6
, 8) 219.5(4) av (16 values); C
C(Ph)ꢀLi contacts 244.9(4) av (6 values); ipso-C
71.6(4). b) Molecular Li core of compound 5; ellipsoids are drawn at the 40% level. c) Li
level. Connecting lines between Li atoms are drawn to show the geometry, not to imply LiꢀLi interactions.
A
H
U
G
R
N
U
(102, 202)ꢀLi
A
T
N
T
E
N
G
A
H
U
G
R
N
U
G
ACTHUNGTRENNGNU( 5, 7) 242.4(4) av (8 values); C CAHTUNGTRENNUNG
A
H
U
G
R
N
U
G
ACHTUNGTRENNUNG
2
8
C
8
8
[
5]
[31]
polymeric LiCH
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(SiMe )
and the oligomeric aggregates
um
compounds
[(Ph)C H (Li)C=C(Li)nPr]
and
3
2
6
4
[32]
discussed above, but long-range p contacts and hyperconju-
(nBu)C H (Li)C=C(Li)Ph,
with the lithium atom bound
6
4
gative interactions can extend well beyond 280 pm.
to the ipso-C atom of the phenyl group being shifted to
lower field relative to the vinylic lithium atom. The solution
structures of the above compounds in the presence of polar
The dilithium compound [(C H Li)HC=C ACHTUNGTRENUNG( SiPh Me)Li]
2 4
6
4
(
5) is tetrameric in the solid state (Figure 3a) and leads to a
molecular aggregate with eight lithium atoms. Its structure
may be derived from that of compound 4 by removing the
two molecules of tert-butyllithium and dimerising the re-
maining hetero-cubane by means of additional Liꢀipso-C
solvents
(Et O,
THF,
tetramethylethylenediamine
2
(TMEDA)) have been studied in detail by multinuclear
one- and two-dimensional NMR spectroscopy on Li-en-
riched
6
samples.
According
(TMEDA)
2
to
these
was found to be
studies,
[
33]
atom contacts (Figure 3b). The eight lithium atoms form a
short chain of three Li4 tetrahedra, which share two
common edges (Figure 3c). The LiꢀC distances within the
(nBu)C H (Li)C=C(Li)Ph
ACHTUNGTRENNUNG
6
4
monomeric in solution and the solid state, whereas solutions
of both compounds in Et O or THF in the absence of
TMEDA led to dimeric heterocubane-type structures or a
mixture of monomers and dimers, respectively.
2
central hetero-cubane (Li1, Li2, Li5, Li7, C102, C202, C302,
C402) have bond lengths of 229.7(4) to 245.3(4) pm, which
are significantly larger than the remaining distances within
[31,32]
Compound 6 has a unique molecular structure (Figure 4a)
with nine lithium atoms that are arranged in such a way as
to generate two octahedra (Figure 4c) that share a common
face (Li3, Li4, Li4’). The ipso-C atoms of the phenyl sub-
stituents (C102, C302, C302’) are located near the edge of
two adjacent faces and have contact to four lithium atoms,
whereas the vinylic carbon atoms (C1, C2, C3) are located
above six of the remaining triangular faces in such a way
that two opposite faces (Li1, Li2’, Li5; Li1’, Li2, Li5’) are
unoccupied. Alternatively, the structure may be visualized
as an aggregate of three Li C heterocycles that constitute
the Li C8 framework (216.8(4)–222.6(5) pm). Additional
8
short LiꢀC contacts to the ortho-carbon atoms (236.0(4)–
253.3(4) pm), the bridging vinylic carbon atoms of the sty-
rene backbone (239.2(4)–258.8(4) pm) and the ipso- and
ortho-carbon atoms of one of the SiPh Me substituents
2
(
243.5(5)–252.7(4) pm) complete the coordination sphere of
the lithium atoms in such a way that each lithium atom is
coordinated to at least four carbon atoms in a distorted tet-
rahedral fashion. Additional relatively short LiꢀC contacts
of up to 272 pm verify the complicated coordination pattern
of the metal atoms, which is not discussed in greater detail.
