Addition of Organometallic Reagents to a Stable Silene and Germene

Article abstract of DOI:10.1021/acs.organomet.5b00423

A variety of alkyllithium (R = Me, Bu, t-Bu) reagents and potassium tert-butoxide were added to the highly reactive silene Mes₂Si=CHCH₂t-Bu (1) and the germene Mes₂Ge=CHCH₂t-Bu (4) in diethyl ether. 1,2-Addition products were obtained regioselectively and in good yield after treatment with a weak acid with no evidence for any rearrangement products and no polymerization observed. The reactivity of the silene 1 and germene 4 toward organometallic reagents is compared to previous studies of analogous silenes and germenes. (Chemical Equation Presented).

Full text of DOI:10.1021/acs.organomet.5b00423

Article
pubs.acs.org/Organometallics
Addition of Organometallic Reagents to a Stable Silene and Germene
Bahareh Farhadpour, Jiacheng Guo, Laura C. Pavelka, and Kim M. Baines*
Department of Chemistry, University of Western Ontario, London, Ontario N6A 5B7, Canada
S
* Supporting Information
ABSTRACT: A variety of alkyllithium (R = Me, Bu, t-Bu) reagents and potassium
tert-butoxide were added to the highly reactive silene Mes2SiCHCH2t-Bu (1) and
the germene Mes2GeCHCH2t-Bu (4) in diethyl ether. 1,2-Addition products were
obtained regioselectively and in good yield after treatment with a weak acid with no
evidence for any rearrangement products and no polymerization observed. The
reactivity of the silene 1 and germene 4 toward organometallic reagents is compared
to previous studies of analogous silenes and germenes.
reagents to silenes to date was reported by Oehme. His group
studied the addition of organometallic reagents to transient 1,1-
bis(trimethylsilyl)silenes ((Me3Si)2SiCR2), generated by
Petersen elimination of the corresponding carbinols upon
treatment with organolithium reagents.11−15 In most cases, the
excess organolithium reagent or the released lithium silanolate
adds regioselectively to the silicon of the transient silene to give
1,2-addition products in moderate to good yields after
hydrolysis (Scheme 2), although, on occasion, migration of
INTRODUCTION
■
After a quarter century of active research on the synthesis,
characterization, and reactivity of silenes1,2 applications of this
chemistry are now being explored in diverse areas such as
organic synthesis,1f,3 polymer chemistry,4,5 and materials
science.6,7 Pertinent to these applications is the study of the
reactivity of silenes toward organometallic reagents for the
purpose of creating new Si−C bonds either to increase
functionality in molecular compounds for applications in
synthesis or materials chemistry or to initiate anionic
polymerizations. However, there are, for the most part, only
isolated reports on the addition of organometallic reagents to
silenes, and, furthermore, the types of substrates and conditions
of the reactions are quite variable.
Scheme 2. Addition of Organometallic Reagents to
Transient Bis(silyl)silenes11−15
The reactions of Grignard reagents with stable Brook-type
silenes ((Me3Si)2Si(OSiMe3)R) are complicated by the
lability of the trimethylsilyl group,8 and the addition of
MeLi/MgBr or t-BuLi to transient 1,1-dialkylsilenes often
leads to side products due to loss or migration of hydride.9,10 In
one instance, Ishikawa was able to isolate the simple products
of addition (after hydrolysis of the initially formed organo-
metallic adducts) of 1,1-dialkylsilenes in low yield (20−40%,
GPC yields): MeLi (or MeMgBr) added to the transient
Me2SiCPh(CH2SiMe3) regioselectively with the organic
group adding to the silicon atom of the silene (Scheme 1).9
The most extensive study of the addition of organometallic
Scheme 1. Addition of Organometallic Reagents to a
Transient 1,1-Dialkylsilene9
the silyl substituents was observed.14 Only a few studies of the
addition of organometallic reagents to stable, naturally
polarized silenes have been reported. When excess t-BuLi was
added to 1,1-dimesitylneopentylsilene (Mes2SiCHCH2t-Bu,
1)16 in diethyl ether at 0 °C, quantitative and regioselective
formation of Mes2Si(t-Bu)CH2CH2t-Bu (2) was observed.5
Interestingly, at room temperature in diethyl ether, a
rearrangement took place to give 3 (Chart 1).5 In contrast,
the addition of excess t-BuLi to 1,1-dimesitylneopentylgermene
Received: May 18, 2015
Published: July 29, 2015
© 2015 American Chemical Society
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the addition of t-BuLi to fluorovinylsilane 5 (or -germane 6) to
prevent polymerization of the tetrelene. After addition of the
organometallic reagent to the tetrelene and quenching of the
reaction mixture with methanol, the products were purified by
preparative thin-layer chromatography and characterized by IR
and NMR spectroscopy and mass spectrometry.
Chart 1
As previously reported, to prepare Mes2Si(t-Bu)CH2CH2t-
Bu, 2, the addition of t-BuLi to silene 1 was performed in cold
diethyl ether (0 °C); however, at room temperature, the
isomeric tert-butylsilane (3) was produced quantitatively (Chart
1).5 We reasoned that the initial α-silyl anion, formed by the
regioselective addition of tert-butyllithium to silene 1, removed
a proton from an o-methyl group of the mesityl substituent to
form a benzylic anion, followed by a 1,3-silyl shift to form
intermediate 7 (Scheme 4). Anion 7 could abstract a hydrogen
(Mes2GeCHCH2t-Bu, 4) at room temperature in diethyl
ether gave Mes2Ge(t-Bu)CH2CH2t-Bu regioselectively;17 no
evidence for any rearrangement was noted. Alternatively, when
t-BuLi (0.1 equiv) was added to silene 1 or germene 4 dissolved
in pentane, polymeric material was formed in each case.5,18
Given the potential usefulness of the addition of organo-
metallic reagents to silenes in synthesis and materials chemistry,
we wished to examine the reaction under a consistent set of
reaction conditions to determine if addition products could
reliably be obtained in good yields. Therefore, the addition of a
variety of organometallic reagents to the solution-stable silene
Mes2SiCHCH2t-Bu, 1, in diethyl ether at room temperature
is reported, and, for comparison purposes, we have also
examined the addition of the same organometallic reagents to
the analogous solution-stable germene, Mes2GeCHCH2t-Bu,
4. We selected diethyl ether as the solvent since we previously
reported that the addition of t-BuLi to 1 or 4 in a hydrocarbon
solvent, pentane, leads to the formation of polymers,5,18 and
THF is known to complex with silenes and reduce the rate of
addition of alcohols.19,20 Given the well-known stability of aryl-
and silyl-substituted silyl (or germyl) anions, we have always
been intrigued by the exclusive regioselectivity of the isolated
reports on the addition of organometallic reagents to transient
and stable silenes and wished to determine if the same
regiochemistry persisted with germenes as well. Finally, the
addition of t-BuLi to the stable silene 1 has been re-examined in
an effort to understand the different chemistry observed at low
(0 °C) and at room temperature in diethyl ether.
