Selective synthesis of functional alkynylmono- and -trisilanes

Article abstract of DOI:10.1002/ejic.200900769

The selective synthesis of functional alkynylsllanes RC=C(SiMe ₂)_m,-X (m = 1, 3) was investigated. Monofunctionalization with or without protecting groups gave moderate to good yields of alkynyldimethylmonosilanes RC=CMe₂SiX [R = Ph, X = Cl. (1), NEt ₂ (2), OMe (3), H (4), Br (5), I (6), Cp (8), C₅H ₄Li (10), Ph (11); R = Pr, X = Ph (12)]. Compounds 4 and 8 were converted into the (alkyne)transition-metal complexes 4-Cp₂Mo ₂(CO)₄ (13) and 8-Co₂(CO)₆ (14), respectively, which were characterized by X-ray diffraction. Stepwise extension and functionalization of the silane chain starting from 1chloro-2-(diethylamino) tetramethyldisilane (Et₂NMe₂Si-SiMe₂Cl) yielded the trisilanes Ph-(SiMe₂J₃-X [X = NEt₂ (18), OMe (19), Cl (20), H (21), C=CPh (22), C=CPr (23)]. The synthesized compounds were characterized by NMR and IR spectroscopy, 4, 11, 13, and 14 also by UV/Vis spectroscopy.

Full text of DOI:10.1002/ejic.200900769

FULL PAPER
DOI: 10.1002/ejic.200900769
Selective Synthesis of Functional Alkynylmono- and -trisilanes
Florian Hoffmann,[a] Jörg Wagler,[a] and Gerhard Roewer*[a]
Keywords: Alkyne complexes / Alkynylsilanes / Cobalt / Molybdenum / Protecting groups
The selective synthesis of functional alkynylsilanes RCϵC–
(SiMe2)m–X (m = 1, 3) was investigated. Monofunctionali-
zation with or without protecting groups gave moderate to
good yields of alkynyldimethylmonosilanes RCϵCMe2SiX [R
= Ph, X = Cl (1), NEt2 (2), OMe (3), H (4), Br (5), I (6), Cp (8),
C5H4Li (10), Ph (11); R = Pr, X = Ph (12)]. Compounds 4 and 8
were converted into the (alkyne)transition-metal complexes
4·Cp2Mo2(CO)4 (13) and 8·Co2(CO)6 (14), respectively, which
were characterized by X-ray diffraction. Stepwise extension
and functionalization of the silane chain starting from 1-
chloro-2-(diethylamino)tetramethyldisilane (Et2NMe2Si–Si-
Me2Cl) yielded the trisilanes Ph–(SiMe2)3–X [X = NEt2 (18),
OMe (19), Cl (20), H (21), CϵCPh (22), CϵCPr (23)]. The
synthesized compounds were characterized by NMR and IR
spectroscopy, 4, 11, 13, and 14 also by UV/Vis spectroscopy.
Introduction
Results and Discussion
α,ω-Heterodifunctional methylsilanes A–(SiMe2)m–B are
key compounds in organosilicon chemistry. They are mostly
prepared by monofunctionalization of the corresponding
α,ω-homodifunctional silanes (Scheme 1).
Monosilanes
The first synthetic target was chlorodimethyl(phenyleth-
ynyl)silane (PhCϵCMe2SiCl, 1).[3] The preparation of this
compound by monofunctionalization of dichlorodimethyl-
silane (Me2SiCl2) with phenylethynylmagnesium or -alkali
compounds has a low selectivity: only moderate yields of
30–37% (Mg)[3–5] and 44–55% (Li, Na)[6,7] are reported.
Our own experiments with phenylethynylmagnesium bro-
mide (PhCϵCMgBr) gave 27–38% of 1 {as judged by 29Si
NMR spectroscopy; other products: dimethylbis(phenyl-
ethynyl)silane [Me2Si(CϵCPh)2] and dichlorodimethylsil-
ane (Me2SiCl2)} and thus confirmed the literature results. A
catalyzed reaction between Me2SiCl2 and phenylacetylene
(PhCϵCH) gives better yields (60–80%) but requires high-
pressure equipment and is therefore not an easily accessible
preparation method.[8] In conclusion, the monofunction-
alization of Me2SiCl2 appeared not to be the optimum syn-
thetic route to 1.
Hence, all further preparation attempts comprised the
use of protecting groups. Two routes, starting from chloro-
(diethylamino)dimethylsilane (Et2NMe2SiCl) and chlorodi-
methylsilane (HMe2SiCl), respectively, were applied
(Scheme 2).
Alkynylation of Et2NMe2SiCl, which is easily available
from Me2SiCl2 and diethylamine (Et2NH) in 81% yield,[9,10]
with PhCϵCMgBr gave (diethylamino)dimethyl(phenyl-
ethynyl)silane (PhCϵCMe2SiNEt2, 2)[11,12] in 78% yield.
Reaction of 2 with methanol[13] yielded 91% of methoxydi-
methyl(phenylethynyl)silane (PhCϵCMe2SiOMe, 3),[4,14]
which reacted with acetyl chloride (CH3COCl) to give a
90% yield of 1. The total yield was 64% based on Et2NMe2-
SiCl and 52% based on Me2SiCl2, which is still moderate
Scheme 1. Preparation of α,ω-heterodifunctional methylsilanes by
monofunctionalization.
This method works quite well for many monosilanes but
looses selectivity toward the desired product with increasing
chain length, finally approaching the statistical product dis-
tribution of 25:50:25. Eventually, this leads to separation
difficulties and diminished yields. Thus, alternative and es-
pecially more selective routes are desirable.
Our group faced this problem when we started a study
on the preparation of functional alkynylsilanes. They were
required for the synthesis of (alkynylsilyl)transition-metal
complexes,[1,2] therefore their functionalities had to include
halogen (for salt elimination), hydrogen (for oxidative ad-
dition), and cyclopentadienyl and phenyl groups (for cyclo-
pentadienyl and arene complexation). In this article we re-
port the selective synthesis of these functional alk-
ynylmono- and -trisilanes by the use of protecting groups.
[a] Institut für Anorganische Chemie, Technische Universität
Bergakademie Freiberg,
Leipziger Str. 29, 09596 Freiberg, Germany
Fax: +49-3731-39-4058
E-mail: Gerhard.Roewer@chemie.tu-freiberg.de
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.200900769.
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FULL PAPER
Instead, for 5 we applied the amino-protected and the
halogenation route (Scheme 2). Reaction of 2 with meth-
anol and subsequently excess acetyl bromide gave 5 in 71%
yield based on Et2NMe2SiCl and 58% based on Me2SiCl2.
The bromination of 4 was examined with elemental bro-
mine (Br2), hydrogen bromide (HBr), tetrabromomethane
(CBr4), and N-bromosuccinimide (NBS), with NBS giving
the best results.[16] The other reagents did not react or led
to side products. Thus, 5 was obtained in 70% yield based
on 4 and 52% based on HMe2SiCl. In conclusion, both
routes gave comparable results. The somewhat lower yield
of the bromination route is balanced by the higher purity
of the product (98% vs. 95% by NMR spectroscopy).
Because of the difficult handling of acetyl iodide the
amino-protected route was not applicable to the synthesis
of 6. Additionally, the iodination of 4 with elemental iodine
proved to be too slow to be of preparative usefulness. Fi-
nally, only halide exchange of 1 with lithium iodide (LiI)
in dichloromethane was successful (Scheme 2). The hitherto
unknown iodosilane 6 was thus synthesized in 79% yield
with 90% purity (the balance is unreacted 1).
A problem in proving the identity of 5 and 6 was their
extreme hydrolytic sensitivity and corrosivity. For this
reason no satisfactory elemental analyses could be ob-
tained. Furthermore, by GC-MS analysis only the corre-
sponding disiloxane 1,3-bis(phenylethynyl)-1,1,3,3-tet-
ramethyldisiloxane [(PhCϵCMe2Si)2O, 7][18,19] was ob-
served. For comparison, a sample of 7 was prepared by hy-
drolysis of 5 in diethyl ether in 98% yield. Analysis of the
29Si NMR and IR spectra of 5, 6, and 7 finally proved that
the reaction products supposed to be 5 and 6 were not the
disiloxane 7. This was supported by their markedly higher
densities (1.4–1.5 g/cm3 vs. 1.0 g/cm3) and their chemical
behavior (on contact with air and humidity brown or pink
color, respectively, and fuming, whereas 7 was inert to air
and moisture). In addition, their 29Si NMR signals showed
an upfield shift of about 5 ppm or 25–30 ppm from that of
1, which is characteristic for a replacement of Cl by Br or
I, respectively.[20,21] We therefore conclude that the obtained
substances are the anticipated bromo- and iodosilanes 5
and 6.
Scheme 2. Syntheses of alkynylsilanes 1–6 (R = PhCϵC).
and comparable to the use of alkynylalkali salts but dis-
tinctly better than by the unprotected Grignard route.