The angles within the Li C heterocycles differ considerably,
3
3
two hexagonal prisms (Figure 4b) with a common hexagonal
face (Li3, C102, Li4, C302, Li4’, C102’). The LiꢀC distances
2
2
with the Li C angles being much more acute than the C Li
in the central Li C heterocycle are significantly larger
2
2
3
3
angles (71.9(2) versus 102.6(2)8). There is an approximate
C axis that passes through the centre of all four C Li het-
(228.0(2)–229.5(3) pm) than those bond lengths within the
two terminal heterocylces (212.7(3)–213.1(3) pm) or those
that connect them (219.3(2)–223.2(3) pm). There are addi-
tional small LiꢀC contact distances to ortho- and vinyl-C
2
2
2
erocycles. The solution NMR spectrum shows, in agreement
with the solid-state structure, two different lithium environ-
7
ments in a ratio of 1:1. Their Li NMR spectroscopic chemi-
atoms in the range of 238.0(3) to 262.5(3) pm. The C=C
cal shifts show the same trend as found in the related dilithi-
double bond and other intermolecular distances are unex-
Chem. Eur. J. 2011, 17, 13553 – 13561
ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
13557

W. Uhl et al.
Figure 4. a) Molecular structure of compound 6; ellipsoids are drawn at the 40% level. Selected bond lengths [pm]: C
values); C (1, 2, 5) 213.8(3) av (6 values); C (3, 4), C
(1, 2, 3)ꢀLi (1, 2, 3)ꢀLi (102, 302)ꢀLi(1’, 2, 5) 221.7(3) av (6 values); contact distances C101ꢀLi3,
C103ꢀLi4, C301ꢀLi4 261.5(3) av; C101ꢀLi5, C10ꢀLi3, C10ꢀLi5, C103ꢀLi1’, C20ꢀLi1’, C20ꢀLi4, C301ꢀLi2, C30ꢀLi2, C30ꢀLi4’ 241.4(3) av. Symmetry
polyhedron of compound 6; ellipsoids are drawn at the 40% level. c) Li polyhedron of compound 6; ellip-
A
H
U
G
R
N
N
(102, 302)ꢀLi
ACHTUNGTRENNUN(G 3, 4) 228.8(3) av (3
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
A
H
N
T
E
N
N
A
H
U
G
R
N
U
A
H
U
G
R
N
N
ACHTUNGTRENNUNG
transformations: ꢀx+1, y, ꢀz+0.5. b) Li
9
C
9
9
soids are drawn at the 40% level. Connecting lines between Li atoms are drawn to show the geometry, not to imply LiꢀLi interactions. Symmetry trans-
formations: ꢀx+1, y, ꢀz+0.5.
ceptional. Ignoring longer contacts, the lithium atoms are
coordinated in a trigonal pyramidal (terminal Li C rings) or
and an ortho-carbon atom of a single phenyl group attached
to silicon (244 to 270 pm). The basic structural motifs and
the facile synthetic procedures should give access to a
broader variety of these types of compounds by means of
gallium–lithium exchange reactions, for instance, starting
with tri- or tetragalliumvinylbenzene derivatives. The appli-
cation of these lithium compounds for the generation of
new main-group or transition-metal compounds is a further
promising and challenging task for future investigations.
3
3
seesaw (central Li C ring) fashion. The molecule has a crys-
3
3
tallographic C axis that passes through Li3 and one of the
2
phenyl rings (atoms C302 and C304). In accordance with the
observed molecular structure, there are two signals in a
7
ratio of 2:1 (vinyl/ipso-C) in the Li NMR spectrum.
In conclusion, we were able to generate unprecedented
and highly interesting lithium–carbon cluster compounds
along facile routes by means of transmetalation and depro-
tonation. Whereas GaꢀLi transmetalation has not been ob-
served previously, o-lithiation facilitated by a vinyllithium
substituent in the presence of N,N,N’,N’-tetramethylethyle-
Experimental Section
[32]
nediamine (tmen) has at least one predecessor. The mo-
lecular structures of these novel compounds comprise
unique structural motifs with hitherto unknown arrange-
ments of the metal atoms and considerably extend the
knowledge on the diversity of organolithium compounds.
All structures follow a particular structural pattern. They
are based on vinylbenzene backbones with a singly depro-
tonated benzene ring and up to two vinylic carbanions in
the side chains. The latter are coordinated by three lithium
atoms with three relatively small LiꢀC distances of 212 to
General: All manipulations were carried out under purified argon using
standard Schlenk techniques. Solvents were distilled from drying agents
and degassed (diethyl ether and benzene over sodium/benzophenone; n-
pentane and n-hexane over LiAlH
]benzene or [D ]THF at ambient probe temperature using the follow-
ing Bruker instruments: Avance I ( H 400.13 MHz, C 100.6 MHz, Si
4
). NMR spectra were recorded in
[
D
6
8
1
13
29
13
7
1
7
1
9.49 MHz, Li 155.51 MHz), Avance III ( H 400.03 MHz,
00.59 MHz, Si 79.47 MHz, Li 155.51 MHz) and referenced internally
C
2
9
7
1
3
29
to residual solvent resonances (chemical shift data in d). C, Si and
7
Li NMR spectra were all proton-decoupled. Phenyl rings are labelled in
the NMR spectra in such a way that the C atom connected to Li is called
the ipso-C-atom or C-1. Elemental analyses were determined by the mi-
croanalytic laboratory of the Westfꢁlische Wilhelms Universitꢁt Mꢀnster.