Scheme 4. Proposed Mechanism for the Formation of 3
RESULTS AND DISCUSSION
■
Silene 116 and germene 417 were synthesized by the addition of
t-BuLi to fluorodimesitylvinylsilane (5) or -germane (6) in
diethyl ether in the cold (dry ice/acetone) prior to each
reaction and used in situ without purification (Scheme 3).
to form the more stable benzylic, α-silyl-substituted anion 8. To
test the validity of the hypothesis and to unequivocally
determine the identity of the anion in solution immediately
prior to quenching (i.e., 7 or 8), the reaction of silene 1 with
excess tert-butyllithium in diethyl ether at room temperature
was quenched with D2O; silane 3 was isolated with a deuterium
Scheme 3. Preparation of Silene 1 and Germene 4 in Diethyl
Ether
1
at the benzylic position (3D). The H NMR spectrum of 3
contained an AB spin system (J = 15 Hz) at 2.61 and 2.65 ppm,
which was assigned to the inequivalent hydrogens of the benzyl
5
1
moiety. The AB pattern was not apparent in the H NMR
spectrum of 3D, and only a singlet was observed at
2
approximately the same chemical shift (2.65 ppm). The H
NMR spectrum of 3D also revealed a signal at 2.60 ppm. The
results demonstrate that 8 is indeed the anion quenched in the
reaction. The strain around silicon is likely the major driving
force for the rearrangement. Conversely, the previously
reported addition of t-BuLi to germene 4 in diethyl ether at
room temperature does not yield any rearrangement products.
Undoubtedly, the longer bonds to germanium ease the steric
strain around the central metalloid, and thus, the driving force
for rearrangement is diminished. We hypothesized that the use
of less bulky organometallic reagents, such as MeLi, BuLi, and
We have improved the overall yield for the synthesis of the
precursor germane 6 from approximately 50%17,21 to
approximately 84% by synthesizing difluorodimesitylgermane,
the required starting material for the synthesis of 6, in one step
from dichlorodimesitylgermane using silver tetrafluoroborate
rather than in two steps via dimesityldimethoxygermane.
Germane 6 is then made from the addition of vinylmagnesium
bromide to Mes2GeF2 according to the published procedure.17
As a precaution, slightly less than 1 equiv of t-BuLi was used in
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even t-BuOK, may avoid rearrangement at room temperature
by relieving the congestion at silicon in the initially formed
anion.
The addition of MeLi, BuLi, or t-BuOK to silene 1 or
germene 4 in diethyl ether results in the regioselective
formation of simple 1,2-addition products, which, after
treatment with a weak acid, gave the corresponding silanes
9−11 or germanes 12−14, respectively, in good to excellent
yields (Scheme 5). Silanes 9−11 and germanes 12−14 were the
only products derived from the tetrelenes isolated.
formed in ether at room temperature.17 In these cases, there is
clearly an effect of solvent, although a clear understanding of
the effect is difficult to discern. The changes observed may be
due to the difference in the degree of aggregation of t-BuLi in
pentane (tetramer) compared to diethyl ether (dimer)23 and/
or a change in the energies of key transition states and
intermediates along the reaction pathway due to solvation,
especially of the initially formed α-silyl (or germyl) lithium
species (Scheme 4). Further studies are required to understand
the influence of the solvent in these reactions. In the addition of
excess MeLi and BuLi to silene 1 or germene 4 in ether, in
addition to the factors just mentioned, the use of an anionic
reagent with a less bulky organic moiety may also increase the
rate of addition of the reagent to the tetrelene relative to the
subsequent dimerization (oligomerization), resulting in the lack
of polymer formation. These are the kinetics needed to achieve
a controlled anionic polymerization, and the use of less bulky
anionic initiators in ether for the controlled polymerization of
silenes and germenes will be the subject of further research in
this laboratory.
Scheme 5. Addition of Organometallic Reagents to Silene 1
and Germene 4
In all reports of the addition of organometallic reagents to
silenes and germenes, including the results presented in this
study, the addition is completely regioselective, with the
organometallic reagent adding to the silicon (or germanium)
atom. We found the regioselectivity to be somewhat surprising
since the reverse regiochemistry would result in the formation
of relatively stable diaryl- or bis(silyl)-substituted silyl (or
germyl) anions. There have been few mechanistic studies on
the addition of nucleophiles to silenes. Water and alcohols have
been shown to undergo nucleophilic addition.1h,i Again, the
reaction is regioselective, with the nucleophilic moiety adding
to the silicon. The bond polarity of the SiC bond is the most
important factor governing the reactivity of the silene and plays
a significant role in the regioselectivity of the addition of water
and alcohols. For silenes of natural polarity, such as silene 1 or
Me2SiCPh(CH2SiMe3) studied by Ishikawa,9 or even silenes
of reduced polarity, such as the bis(silyl)-substituted silenes
studied by Oehme,11−15 the regiochemistry might be expected.
On the other hand, the complete regioselectivity of the addition
of organometallic reagents to Brook silenes ((Me3Si)2Si
C(OSiMe3)R), which have reversed polarity, is, at first,
surprising. Interestingly, it was noted in the addition of
alcohols1h or water24 to silenes that the regiochemistry of the
addition is substituent-independent and that the silicon atom is
always the most electrophilic atom in the double bond of a
range of substituted silenes. Thus, it appears as if the addition
of organometallic reagents to silenes follows the same reactivity
pattern, although the reaction may be further complicated by
the influence of the solvent and the counterion on the nature
and aggregation of the organometallic reagent. The same
factors appear to govern the regiochemistry of the addition of
organometallic reagents toward germenes.
No rearrangement products were observed in the reactions,
in contrast to the addition of organometallic reagents to some
1,1-bis(trimethylsilyl)silenes8,14 or the addition of t-BuLi to the
same silene (1) at room temperature. The lack of rearrange-
ment in the systems studied here is likely because of the
absence of substituents that readily migrate, such as a silyl
group. Although the previously reported addition of t-BuLi to
silene 1 in diethyl ether did result in the formation of a
rearranged product (3),5 our results now demonstrate that such
a rearrangement can easily be avoided by the use of less
sterically demanding organometallic reagents, which supports
our earlier hypothesis that the driving force of the rearrange-
ment to give 3 is indeed the relief of steric strain about the
silicon.
Polysilene or polygermene was not formed in the addition of
MeLi, BuLi, or t-BuOK to silene 1 or germene 4, respectively.