The reaction of PhCϵCMgBr with HMe2SiCl gave di-
methyl(phenylethynyl)silane (PhCϵCMe2SiH, 4)[15] in 74%
yield. Compound 4, which is also commercially available
(Fluka), is both an intermediate for the preparation of 1
and a target molecule itself (for oxidative addition). The
chlorination of 4 to obtain 1 was examined with hydrogen
chloride (HCl), tetrachloromethane [CCl4; with and with-
out aluminum chloride (AlCl3)], ferric chloride (FeCl3), sul-
furyl chloride (SO2Cl2), and phosphorus pentachloride
(PCl5), with the lattermost giving the best results.[16] The
other reagents did not react or led to side products. The
preparation of 1 was thus easily accomplished with PCl5 in
85% yield. The total yield based on HMe2SiCl was 63%.
In conclusion the most effective (but also most expens-
ive) preparation method for 1 is the chlorination of com-
mercially available 4 with PCl5. Nevertheless, functionaliza-
tion with the use of a protecting group is a competitive
route because of its lower cost (cf. Table 1).
Silyl bromides and iodides are better electrophiles than
silyl chlorides and thus facilitate the preparation of silyl
transition-metal complexes. Hence, feasible syntheses of
bromodimethyl(phenylethynyl)silane
(PhCϵCMe2SiBr,
5)[17] and iododimethyl(phenylethynyl)silane (PhCϵCMe2-
For the hitherto unknown cyclopentadienyl-function-
SiI, 6)[16] were desirable. As a result of the experiments on alized alkynylsilane cyclopentadienyldimethyl(phenyleth-
the preparation of 1, synthesis routes starting from dibro- ynyl)silane (CpSiMe2CϵCPh, 8a–c),[22] two alternative syn-
mo- and diiododimethylsilane were suspended from the be- thetic pathways can be considered (Scheme 3). These are
ginning.
the reaction of 1 with sodium cyclopentadienide (NaCp)
Table 1. Comparison of preparation methods for 1.
Starting silane
Reagent
Steps
Yield
Remark
[3–5]
Me2SiCl2
Me2SiCl2
Me2SiCl2
Me2SiCl2
Me2SiCl2
Me2SiHCl
PhCϵCMe2SiH
PhCϵCMgBr
PhCϵCMgBr
PhCϵCLi/Na
PhCϵCH
PhCϵCMgBr
(1) PhCϵCMgBr, (2) PCl5
PCl5
1
1
1
1
4
2
1
30–37%
27–38%
44–55%
60–80%
52%
63%
85%
yield by NMR, Cl/Br exchange
[6,7]
autoclave[8]
amino route
costly silane
costly silane
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Selective Synthesis of Functional Alkynylmono- and -trisilanes
and the reaction of chloro(cyclopentadienyl)dimethylsilane scopic data of 13 were in agreement with the anticipated
(CpMe2SiCl, 9a–c),[23] which is easily available from Me2- structure. It was also supported by comparison with the
SiCl2 and NaCp, with PhCϵCMgBr. Both routes were ex- 95Mo NMR, IR, and UV/Vis data of the analogous tolane
[34]
amined and gave comparable total yields of about 30% complex PhCϵCPh·Cp2Mo2(CO)4
as well as literature
based on Me2SiCl2. However, because of the above- data[35–37] and finally confirmed by single-crystal X-ray dif-
described difficulties in the preparation of 1, only the sec- fraction analysis (Figure 1).
ond route is recommended.
Scheme 4. Synthesis of complex 13.
Scheme 3. Syntheses of alkynylsilanes 8–12.
Cyclopentadienylsilane 8 was found to be unstable on
prolonged storage giving a compound that is likely to be a
Diels–Alder product. The reaction is slow (days–weeks) and
can be reversed by heating to 150 °C for 1 h or distillation
in vacuo. Thus, freshly prepared 8 should be immediately
used or stored at –20 °C or below. It can also be converted
to its stable lithium salt LiC5H4SiMe2CϵCPh (10) in 93%
yield by action of n-butyllithium (nBuLi) (Scheme 3).
The target arylsilanes were chosen to be dimethyl(phen-
yl)(phenylethynyl)silane (PhMe2SiCϵCPh, 11)[24] and the
hitherto unknown dimethyl(pent-1-yn-1-yl)phenylsilane
(PhMe2SiCϵCPr, 12). Analogously to 8, there are two pos-
sible synthetic routes: via 1 or its propyl analogue, respec-
tively, or via PhMe2SiCl. Because of the easy availability of
the latter reagent (also commercially), the second route was
used throughout (Scheme 3). Compounds 11 and 12 were
thus obtained in about 90% yield.
Figure 1. Molecular structure of 13 (ORTEP diagram with 20%
ellipsoids, hydrogen atoms omitted for clarity, only the predomi-
nant part of the disordered structure is depicted). Selected bond
lengths [pm]: Mo11–Mo21 293.38(4), Mo(11)–C(211) 211.1(3),
Mo(11)–C(221) 218.0(3), Mo(21)–C(211) 220.5(3), Mo(21)–C(221)
217.6(3), C(211)–C(221) 134.7(4), Si(11)–C(221) 180.2(3), C(201)–
C(211) 146.6(4).
Alkyne Complexes
In order to synthesize solid derivatives for structural
characterization, especially of the hitherto unknown silane
Complex 13 crystallizes in the monoclinic space group
8, complexation of the alkyne triple bonds of 1, 4, 8, 11, P21/c without solvent. The packing of the molecules in the
and 12 with transition-metal moieties was attempted. crystal consists of head-to-tail chains of molecules, which
Since complexes of functional alkynylsilanes with octa- are stacked in a parallel manner. Thirteen percent of the
carbonyldicobalt [Co2(CO)8] are already well molecules exhibit a different orientation in statistical distri-
known,[16,25–33] we chose the tetracarbonyldicyclopentadi- bution. This fact handicaps the evaluation of the structural
enyldimolybdenum fragment Cp2Mo2(CO)4 for 1 and 4. parameters. Notwithstanding the disorder, selected bond
However, after reaction of 1 with Cp2Mo2(CO)4 only its lengths are listed in the caption of Figure 1. The former
decomposition product hexacarbonyldicyclopentadienyldi- alkyne triple bond exhibits a C–C distance of 135 pm,
molybdenum [Cp2Mo2(CO)6] was obtained. Nevertheless, which corresponds to a double bond. The situation of the
with 4 the expected {µ-dimethyl[(1,2-η:1,2-η)-phenyleth- carbonyl ligands resembles the one already described in the
ynyl]silane}bis[dicarbonyl(η5-cyclopentadienyl)molybdenum- literature for alkyne complexes of Cp2Mo2(CO)4: one CO
(I)](Mo–Mo) [PhCϵCSiMe2H·Cp2Mo2(CO)4, 13] could be group (C071–O21) is markedly bent with the C atom dis-
isolated in 42% yield as dark red crystals which were air- placed toward the opposite Mo atom (Mo21), two ligands
stable for at least several days (Scheme 4). The spectro- (C061–O11, C131–O31) are slightly bent, and only one
Eur. J. Inorg. Chem. 2010, 1133–1142
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F. Hoffmann, J. Wagler, G. Roewer
FULL PAPER
carbonyl ligand (C141–O41) is linear. This was interpreted
Complex 14a crystallizes solvent-free in the monoclinic
as a transition situation between terminal and bridging car- space group Cc. The molecules form double layers with the
bonyl ligands.[38,39]
carbonyl ligands inside and the organic groups outside the
In order to characterize compound 8 structurally, it was layers. Selected bond lengths are listed in the caption of
converted into {µ-cyclopentadienyldimethyl[(1,2-η:1,2-η)- Figure 2. The Co2C2 tetrahedron is somewhat distorted,
phenylethynyl]silane}bis[tricarbonylcobalt(0)](Co–Co) probably because of the steric demand of the silyl group.
(14a–c)[22] by reaction with Co2(CO)8 (Scheme 5). This For the same reason the two Co(CO)3 moieties, which are
complex was isolated as dark brown crystals (air-stable for eclipsed in complexes of symmetrical alkynes, are twisted
at least some hours) in 39% yield. At first, the situation against each other. The length of the former triple bond is
seemed to be troubled by the existence of three isomers each 135 pm and thus indicates a double-bond character in this
for the starting silane and the product, but spectral proper- complex. Interestingly, the phenyl and the silyl substituent
ties and single-crystal X-ray analysis showed the obtained are bent away from the axis of the former triple bond at
solid to be solely the cyclopenta-2,4-dien-1-yl isomer 14a different angles: 37.9(2)° for the phenyl and 28.9(2)° for the
1
(Figure 2). However, broadened H and 13C NMR signals silyl group. The cyclopentadienyl ring is almost planar. The
for the cyclopentadienyl group and small additional peaks C–C single bond between the two double bonds is markedly
indicated that isomerization processes occurred in solution. shortened in comparison with the average value of cyclo-
The 59Co NMR, IR, and UV/Vis data were typical for al- pentane (143.6 vs. 148 pm[45]), whereas the lengths of the
kyne Co2(CO)6 complexes.[40–44]
two other single bonds are not reduced. This points to con-
jugation and delocalization of the two double bonds.