IR spectra were recorded as Nujol mull between KBr, CsBr or CsI plates
using a Shimadzu Prestige 21 spectrometer. Electron impact mass spectra
223 pm. The vinylic carbon atoms attached to the central
phenyl rings have two short contacts to lithium atoms in dif-
ferent ranges (238 to 242 and 245 to 259 pm). The deproton-
ated carbon atoms of the benzene rings are connected to
four lithium atoms with LiꢀC distances that range between
[13]
[33]
were analysed using a Varian mass spectrometer. HGaCl
2
,
EtLi, Ph
and 1,3-[C(H)=C-
were synthesized according to literature
ꢀ
[
34]
[12]
CꢁC-SiPh
(SiMe
)ꢀGaCl
procedures.
(1a),
3 2
PhC(H)=C ACHTUNGTRENNG(U SiPh )GaCl (2a)
] C H (2c)
2 2 6 4
3
[
12]
A
H
U
G
R
N
U
G
3
217 and 248 pm. Two small and two large distances were ob-
Synthesis of 1b: A solution of phenyl ethyne (4.02 g, 39.4 mmol) in dieth-
yl ether (150 mL) was treated with n-butyllithium (24.6 mL, 1.6m in n-
hexane) at ꢀ788C. The solution was allowed to warm to room tempera-
ture and stirred for 2 h. Diphenylmethylchlorosilane (9.17 g, 39.4 mmol)
was added and the reaction mixture was then stirred for three days under
reflux conditions. The reaction mixture was quenched with HCl (6%,
served in compounds 4 and 6, whereas in 5, three different
ranges were detected (217 to 222, 230 to 238 and 240 to
245 pm). Interactions with the ortho-carbon atoms of the
central phenyl rings should also be considered. Two contacts
were detected to the carbon atoms that bear the vinyl group
1
00 mL), and the organic phase was then separated from the aqueous
(
234 to 240 and 261 to 274 pm), whereas the ortho-CꢀH
phase. The organic phase was washed with a saturated solution of sodium
bicarbonate and dried with anhydrous magnesium sulfate. Removal of
the solvent under vacuum and re-crystallization of the residue from a
groups have contact to only one lithium atom (245 to
253 pm). In 4 and 5, additional contacts exist to the ipso-
13558
www.chemeurj.org
ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 13553 – 13561

Oligolithium Cages
FULL PAPER
mixture of dichloromethane and n-pentane at ꢀ308C yielded 1b as a
(vs), 1402 (w), 1377 (vs) (nujol); 1342 (w); 1304 (w), 1258 (vw), 1184 (w),
1171 (w), 1155 (m), 1103 (s), 1078 (m), 1067 (w), 966 (w), 937 (vw), 918
(w), 876 (m), 851 (w), 799 (m) n(CC), d(CH); 739 (s), 723 (s), 702 (vs),
1
pale-yellow semi-solid (6.12 g, 52%). H NMR (400 MHz, C
6
D
6
, 278C):
3
4
d=7.80 (m, 4H; ortho-H of Si-phenyl), 7.43 (dd,
(H,H)=1.6 Hz, 2H; ortho-H of C=C-phenyl), 7.20 (m, 4H; meta-H of Si-
phenyl), 7.20 (m, 2H; para-H of Si-phenyl), 6.93 (m, 1H; para-H of C=
J AHCTUNGTERNNNU(G H,H)=7.9 Hz, J-
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
677 (m), 619 (w) nACHTUNGTRENNUNG
ꢀ
1
426 cm (w) nACTHUNGTRENNUNG
1
C-phenyl), 6.90 (m, 2H; meta-H of C=C-phenyl), 0.74 ppm (s, J
A
H
U
G
R
N
U
tensities agree with expected isotopic distribution; only the most intense
2
13
5
8.9 Hz,
J
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(Si,H)=7.1 Hz, 3H; Si
A
H
U
T
E
N
N
(CH
3
6
D
6
,
peak of each fragment is given): 487 (100) [M+ꢀtBu], 362 (9) [(H C ꢀ
5
6
+
2
C=CꢀSiPh ) ]; microanalysis gave unsatisfactory results (possibly due to
3
(
ortho-C of C=C-phenyl), 130.0 (para-C of Si-phenyl), 129.0 (para-C of
carbide formation); HRMS (EI, 20 eV, 258C): m/z calcd for C H GaSi
3
0
30
C=C-phenyl), 128.5 (meta-C of C=C-phenyl), 128.4 (meta-C of Si-
phenyl), 123.4 (ipso-C of C=C-phenyl), 109.0 (PhꢀCꢁC-Si), 91.1 (PhꢀCꢁ
[M+ꢀtBu]: 487.137; found: 487.137.