Some comparative experiments are instructive. The addition of
0.1 equiv of t-BuLi to either the silene or germene in pentane
results in the rapid formation of the polysilene,5 or -germene,18
respectively. In preliminary experiments, we have demonstrated
that both silene 1 and germene 4 do polymerize under the same
conditions in ether, and thus, the solvent does not appear to
have much of an influence; however, we have not yet
investigated the molecular weight of the polymers formed in
ether. We have also added excess t-BuLi to silene 1 and
germene 4 in pentane at room temperature and compared the
results to those obtained in diethyl ether. For silene 1, where
only the rearranged silane 3 is obtained after the addition of
methanol in ether at room temperature,5 polysilene is the
predominate product in pentane, with silane 2 also being
present in small amounts.22 For germene 4, both Mes2Ge(t-
Bu)CH2CH2t-Bu and polygermene are formed (after quench-
ing) in pentane,22 whereas only Mes2Ge(t-Bu)CH2CH2t-Bu is
The reactions shown in Scheme 5 are complicated because of
the salt elimination method used to make silene 1 and germene
4. It can be difficult to achieve high conversions of fluorosilane
5 to silene 1 or fluorogermane 6 to germene 4 (Scheme 3)
while, at the same time, avoiding polymerization of the
tetrelenes. Therefore, the presence of residual fluorosilane
and -germane in the reaction mixtures is unavoidable, and the
amount present is directly related to the degree of conversion
achieved in a given reaction. Not surprisingly, the residual
fluorosilane and germane also react with the organometallic
reagent (MeLi, BuLi, and t-BuOK), added in the second step of
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the reaction sequence, to give byproducts25 that can be difficult
to separate from the products derived from the silene (or
germene) because of the similarities in the polarities of the two
compounds. To unambiguously identify all possible products,
the anticipated byproducts were synthesized directly by
treatment of fluorosilane 5 and fluorogermane 6 with MeLi,
BuLi, or t-BuOK (Scheme 6).
cation, the solvent, and the reaction temperature may influence
the reaction pathway followed, and thus, appropriate caution
must be exercised.8,12,14 No polymer was observed during
addition of MeLi, BuLi, and t-BuOK to silene 1 and germene 4
in diethyl ether, suggesting that the rate of addition to the
tetrelene is significantly faster than the rate of propagation in
this solvent. Further studies are needed to examine the effect of
the use of MeLi and BuLi in comparison with t-BuLi as anionic
initiators in the polymerization of silenes and germenes.
Scheme 6. Reaction of Fluorosilane 5 and Fluorogermane 6
with Organometallic Reagents
EXPERIMENTAL SECTION
■
General Procedures. All air- and moisture-sensitive reactions
were carried out in flame-dried Schlenk tubes under an argon
atmosphere. C6D6 was distilled from LiAlH4, stored over 4 Å
molecular sieves, and degassed prior to use. All other solvents were
dried using a solvent purification system (Innovative Technology Ltd.)
by passing the solvent through an alumina column. All reagents were
purchased from the Aldrich Chemical Co. and were used as received.
1,1-Dimesitylneopentylsilene, 1,16b fluorovinylsilane, 5,16b 1,1-dimesi-
tylneopentylgermene, 4,17 and fluorovinylgermane, 6,17 were prepared
according to the previously reported procedures. Caution: t-BuLi is
highly pyrophoric and should be handled with the necessary precautions.
1H NMR spectra were recorded on a Varian Mercury 400 MHz
spectrometer, a Varian Inova 400 MHz spectrometer, or a Varian
Inova 600 MHz spectrometer and are referenced to residual C6D5H
(7.15 ppm) or CHCl3 (7.25 ppm). IR spectra were recorded (cm−1)
from thin films on a Bruker Tensor 27 FT-IR spectrometer. Electron
impact mass spectra were obtained using a MAT model 8400 mass
spectrometer. Mass spectral data are reported in mass-to-charge ratios
(m/z).
Indeed vinylsilane 15 and vinylgermanes 16−18 were
present in the crude product mixtures. Vinylgermanes 16 and
17 could not be separated from the products derived from the
germene (i.e., 12 and 13); however, in each of the other cases,
separation was achieved. Interestingly, in the addition of excess
BuLi to silene 1, derived from 5, in diethyl ether,
butylhexyldimesitylsilane (19) (Chart 2) was formed in
Chart 2
Synthesis of Difluorodimesitylgermane. Silver tetrafluorobo-
rate (1.94 g, 9.96 mmol) was added to a solution of dichlorodime-
sitylgermane (1.0 g, 2.6 mmol) dissolved in dichloromethane (75 mL)
under an inert atmosphere. The solid immediately dissolved, and a
white precipitate was observed. The mixture was allowed to stir for 3−
4 min. Water (10 mL) was then added, and the mixture filtered. The
organic layer and the aqueous layer were separated. The aqueous layer
was washed with dichloromethane (3 × 10 mL). The combined
organic phase was dried using MgSO4. The solids were removed by
filtration, and the solvent was removed on a rotary evaporator to give a
white solid in quantitative yield. The isolated yield depends on the
number of times the product is washed with water. The 1H NMR data
of Mes2GeF2 in CDCl3 agreed with those published in the literature.21
Mes2GeF2: 1H NMR (C6D6) δ 1.98 (s, 6 H, p-Me), 2.45 (s, 12 H, o-
Me), 6.58 (s, 4 H, Mes-H).
addition to silane 10. Silane 19 was clearly formed by the
reaction of 2 equiv of BuLi to fluorovinylsilane 5, as
demonstrated by the direct synthesis of 19 from the addition
of excess BuLi to silane 5 in diethyl ether. Interestingly, when
an excess of BuLi was added to silane 5 in pentane, only 1 equiv
of BuLi added to give Mes2Si Bu(CHCH2). Finally, in the
addition of t-BuOK to silene 1 (or germene 4), silanol 20 (or
germanol 21) was also present in the crude reaction mixture
and presumably arises from direct reaction of hydroxide present
in the alkoxide reagent with residual 5 (or 6).
Synthesis of 3D. tert-Butyllithium (1.7 M in pentane, 0.10 mL,
0.17 mmol) was added to a solution of 5 (57 mg, 0.17 mmol)
dissolved in pentane (3 mL) and cooled in a dry ice/acetone bath. The
solution was allowed to warm to room temperature. After 10 min at
room temperature, the pentane was removed under vacuum and the
residue was dissolved in diethyl ether (3 mL). A second portion of tert-
butyllithium (1.7 M in pentane, 0.30 mL, 0.54 mmol) was added to the
solution, which was then allowed to stir at room temperature for 2 h.