In order to obtain (OC)Mo(alkyne)3-type[46–52] deriva-
tives of 11 and 12, these silanes were refluxed with tris(ace-
tonitrile)tricarbonylmolybdenum [Mo(CO)3(MeCN)3] in
ethanol,[46,47] but apart from decomposition of the starting
molybdenum complex no reaction occurred.
Complexes 13 and 14a contain reactive groups that allow
for further complexation. Hence, 13 was mixed with
Co2(CO)8 in toluene to examine the reactivity of the Si–H
bond, but it did not react, neither at room temperature
(1 week) nor at 50 °C (24 h). This is in contrast to hexacar-
bonyldicobalt complexes of alkynylhydrosilanes which react
easily with Co2(CO)8 to form trinuclear cobalt com-
pounds.[25–31] Complex 14a, instead, was expected to react
at the Cp ring (Scheme 5), and indeed on addition of
Co2(CO)8 a gas evolution occurred. Workup of the reaction
mixture gave a dark brown oil in quantitative yield whose
1H, 13C, and 29Si NMR spectra suggested it to be the antici-
pated trinuclear cobalt complex {13C NMR: δ = +204.5
[C5H4Co(CO)2], +199.7 [Co2(CO)6·CϵC] ppm; 29Si NMR:
δ = –8.3 ppm}. Unfortunately, no crystals for further char-
acterization could be obtained. The lithiation of the cyclo-
pentadienyl ring in 14a was attempted by addition of nBuLi
in hexane, yet the only identifiable product was LiCo-
(CO)4, thus hinting at decomposition.
Scheme 5. Synthesis of complex 14 and complexation with
Co2(CO)8.
Trisilanes
Functional alkynyl trisilanes were synthesized by exten-
sion of the silicon chain of a chlorodisilane with a silyllith-
ium compound. Thus, the product of the reaction of di-
methyl(phenyl)silyllithium (PhMe2SiLi) and Et2NMe2Si–Si-
Me2Cl was identified by 29Si NMR spectroscopy as the an-
ticipated 1-(diethylamino)-1,1,2,2,3,3-hexamethyl-3-phenyl-
trisilane (Et2NMe2Si–SiMe2–SiMe2Ph, 18) (Scheme 6).
Subsequent reaction with methanol afforded 1-methoxy-
Figure 2. Molecular structure of 14a (ORTEP diagram with 50%
ellipsoids, hydrogen atoms omitted for clarity). Selected bond
lengths [pm]: Co(1)–Co(2) 246.28(3), Co(1)–C(13) 197.26(18),
Co(1)–C(14) 200.45(19), Co(2)–C(13) 197.37(17), Co(2)–C(14)
199.90(18), C(13)–C(14) 134.6(3), C(12)–C(13) 146.4(3), Si(1)–
C(14) 185.1(2), Si(1)–C(17) 191.0(2), C(17)–C(18) 148.6(3), C(17)–
C(21) 148.8(3), C(18)–C(19) 134.8(3), C(19)–C(20) 143.6(4), C(20)–
C(21) 135.1(3).
1,1,2,2,3,3-hexamethyl-3-phenyltrisilane
(MeOMe2Si–Si-
Me2–SiMe2Ph, 19), which reacted with CH3COCl to 1-
chloro-1,1,2,2,3,3-hexamethyl-3-phenyltrisilane (ClMe2Si–
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Selective Synthesis of Functional Alkynylmono- and -trisilanes
SiMe2–SiMe2Ph, 20)[53,54] in 92% crude yield. Hydrode- 29Si NMR, 13C NMR, and IR Spectroscopy
halogenation of 20 with lithium aluminum hydride (Li-
The 29Si NMR spectroscopic data of the synthesized
compounds are listed in Table 2. All signals appeared in the
expected ranges. The 13C NMR shifts and IR data of the
RCϵCSi moieties are listed in Table 3. Both depend on the
substituents of the silicon atom and on the organic substitu-
ent R. As expected the carbon atom neighboring the silicon
atom is more shielded than the other carbon atom (assign-
ment proved by 29Si satellites). Surprisingly, its chemical
shift is also markedly influenced by the organic group R,
whereas the shift of the second carbon signal does not
change with R.
AlH4)
gave
1,1,2,2,3,3-hexamethyl-1-phenyltrisilane
(HMe2Si–SiMe2–SiMe2Ph, 21) in 91% crude yield, whereas
alkynylation with PhCϵCMgBr or PrCϵCMgBr gave
1,1,2,2,3,3-hexamethyl-1-phenyl-3-(phenylethynyl)trisilane
(PhCϵCMe2Si–SiMe2–SiMe2Ph, 22) and 1,1,2,2,3,3-hexa-
methyl-1-(pent-1-yn-1-yl)-3-phenyltrisilane (PrCϵCMe2Si–
SiMe2–SiMe2Ph, 23) (23: 99% crude yield), respectively.
Furthermore, it is conspicuous that the 13C NMR shifts
of the alkyne carbon atoms only slightly alter on complex-
ation of the triple bond. This phenomenon has been ob-
served several times in the literature.[38,40,55–67] Considering
the correlation between 13C NMR chemical shift and hy-
bridization,[68] it indicates an intermediate state between sp2
and sp3 hybridization corresponding to a C–C bond order
between 2 and 1. This is supported by the X-ray and IR
data of 13 and 14a, which, in contrast to the Lewis formu-
lae (C–C single bond, Schemes 4 and 5), suggest a C=C
double bond in these complexes.
Scheme 6. Syntheses of 1,3-heterodifunctional trisilanes 18–23.
Table 2. 29Si NMR spectroscopic data of compounds 1–14 and 18–23.
Compound
δ [ppm]
Compound
δ [ppm]
PhCϵCMe2SiCl (1)
PhCϵCMe2SiNEt2 (2)
PhCϵCMe2SiOMe (3)
PhCϵCMe2SiH (4)
PhCϵCMe2SiBr (5)
PhCϵCMe2SiI (6)
(PhCϵCMe2Si)2O (7)
PhCϵCMe2SiCp (8a)
8b
+0.4
–17.6
–6.2
–37.4
–6.7
–29.5
–16.5
–18.6
–28.3
–28.7
+25.4
+14.7
+15.0
PhCϵCMe2SiC5H4Li (10)
PhCϵCMe2SiPh (11)
PrCϵCMe2SiPh (12)
4·Cp2Mo2(CO)4 (13)
8a·Co2(CO)6 (14a)
14b
–30.4
–21.7
–22.9
–9.5
–0.6
–10.6
–10.8
–0.6/–51.0/–19.5
+19.3/–50.4/–18.8
+26.3/–45.6/–19.2
–36.3/–47.4/–18.3
–34.0/–47.2/–18.4
–35.2/–47.6/–18.4
14c
Et2N–(SiMe2)3–Ph (18)
MeO–(SiMe2)3–Ph (19)
Cl–(SiMe2)3–Ph (20)
H–(SiMe2)3–Ph (21)
PhCϵC–(SiMe2)3–Ph (22)
PrCϵC–(SiMe2)3–Ph (23)
8c
CpMe2SiCl (9a)
9b
9c
Table 3. Selected 13C NMR and IR spectroscopic data of the herein reported alkynes.
Compound
δ(CϵC–Si) [ppm]
δ(CϵC–Si) [ppm]
ν(CϵC) [cm–1]
PhCϵCMe2SiCl (1)
PhCϵCMe2SiNEt2 (2)
PhCϵCMe2SiOMe (3)
PhCϵCMe2SiH (4)
107.0
103.8
105.4
106.4
107.5
108.2
104.2
105.8
105.7
106.8
107.6
109.4
109.9
111.0
106.6
89.8
94.2
91.2
91.1
89.2
89.0
93.3
92.8
98.1
92.0
93.4
82.4
83.2
2161[a]
2155[a]
2157[a]
2158[a]
2162[a]
2160[a]
2161[a]
2156[a]
2153[b]
2156[a]
2150[a]
2173[a]
2166[a]
1512[d]
1579[d]
PhCϵCMe2SiBr (5)
PhCϵCMe2SiI (6)
(PhCϵCMe2Si)2O (7)
PhCϵCMe2SiCp (8)
PhCϵCMe2SiC5H4Li (10)
PhCϵCMe2SiPh (11)
PhCϵC–(SiMe2)3–Ph (22)
PrCϵCMe2SiPh (12)
PrCϵC–(SiMe2)3–Ph (23)
4·Cp2Mo2(CO)4 (13)
8a·Co2(CO)6 (14a)
[c]
–
78.8
[a] Neat liquid. [b] Solution in THF. [c] Signal hidden. [d] Solid in KBr.
Eur. J. Inorg. Chem. 2010, 1133–1142
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1137

F. Hoffmann, J. Wagler, G. Roewer
FULL PAPER
ORTEP32.[87] CCDC-642200 (13) and CCDC-642204 (14a) contain
the supplementary crystallographic data for this paper. These data
can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Conclusions
Functional alkynyldimethylmonosilanes RCϵCMe2SiX
are obtained in acceptable yields by monofunctionalization
with the aid of protecting groups, whereas functional 1-
phenyltrisilanes Ph–(SiMe2)3–X can be synthesized by ex-
tension of a protected disilane chain with dimethylphenyl-
silyllithium (PhMe2SiLi). Both methods should also be
applicable to the synthesis of heterodifunctional disilanes.