Characterization of 3b: Yield: 61%; m.p. 2228C; H NMR (400 MHz,
1
2
9
CꢀSi), ꢀ1.7 ppm (Si
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(CH
)); Si NMR (79 MHz , C
D
6
, 278C): d=
3
3
3
6
6 6
C D , 278C): d=8.07 (s, JACTHNUTRGENNUG
ꢀ
25.4 ppm; IR (KBr plates, nujol): n˜ =2722 (vw), 2696 (w), 2615 (w),
561 (w), 2160 (vs) n
(CꢁC); 1955 (m), 1882 (m), 1818 (m), 1764 (w),
654 (w), 1589 (s), 1487 (s) n(C=C), phenyl; 1456 (m), 1440 (m), 1427 (s),
377 (s) (nujol); 1325 (m), 1301 (m), 1251 (s), 1217 (m), 1190 (m), 1116
4
ACTHNGUTRENNUG( H,H)=7.7 Hz, J ACHNUTGTRENNUNG
2
1
1
ACHTUNGTRENNUNG
4
2
H; meta-H of Si-phenyl), 7.21 (m, 2H; para-H of Si-phenyl), 7.05 (m,
H; meta-H of C=C-phenyl), 6.97 (m, 1H; para-H of C=C-phenyl), 6.96
AHCTUNGTRENNUNG
(
3
m, 2H; ortho-H of C=C-phenyl), 0.99 (s, 18H; C
H; Si ACHTUNGTRNNEUG( CH )); C NMR (100 MHz , C D
3 6 6
A
H
U
G
R
N
N
3 3
) ), 0.76 ppm (s,
(
vs), 1068 (w), 1026 (m), 997 (m), 916 (w), 839 (s), 794 (m), 756 (m)
13
n(CC), d(CH), d(CC); 725 (m) (nujol); 696 (s), 611 (s), 536 (s), 486 (vs),
C(Ga)), 154.7 (C(H)=C(Ga)), 146.5 (ipso-C of C=C-phenyl), 138.2
ipso-C of Si-phenyl), 135.4 (ortho-C of Si-phenyl), 130.3 (meta-C of C=
C-phenyl), 129.6 (para-C of Si-phenyl), 128.5 (meta-C of Si-phenyl), 128.4
ꢀ
1
+
4
(
47 cm (s) n ACHTUNGTRENNUNG( SiC); MS (EI, 20 eV, 408C): m/z (%): 298 (26) [M ], 283
+ +
(
33) [M ꢀMe], 197 (100) [SiPh
18Si (298.5): C 84.5, H 6.1; found: C 84.6, H 6.3.
Synthesis of 2b: Solid HꢀGaCl
(2.11 g, 14.9 mmol) was suspended in n-
2
Me ]; elemental analysis calcd (%) for
21
C H
(
para-C of C=C-phenyl), 124.5 (ortho-C of C=C-phenyl), 30.6 (C
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(CH
3 3
) ),
2
9
2
29.0 (C
A
H
U
G
R
N
N
(CH ) ), ꢀ1.5 ppm (Si
3
3
ACHTUNGTNER(NUNG CH )); Si NMR (79 MHz, C D , 278C):
3
6
6
hexane (100 mL) and treated at room temperature with (diphenylme-
thyl)silylethynylbenzene (4.45 g, 14.9 mmol). The product started to pre-
cipitate after the reaction mixture had been stirred for several hours. Stir-
ring was continued for another 12 h. The colorless precipitate was then
filtered, washed twice with n-hexane (10 mL) and dried under vacuum to
d=ꢀ14.8 ppm; IR (KBr plates, nujol): n˜ =1958 (w), 1890 (vw), 1826
(vw), 1579 (m), 1562 (m), 1527 (m) n(C=C), phenyl; 1462 (vs), 1427 (s),
AHCTUNGTRENNUNG
1377 (s) (nujol); 1305 (w), 1259 (vw), 1186 (w), 1105 (s), 1076 (w), 1026
(w), 997 (w), 921 (m), 877 (s), 796 (m) n(CC), d(CH); 740 (s), 700 (s),
ꢀ
1
619 (w) n AHCUTNGRENNU(G SiC); 588 (m), 547 (s), 513 (m), 495 (s), 470 cm (m) n ACHTUNGTRENNUNG( GaC);
1
give analytically pure 2b. Yield: 3.42 g (52%). M.p. 1288C; H NMR
400 MHz, [D
.58 (m, 4H; ortho-H of Si-phenyl), 7.50 (d, J
MS (EI, 20 eV, 258C): m/z (%) (experimental intensities agree with ex-
pected isotopic distribution; only the most intense peak of each fragment
3
(
7
8
]THF, 278C): d=7.77 (s, J
A
H
U
G
R
N
U
3
+
+
A
H
U
G
R
N
U
G
is given): 425 (100) [M ꢀtBu], 369 (9) [M ꢀtBuꢀH C=CMe ], 300 (11)
2
2
+
+
+
H of C=C-phenyl), 7.33 (m, 4H; meta-H of Si-phenyl), 7.33 (m, 2H;
para-H of Si-phenyl), 7.31 (m, 2H; meta-H of C=C-phenyl), 7.26 (m, 1H;
[H C ꢀC=CꢀSiPh Me ], 285 (20) [M ꢀGatBu ꢀMe], 222 (36) [M
5
6
2
2
ꢀGatBu ꢀPh]; microanalysis gave unsatisfactory results.