D2O (1 drop) was added to the reaction mixture. The solution was
washed with saturated ammonium chloride (3 × 10 mL). The
combined aqueous solution was washed with diethyl ether (3 × 10
mL). The combined organic solution was dried over MgSO4 and
filtered. The solvent was removed under vacuum to give a viscous,
clear oil (58 mg, 85% yield). 3D was purified by thin-layer
chromatography (95:5 pentane/diethyl ether) (22 mg, 32% yield).
CONCLUSION
■
We have examined the reactivity of the naturally polarized
silene 1 and germene 4 toward organometallic reagents in
diethyl ether. The organometallic reagent adds regioselectively
to the tetrelene, with the organic moiety always adding to the
group 14 atom of the unsaturated bond. In combination with
previously published results on silene chemistry, the addition is
always regioselective despite a range of substituents on the
silicon. As in the addition of oxygen nucleophiles to silenes, the
electrophilicity of the unsaturated group 14 element appears to
be the governing factor in the regiochemistry of the reaction.
Rearrangements are possible after initial addition of the
organometallic moiety if there is a substituent that readily
undergoes migration, such as a silyl substituent, or if there is
considerable congestion about the group 14 atom. The
straightforward, selective addition of organometallic reagents
to silenes and germenes makes this reaction synthetically useful
and may be used to introduce functionality into the compound.
However, as we and others have observed, the nature of the
1
3D: H NMR (CDCl3) δ 0.70 (s, 9 H, C(CH3)3), 1.02 (s, 9 H,
SiC(CH3)3), 0.79−0.84 (XX′ portion of an AA′XX′ spin system, 2 H,
SiCH2CH2), 0.87−0.92 (AA′ portion of an AA′XX′ spin system, 2 H,
SiCH2CH2), 2.20 (s, 6 H, ArCH3), 2.27 (s, 3 H, Mes p-CH3), 2.50 (s,
6 H, Mes o-CH3), 2.63 (s, 1 H, SiCHDAr), 6.70 (s, 1 H, Ar p-H), 6.75
2
(s, 2 H, Ar o-H), 6.84 (s, 2 H, Mes-H); H NMR (CDCl3) 2.60 (s, 1
H, SiCHDAr).
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Representative Procedure for the Addition of MeLi to 1. tert-
Butyllithium (1.7 M in pentane, 0.09 mL, 0.15 mmol) was added to a
solution of 5 (57 mg, 0.17 mmol) dissolved in diethyl ether (3 mL)
and cooled in a dry ice/acetone bath. The solution was allowed to
warm to room temperature and then stirred for 1.5 h. Methyllithium
(1.6 M in diethyl ether, 0.30 mL, 0.48 mmol) was added to the
solution, which was then allowed to stir for 10 min. Methanol (1 drop)
was added to the reaction mixture. The solution was washed with a
saturated ammonium chloride solution (3 × 10 mL). The combined
aqueous solution was washed with diethyl ether (3 × 10 mL). The
combined organic solution was dried over MgSO4 and filtered. The
solvent was removed under vacuum to give a viscous, light yellow oil
consisting of a mixture of 9, 15, and the water adduct of the silene (53
mg). 9 (20 mg, 31% yield) and 15 (4 mg, 6% yield) were separated by
thin-layer chromatography (80:20 hexanes/DCM) to give each as a
clear oil.
× 10 mL). The combined aqueous solution was washed with diethyl
ether (3 × 10 mL). The combined organic phase was dried over
MgSO4 and filtered. The solvent was removed under vacuum to give
15 as a viscous, colorless liquid (10 mg, 10% yield). Similarly, the
addition of methyllithium to 6 gave 16 (58 mg, 59% yield).
Representative Procedure for the Addition of BuLi to 1. tert-
Butyllithium (1.7 M in pentane, 0.10 mL, 0.17 mmol) was added to a
solution of 5 (58 mg, 0.18 mmol) dissolved in diethyl ether (3 mL)
and cooled in a dry ice/acetone bath. The solution was allowed to
warm to room temperature and then stirred for 1.5 h. Butyllithium
(1.6 M in hexane, 0.34 mL, 0.54 mmol) was added to the solution,
which was then allowed to stir for 10 min. Methanol (1 drop) was
added to the reaction. The solution was washed with a saturated
ammonium chloride solution (3 × 10 mL). The combined aqueous
solution was washed with diethyl ether (3 × 10 mL). The combined
organic phase was dried over MgSO4 and filtered. The solvent was
removed under vacuum to give a viscous, colorless oil (58 mg, 78%
yield) identified as a mixture of 10 and 19 in a ratio of 1:1. The
mixture was purified by thin-layer chromatography (70:30 hexane/
DCM) to give a clear oil (38 mg).
Mes2Si(Me)CH2CH2t-Bu (9): 1H NMR (C6D6) δ 0.74 (s, 3 H,
SiCH3), 0.82 (s, 9 H, C(CH3)3), 1.25−1.31 (AA′XX′ spin system, 4 H,
SiCH2CH2), 2.09 (s, 6 H, Mes p-CH3), 2.34 (s, 12 H, Mes o-CH3),
6.71 (s, 4 H, Mes-H); 13C NMR (C6D6) δ 4.3 (SiCH3), 15.62
(SiCH2CH2), 20.93 (Mes p-CH3), 24.36 (Mes o-CH3), 28.97
(C(CH3)3), 31.09 (C(CH3)3), 39.03 (SiCH2CH2), 129.73 (Mes m-
C), 134.78 (Mes i-C), 138.19 (Mes p-C), 143.36 (Mes o-C); 29Si
NMR (C6D6) δ −6.7; EI-MS m/z 366 (M+, 6%), 351 (M+ − CH3,
4%), 281 (M+ − CH2CH2C(CH3)3, 100%), 246 (M+ − Mes, 44%);
high-resolution EI-MS for C25H38Si m/z calcd 366.2743, found
366.2732.
Mes2Si(Bu)CH2CH2t-Bu (10): 1H NMR (C6D6) δ 0.83 (t, 3 H, J = 7
Hz, Si(CH2)3CH3), 0.84 (s, 9H, C(CH3)3), 1.46−1.15 (m,
SiCH2CH2CH2CH3), 2.09 (s, 6 H, Mes p-CH3), 2.38 (s, 12 H, Mes
o-CH3), 6.71 (s, 4 H, Mes-H); 13C NMR (C6D6) δ 9.14, 13.15
(SiCH2CH2 and SiCH2CH2CH2CH3), 18.70, 27.06, 27.43
(SiCH2CH2CH2CH3, SiCH2CH2CH2CH3 and SiCH2CH2CH2CH3),
20.94 (Mes p-CH3), 24.52 (Mes o-CH3), 28.97 (C(CH3)3), 31.13
(C(CH3)3), 39.14 (SiCH2CH2), 129.76 (Mes m-C), 134.30 (Mes i-C),
138.17 (Mes p-C), 143.59 (Mes o-C); 29Si NMR (C6D6) δ −4.1; EI-
MS m/z 408 (M+, 1%), 351 (M+ − (CH2)3CH3, 14%), 323 (M+ −
(CH2)5CH3, 18%), 288 (M+ − MesH, 26%), 267 (Mes2Si+, 100%);
high-resolution EI-MS for C28H44Si m/z calcd 408.3212, found
408.3214.