Alkynyldimethylmonosilanes
Chlorodimethyl(phenylethynyl)silane (PhCϵCMe2SiCl, 1). (a) From
Methoxydimethyl(phenylethynyl)silane (3): A solution of silane 3
(13.40 g, 70.4 mmol) in hexane (20 mL) was cooled to 0 °C, and a
solution of acetyl chloride (10.0 mL, 11.0 g, 140.8 mmol) in hexane
(10 mL) was added dropwise. After warming up and stirring at
room temperature for 16 d, the volatiles were evaporated in vacuo,
and the residue was distilled under reduced pressure furnishing a
colorless oil. Yield: 12.28 g (63.1 mmol, 90%). B.p. 70–71 °C
(0.3 kPa). C10H11ClSi (194.737 g/mol). Spectral data: see (b). (b)
From Dimethyl(phenylethynyl)silane (4): Silane 4 (6.67 g, 7.2 mL,
41.6 mmol) was dissolved in THF (50 mL), and PCl5 (95%) (9.12 g,
41.6 mmol) was added in small portions at room temperature with
stirring. The mixture became warm, and the PCl5 dissolved within
a few hours. After cooling to room temperature, the solvent was
removed in vacuo. The remaining oil was distilled under reduced
pressure yielding a colorless oil. Yield: 6.87 g (35.3 mmol, 85%).
B.p. 58–63 °C (0.2 kPa). Density: 1.06 g/mL. C10H11ClSi
(194.737 g/mol). 1H NMR (400.1 MHz, CDCl3, 22 °C): δ = 7.49
(m, 2 H, Phortho), 7.33 (m, 3 H, Phmeta + para), 0.64 (s, 1JHC = 122.2,
2JHSi = 7.5 Hz, 6 H, SiMe2) ppm. 13C NMR (100.6 MHz, CDCl3,
22 °C): δ = 132.2 (s, 2 C, Phortho), 129.4 (s, 1 C, Phpara), 128.3 (s, 2
C, Phmeta), 121.9 (s, 1 C, Phipso), 107.0 (s, 2JCSi = 21 Hz, 1 C, CϵC–
Experimental Section
General Remarks:[71] All operations were carried out under dry
purified argon by using Schlenk or glovebox techniques. Solvents
were dried by distillation from the following reagents and stored
under argon until use: Na/benzophenone-ketyl [tetrahydrofuran
(THF), diethyl ether (Et2O), benzene, toluene, hexane], CaH2
[CDCl3, dichloromethane (CH2Cl2)], LiAlH4 (pentane), magne-
sium (methanol), Na/K alloy (C6D6). Chlorosilanes were distilled
and stored under argon before use. Acetyl chloride and acetyl bro-
mide were distilled from iron powder under argon and then stored
under argon. The following chemicals were prepared according to
known procedures: Et2NMe2SiCl,[9,10] Et2NMe2Si–SiMe2Cl,[10,72]
NaCp,[73] PhMe2SiCl,[74a] Cp2Mo2(CO)4,[75a] Cp2Mo2(CO)4·
PhCϵCPh,[76] Co2(CO)6·PhCϵCPh,[77] K3[Co(CN)6].[75b] Pow-
dered anhydrous lithium iodide (LiI) was prepared by drying the
diethyl ether solvate LiI·Et2O at 100 °C in vacuo for 2 h. All other
chemicals were laboratory stock or purchased from the sources
given below and used as received: Acros (2.5  nBuLi in hexane,
NBS), Aldrich (PCl5), Fluka [Co2(CO)8, Na2SO4, NH4Cl,
PhCϵCH], Merck (acetyl bromide, acetyl chloride, lithium, Me2-
SiHCl, Me2SiCl2, PrCϵCH). Densities were determined by weigh-
ing a measured volume of liquid. Melting points were determined
in sealed capillaries (under argon) and between thin glass plates (in
air) with a Boëtius-type heating microscope. The heating rate was
about 4 K/min. Elemental analyses were performed in duplicate
with a CHN-O-Rapid (Heraeus) and the values averaged. The mass
spectra were recorded with an HP 5890 Series II/HP 5989 A/HP
5971 Series (Hewlett–Packard). NMR spectra were measured with
a DPX 400 Avance (Bruker) with tetramethylsilane Me4Si (TMS)
1
Si), 89.8 (s, 1 C, CϵC–Si), 3.8 (s, JCSi = 66 Hz, 2 C, SiMe2) ppm.
29Si NMR (79.5 MHz, CDCl3, 22 °C): δ = +0.4 [s (1H-coupled:
2
1
1
sept), JSiH = 7.5, JSiC(Me) = 65 (2 C), JSiC(CϵC) = 103 (1 C),
2JSiC(CϵC) = 21 Hz (1 C)] ppm.
Bromodimethyl(phenylethynyl)silane (PhCϵCMe2SiBr, 5). (a) From
Chloro(diethylamino)dimethylsilane: A solution of Et2NMe2SiCl
(5 mL, 4.59 g, 27.7 mmol) in Et2O (5 mL) was added to a solution
of PhCϵCMgBr in Et2O [prepared according to standard pro-
cedures[88] from Mg (690 mg, 28.4 mmol), 1,2-dibromoethane
(three drops), EtBr (3 mL, 4.38 g, 40.2 mmol), PhCϵCH (3.2 mL,
2.98 g, 29.2 mmol), and Et2O (60 mL)] at room temperature. The
resulting mixture was refluxed for 2 h and then concentrated in
vacuo. The residue was extracted with hexane in small portions. To
the combined filtrates methanol (1.5 mL, 1.19 g, 37.0 mmol) was
added dropwise at room temperature whereupon a white precipitate
formed. After stirring at room temperature for 6 h, the solvent was
evaporated in vacuo and the residue extracted with hexane (20 mL).
The resulting hexane solution was cooled to 0 °C, and acetyl bro-
mide (6 mL, 6.35 g, 80.9 mmol) was added dropwise whereupon
again a white precipitate deposited. After warming up and stirring
at room temperature for 2 d, the volatiles were evaporated in vacuo,
and the liquid residue was distilled under reduced pressure furnish-
ing a pale yellow oil. It turned brownish yellow after some time
even under argon and fumed on contact with air. Yield: 4.71 g
(19.7 mmol, 71%). B.p. 120–125 °C (1.5 kPa, ref.[17] 124 °C/
1.3 kPa). C10H11BrSi (239.188 g/mol). Spectral data: see (b). (b)
From Dimethyl(phenylethynyl)silane (4): A solution of 4 (4.6 mL,
4.28 g, 26.7 mmol) in CH2Cl2 (40 mL) was cooled to 0 °C in an ice
bath. Then NBS (10.26 g, 57.6 mmol) was added slowly in small
portions with stirring. At first it dissolved with effervescence, and
the solution became yellow. Later on dissolution was incomplete,
and the mixture gradually turned dark red brown. After stirring at
0 °C for 4 h and warming up to room temperature, the volatiles
were removed in vacuo. The remaining black solid residue was ex-
tracted with hexane (70 mL) furnishing a red violet solution and a
as internal standard for H, 13C, and 29Si. The external standards
1
for 14N, 59Co, and 95Mo were nitromethane (CH3NO2), 0.1 
K3[Co(CN)6] solution in D2O, and 1  alkaline Na2MoO4 solution
in H2O, respectively.[78] IR spectra were recorded with a Specord
M 82 (VEB Carl Zeiss JENA) or a Nicolet 510 spectrometer. Li-
quid samples were prepared between NaCl plates, whereas solids
were examined in KBr disks. UV/Vis spectra were recorded with a
Specord S 100 (Analytik Jena AG) in the range 190–1000 nm. All
reactions were monitored by NMR or IR spectroscopy. Assign-
ments were made by comparison of the spectra with each other and
with literature data.[21,69,70,78–85] Missing NMR peaks are hidden by
other peaks, mostly by those of the solvent. The crystal structures
of 13 and 14a were determined with a Bruker-Nonius X8 dif-
fractometer with an APEX2-CCD detector using Mo-Kα radiation.
Suitable crystals were grown from [D6]benzene/hexane at room
temperature (13) or by slow warming of a hexane solution from
–78 °C to –20 °C (14a). The structures were solved by direct meth-
ods (SHELXS-97)[86a] and full-matrix least squares refined on F2
(SHELXL-97).[86b] Non-H atoms were refined anisotropically,
whereas H atoms were considered in idealized positions (riding
model). A population of 13% of the molecules of 13 were found
disordered. Of these only the molybdenum and silicon atoms were
refined anisotropically. Graphical representations were created with
1138
www.eurjic.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 1133–1142

Selective Synthesis of Functional Alkynylmono- and -trisilanes
dark brown solid, which was identified by NMR as succinimide.