2
1
para-H of C=C-phenyl), 0.86 ppm (s,
3
J ACHTUNGERTNNUNG( Si,C)=55.7 Hz, 3H; Si ACHTUGNTRENNUNG( CH ));
Synthesis of 4: A solution of tert-butyllithium (1.88 mL, 3.00 mmol, 1.6m
1
3
C NMR (100 MHz, [D
C(Ga)), 142.8 (ipso-C of C=C-phenyl), 137.7 (ipso-C of Si-phenyl), 136.1
ortho-C of Si-phenyl), 129.9 (para-C of Si-phenyl), 129.0 (para-C of C=
C-phenyl), 128.8 (meta-C of C=C-phenyl), 128.6 (ortho-C of C=C-
8
]THF, 278C): d=161.2 (C(H)=C), 144.8 (C(H)=
in pentane) was added to a solution of H
0.545 g; 1.00 mmol) in benzene (25 mL) at room temperature. The reac-
tion mixture was allowed to warm to room temperature and stirred for
d. During this time, the color of the mixture changed to black and a
5
C
6
ꢀC(H)=C
A
H
U
G
R
N
U
G
3
)ꢀGatBu
2
(
(
2
2
9
phenyl), 128.5 (meta-C of Si-phenyl), ꢀ2.1 ppm (Si
A
H
U
G
R
N
U
G
3
)); Si NMR
colorless solid precipitated. It was filtered, the filtrate was concentrated
and refrigerated at 58C to give pale yellow crystals of 4 that were washed
with n-pentane. NMR spectroscopy showed the crystals to be contaminat-
ed with tBuLi, which could not be completely removed by washing or re-
(
(
(
79 MHz, [D
8
ACHTUNGTRENNUNG
7
5
93 (m), 777 (m), 729 (s) n(CC), d(CH); 698 (s), 667 (w), 621 (w) n
90 (w), 554 (m), 487 (m), 468 (m), 437 cm (m) n CAHUTGTNRENUNG( GaCl), n ACHTUGNTRENNNUG
A
H
U
G
R
N
U
G
1
crystallization. Yield: 0.120 g (27%); m.p. 1338C (decomp); H NMR
ꢀ
1
(
400 MHz, C
6
D
6
, 278C): d=9.15 (s, 2H; C(H)=C), 7.61 (d, J
ACHTUNGTRENNUNG( H,H)=
(
EI, 20 eV, 258C): m/z (%) (experimental intensities agree with expected
6
7
7
6
.9 Hz, 2H; 6-H of C=C-phenyl), 7.50 (m, 12H; ortho-H of Si-phenyl),
.17 (m, 2H; 3-H of C=C-phenyl), 7.12 (m, 2H; 4-H of C=C-phenyl),
isotopic distribution; only the most intense peak of each fragment is
+
+
+
given): 425 (2) [M ꢀMe], 403 (3) [M ꢀCl], 334 (100) [M ꢀGaCl], 299
.11 (m, 6H; para-H of Si-phenyl), 7.08 (m, 12H; meta-H of Si-phenyl),
+
(
(
31) [M ꢀGaCl
2
]; elemental analysis calcd (%) for
440.1): C 57.3, H 4.3; found: C 57.2, H 4.3.