Mes2Si(Me)CHCH2 (15): IR (cm−1) 793 (m), 847 (m), 1285 (m),
1
1449 (m), 1605 (m), 2978 (s); H NMR (C6D6) δ 0.76 (s, 3 H,
SiCH3), 2.10 (s, 6 H, Mes p-CH3), 2.29 (s, 12 H, Mes o-CH3), 5.63
(dd, J = 5, 20 Hz, 1 H, SiCHCH2), 5.86 (dd, J = 4, 14 Hz, 1 H,
SiCHCH2), 6.68 (dd, J = 5, 20 Hz, 1 H, SiCHCH2), 6.70 (s, 4 H,
Mes-H); 13C NMR (C6D6) δ 4.18 (SiCH3), 21.00 (Mes p-CH3), 24.63
(Mes o-CH3), 129.64 (Mes m-C), 130.48 (SiCHCH2), 133.58 (Mes
i-C), 138.43 (Mes p-C), 141.48 (SiCHCH2), 143.59 (Mes o-C); EI-
MS m/z 308 (M+, 28%), 293 (M+ − CH3, 24%), 281 (M+ − CH
CH2, 7%), 188 (M+ − MesH, 100%); high-resolution EI-MS for
C21H28Si m/z calcd 308.1960, found 308.1971.
1
Mes2Si(Bu)Hex (19): H NMR (C6D6) δ 0.815 (t, J = 7 Hz) 0.821
(t, J = 7 Hz) (6 H, Si(CH2)3CH3 and Si(CH2)5CH3), 1.16−1.21 (br, 4
H, SiCH2), 1.30−1.46 (m, SiCH2(CH2)2CH3 and SiCH2(CH2)4CH3),
2.10 (s, 6 H, Mes p-CH3), 2.37 (s, 12 H, Mes o-CH3), 6.71 (s, 4 H,
Mes-H); 13C NMR (C6D6) δ 13.90, 14.25 (SiCH2CH2CH2CH3 and
SiCH2(CH2)4CH3), 18.98, 19.24 (SiCH2CH2CH2CH3 and
SiCH2CH2(CH2)3CH3), 20.95 (Mes p-CH3), 22.98, 25.24 (Si-
(CH2)3CH2CH2CH3 and Si(CH2)2CH2(CH2)2CH3), 24.56 (Mes o-
CH3), 27.48, 31.82 (SiCH2CH2CH2CH3 and Si(CH2)4CH2CH3),
27.14, 33.96 (SiCH2CH2CH2CH3 and Si(CH2)5CH3), 129.75 (Mes
m-C), 134.40 (Mes i-C), 138.14 (Mes p-C), 143.58 (Mes o-C); 29Si
In the addition of MeLi to 4, a viscous, colorless oil, identified as a
mixture of 12 and 16, was obtained in a ratio of 1:0.03 (10 mg, 92%
yield).
1
Mes2Ge(Me)CH2CH2t-Bu (12): H NMR (C6D6) δ 0.825 and 0.829
(s, C(CH3)3 and s, GeCH3, 12 H), 1.23−1.33 (XX′ of an AA′XX′ spin
system, 2 H, GeCH2CH2), 1.46−1.50 (AA′ of an AA′XX′ spin system,
2 H, GeCH2CH2), 2.10 (s, 6 H, Mes p-CH3), 2.33 (s, 12 H, Mes o-
CH3), 6.72 (s, 4 H, Mes-H); 13C NMR (C6D6) δ 4.16 (GeCH3), 17.46
(GeCH2CH2), 20.93 (Mes p-CH3), 24.19 (Mes o-CH3), 28.96
(C(CH3)3), 31.21 (C(CH3)3), 39.78 (GeCH2CH2), 129.41 (Mes m-
C), 137.53 (Mes p-C), 137.71 (Mes i-C), 142.79 (Mes o-C); EI-MS
NMR (C6D6) δ −5.1; EI-MS m/z 408 (M+, 1%), 351 (M+
−
(CH2)3CH3, 10%), 323 (M+ − (CH2)5CH3, 13%), 288 (M+ − MesH,
13%), 267 (Mes2Si+, 100%); high-resolution EI-MS for C28H44Si m/z
calcd 408.3212, found 408.3205.
In the addition of BuLi to 4, a viscous, colorless oil identified as a
mixture of 13 and 17 was obtained in a ratio of 1:0.2 (28 mg, 47%
yield).
m/z 411 (M+, 11%), 397 (M+ − CH3, 41%), 293 (M+
−
CH2CH2C(CH3)3, 100%); high-resolution EI-MS for C25H3870Ge
m/z calcd 407.2138, found 407.2130.
Mes2Ge(Bu)CH2CH2t-Bu (13): 1H NMR (C6D6) δ 0.82 (t, 3 H, J = 7
Hz, Ge(CH2)3CH3), 0.84 (s, 9 H, C(CH3)3), 1.29−1.63 (m,
GeCH2CH2CH2CH3), 2.10 (s, 6 H, Mes p-CH3), 2.37 (s, 12 H,
Mes o-CH3), 6.73 (s, 4 H, Mes-H); 13C NMR (C6D6) δ 13.84
(GeCH2 CH2 CH2 CH3 ), 15.09 (GeCH2 CH2 t-Bu), 20.26
(GeCH2CH2CH2CH3), 20.94 (Mes p-CH3), 24.35 (Mes o-CH3),
26.75 (GeCH2CH2CH2CH3), 28.30 (GeCH2CH2CH2CH3), 28.97
(C(CH3)3), 31.26 (C(CH3)3), 39.94 (GeCH2CH2t-Bu), 129.40 (Mes
m-C), 137.11 (Mes i-C), 137.68 (Mes p-C), 142.99 (Mes o-C); EI-MS
Mes2Ge(CHCH2)Me (16): IR (cm−1) 799 (s), 848 (s), 946 (m),
1
1009 (s), 1239 (m), 1261 (m), 1449 (m), 1603 (s), 2804 (w); H
NMR (C6D6) δ 0.84 (s, 3 H, GeCH3), 2.11 (s, 6 H, Mes p-CH3), 2.29
(s, 12 H, Mes o-CH3), 5.58 (dd, J = 3, 20 Hz, 1 H, GeCHCH2),
5.85 (dd, J = 3, 13 Hz, 1 H, GeCHCH2), 6.71 (s, 4 H, Mes-H), 6.78
(dd, J = 13, 20 Hz, 1 H, GeCHCH2); 13C NMR (C6D6) δ 4.53
(GeCH3), 20.98 (Mes p-CH3), 24.42 (Mes o-CH3), 128.18 (GeCH
CH2), 129.38 (Mes m-C), 136.39 (Mes i-C), 137.94 (Mes p-C),
142.76 (GeCHCH2), 142.96 (Mes o-C); EI-MS m/z 354 (M+,
11%), 339 (M+ − CH3, 70%), 327 (M+ − CHCH2, 33%), 234 (M+
− Mes, 81%), 219 (M+ − CH3 − Mes, 100%); high-resolution EI-MS
for C21H2874Ge m/z calcd 354.1407, found 354.1402.