The extract was then concentrated in vacuo, and the remaining
oil was distilled under reduced pressure to yield a colorless liquid
containing a small amount of a white precipitate supposed to be
co-sublimed succinimide. Yield: 4.46 g (18.6 mmol, 70%). B.p. 106–
110 °C (0.7 kPa). Density: 1.4 g/mL (ref.[17] 1.343 g/mL).
∆ν1/2 = 4 Hz, 2 C, Phmeta), 122.9 (s, ∆ν1/2 = 6 Hz, 1 C, Phipso), 105.7
(s, ∆ν1/2 = 4 Hz, 1 C, CϵC–Si), 92.4 (s, ∆ν1/2 = 3 Hz, 1 C, CϵC–
Si), 51.0 (br. s, ∆ν1/2 = 13 Hz, 1 C, SiCHCp), –3.0 (s, ∆ν1/2 = 4, 1JCSi
= 59 Hz, 2 C, SiMe2) ppm (8a); δ = 143.4 (s, 1 C, CHCp), 138.7 (s,
1 C, CHCp), 132.9 (s, 1 C, SiCCp), 132.0 (s, 2 C, Phortho), 128.5 (s,
1 C, CHCp), 128.2 (s, 2 C, Phmeta), 123.2 (s, 1 C, Phipso), 105.8 (s, 1
C10H11BrSi (239.188 g/mol). 1H NMR (400.1 MHz, CDCl3, 22 °C): C, CϵC–Si), 92.8 (s, 1 C, CϵC–Si), 45.3 (s, 1 C, CH2), –0.6 (s, 2
1
δ = 7.49 (m, 2 H, Phortho), 7.31 (m, 3 H, Phmeta + para), 0.79 (s, JHC
C, SiMe2) ppm (8b); δ = 44.0 (s, 1 C, CH2), –1.1 (s, 2 C, SiMe2) ppm
2
= 122.6, JHSi = 7.5 Hz, 6 H, SiMe2) ppm. 13C NMR (100.6 MHz,
(8c). 29Si NMR (79.5 MHz, CDCl3, 22 °C): δ = –18.6 [s, 1JSiC(sp3)
=
CDCl3, 22 °C): δ = 132.1 (s, 2 C, Phortho), 129.4 (s, 1 C, Phpara), 59 (3 C), 1JSiC(CϵC) = 87 (1 C), 2JSiC(CϵC) = 16 Hz (1 C), 8a], –28.3
2
1
1
1
128.3 (s, 2 C, Phmeta), 121.7 (s, 1 C, Phipso), 107.5 (s, JCSi = 20 Hz, [s, JSiC(Me) = 58 (2 C), JSiC(Cp) = 78 (1 C), JSiC(CϵC) = 87 (1 C),
1
1
1 C, CϵC–Si), 89.2 (s, JCSi = 101 Hz, 1 C, CϵC–Si), 4.6 (s, JCSi
2JSiC(CϵC) = 16 Hz (1 C), 8b], –28.7 (s, 8c) ppm.
= 64 Hz, 2 C, SiMe2) ppm. 29Si NMR (79.5 MHz, CDCl3, 22 °C):
δ = –6.7 [s, JSiC(Me) = 64 (2 C), JSiC(CϵC) = 101 (1 C), JSiC(CϵC)
Lithium [Dimethyl(phenylethynyl)silyl]cyclopentadienide (PhCϵ
CMe2SiC5H4Li, 10): A solution of silane 8 (5.19 g, 23.1 mmol) in
pentane (50 mL) was cooled to 0 °C. On adding 2.5  nBuLi in
hexane (10 mL, 25 mmol, diluted with 10 mL pentane) a white so-
lid precipitated. After warming up to room temperature, stirring
was continued for 3 h. The solid was then filtered off, washed with
pentane, and dried in vacuo. Complex 10 is an air-sensitive white
powder, which is well soluble in THF. Yield: 4.98 g (21.6 mmol,
93%). M.p. 150 °C (dec.). C15H15LiSi (230.312 g/mol): calcd. C
78.23, H 6.57; found C 77.10, H 6.90. 1H NMR (400.1 MHz, 1.2 
in THF, 22 °C): δ = 7.33 (m, 2 H, Phortho), 7.19 (m, 3 H,
Phmeta + para), 5.91 (m/br, 2 H, C5H4), 5.77 (br. m, 2 H, C5H4), 0.34
1
1
2
= 20 Hz (1 C)] ppm.
Iododimethyl(phenylethynyl)silane (PhCϵCMe2SiI, 6): Powdered
anhydrous LiI (6.13 g, 45.8 mmol) was placed in a Schlenk tube,
and silane 1 (6.5 mL, 6.70 g, 34.4 mmol) dissolved in CH2Cl2
(40 mL) was added at room temperature. A yellowish suspension
formed, which gradually turned brownish and then violet. After
stirring at room temperature for 2 d, the mixture was filtered and
the residue washed with CH2Cl2. From the combined filtrate and
washings the volatiles were removed in vacuo. The remaining liquid
was distilled under reduced pressure furnishing a colorless to pale
pink oil. It fumed and turned bright pink on contact with air.
Yield: 7.77 g (27.2 mmol, 79%). B.p. 110–115 °C (0.6 kPa). Den-
sity: 1.5 g/mL. C10H11ISi (286.184 g/mol). 1H NMR (400.1 MHz,
CDCl3, 22 °C): δ = 7.47 (m, 2 H, Phortho), 7.30 (m, 3 H,
1
(s, JHC = 119.3 Hz, 6 H, SiMe2) ppm. 13C NMR (100.6 MHz,
1.2  in THF, 22 °C): δ = 132.0 (s, 2 C, Phortho), 128.7 (s, 2 C,
Phmeta), 128.3 (s, 1 C, Phpara), 125.1 (s, 1 C, Phipso), 112.4 (s, 2 C,
CHCp), 107.6 (s, 2 C, CHCp), 105.7 (s, 1 C, CϵC–Si), 103.9 (s, 1 C,
1
2
C
Cp), 98.1 (s, 1 C, CϵC–Si), 1.3 (s, 1JCSi = 55 Hz, 2 C, SiMe2) ppm.
Phmeta + para), 0.99 (s, JHC = 123.3, JHSi = 7.7 Hz, 6 H, SiMe2)
ppm. 13C NMR (100.6 MHz, CDCl3, 22 °C): δ = 132.1 (s, 2 C,
Phortho), 129.4 (s, 1 C, Phpara), 128.2 (s, 2 C, Phmeta), 121.6 (s, 1 C,
1
29Si NMR (79.5 MHz, 1.2  in THF, 22 °C): δ = –30.4 [s, JSiC(Me)
= 56 (2 C), JSiC(C5H4) = 80 (1 C), JSiC(CϵC) = 88 (1 C), 2JSiC(CϵC)
1
1
2
1
Phipso), 108.2 (s, JCSi = 20 Hz, 1 C, CϵC–Si), 89.0 (s, JCSi
=
= 15 Hz (1 C)] ppm.
99 Hz, 1 C, CϵC–Si), 5.8 (s, JCSi = 61 Hz, 2 C, SiMe2) ppm. 29Si
1
Dimethyl(pent-1-yn-1-yl)phenylsilane (PrCϵCMe2SiPh, 12):
solution of PhMe2SiCl (8.0 mL, 8.64 g, 50.6 mmol) in Et2O
(17 mL) was added at room temperature to solution of
A
NMR (79.5 MHz, CDCl3, 22 °C): δ = –29.5 [s, 1JSiC(Me) = 62 (2 C),
1JSiC(CϵC) = 99 (1 C), JSiC(CϵC) = 19 Hz (1 C)] ppm.
2
a
Cyclopentadienyldimethyl(phenylethynyl)silane (PhCϵCMe2SiCp,
8a–c): A solution of PhCϵCMgBr in Et2O [prepared according to
standard procedures[88] from Mg (1.455 g, 59.9 mmol), 1,2-dibro-
moethane (50 µL), EtBr (4.7 mL, 6.87 g, 63.0 mmol), PhCϵCH
(6.5 mL, 6.05 g, 59.2 mmol), and Et2O (120 mL)] was added drop-
wise with stirring at room temperature to a solution of freshly dis-
tilled 9a–c (7.56 g, 47.6 mmol) in Et2O (60 mL). After stirring over-
night, the mixture was heated to reflux for 14 h. The solution was
then cautiously hydrolyzed with 2  NH4Cl solution, washed with
water, and dried with Na2SO4. After evaporation of the Et2O in
vacuo, the residual oil was distilled under reduced pressure. The
small first fraction up to 110 °C was discarded. The main fraction
contained the product, which was obtained as a light yellow oil.
