Addition reactions of lithiodimethylphenylsilane to (η4-1,3-diene)-Fe(CO)3 and (η6-arene)Cr(CO)3 complexes

Article abstract of DOI:10.1016/S0022-328X(03)00219-5

Treatments of (η⁴-cyclohexa-1,3-diene)Fe(CO)₃ complex with 1.2 equivalents of PhMe₂SiLi, followed by quenching the reactive intermediate with CF₃COOH generated 1-dimethyl(phenyl)silylcyclohex-1-ene and with 2-(p

Full text of DOI:10.1016/S0022-328X(03)00219-5

Journal of Organometallic Chemistry 675 (2003) 13Á20
/
www.elsevier.com/locate/jorganchem
Addition reactions of lithiodimethylphenylsilane to (h4-1,3-diene)-
Fe(CO)3 and (h6-arene)Cr(CO)3 complexes
Ming-Chang P. Yeh *, Peng-Yu Sheu, Jin-Xuan Ho, Yi-Lin Chiang, Dai-Yu Chiu,
U. Narasimha Rao
Department of Chemistry, National Taiwan Normal University, 88, Ding-Jou Road, Sec. 4, Taipei 117, Taiwan
Received 9 September 2002; received in revised form 22 January 2003; accepted 17 March 2003
Abstract
Treatments of (h4-cyclohexa-1,3-diene)Fe(CO)3 complex with 1.2 equivalents of PhMe2SiLi, followed by quenching the reactive
intermediate with CF3COOH generated 1-dimethyl(phenyl)silylcyclohex-1-ene and with 2-(phenylsulfonyl)-3-phenyloxaziridine
produced [h4-2-dimethyl(phenyl)silylcyclohexa-1,3-diene]Fe(CO)3 complex as the major product. Additions of the silyl anion to (h6-
arene)Cr(CO)3 and (h6-cyclohepta-1,3,5-triene)Cr(CO)3 complexes produce dienylsilanes after acid quenching.
# 2003 Elsevier Science B.V. All rights reserved.
Keywords: Iron; Cyclohexadiene; Silane; Chromium; Arene
1. Introduction
(h6-arene)Cr(CO)3 complexes result in deprotonation at
the arene ligand [6]. Carbon nucleophiles, such as ketone
enolates, organocopper or -zinc reagents, fail to react
with both complexes. Moreover, reports on the addition
of silyl anions to (h4-1,4-diene)Fe(CO)3 and (h6-are-
ne)Cr(CO)3 complexes are not found. Although the
Nucleophilic additions to conjugated dienes and
arenes coordinated to a transition metal have attracted
considerable interest in organic synthesis. Transition
metals, such as molybdenum, palladium or iron, have
been used to activate dienes toward nucleophilic addi-
tion reactions [1], and chromium, manganese, iron, or
ruthenium have been utilized to activate arenes toward
nucleophilic substitution and addition reactions [2].
Among them, nucleophilic additions to (h4-1,3-die-
ne)Fe(CO)3 [3] and (h6-arene)Cr(CO)3 [4] complexes
have been studied intensively and used in the synthesis
of a number of complex molecules. The disadvantage of
the additions, however, is the relatively narrow range of
stabilized carbon nucleophiles. For example, organo-
magnesium or -lithium reagents suffer competitive
addition to the carbon monoxide ligand of diene-
Fe(CO)3 complexes [5], and treatments of n-BuLi with
addition reactions of siliconÁ
Si)3MnMgMe] [7] and siliconÁ
/
magnesium [(PhMe2-
copper [PhMe2Si-
/
Cu(CN)Li] [8] reagents to 1,3-dienes were reported to
give homoallyl- and allylsilanes after electrophilic
quenching, both silylations were limited to acyclic 1,3-
dienes bearing nonsubstituted terminal double bonds. It
will be of great interest to extend the silylation reaction
to cyclic 1,3-dienes. Here, we report, for the first time,
on the addition of PhMe2SiLi to both cyclic and acyclic
dienes activated by Fe(CO)3. The intermediates ob-
tained from the addition can be directly treated with
CF3COOH to produce vinyl- and allylsilanes or with 2-
(phenylsulfonyl)-3-phenyloxaziridine
as Davis reagent) to afford nucleophilic substituted
ironÁdiene complexes. Moreover, nucleophilic addition
reactions of (h6-arene)Cr(CO)3 and (h6-cyclohepta-
(also
known
/
* Corresponding author. Tel.: ꢀ
E-mail address: cheyeh@scc.ntnu.edu.tw (M.-C.P. Yeh).