C
21
H
19Cl
2
GaSi
3
.96 (t,
JACHTUNGTRENNUNG
13
6 6
tBu); C NMR (100 MHz, C D
Synthesis of 3a and 3b
(
General procedure: tert-Butyllithium (1.6m in pentane, two equivalents)
was added to a suspension of the corresponding dichlorogallium com-
pound in n-hexane (50 mL) at ꢀ788C. The suspension was allowed to
warm to room temperature and stirred for 3 h. The reaction mixture was
filtered, the filtrate was concentrated and kept at 58C to yield crystalline
138.7 (6-C of C=C-phenyl), 137.9 (ipso-C of Si-phenyl), 135.7 (ortho-C of
Si-phenyl), 134.1 (3-C of C=C-phenyl) 129.4 (4-C of C=C-phenyl), 129.4
(para-C of Si-phenyl), 129.2 (5-C of C=C-phenyl), 128.6 (meta-C of Si-
7
phenyl), 31.5 (C
A
H
U
G
R
N
U
G
3
)
3
), 11.8 ppm (C
A
H
U
G
R
N
U
G
3
)
3
); Li NMR (155.5 MHz,
C
6
D
6
,
278C): d=1.73 (LiꢀtBu), 1.18 (C=C(Li)), 1.18 ppm (PhꢀLi);
Si NMR (79 MHz, C
, 278C): d=ꢀ20.2 ppm; IR (KBr plates, nujol):
n˜ =1579 (w) n(C=C), phenyl; 1462 (vs), 1377 (vs) (nujol); 1302 (w), 1259
(vw) d(CH ); 1213 (w), 1153 (w), 1107 (m), 1028 (vw), 993 (w), 975 (w),
25 (vw), 840 (m), 788 (m), 771 (m), 734 (s) n(CC); 700 (s), 673 (w), 623
2
9
3
a or 3b, respectively.
6 6
D
1
ACHTUNGTRENNUNG
Characterization of 3a: Yield: 52%; m.p. 1528C; H NMR (400 MHz,
C
3
ACHTUNGTRENNUNG
D
6
, 278C): d=8.20 (s,
J
A
T
N
T
E
N
N
(Si,H)=11.4 Hz, 1H; C(H)=C), 7.79 (m, 6H;
3
6
9
ortho-H of Si-phenyl), 7.23 (m, 3H; para-H of Si-phenyl), 7.22 (m, 6H;
meta-H of Si-phenyl), 7.07 (m, 2H; meta-H of C=C-phenyl), 7.03 (m,
ꢀ
1
(
w) n
A
H
U
G
R
N
U
G
+
2
0 eV, 25–2008C): m/z (%): 362 (35) [PhꢀC=CꢀSiPh
] , 284 (100) [Phꢀ
2
0
H; ortho-H of C=C-phenyl), 6.97 (m, 1H; para-H of C=C-phenyl),
1
3
C=CꢀSiPh ] ; microanalysis gave unsatisfactory results (the compound is
.98 ppm (s, 18H; C
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(CH
3
)
3
); C NMR (100 MHz, C
6
D
6
, 278C): d=161.5
extremely air- and moisture-sensitive and contaminated with free tBuLi)
(
1
C(H)=C(Ga)), 156.5 (C(H)=C(Ga)), 145.9 (ipso-C of C=C-phenyl),
36.6 (ipso-C of Si-phenyl), 136.5 (ortho-C of Si-phenyl), 130.1 (meta-C
of C=C-phenyl), 129.9 (para-C of Si-phenyl), 128.6 (meta-C of Si-phenyl),
28.5 (para-C of C=C-phenyl), 124.8 (ortho-C of C=C-phenyl), 30.8 (C-
Synthesis of 5: A solution of H
5
C
6
ꢀC(H)=C
A
H
U
G
E
N
N
(SiPh
2
Me)ꢀGatBu
2
(1.03 g,
2.13 mmol) in benzene (20 mL) was treated at room temperature with
tert-butyllithium (3.99 mL, 6.39 mmol, 1.6m in n-pentane). The reaction
mixture was stirred for 2 d. During this period, the color of the mixture
changed to dark red and a solid precipitated. The solvent was removed
under vacuum and the residue was then extracted three times with hot n-
1
2
9
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(CH
15.8 ppm; IR (KBr plates, nujol): n˜ =2025 (vw), 1960 (vw), 1892 (w),
820 (vw), 1773 (vw), 1580 (m), 1562 (w), 1535 (w) n(C=C), phenyl; 1460
3 3 3 3 6 6
) ), 29.5 ppm (C ACHTUNGTRENNUNG( CH ) ); Si NMR (79 MHz, C D , 278C): d=
ꢀ
1
ACHTUNGTRENNUNG
Chem. Eur. J. 2011, 17, 13553 – 13561
ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
13559

W. Uhl et al.
ꢀ
1
hexane (10 mL). Concentrating the combined extracts and cooling to
(w) n
(%): 877 (31) [M] , 870 (54) [MꢀLi] , 804 (100), [MꢀSiMe
[ = M] ; elemental analysis calcd (%) for C48 Si
65.7, H 7.9; found: C 65.7, H 8.0.