According to its NMR spectrum it consisted of the three isomers
of 8 (ca. 75% 8a, ca. 25% 8b, traces 8c).[89] Yield: 6.82 g
(30.4 mmol, 64%). B.p. 110–120 °C (0.2–0.3 kPa). C15H16Si
(224.379 g/mol): calcd. C 80.29, H 7.19; found C 81.21, H 7.41. 1H
NMR (400.1 MHz, CDCl3, 22 °C): δ = 7.48 (m, 2 H, Phortho), 7.31
(m, 3 H, Phmeta + para), 6.67 (br., ∆ν1/2 = 11 Hz, 2 H, CHCp), 6.60
(br., ∆ν1/2 = 15 Hz, 2 H, CHCp), 3.58 (br., ∆ν1/2 = 13 Hz, 1 H,
PrCϵCMgBr in Et2O [prepared according to standard pro-
cedures[88] from Mg (1.44 g, 59.2 mmol), 1,2-dibromoethane
(0.15 mL), EtBr (5.3 mL, 7.74 g, 71.0 mmol), 1-pentyne (6.5 mL,
4.47 g, 65.7 mmol), and Et2O (110 mL)]. The mixture was then
heated to reflux for 3 h. After cooling to room temperature, the
solution was cautiously hydrolyzed with 2  NH4Cl solution,
washed with water, and dried with Na2SO4. The Et2O was evapo-
rated by standing in the fume hood overnight. Distillation of the
residue under reduced pressure furnished 12 as a colorless oil.
Yield: 8.99 g (44.4 mmol, 88%). Density: 0.90 g/mL. B.p. 68–71 °C
(0.2 kPa). C13H18Si (202.373 g/mol): calcd. C 77.16, H 8.97; found
C 76.92, H 8.93. 1H NMR (400.1 MHz, CDCl3, 22 °C): δ = 7.63
(m, 2 H, Phortho), 7.35 (m, 3 H, Phmeta + para), 2.23 (t, 3JHH = 7.0 Hz,
3
2 H, –CH2–CH2–CH3), 1.55 (apparent sext, JHH = 7.2 Hz, 2 H,
3
–CH2–CH2–CH3), 0.99 (t, JHH = 7.4 Hz, 3 H, –CH2–CH2–CH3),
1
2
0.39 (s, JHC = 120.4, JHSi = 7.0 Hz, 6 H, SiMe2) ppm. 13C NMR
1
(100.6 MHz, CDCl3, 22 °C): δ = 137.7 (s, JCSi = 74 Hz, 1 C,
Phipso), 133.7 (s, 2 C, Phortho), 129.2 (s, 1 C, Phpara), 127.8 (s, 2 C,
1
Phmeta), 109.4 (s, 1 C, CϵC–Si), 82.4 (s, JCSi = 91 Hz, 1 C, CϵC–
Si), 22.1 (s, 1 C, –CH2–), 21.9 (s, 1 C, –CH2–), 13.4 (s, 1 C, –CH3),
1
2
1
–0.6 (s, JCSi = 57 Hz, 2 C, SiMe2) ppm. 29Si NMR (79.5 MHz,
SiCHCp), 0.10 (s, ∆ν1/2 = 2, JHC = 121.1, JHSi = 7.0 Hz, 6 H,
3
4
1
1
SiMe2) ppm (8a); δ = 7.00 (m, CHCp), 6.73 (dq, JHH = 5, JHH
=
CDCl3, 22 °C): δ = –22.9 [s, JSiC(Me) = 57 (2 C), JSiC(Ph) = 73 (1
3
4
1
2
1 Hz, CHCp), 6.62 (dq, JHH = 5, JHH = 1.5 Hz, CHCp), 3.15 (q,
C), JSiC(CϵC) = 91 (1 C), JSiC(CϵC) = 17 Hz (1 C)] ppm.
3/4
J
J
= 1.5 Hz, CH2), 0.40 (s, SiMe2) ppm (8b); δ = 3.07 (q,
HH
Alkyne Complexes
= 1.5 Hz, CH2), 0.41 (s, SiMe2) ppm (8c). 13C NMR
3/4
HH
(100.6 MHz, CDCl3, 22 °C): δ = 133.1 (br. s, ∆ν1/2 = 15 Hz, 2 C, {µ-Dimethyl[(1,2-η:1,2-η)-phenylethynyl]silane}bis[dicarbonyl(η5-cy-
CHCp), 132.1 (s, ∆ν1/2 = 4 Hz, 2 C, Phortho), 131.1 (br. s, ∆ν1/2
=
clopentadienyl)molybdenum(I)](Mo–Mo)
[PhCϵCMe2SiH·Cp2-
9 Hz, 2 C, CHCp), 128.7 (s, ∆ν1/2 = 7 Hz, 1 C, Phpara), 128.2 (s,
Mo2(CO)4, 13]: Cp2Mo2(CO)4 (434 mg, 1.00 mmol) was dissolved
Eur. J. Inorg. Chem. 2010, 1133–1142
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1139

F. Hoffmann, J. Wagler, G. Roewer
FULL PAPER
in THF (20 mL), and silane 4 (190 µL, 180 mg, 1.12 mmol) was
added. After stirring at room temperature for 6 d, the volatiles were
evaporated in vacuo and the residue extracted with toluene (4 mL).
The extract was concentrated in vacuo to 2 mL and layered with
hexane (4 mL). On cooling to –78 °C a solid precipitated, which
was separated, washed with hexane, and dried in vacuo (400 mg,
67% crude yield). The solid was recrystallized from hexane
(135 mL) at –20 °C and then once again from benzene (3 mL)/hex-
ane (12 mL) at –20 °C to give dark brownish-red crystals, which
were separated, washed with hexane, and dried in vacuo. The by-
product Cp2Mo2(CO)6, which was easily recognized by its violet
color, was removed mechanically under a microscope. Complex 13
is air-stable for at least some days but should be stored under ar-
gon. It is soluble in benzene, toluene, and THF but only sparingly
soluble in hexane. Yield: 250 mg (0.42 mmol, 42%). M.p. 179–
181 °C (argon), 165 °C (dec., air). C24H22Mo2O4Si (594.402): calcd.
C 48.50, H 3.73; found C 48.55, H 3.73. 1H NMR (400.1 MHz,
Trisilanes: Compounds 18 and 19 were not isolated and directly
used in the next step. Silanes 20–23 were isolated, but not purified
by distillation because of the small amounts and their high boiling
points. Hence, elemental analyses were not carried out except for
silane 23. Nevertheless, the spectroscopic data confirm the identity
of 18–23.
1-(Diethylamino)-1,1,2,2,3,3-hexamethyl-3-phenyltrisilane [Ph–(Si-
Me2)3–NEt2, 18]: A solution of Et2NMe2Si–SiMe2Cl (5.1 mL,
4.57 g, 20.4 mmol) in THF (10 mL) was cooled to 0 °C, and a solu-
tion of PhMe2SiLi [21.1 mmol, prepared from PhMe2SiCl
(3.34 mL, 3.61 g, 21.1 mmol), Li (295 mg, 42.5 mmol), and THF
(40 mL)][74b] was added within 45 min. The mixture slowly turned
red. After stirring at room temperature overnight, a clear honey-
colored solution of 18 in THF was obtained. As judged by 29Si
NMR spectroscopy it contained some impurities but was suffi-
ciently pure for the next step. C16H33NSi3 (323.705 g/mol). 29Si
1
1
NMR (79.5 MHz, THF, 22 °C): δ = –0.6 [s, JSiC(Me) = 48, JSiSi
=
3
0.09  in C6D6, 22 °C): δ = 7.44 (dm, JHH = 7.7 Hz, 2 H, Phortho),
2
1
84, JSiSi = 8 Hz, 1 Si, –SiMe2NEt2], –19.5 [s, JSiC(Me) = 45 (2 C),
3
3
4
7.13 (“t”, JHH = 7.7 Hz, 2 H, Phmeta), 6.90 (tt, JHH = 7.3, JHH
1JSiC(Ph) = 59 (1 C), 1JSiSi = 71, 2JSiSi = 9 Hz, 1 Si, –SiMe2Ph], –51.0
3
= 1 Hz, 1 H, Phpara), 4.93 (sept, JHH = 3.7 Hz, 1 H, SiH), 4.82 (s,
1
1
1
[s, JSiC(Me) = 37, JSiSi = 71, JSiSi = 84 Hz, 1 Si, –SiMe2–] ppm.
3
1
10 H, Cp), 0.33 (d, JHH = 3.7, JHC = 120 Hz, 6 H, SiMe2) ppm.
13C NMR (100.6 MHz, 0.09  in C6D6, 22 °C): δ = 230.9 (s, CO),
230.5 (s, CO), 147.5 (s, 1 C, Phipso), 129.8 (s, 2 C, Phortho), 128.5 (s,
2 C, Phmeta), 126.5 (s, 1 C, Phpara), 111.0 (s, 1 C, CϵC–Si·Mo2),
1-Methoxy-1,1,2,2,3,3-hexamethyl-3-phenyltrisilane [Ph–(SiMe2)3–
OMe, 19]: Methanol (2.0 mL, 49.4 mmol) was added at room tem-
perature with stirring to the crude THF solution obtained in the
synthesis of 18. The mixture quickly turned greenish-yellow. Evap-
oration of the solvent in vacuo after 1 h left a brownish-yellow oil
(19) and a white solid (LiCl), which could be used for the next
step without separation. C13H26OSi3 (282.608 g/mol). 29Si NMR
92.1 (s, 10 C, Cp),[90] –1.1 (s, JCSi = 51 Hz, 2 C, SiMe2) ppm. 29Si
1
NMR (79.5 MHz, 0.09  in C6D6, 22 °C): δ = –9.5 [s (1H-coupled:
1
2
1
1
dsept), JSiH = 195, JSiH = 7, JSiC(Me) = 52 (2 C), JSiC(CϵC·Mo2)
= 77 Hz (1 C)] ppm. 95Mo NMR (26.0 MHz, 0.09  in C6D6,
22 °C): δ = –1.887 (br., ∆ν1/2 = 500 Hz) ppm.