m/z 454 (M+, 1%), 397 (M+ − (CH2)3CH3, 55%), 369 (M+
−
(CH2)2(CH3)3, 67%), 191 (M+ − MesH, 26%), 313 (Mes274GeH+,
100%); high-resolution EI-MS for C28H4374Ge m/z calcd 453.2582,
found 453.2594.
Synthesis of Mes2Si(CHCH2)CH3 (15). Methyllithium (1.6 M
in diethyl ether, 0.40 mL, 0.64 mmol) was added to a solution of 5
(100 mg, 0.32 mmol) dissolved in diethyl ether (6 mL). The solution
was allowed to stir overnight at room temperature. An ammonium
chloride solution (2 mL) was added to the reaction mixture. The
solution was washed with a saturated ammonium chloride solution (3
Synthesis of Mes2Si(Bu)Hex (19). Butyllithium (1.6 M in hexane,
0.5 mL, 0.8 mmol) was added to a solution of 5 (47 mg, 0.15 mmol)
dissolved in diethyl ether (3 mL). The solution was allowed to stir for
2 h at room temperature. Methanol (1 drop) was added to the
reaction mixture. The solution was washed with saturated ammonium
chloride (3 × 10 mL). The combined aqueous solution was washed
3752
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Organometallics 2015, 34, 3748−3755

Organometallics
Article
with diethyl ether (3 × 10 mL). The combined organic phase was
dried over MgSO4 and filtered. The solvent was removed under
vacuum to give a viscous, colorless liquid (55 mg, 90% yield). 19 was
purified by thin-layer chromatography (70:30 hexanes/DCM) to give
a colorless oil (37 mg, 61% yield).
(C(CH3)3), 31.04 (C(CH3)3), 31.69 (OC(CH3)3), 38.31
(SiCH2CH2), 74.16 (OC(CH3)3), 129.89 (Mes m-C), 134.88 (Mes
i-C), 138.46 (Mes p-C), 143.64 (Mes o-C); 29Si NMR (C6D6) δ −8.1;
EI-MS m/z 424 (M+, 0.1%), 339 (M+ − CH2CH2C(CH3)3, 55%), 283
(Mes2SiO+, 100%); high-resolution EI-MS for C28H44OSi m/z calcd
424.3161, found 424.3156.
Synthesis of Mes2Si(CHCH2)Bu. Butyllithium (1.6 M in
hexane, 0.50 mL, 0.80 mmol) was added to a solution of 5 (47 mg,
0.15 mmol) dissolved in pentane (3 mL). The solution was allowed to
stir for 2 h at room temperature. Methanol (1 drop) was added to the
reaction mixture. The solution was washed with a saturated
ammonium chloride solution (3 × 10 mL). The combined aqueous
solution was washed with diethyl ether (3 × 10 mL). The combined
organic phase was dried over MgSO4 and filtered. The solvent was
removed under vacuum to give a viscous, colorless liquid (50 mg, 96%
yield). Mes2Si(CHCH2)Bu was purified by thin-layer chromatog-
raphy (80:20 hexanes/DCM) to give a clear oil (38 mg, 72% yield).
Vinylgermane 17 was synthesized in a similar manner to give a viscous,
colorless oil (55 mg, 50% yield).
Mes2Si(OH)CHCH2 (20): IR (cm−1) 632 (m), 801 (m), 1179 (w),
1234 (m), 1263 (s), 1405 (m), 1448 (m), 1548 (m), 1605 (s), 2734
1
(w), 2860 (m), 2922 (s), 2965 (s); H NMR (C6D6) δ 2.10 (s, 6 H,
Mes p-CH3), 2.37 (s, 12 H, Mes o-CH3), 5.81 (dd, J = 4, 20 Hz, 1 H,
SiCHCH2), 5.91 (dd, J = 4, 14 Hz, 1 H, SiCHCH2), 6.57 (dd, J =
14, 20 Hz, 1 H, SiCHCH2), 6.70 (s, 4 H, Mes-H); 13C NMR
(C6D6) δ, 21.05 (Mes p-CH3), 24.18 (Mes o-CH3), 129.56 (Mes m-
C), 131.61 (SiCHCH2), 132.97 (Mes i-C), 139.06 (Mes p-C),
140.78 (SiCHCH2), 143.97 (Mes o-C); EI-MS m/z 310 (M+, 12%),
283 (M+ − CHCH2, 8%), 191 (M+ − Mes, 14%), 84 (100%); high-
resolution EI-MS for C20H26OSi m/z calcd 310.1753, found 310.1748.
In the addition of potassium tert-butoxide to 4, a clear oil was
obtained, which was identified as a mixture of 14, 18, and 21 (in a ratio
of 1:0.5:0.5) and a trace of an unknown. The mixture was purified by
thin-layer chromatography (80:20 hexanes/DCM) to give 14 as a clear
oil contaminated with a minor impurity (15 mg, 12% yield).
1
Mes2Si(CHCH2)Bu: H NMR (C6D6) δ 0.80 (t, J = 7 Hz, 3 H,
SiCH2CH2CH2CH3), 1.29−1.43 (m, SiCH2CH2CH2CH3), 2.10 (s, 6
H, Mes p-CH3), 2.32 (s, 12 H, Mes o-CH3), 5.65 (dd, J = 3, 20 Hz, 1
H, SiCHCH2), 5.91 (dd, J = 4, 14 Hz, 1 H, SiCHCH2), 6.71 (s, 4
H, Mes-H), 6.82 (dd, J = 14, 20 Hz, 1 H, SiCHCH2); 13C NMR
(C6D6) δ 13.84 (SiCH2CH2CH2CH3), 20.03 (SiCH2CH2CH2CH3),
20.99 (Mes p-CH3), 24.76 (Mes o-CH3), 27.09 (SiCH2CH2CH2CH3),
27.58 (SiCH2CH2CH2CH3), 129.63 (Mes m-C), 130.83 (SiCH
CH2), 133.05 (Mes i-C), 138.42 (Mes p-C), 140.11 (SiCHCH2),
143.87 (Mes o-C); 29Si NMR (C6D6) δ −13.8; EI-MS m/z 350 (M+,
33%), 335 (M+ − CH3, 10%), 293 (M+ − C4H9, 100%), 230 (M+ −
MesH, 30%); high-resolution EI-MS for C24H34Si m/z calcd 350.2430,
found 350.2441.