/
2-29350750; fax: ꢀ2-29324249.
/
0022-328X/03/$ - see front matter # 2003 Elsevier Science B.V. All rights reserved.
doi:10.1016/S0022-328X(03)00219-5

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/
1,3,5-triene)-Cr(CO)3 complexes with PhMe2SiLi to give
dienylsilanes after acid quenching will also be described.
homoallyl protons was found (compared to the integral
of phenyl and dimethyl groups at the silicon). Trapping
of 5 with Davis reagent afforded the C-2 silyl-substi-
tuted complex 3a as the major product and a trace of the
C-1 silyl-substituted complex 3b (Eq. (1)). Reaction of
the allyl anion 5 with Davis reagent gave 3a and 3b
together with isolation of PhSO2NH2 and PhCHO.
Migration of b-hydrides from 5 occurred at both C-4
and C-6 position to Davis reagent afforded PhSO2NH2
and PhCHO after aqueous process. Moreover, quench-
ing 5 with benzoyl chloride followed by aqueous process
produced vinylsilane 2a as the major product in 37%
yield together with the C-1 substituted silyl diene 6 as
the minor product in 15% yield (Eq. (2)). It was
reasonable to view that quenching of 5 with benzoyl
chloride was inefficient and vinylsilane 2a was generated
during aqueous work up. Reaction of 5 with benzoyl
chloride may produce the postulate intermediate 7a
(Scheme 2). The intermediate 7a may undergo b-hydride
elimination at C-4 to give 7b. Reductive elimination of
7b (to release benzaldehyde) followed by detachment of
the double bond from the iron center furnished silyl
diene 6. The reaction mechanism was proposed based
upon isolation of benzaldehyde after flash column
chromatography of the reaction mixture. It is important
to mention that unlike stabilized carbanions attack at
2. Results and discussion
2.1. Addition of lithiodimethylphenylsilane to cyclic
diene-irontricarbonyl complexes followed by electrophilic
quenching
Lithiodimethylphenylsilane (PhMe2SiLi) was pre-
pared in tetrahydrofuran (THF) under argon according
to a literature procedure [9]. Addition of a THF solution
of PhMe2SiLi (1.2 equivalents) to (h4-cyclohexa-1,3-
diene)Fe(CO)3 complex (1a) in THF for 20 h at 25 8C
under argon followed by quenching the reaction mixture
with CF3COOH produced 1-dimethyl(phenyl)silylcyclo-
hex-1-ene (2a) in 55% after purification by flash column
chromatography on silica gel and short-path distillation
under reduced pressure. Under the same reaction
conditions, quenching the reactive intermediate with
Davis reagent produced [h4-2-dimethyl(phenyl)silylcy-
clohexa-1,3-diene]Fe(CO)3 complex (3a) in 40% yield
and a trace of [h4-1-dimethyl(phenyl)silylcyclohexa-1,3-
diene]Fe(CO)3 complex (3b). A mechanism for the
generation of 2a is suggested in Scheme 1. The addition
of the silyl anion to complex 1a occurred at internal
positions of the diene ligand to generate homoallyl
anion intermediate 4. Hydride migration may occur via
b-hydride elimination and re-addition to give more
stable h3-allyl anion intermediate 5. Quenching of 5
with CF3COOH led to the formation of vinylsilane 2a
after reductive elimination and detachment of the olefin
ligand from the iron center. Moreover, quenching 5 with
CF3COOD gave 2b with a deuterium at the allyl carbon.