1
1
(79.5 MHz, THF, 22 °C): δ = +19.3 [s, JSiC(Me) = 48, JSiSi = 85,
2JSiSi = 9 Hz, 1 Si, –SiMe2OMe], –18.8 [s, JSiC(Me) = 45 (2 C),
1
1JSiC(Ph) = 58 (1 C), 1JSiSi = 73, 2JSiSi = 8 Hz, 1 Si, –SiMe2Ph], –50.4
{µ-(Cyclopenta-2,4-dien-1-yl)dimethyl[(1,2-η:1,2-η)-phenylethynyl]-
1
1
1
[s, JSiC(Me) = 38, JSiSi = 73, JSiSi = 85 Hz, 1 Si, –SiMe2–] ppm.
silane}bis[tricarbonylcobalt(0)](Co–Co)
[PhCϵCMe2SiCp·Co2-
(CO)6, 14a–c]: A solution of Co2(CO)8 (1.710 g, 5.00 mmol) in hex-
ane (30 mL) was added with stirring at room temperature to a solu-
tion of 8 (1.130 g, 5.04 mmol) in hexane (25 mL). The mixture
turned dark brown, and a gas evolution commenced. After 1 d, the
solution was filtered, concentrated in vacuo to 10 mL, and cooled
to –78 °C. On warming up to –20 °C a solid precipitated, which
was separated, washed with hexane, and dried in vacuo. Complex
14 forms dark brown crystals, which can be handled in air but
should be stored under argon. It is soluble in hexane and benzene.
Yield: 990 mg (1.94 mmol, 39%). M.p. 42–45 °C (argon), 43–46 °C
(air). C21H16Co2O6Si (510.305 g/mol): calcd. C 49.43, H 3.16;
found C 50.15, H 3.16. 1H NMR (400.1 MHz, 0.11  in C6D6,
1-Chloro-1,1,2,2,3,3-hexamethyl-3-phenyltrisilane [Ph–(SiMe2)3–Cl,
20]: The mixture obtained in the synthesis of 19 was dissolved in
hexane (15 mL). Then acetyl chloride (5 mL, 70.4 mmol) was
added at room temperature with stirring. After 1 h, the solution
was filtered and the residue washed with hexane. From the com-
bined filtrates and washings the volatiles were removed in vacuo
leaving an orange-yellow oil. According to its 29Si NMR spectrum
it consisted of 20 and some impurities and was sufficiently pure for
further reactions. Yield: 5.42 g (18.9 mmol, 92% crude).
C12H23ClSi3 (287.027 g/mol). 29Si NMR (79.5 MHz, hexane,
1
1
2
22 °C): δ = +26.5 [s, JSiC(Me) = 46, JSiSi = 79, JSiSi = 10 Hz, 1
1
1
Si, –SiMe2Cl], –19.2 [s, JSiC(Me) = 46 (2 C), JSiC(Ph) = 59 (1 C),
3
3
22 °C): δ = 7.62 (d, JHH = 7.3 Hz, 2 H, Phortho), 7.04 (“t”, JHH
7.3 Hz, 2 H, Phmeta), 6.97 (t, JHH = 7.3 Hz, 1 H, Phpara), 6.61 (br.,
=
2
1JSiSi = 75, JSiSi = 10 Hz, 1 Si, –SiMe2Ph], –45.6 [s, 1JSiC(Me) = 40,
3
1JSiSi = 74, JSiSi = 80 Hz, 1 Si, –SiMe2–] ppm.
1
∆ν1/2 = 15 Hz, 2 H, CHCp), 6.48 (br., ∆ν1/2 = 23 Hz, 2 H, CHCp),
1,1,2,2,3,3-Hexamethyl-1-phenyltrisilane [Ph–(SiMe2)3–H, 21]: A
solution of 20 (1.45 g, 5.1 mmol) in Et2O (10 mL) was added at
0 °C to excess LiAlH4 (1.5 mmol) in Et2O (10 mL). After warming
up to room temperature, the solvent was distilled off in vacuo, and
the residue was extracted with hexane. The extract was then con-
centrated in vacuo leaving a colorless oil. According to its 29Si
NMR spectrum it consisted of 21 and minor impurities. Yield:
1.16 g (4.6 mmol, 91% crude). C12H24Si3 (252.582 g/mol). 29Si
NMR (79.5 MHz, Et2O, 22 °C): δ = –18.3 [s, 1JSiC(Me) = 45, 1JSiC(Ph)
1
3.56 (br., ∆ν1/2 = 20 Hz, 1 H, SiCHCp), 0.20 (s, ∆ν1/2 = 4, JHC
=
121 Hz, 6 H, SiMe2) ppm. 13C NMR (100.6 MHz, 0.11  in C6D6,
22 °C): δ = 200.3 (br., ∆ν1/2 = 41 Hz, CO), 138.2 (s, ∆ν1/2 = 4 Hz,
1 C, Phipso), 133.1 (br., ∆ν1/2 = 29 Hz, 2 C, CHCp), 131.9 (br.,
∆ν1/2 = 18 Hz, 2 C, CHCp), 130.3 (s, ∆ν1/2 = 5 Hz, 2 C, Phortho),
129.3 (s, ∆ν1/2 = 4 Hz, 2 C, Phmeta), 128.6 (s, ∆ν1/2 = 5 Hz, 1 C,
Phpara), 106.6 (s, ∆ν1/2 = 9 Hz, 1 C, CϵC–Si·Co2), 78.8 (s, ∆ν1/2
=
7 Hz, 1 C, CϵC–Si·Co2), 52.4 (br., ∆ν1/2 = 31 Hz, 1 C, SiCHCp),
1
–1.9 (s, ∆ν1/2 = 5, JCSi = 58 Hz, 2 C, SiMe2) ppm (14a); δ = 144.8
1
2
not observed, JSiSi = 74, JSiSi = 8 Hz, 1 Si, –SiMe2Ph], –36.3 (s,
(s, 1 C, CHCp), 139.0 (s, 1 C, CHCp), 133.2 (s, 1 C, CHCp), 130.1
(s, 2 C, Phortho), 129.3 (s, 1 C, Phmeta), 106.2 (s, 1 C, CϵC–Si·Co2),
79.9 (s, 1 C, CϵC–Si·Co2), 45.8 (s, 1 C, CH2), –0.1 (s, 2 C, SiMe2)
ppm (14b); δ = 44.0 (s, 1 C, CH2), –0.6 (s, 2 C, SiMe2) ppm (14c).
nJAB not observed, 1 Si, –SiMe2H), –47.4 [s, JSiC(Me) = 39, 1JSiSi
74, JSiSi = 71 Hz?, 1 Si, –SiMe2–] ppm.
=
1
1
1,1,2,2,3,3-Hexamethyl-1-(pent-1-yn-1-yl)-3-phenyltrisilane [Ph–(Si-
29Si NMR (79.5 MHz, 0.11  in C6D6, 22 °C): δ = –0.6 [s, Me2)3–CϵCPr, 23]: A solution of PrCϵCMgBr in Et2O [prepared
1
1JSiC(Me/Cp) = 58 (3 C), JSiC(CϵC·Co2) = 68 Hz (1 C), 14a], –10.6 (s, according to standard procedures[88] from Mg (390 mg,
14b), –10.8 (s, 14c) ppm. 59Co NMR (94.7 MHz, 0.11  in C6D6,
22 °C): δ = –2300Ϯ100 (br., ∆ν1/2 = 27 kHz) ppm.
16.0 mmol), 1,2-dibromoethane (50 µL), EtBr (2.0 mL, 2.9 g,
26.8 mmol), 1-pentyne (2.0 mL, 1.38 g, 20.2 mmol), and Et2O
1140
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© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 1133–1142

Selective Synthesis of Functional Alkynylmono- and -trisilanes
[4]
[5]
[6]
[7]
[8]
C. Eaborn, W. A. Stanczyk, J. Chem. Soc. Perkin Trans. 2 1984,
12, 2099–2103.
(32 mL)] was added to 20 (2.275 g, 7.9 mmol) in Et2O (20 mL). The
mixture was stirred at room temperature for 1 h and heated to re-
flux for another hour. Then it was cautiously hydrolyzed with 2 
NH4Cl solution, washed with water, and dried with Na2SO4. After
removal of the Et2O, the residue was dissolved in hexane, filtered,
and the filtrate concentrated in vacuo leaving a light yellow oil.