Mes2Ge(Ot-Bu)CH2CH2t-Bu (14): IR (cm−1) 848 (m), 1021 (m),
1
1466 (m), 1604 (m), 2965 (s); H NMR (C6D6) δ 0.83 (s, 9 H,
C(CH3)3), 1.19−1.21 (XX′ portion of an AA′XX′ spin system, 2 H,
GeCH2CH2), 1.32 (s, 9 H, OC(CH3)3), 1.6−1.62 (AA′ portion of an
AA′XX′ spin system, 2 H, GeCH2CH2), 2.10 (s, 6 H, Mes p-CH3),
2.32 (s, 12 H, Mes o-CH3), 6.73 (s, 4 H, Mes-H); 13C NMR (C6D6) δ
14.82 (GeCH2CH2), 20.87 (Mes p-CH3), 25.32 (Mes o-CH3), 28.99
(C(CH3)3), 30.01 (C(CH3)3), 31.44 (OC(CH3)3), 41.08
(GeCH2CH2), 84.06 (OC(CH3)3), 129.44 (Mes m-C), 137.31 (Mes
p-C), 142.62 (Mes o-C); EI-MS m/z 395 (M+ − Ot-Bu, 66%), 312
(Mes2Ge+, 81%), 84 (100%).
Mes2GeBu(CHCH2) (17): IR (cm−1) 697 (s), 847 (m), 1008 (m),
1289 (w), 1377 (m), 1392 (m), 1450 (s), 1603 (s), 2731 (w), 2858
1
(m), 2924 (s), 2957 (s); H NMR (C6D6) δ 0.79 (t, J = 7 Hz, 3 H,
Synthesis of Mes2Ge(OH)CHCH2 (21). Aqueous sodium
hydroxide (15%, 5.0 mL, 1.4 mmol) was added to a solution of 6
(50 mg, 0.14 mmol) dissolved in THF (20 mL), which was then
allowed to stir for 1 h at room temperature. The aqueous solution was
washed with diethyl ether (3 × 10 mL), and the organic layer was
washed with water (3 × 10 mL). The combined organic phase was
dried over MgSO4 and filtered. The solvent was removed under
vacuum to give a viscous, colorless oil (25.0 mg, 50% yield). The oil
consisted of 21 and 6 in a ratio of 1:0.04. The mixture was purified by
thin-layer chromatography on silica gel (50:50 hexane/DCM) to give
21 as a clear oil (2.2 mg). Silanol 20 was synthesized using the same
procedure (99 mg, 98% yield).
GeCH2CH2CH2CH3), 1.25−1.60 (m, GeCH2CH2CH2CH3), 2.11 (s,
6 H, Mes p-CH3), 2.31 (s, 12 H, Mes o-CH3), 5.60 (dd, J = 3, 19 Hz, 1
H, GeCHCH2), 5.90 (dd, J = 3, 13 Hz, 1 H, GeCHCH2), 6.72 (s,
4 H, Mes-H), 6.93 (dd, J = 13, 19 Hz, 1 H, GeCHCH2); 13C NMR
(C6D6) δ 13.80 (GeCH2CH2CH2CH3), 20.97 (Mes p -CH3), 22.00
(GeCH2 CH2 CH2 CH3 ), 24. 55 (Mes o-CH3 ), 26. 74
(GeCH2CH2CH2CH3), 28.43 (GeCH2CH2CH2CH3), 128.48
(GeCHCH2), 129.35 (Mes m-C), 135.91 (Mes i-C), 137.93 (Mes
p-C), 141.49 (GeCHCH2), 143.19 (Mes o-C); EI-MS m/z 396
(M+, 2%), 369 (M+ − CHCH2, 1%), 339 (M+ − C4H9, 100%), 276
(M+ − MesH, 11%); high-resolution EI-MS for C24H3474Ge m/z calcd
396.1877, found 396.1869.
Mes2Ge(OH)CHCH2 (21): IR (cm−1) 848 (s), 962 (m), 1449 (s),
1602 (s), 2922 (s) 3430 (br, m); 1H NMR (C6D6) δ 2.08 (s, 6 H, Mes
p-CH3), 2.40 (s, 12 H, Mes o-CH3), 5.77 (dd, J = 3, 20 Hz, 1 H,
GeCHCH2), 5.87 (dd, J = 3, 13 Hz, 1 H, GeCHCH2), 6.65 (dd, J
= 13, 20 Hz, 1 H, GeCHCH2), 6.69 (s, 4 H, Mes-H). 13C NMR
(C6D6) δ 20.99 (Mes p-CH3), 23.77 (Mes o-CH3), 129.43 (Mes m-C),
130.02 (GeCHCH2), 134.97 (Mes i-C), 138.99 (Mes p-C), 141.37
(GeCHCH2), 143.25 (Mes o-C); EI-MS m/z 356 (M+, 7%), 338
(M+ − OH, 11%), 329 (M+ − CHCH2, 26%), 236 (M+ − Mes-H,
52%), 145 (100%); high-resolution EI-MS for C20H26O74Ge m/z calcd
356.1200, found 356.1189.
Synthesis of Mes2Si(CHCH2)Ot-Bu. Potassium tert-butoxide
(153 mg, 1.37 mmol) was added to a solution of 5 (94 mg, 0.30
mmol) dissolved in THF (9 mL). The solution was allowed to stir for
24 h. Saturated ammonium chloride (1 drop) was added to the
reaction mixture. The solution was washed with a saturated
ammonium chloride solution (3 × 10 mL). The combined aqueous
solution was washed with THF (3 × 10 mL). The combined organic
phase was dried over MgSO4 and filtered. The solvent was removed
under vacuum to give an orange powder (100 mg, 90% yield). The
powder consisted of Mes2Si(CHCH2)Ot-Bu and a small amount of
an unknown. The mixture was purified by thin-layer chromatography
on silica gel (70:30 hexane/DCM) to give Mes2Si(CHCH2)Ot-Bu
(59 mg, 53%). Vinylgermane 18 was synthesized in a similar manner
Representative Procedure for the Addition of KOt-Bu to 1.
tert-Butyllithium (1.7 M in pentane, 0.1 mL, 0.2 mmol) was added to a
solution of 5 (57.8 mg, 0.18 mmol) dissolved in diethyl ether (3 mL)
and cooled in a dry ice/acetone bath. The solution was allowed to
warm to room temperature and then stirred for 1.5 h. Potassium tert-
butoxide (90 mg, 0.80 mmol) was added to the solution, which was
then allowed to stir for 10 min. The potassium tert-butoxide did not
dissolve completely. Methanol (1 drop) was added to the reaction.