None of the decrease in integration on the vinyl or
the internal position of the diene ligand of 1a at ꢁ78 8C
/
(kinetically controlled reaction conditions) to give
homoallyl anion intermediates and at the terminal
position of the diene ligand at 25 8C (thermodynami-
cally controlled reaction conditions) to afford allyl
anion intermediates [3], the silyllithium reagent (PhMe2-
SiLi) does not add to 1a at ꢁ78 8C and the addition
/
occurs at internal positions of the cyclohexa-1,3-diene
ligand at 25 8C to give 5. Attempts to trap 5 with other
electrophiles such as benzyl bromide and CO failed.
Scheme 1.

M.-C.P. Yeh et al. / Journal of Organometallic Chemistry 675 (2003) 13Á
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15
Scheme 2.
Vinylsilane 2a was isolated as the major product in each
case in 20Á40% yield after aqueous work up and column
chromatography of the crude mixture.
formation of 3a is difficult to understand since it
formally involves a kind of cine-substitution for meth-
oxide. A possible reaction path involving a-methoxy
/
(1)
(2)
Surprisingly, addition of PhMe2SiLi to (h4-1-methox-
ycyclohexa-1,3-diene)Fe(CO)3 complex (1b) also pro-
duced 3a in 60% yield after acid quenching. The
elimination of the homoallyl anion intermediate 8 to
generate the carbene intermediate 9 is proposed (Scheme
3). The postulate carbene intermediate 9 may undergo b-
Scheme 3.

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/
hydride elimination (to give 10) followed by reductive
elimination to provide 11. Recoordination of the
pendant double bond to the iron center of 11 produced
complex 3a. An additional methyl group at the C-5
position of the ring, for example, with complex 12 [10],
the silylation occurred only at the less hindered C-2
position of the diene ligand to produce vinylsilane 13 in
41% yield after acid quenching. None of vinylsilane
derived from silyl anion addition at hindered terminal
C-1 or C-4 positions was found.
of 16a and 16b with CF3COOH gave allylsilanes 15a
and 15b. To further prove the proposed allyl anion
intermediate 16a, the anion intermediate 16a was
quenched with CF3COOD. Allylsilane 17 was isolated
in 40% yield. 1H-NMR of 17 shows that only two
protons appear at the allylic carbon cis to the di-
methyl(phenyl)silyl group. Moreover, the silylation
failed to cyclic ironÁdiene complexes bearing an addi-
/
tional substituent at the C-2 position of the diene ligand.
For example, addition of PhMe2SiLi to [h4-2-methylcy-
clohexa-1,3-diene]Fe(CO)3 complex (18a) and [h4-2-
methoxycyclohexa-1,3-diene]Fe(CO)3 complex (18b)
failed to give any additional product. The starting
complexes 18a and 18b were recovered quantitatively
in both cases. This result further indicated that the
silylation was limited to the diene ligand containing a
substituent at the C-2 position, especially for C-2
substituted cyclic 1,3-diene iron complexes.
2.2. Addition of lithiodimethylphenylsilane to acyclic
diene-irontricarbonyl complexes followed by electrophilic
quenching
2.3. Addition of lithiodimethylphenylsilane to arene-
chromiumtricarbonyl complexes followed by electrophilic
quenching
Acyclic ironÁ
/
diene complexes 14a and 14b also
The above reaction patterns were also observed for
(h6-arene)Cr(CO)3 complexes. For example, addition of
PhMe2SiLi to (h6-benzene)Cr(CO)3 (19a) at 25 8C
followed by acid quenching afforded dienylsilanes 6
underwent silylation, however, at the less hindered
terminal position (C-4) of the diene ligand to produce
allylsilanes 15a [8] (37%) and 15b [8] (32%), respectively,
as a single olefinic regioisomer in each case. None of the
addition at the other terminus (C-1) and the internal
position (C-3) of the diene ligand was found. Although