Yield: 2.52 g (7.9 mmol, 99% crude). C17H30Si3 (318.685 g/mol):
calcd. C 64.07, H 9.49; found C 65.65, H 9.65. 1H NMR
(400.1 MHz, CDCl3, 22 °C): δ = 7.46 (m, 2 H, Phortho), 7.32 (m, 3
J. Chmielecka, J. Chojnowski, C. Eaborn, W. A. Stanczyk, J.
Chem. Soc. Perkin Trans. 2 1985, 11, 1779–1783.
N. V. Komarov, L. I. Ol’khovskaya, K. S. Pushkareva, L. A.
Soboleva, Zh. Obshch. Khim. 1984, 54, 1584–1587.
B. Wrackmeyer, G. Kehr, J. Süß, Chem. Ber. 1993, 126, 2221–
2226.
P. Lapouyade, G. Deleris, J. Dunoguès, R. Calas, J. Organomet.
Chem. 1974, 80, C45–C46.
K. Tamao, E. Nakajo, Y. Ito, Tetrahedron 1988, 44, 3997–4007.
S. I. Nitsche, Ph. D. Thesis, TU Bergakademie Freiberg, 2002.
L. I. Ol’khovskaya, N. V. Komarov, K. S. Pushkareva, G. V.
Pletneva, Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.
1988, 31, 29–32.
3
H, Phmeta + para), 2.21 (t, JHH = 7.0 Hz, 2 H, –CH2–CH2–CH3),
[9]
[10]
[11]
1.53 (apparent sext, 3JHH = 7.2 Hz, 2 H, –CH2–CH2–CH3), 0.98 (t,
3JHH = 7.4 Hz, 3 H, –CH2–CH2–CH3), 0.41 (s, 6 H, SiMe2), 0.11
(s, 12 H, SiMe2) ppm. 13C NMR (100.6 MHz, CDCl3, 22 °C): δ =
139.7 (s, 1 C, Phipso), 133.8 (s, 2 C, Phortho), 128.3 (s, 1 C, Phpara),
127.7 (s, 2 C, Phmeta), 109.9 (s, 1 C, CϵC–Si), 83.2 (s, 1 C, CϵC–
Si), 22.2 (s, 1 C, –CH2–), 22.1 (s, 1 C, –CH2–), 13.5 (s, 1 C, –CH3),
[12]
[13]
I. M. Gverdtsiteli, M. I. Dzheliya, L. V. Baramidze, Soobshch.
Akad. Nauk Gruz. SSR 1976, 84, 381–384.
The detour via the methoxysilane was chosen because the di-
rect reaction of (diethylamino)silane with acetyl chloride would
give N,N-diethylacetamide, which is a liquid with a high boiling
point and hardly possible to separate from the product. Dieth-
ylamine and methyl acetate are, however, volatile liquids and
easy to remove in vacuo.
Z. H. Aiube, J. Chojnowski, C. Eaborn, W. A. Stanczyk, J.
Chem. Soc., Chem. Commun. 1983, 9, 493–495.
V. E. Baikov, L. P. Danilkina, K. A. Ogloblin, Zh. Obshch.
Khim. 1983, 53, 1330–1335.
1
1
–1.9 (s, JCSi = 50 Hz, 2 C, –SiMe2CϵCPr), –3.1 (s, JCSi = 46 Hz,
2 C, –SiMe2Ph), –6.8 (s, JCSi = 39 Hz, 2 C, –SiMe2–) ppm. 29Si
1
NMR (79.5 MHz, CDCl3, 22 °C): δ = –18.4 [s, 1JSiC(Me) = 45 (2 C),
1JSiC(Ph) = 58 (1 C), 1JSiSi = 73, 2JSiSi = 9 Hz, 1 Si, –SiMe2Ph], –35.2
1
1
2
[s, JSiC(Me) = 49 (2 C), JSiC(CϵC) not observed, JSiC(CϵC) = 14 (1
C), 1JSiSi = 79, 2JSiSi = 8 Hz, 1 Si, –SiMe2CϵCPr], –47.6 [s, 1JSiC(Me) [14]
1
1
= 39, JSiSi = 73, JSiSi = 79 Hz, 1 Si, –SiMe2–] ppm.
[15]
[16]
1,1,2,2,3,3-Hexamethyl-1-phenyl-3-(phenylethynyl)trisilane [Ph–(Si-
Me2)3–CϵCPh, 22]: Compound 22 was prepared analogously to
23 from Mg (300 mg, 12.3 mmol), 1,2-dibromoethane (50 µL), EtBr
(2.0 mL, 2.9 g, 26.8 mmol), PhCϵCH (1.4 mL, 1.30 g, 12.8 mmol),
20 (1.75 g, 6.1 mmol), and Et2O (45 mL). It was obtained as an
orange oil (2.62 g, theoretical yield: 2.15 g). According to its NMR
spectra it was contaminated with PhCϵCH (ca. 15%) and minor
amounts of other impurities, which could not be removed in vacuo.
R. J. P. Corriu, J. J. E. Moreau, H. Praet, Organometallics 1990,
9, 2086–2091.
[17]
[18]
E. T. Bogoradovskii, Zh. Obshch. Khim. 1992, 62, 957–958.
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380.
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1310.
U. Herrmann, H. Marsmann, F. Uhlig, Silicon NMR Database
V2.0, Dortmund, 1999–2000.
Three isomers: (cyclopenta-2,4-dien-1-yl)- (8a), (cyclopenta-
2,4-dien-2-yl)- (8b), and (cyclopenta-2,4-dien-3-yl)dimethyl-
(phenylethynyl)silane (8c).
R. W. Martin, General Electric Co., US 2667501, 1954.
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436, 265–276.
[19]
[20]
[21]
[22]
1
C20H28Si3 (352.702 g/mol). H NMR (400.1 MHz, CDCl3, 22 °C):
δ = 7.46 (m, 4 H, Phortho), 7.29 (m, 6 H, Phmeta + para), 0.44 (s, 6 H,
SiMe2), 0.21 (s, 6 H, SiMe2), 0.18 (s, 6 H, SiMe2) ppm. 13C NMR
(100.6 MHz, CDCl3, 22 °C): δ = 139.4 (s, 1 C, Phipso), 133.8 (s, 2
C, Phortho), 131.8 (s, 2 C, PhCϵCortho), 128.4 (s, 1 C, Phpara), 128.3
(s, 1 C, Phpara), 128.2 (s, 2 C, PhCϵCmeta), 127.7 (s, 2 C, Phmeta),
123.4 (s, 1 C, PhCϵCipso), 107.6 (s, 1 C, CϵC–Si), 93.4 (s, 1 C,
CϵC–Si), –2.2 (s, 1JCSi = 49 Hz, 2 C, –SiMe2CϵCPh), –3.1 (s, 1JCSi
[23]
[24]
1
= 46 Hz, 2 C, –SiMe2Ph), –6.8 (s, JCSi = 39 Hz, 2 C, –SiMe2–)
1
ppm. 29Si NMR (79.5 MHz, CDCl3, 22 °C): δ = –18.4 [s, JSiC(Me)
[25]
[26]
[27]
1
1
2
= 46 (2 C), JSiC(Ph) = 59 (1 C), JSiSi = 74, JSiSi = 8 Hz, 1 Si,
1
1
–SiMe2Ph], –34.0 [s, JSiC(Me) = 49 (2 C), JSiC(CϵC) not observed
because of impurities, JSiC(CϵC) = 13 (1 C), JSiSi = 79, JSiSi
2
1
2
=
1
1
8 Hz, 1 Si, –SiMe2CϵCPh], –47.2 [s, JSiC(Me) = 39, JSiSi = 74,
1JSiSi = 78 Hz, 1 Si, –SiMe2–] ppm.
[28]
[29]
Supporting Information (see footnote on the first page of this arti-
cle): GC-MS, IR, and UV/Vis data of the reported compounds as
well as experimental details and spectroscopic data of 2, 3, 4, 7, 9,
and 11; experimental details of the crystal structure determinations
and tables with bond lengths and angles.
[30]
[31]
[32]
[33]
[34]
H. Lang, M. Weinmann, L. Zsolnai, J. Organomet. Chem.
1996, 522, 277–289.
K. H. Pannell, A. R. Bassindale, J. W. Fitch, J. Organomet.
Acknowledgments
Chem. 1981, 209, C65–C68.
The authors thank the Fonds der Chemischen Industrie for finan-
cial support of this work.
95Mo NMR (26.0 MHz, C6D6, 22 °C): δ = –1854 (∆ν1/2 =
470 Hz) ppm. IR (THF): νЈ = 1983, 1925, 1840 (CϵO) cm–1.
˜
UV/Vis (hexane): λ (ε) = 216 (70000, sh up to 300 nm), 363
(12000), 544 (1500 Lmol–1 cm–1) nm.
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Eur. J. Inorg. Chem. 2010, 1133–1142
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www.eurjic.org
1141

F. Hoffmann, J. Wagler, G. Roewer
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Received: August 5, 2009
Published Online: January 13, 2010
1142
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