The solution was washed with a saturated ammonium chloride
solution (3 × 10 mL). The combined aqueous solution was washed
with diethyl ether (3 × 10 mL). The combined organic phase was
dried over MgSO4 and filtered. The solvent was removed under
vacuum to give a clear, colorless liquid (60 mg). The liquid consisted
1
of 11 and 20 in a 1:2 ratio as determined by H NMR spectroscopy.
The mixture was separated twice by thin-layer chromatography (80:20
hexane/DCM) to give 11 (17 mg, 23% yield) and 20 (13 mg, 17%).
Compound 11 remains contaminated with trace amounts of an
unknown.
1
Mes2Si(Ot-Bu)CH2CH2t-Bu (11): H NMR (C6D6) δ 0.87 (s, 9 H,
C(CH3)3), 1.23 (s, 9 H, OC(CH3)3), 1.33−1.35 (XX′ portion of an
AA′XX′ spin system, 2 H, SiCH2CH2), 1.48−1.50 (AA′ portion of an
AA′XX′ spin system, 2 H, SiCH2CH2), 2.09 (s, 6 H, Mes p-CH3), 2.48
(s, 12 H, Mes o-CH3), 6.73 (s, 4 H, Mes-H); 13C NMR (C6D6) δ
18.53 (SiCH2CH2), 21.02 (Mes p-CH3), 24.29 (Mes o-CH3), 29.08
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to give a viscous, colorless oil (106 mg, 92% yield) consisting of 18
and 21 in a ratio of 1:0.06.
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Mes2Si(CHCH2)Ot-Bu: IR (cm−1) 632 (s), 697 (s), 848 (m), 959
(m), 1021 (s), 1040 (s), 1189 (s), 1363 (m), 1450 (m), 1605 (m),
1
2799 (m), 2948 (m), 3100 (br, s); H NMR (C6D6) δ 1.20 (s, 9 H,
OC(CH3)3), 2.11 (s, 6 H, Mes p-CH3), 2.44 (s, 12 H, Mes o-CH3),
5.70 (dd, J = 3, 20 Hz, 1 H, SiCHCH2), 5.90 (dd, J = 3, 14 Hz, 1 H,
SiCHCH2), 6.73 (s, 4 H, Mes-H), 6.76 (dd, J = 14, 20 Hz, 1 H,
SiCHCH2); 13C NMR (C6D6) δ 21.07 (Mes p-CH3), 24.52 (Mes o-
CH3), 31.80 (C(CH3)3), 74.20 (OC(CH3)3), 129.73 (Mes m-C),
131.45 (SiCHCH2), 133.64 (Mes i-C), 138.72 (Mes p-C), 141.77
(SiCHCH2), 144.08 (Mes o-C); EI-MS m/z 366 (M+, 58%), 190
(100%), 293 (M+ − C4H9O, 13%), 246 (M − Mes-H+, 37%); high-
resolution EI-MS for C24H34OSi m/z calcd 366.2379, found 366.2389.
1
Mes2Ge(CHCH2)Ot-Bu (18): H NMR (C6D6) δ 1.26 (s, 9 H,
OC(CH3)3), 2.09 (s, 6 H, Mes p-CH3), 2.46 (s, 12 H, Mes o-CH3),
5.64 (dd, J = 3, 20 Hz, 1 H, GeCHCH2), 5.86 (dd, J = 3, 13 Hz, 1
H, GeCHCH2), 6.72 (s, 4 H, Mes-H), 6.88 (dd, J = 13, 20 Hz, 1 H,
GeCHCH2); 13C NMR (C6D6) δ 21.03 (Mes p-CH3), 24.05 (Mes
o-CH3), 32.65 (C(CH3)3), 73.53 (OC(CH3)3), 129.60 (Mes m-CH),
130.10 (GeCHCH2), 135.55 (Mes i-C), 138.69 (Mes p-C), 142.62
(GeCHCH2), 143.43 (Mes o-C); EI-MS m/z 412 (M+, 0.5%), 385
(M+ − CHCH2, 4%), 339 (M+ − C4H9O, 100%), 311 (Mes2Ge −
H+, 24%); high-resolution EI-MS for C24H34O70Ge m/z calcd
408.1852, found 408.1857.
Addition of Excess t-BuLi to Silene 1 in Pentane. tert-
Butyllithium (1.7 M in pentane, 0.11 mL, 0.19 mmol) was added to a
solution of 5 (60 mg, 0.19 mmol) dissolved in pentane (3 mL) and
cooled in a dry ice/acetone bath. The cloudy, pale yellow solution was
allowed to warm to room temperature to give an orange solution. After
10 min at room temperature, a second portion of tert-butyllithium (1.7
M in pentane, 0.35 mL, 0.60 mmol) was added to the solution, which
was then allowed to stir at room temperature for 2 h. The color of the
solution deepened. MeOH (1 drop) was added to the reaction
mixture. The solution was washed with saturated ammonium chloride
(3 × 10 mL). The combined aqueous solution was washed with
diethyl ether (3 × 10 mL). The combined organic solution was dried
over MgSO4 and filtered. The solvent was removed under vacuum to
give a white solid (64 mg) consisting of silane 2, polysilene, and
unknown compounds. Similarly, excess t-BuLi was added to germene 4
in pentane to give a mixture of Mes2(t-Bu)GeCH2CH2t-Bu and
polygermene.
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ASSOCIATED CONTENT
■
(6) Lofas, H.; Orthaber, A.; Jahn, O. B.; Rouf, M. A.; Grigoriev, A.;
̈
̊
S
* Supporting Information
Ott, S.; Ahuja, R.; Ottosson, H. J. Phys. Chem. C 2013, 117, 10909−
1
A PDF file containing H and 13C NMR spectra of all new
10918.
compounds. The Supporting Information is available free of
charge on the ACS Publications website at DOI: 10.1021/
acs.organomet.5b00423.
̌
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AUTHOR INFORMATION
Corresponding Author
*E-mail: kbaines2@uwo.ca.
■
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Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS
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We thank the Natural Sciences and Engineering Research
Council of Canada and the University of Western Ontario for
financial support.
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