and 20 (6:20ꢂ4:1) in 62% yield (Eq. (3)). The initial
/
nucleophilic addition generated the (h5-cyclohexadie-
nyl)Cr(CO)3 anion intermediate 21. Protonation of 21
followed by hydride transfer (via supra) afforded 6 and
20. Quenching 21 with Davis reagent also resulted in
hydride abstraction to generate [h6-dimethyl(phenyl)si-
lylbenzene]Cr(CO)3 complex (19e) in 30% yield together
with the isolation of PhSO2NH2 and PhCHO. More-
the yields of the silyl addition to acyclic ironÁdiene
/
complexes are low, the addition provides only a single
allylsilane [8]. Thus, the steric hindrance imposed by an
adjacent alkyl group at the C-2 position of acyclic diene
ligands may impede the silyl anion attack at C-1 and C-3
positions of the diene ligands. Addition of the silyl anion
at the less hindered terminal position (C-4) of the diene
ligand generated allyl anions 16a and 16b. Protonation
over, addition of PhMe2SiLi to areneÁchromium com-
/
plex containing a fluorine (19b), a chlorine (19c) or a
methoxy (19d) group proceeded in an addition/elimina-

M.-C.P. Yeh et al. / Journal of Organometallic Chemistry 675 (2003) 13Á
/20
17
(3)
tion process to afford complex 19e in fair to good yields
(19b, 70%; 19c, 36%; 19d, 56%). Changing to the seven-
membered ring with (h6-cyclohepta-1,3,5-triene)-
Cr(CO)3 complex (22) also allowed the silyl anion
addition to give silylated cyclohepta-1,3-diene deriva-
4. Experimental
4.1. General
All reactions were run under an argon atmosphere in
oven-dried glassware unless otherwise indicated. Anhy-
drous solvents or reaction mixtures were transferred via
tives 23a and 23b (23a:23bꢂ3:1) in 68% yield after acid
/
quenching.
3. Conclusion
an oven-dried syringe or cannula. THF was distilled
under nitrogen from a deep blue sodium benzophenone
ketyl solution. Complexes 1a and 1b and 14a and 14b
were prepared by heating Fe2(CO)9 and the correspond-
The reaction outlined herein demonstrates that the
addition of PhMe2SiLi to diene-Fe(CO)3 complexes
produces vinyl- or allylsilanes after acid quenching.
Treatments of the same reaction intermediate with Davis
reagent proceeded in hydride abstraction to afford silyl-
substituted diene-Fe(CO)3 complexes. Nucleophilic ad-
dition reactions of (h6-arene)Cr(CO)3 and (h6-cyclo-
hepta-1,3,5-triene)Cr(CO)3 complexes with PhMe2SiLi
generate dienylsilanes after acid quenching.
ing dienes in ether. Complexes 19aÁ19d were obtained
/
by refluxing the corresponding arenes with Cr(CO)6 in
n-butyl ether. Complex 22 was synthesized by refluxing
cyclohepta-1,3,5-triene with Cr(CH3CN)3(CO)3 in THF
[11]. Flash column chromatography, following the
method of Still, was carried out with E. Merck silica
gel (Kieselgel 60, 230Á400 mesh) using the indicated
/

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M.-C.P. Yeh et al. / Journal of Organometallic Chemistry 675 (2003) 13Á20
/
solvents [12]. 1H-NMR spectra were obtained with
JEOL-EX 400 (400 MHz) and Varian G-200 (200
MHz) spectrometers. The chemical shifts are reported
in parts per million with either tetramethylsilane (0.00
ppm) or CHCl3 (7.26 ppm) as internal standard. 13C-
NMR spectra were recorded with JEOL-EX 400 (100.4
MHz) and Varian G-200 (50 MHz) spectrometers with
CDCl3 (77.0 ppm) as the internal standard. Infrared
(IR) spectra were recorded with a JASCO IR-700
spectrometer. Mass spectra were acquired on a JEOL
JMS-D 100 spectrometer at an ionization potential of 70
eV and are reported as mass/charge (m/e) with percent
relative abundance. High-resolution mass spectra were
obtained with an AEI MS-9 double-focusing mass
spectrometer and a JEOL JMS-HX 110 spectrometer
at the Department of Chemistry, Central Instrument
Center, Taichung, Taiwan.