A
H
U
T
E
N
N
(SiC), 596 (m), 514 (s), 459 cm (s); MS (EI, 20 eV, 258C): m/z
+
+
+
room temperature yielded slightly yellow crystals of 5. Yield: 0.185 g
3
] , 583 (52)
(877.0 gmol ): C
1
2
+
ꢀ1
(
28%); m.p. 1658C (decomp); H NMR (400 MHz, C
6
D
6
, 278C): d=8.99
3
H
69Li
9
6
(
s, 4H; C(H)=C), 7.42 (m, 4H; 3-H of C=C-phenyl), 7.42 (m, 4H; 6-H
3
of C=C-phenyl), 7.26 (t, J ACHUTNGRNENGU( H,H)=7.2 Hz 4H; 4-H of C=C-phenyl), 7.16
Crystal structure determinations: Crystals suitable for X-ray crystallogra-
phy were obtained by crystallization from n-hexane (3a, 5) or benzene
4, 6). Intensity data was collected using a Bruker APEX II and a Stoe
IPDS diffractometer with monochromated MoKa (3a, 4) or CuKa (5, 6) ra-
diation. The collection method involved w scans. Data reduction was car-
ried out using the program SAINT+.
solved by direct methods using SHELXTL. Non-hydrogen atoms were
first refined isotropically followed by anisotropic refinement by full-
matrix least-squares calculation based on F using SHELXTL. Hydrogen
atoms were positioned geometrically and allowed to ride on their respec-
tive parent atoms. One phenyl group of a SiPh Me substituent of com-
and 7.05 (m, 16H; ortho-H of Si-phenyl), 7.12 and 7.12 (m, 8H; para-H
of Si-phenyl), 7.12 (m, 4H; 5-H of C=C-phenyl), 7.07 and 7.01 (m, 16H;
(
1
3
meta-H of Si-phenyl), 0.43 ppm (s, 12H; Si
, 278C): d=188.8 (C(H)=C(Li)), 164.5 (1-C), 164.2 (C(H)=C(Li)),
54.7 (2-C of C=C-phenyl), 141.0 (6-C of C=C-phenyl), 140.3 and 139.5
ipso-C of Si-phenyl), 133.9 and 134.2 (ortho-C of Si-phenyl), 133.5 (3-C
3
ACHTUNGTNERNUNG( CH )); C NMR (100 MHz,
6 6
C D
1
[
35]
The crystal structures were
[
36]
(
of C=C-phenyl), 129.2 and 129.2 (para-C of Si-phenyl), 129.0 (4-C of C=
C-phenyl), 129.0 (5-C of C=C-phenyl), 128.8 and 128.9 (meta-C of Si-
2
7
phenyl), ꢀ3.9 ppm (SiCH
3
); Li NMR (155.5 MHz, C
6
D
6
, 278C): d=2.0
278C): d=
17.9 ppm; IR (KBr plates, nujol): n˜ =1579 (s), 1562 (s), 1490 (m) n(C=
2
9
(
PhꢀLi), 0.4 ppm (C=C(Li)); Si NMR (79 MHz,
C
6
D
6
,
2
ꢀ
A
H
U
G
E
N
N
pound 5 is disordered across an edge (C221, C226) of the benzene ring.
The disordered atoms C223ꢀC225 were refined in split positions
C), phenyl; 1460 (vs), 1427 (m), 1404 (m), 1377 (m) (nujol); 1247 (w),
1
107 (m), 840 (m), 804 (m), 785 (m), 731 (s), 719 (s) n(CC), d(CH); 700
(0.49:0.51). Compound 5 was measured at 243 K. At lower temperature
the crystals became amorphous, possibly as a result of a phase transfor-
mation. Further crystallographic data are summarized in Table 1.
ꢀ
1
(
s) n
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(SiC); 592 (w), 559 (w), 513 (w), 480 (s), 445 cm (m); MS (EI,
+
2
2
0 eV, 258C): m/z (%): 300 (43), 301 (13) [PhꢀC=CꢀSiPh
2
Me] , 285 (54),
+
+
86 (14) [PhꢀC=CꢀSiPh
] , 222 (100), 223 (22) [Ph
MeSiꢀC=C] ; ele-
2
2
CCDC-832324 (3a), CCDC-832325 (4), CCDC-832326 (5), and CCDC-
32327 (6) contain the supplementary crystallographic data for this
paper. These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
ꢀ
1
mental analysis calcd (%) for C84
8 4
H72Li Si (1249.3 gmol ): C 80.8, H 5.8;
8
found: C 80.6, H 6.0.
Synthesis of 6: Compound 2c (1.13 g, 2.04 mmol) was dissolved in n-
hexane (50 mL) and treated at ꢀ788C with ethyllithium (13.9 mL,
8
.17 mmol, 0.59m in benzene). The re-
action mixture was allowed to warm to
room temperature and stirred for 16 h.
Separation of the LiCl by filtration
gave a pale yellow filtrate and removal
of the solvent under vacuum yielded
Table 1. Crystal data and structure refinement of compounds 3a and 4 to 6.