4.1.3. [h4-2-Dimethyl(phenyl)silylcyclohexa-1,3-
diene]Fe(CO)3 complex (3a)
Addition of PhMe2SiLi (6.0 mmol) to complex 1a
(1.10 g, 5.0 mmol) followed by quenching the reaction
mixture with 2-(phenylsulfonyl)-3-phenyloxaziridine
(1.57 g) gave 3a (0.71 g, 2.0 mmol, 40%) as a colorless
liquid and a trace of 3b (less than 20 mg). Only complex
3a can be isolated as a pure compound. IR (CH2Cl2)
3688, 3100, 2900, 1968, 1607, 1079, 918 cmꢁ1; 1H-NMR
(400 MHz, CDCl3) d 7.64 (m, 2H), 7.41 (m, 3H), 5.11
(d, Jꢂ8.0 Hz, 1H), 3.44 (m, 1H), 3.30 (m, 1H), 1.70 (m,
/
4H), 0.50 (s, 3H) and 0.49 (s, 3H); 13C-NMR (100.4
MHz, CDCl3) d 212.5, 137.9, 133.9, 129.4, 127.9, 90.6,
89.8, 67.4, 65.9, 24.2, 23.9, ꢁ
/
3.3, ꢁ4.0; MS (20 eV) m/e
/
354 [Mꢀ, 1], 326 (4), 298 (12), 270 (100), 271 (18), 268
(30); HRMS (EI) m/e Calc. for C17H18FeO3Si:
354.0375; Found, 354.0360.
4.1.4. 4-Dimethyl(phenyl)silylcyclohexa-1,3-diene (6)
Addition of PhMe2SiLi (3.75 mmol) to complex 1a
(0.41 g, 1.88 mmol) followed by quenching the reaction
mixture with benzoyl chloride (0.54 g, 3.75 mmol)
afforded 2 (0.15 g, 0.69 mmol, 37%) and 6 (0.06 g,
0.28 mmol, 15%) both as colorless liquid. Compound 6:
IR (CH2Cl2) 3364, 3070, 2986, 2306, 1624, 1282, 1247
4.1.1. General procedure for addition of PhMe2SiLi to
(h4-1,3-diene)Fe(CO)3, (h6-arene)Cr(CO)3 and (h6-
cyclohepta-1,3,5-triene)Cr(CO)3 complexes
In a typical procedure, to a solution of complex 1a
(0.22 g, 5.0 mmol) in 9 ml of THF under argon at 0 8C
was added rapidly, neat, via cannula, a solution of
PhMe2SiLi [9] (6.0 mmol) in 15 ml of THF and via
syringe 3 ml of hexamethylphosphoramide (HMPA).
The reaction was stirred at 25 8C for 20 h. The reaction
mixture was quenched with 0.5 ml of trifluoroacetic acid
via syringe needle at 0 8C and stirred at 25 8C for 1 h,
after which time the reaction mixture was diluted with
hexane (30 ml). The resultant solution was washed with
1
cmꢁ1; H-NMR (400 MHz, CDCl3) d 7.54 (m, 2H),
7.36 (m, 3H), 6.24 (m, 1H), 5.98 (m, 1H), 5.91 (m, 1H),
2.10 (m, 4H), 0.36 (s, 6H); 13C-NMR (50 MHz, CDCl3)
d 138.36, 137.02, 134.06, 133.76, 128.97, 128.24, 127.78,
124.76, 24.14, 22.05, ꢁ
3.72; MS (20 eV) m/e 214 [Mꢀ,
22], 197 (20), 135 (100), 121 (26); HRMS (EI) m/e Calc.
for C14H18Si: 214.1178; Found, 214.1179.
/
water (3ꢃ
/
50 ml) and brine (3ꢃ50 ml), dried over
/
anhydrous magnesium sulfate (5.0 g) and concentrated
to give the crude mixture.