3
a
4
5
6
empirical formula
T [K]
crystal system
space group
a [pm]
C
153(2)
orthorhombic
P2
1101.68(5)
1454.39(7)
1857.09(9)
90
2.9756(2)
4
34
H
39GaSi
C
153(2)
monoclinic
C2/c
1857.0(1)
1287.5(1)
2141.4(2)
96.432(6)
5.0875(7)
4
60
H
58Li
6
Si
2
C
84
H
72Li
8
Si
4
C
153(2)
monoclinic
C2/c
1480.73(5)
1893.14(6)
1968.70(7)
92.908(2)
5.5116(3)
4
48 9 6
H69Li Si
243(2)
monoclinic
P2 /n
1075.21(3)
2345.56(7)
2890.20(9)
90.464(2)
7.2888(4)
4
3
c (0.883 g, 1.67 mmol) as a yellow oil.
[
a]
The crude material was re-dissolved in
benzene (10 mL) and treated with eth-
yllithium (8.35 mmol, 14.15 mL, 0.59m
in benzene) at room temperature. The
reaction mixture was then stirred for
1
2
1
2
1
1
b [pm]
c [pm]
b [8]
V [nm ]
3
1
6 h and heated for another 2 h under
reflux conditions. Subsequent cooling
of the solution gave a colorless, crys-
Z
ꢀ
3
1calcd [gcm
m [mm
]
1.218
0.985 (MoKa
1.145
0.107 (MoKa
1.138
1.072 (CuKa
1.057
1.613 (CuKa)
ꢀ
1
talline solid (LiGaEt
4
), which was re-
]
)
)
)
moved by filtration. The filtrate was
then concentrated under vacuum and
stored at 58C to give compound 6 as
pale green crystals.
crystal size [mm]
qmin/qmax [8]
indep reflns
completeness to qmax [%]
parameters
0.14ꢄ0.12ꢄ0.06
1.78/27.90
0.15ꢄ0.10ꢄ0.10
1.91/27.90
0.18ꢄ0.08ꢄ0.07
2.43/72.35
0.11ꢄ0.09ꢄ0.07
3.79/72.51
7108 (Rint =0.064) 5567 (Rint =0.054) 13620 (Rint =0.039) 5200 (Rint =0.027)
100.0
331
0.0364
0.0760
0.524/ꢀ0.299
91.7
310
0.0499
0.1386
0.437/ꢀ0.246
94.5
906
0.0555
0.1668
0.583/ꢀ0.267
95.2
295
0.0343
0.0976
0.272/ꢀ0.257
Compound 3c: Crude material.
1
R (I>2s(I))
H NMR (400 MHz, C
.85 (s, 2H; C(H)=C(Ga)), 1.15 (t, J-
(H,H)=17.9 Hz, 6H; GaCH CH ),
4H;
), 0.20 ppm (s, 18H; Si-
6
D
6
, 278C): d=
1
3
wR2 (all data)
largest diff. peak/hole [eꢅ
7
ꢀ
3
]
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
2
3
3
0
.72
GaCH
(CH
signed); C NMR (100 MHz,
78C): d=170.3 (C(H)=C(Ga)), 11.1
GaCH ), 10.2 (GaCH CH
), ꢀ0.2 ppm (Si
assigned;
Compound 6: Yield (overall): 0.138 g (28%); m.p. 2588C (decomp);
(q,
CH
3
J
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(H,H)=7.9 Hz,
[a] Flack parameter: 0.008(9).
2
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
3 3
) ), aromatic H could not be as-
1
3
6 6
C D ,
Acknowledgements
2
(
2
2
3
3 3
ACHTUNGRTNNGE(U CH ) ), phenyl C atoms not
We are grateful to the Deutsche Forschungsgemeinschaft for generous fi-
nancial support.
1
3
H NMR (400 MHz,
C
6
D
6
,
278C): d=8.87 (s,
J AHCTUNGTERNNUNG( Si,H)=16 Hz, 6H;
C(H)=C(Li)) 7.34 (m, 6H; 3,5-H of phenyl), 7.32 (m, 3H; 4-H of
1
3
phenyl), ꢀ0.17 ppm (s, 54H; Si
78C): d=187.6 (C(H)=C(Li)), 160.5 (C(H)=C(Li)), 155.8 (1-C of
phenyl), 150.7 (2,6-C of phenyl), 133.6 (3,5-C of phenyl), 131.0 (4-C of
A
H
U
G
R
N
U
G
3
)
3
); C NMR (100 MHz,
C
6
D
6
,
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Chem. Eur. J. 2011, 17, 13553 – 13561

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Received: July 5, 2011
Published online: October 21, 2011
Chem. Eur. J. 2011, 17, 13553 – 13561
ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
13561