4.1.5. 5-Methyl-1-dimethyl(phenyl)silylcyclohex-1-ene
(13)
Addition of PhMe2SiLi (6.0 mmol) to complex 12 [10]
(1.17 g, 5.0 mmol) followed by quenching the reaction
mixture with trifluoroacetic acid (0.5 ml) produced 13
(0.47 g, 2.05 mmol, 41%) as a colorless liquid. IR
(CH2Cl2) 3369, 2986, 1617, 1429, 1078 cmꢁ1; 1H-NMR
(400 MHz, CDCl3) d 7.52 (m, 2H), 7.36 (m, 3H), 6.06
(m, 1H), 2.10 (m, 3H), 1.68 (m, 3H), 1.14 (m, 1H), 0.94
4.1.2. 1-Dimethyl(phenyl)silylcyclohex-1-ene (2a)
The crude mixture from the addition of PhMe2SiLi
(6.0 mmol) to complex 1a (1.10 g, 5.0 mmol) followed by
quenching the reaction mixture with trifluoroacetic acid
(0.5 ml) was purified via flash column chromatography
(silica gel, hexanes) to give 2a (0.60 g, 2.75 mmol, 55%)
as a colorless liquid: IR (CH2Cl2) 3373, 3057, 1622,
(d, Jꢂ
/
6.0 Hz, 3H) and 0.32 (s, 6H); 13C-NMR (100.4
MHz, CDCl3) d 138.9, 137.6, 136.3, 134.0, 128.8, 127.7,
1
1421, 1075 cmꢁ1; H-NMR (400 MHz, CDCl3) d 7.67
35.5, 31.1, 28.2, 27.1, 22.0, ꢁ3.6; MS (20 eV) m/e 230
/
(m, 2H), 7.48 (m, 3H), 6.25 (m, 1H), 2.22 (m, 4H), 1.76
(m, 4H) and 0.49 (s, 6H); 13C-NMR (100.4 MHz,
CDCl3) d 138.8, 137.9, 136.7, 134.0, 128, 127, 26.8,
[Mꢀ, 49], 229 (100), 216 (27), 215 (28), 202 (64), 201
(34), 187 (31), 168 (51), 167 (43), 153 (28); HRMS (EI)
m/e Calc. for C15H22Si: 230.1491; Found, 230.1473.
26.7, 22.9, 22.4, ꢁ
3.7; MS (20 eV) m/e 216 [Mꢀ, 56],
/
215 (23), 202 (62), 156 (12), 137 (16), 136 (13), 135 (100),
121 (20); HRMS (EI) m/e Calc. for C14H20Si: 216.1334;
Found, 216.1334. The reaction mixture was also
quenched with CF3COOD to give 2b with a deuterium
at the allyl carbon. None of the decrease in integration
on the vinyl or homoallyl protons was found (compared
to the integral of phenyl and dimethyl groups at silicon).
4.1.6. 2-Methyl-4-dimethyl(phenyl)silylbut-1-ene (15a)
[8]
Addition of PhMe2SiLi (6.0 mmol) to complex 14a
(1.04 g, 5.0 mmol) followed by quenching the reaction
mixture with trifluoroacetic acid (0.5 ml) produced 15a
(0.38 g, 1.86 mmol, 37%) as a colorless liquid. 1H-NMR
(400 MHz, CDCl3) d 7.53 (m, 2H), 7.36 (m, 3H), 5.17

M.-C.P. Yeh et al. / Journal of Organometallic Chemistry 675 (2003) 13Á
/20
19
(t, Jꢂ
/
8.6 Hz, 1H), 1.68 (s, 3H), 1.63 (d, Jꢂ
/
8.6 Hz, 2H),
1.50 (s, 3H), 0.26 (s, 6H); 13C-NMR (100.4 MHz,
CDCl3) d 133.6, 128.8, 127.7, 119.3, 25.8, 17.7, 17.6,
135.90, 134.06, 129.89, 128.15, 99.97, 97.92, 95.65,
90.26, ꢁ
2.96; MS (20 eV) m/e 348 [Mꢀ, 24], 331 (33),
266 (28), 265 (89), 264 (80); HRMS (EI) m/e Calc. for
/
ꢁ
/
3.2.
C17H16CrO3Si: 348.0274; Found, 348.0270.
4.1.7. 2,6-Dimethyl-8-dimethyl(phenyl)silylocta-2,6-
diene (15b) [8]
4.1.11. 1-Dimethyl(phenyl)silylcyclohepta-1,3-diene
(23a)
Addition of PhMe2SiLi (6.0 mmol) to complex 14b
(1.38 g, 5.0 mmol) followed by quenching the reaction
mixture with trifluoroacetic acid (0.5 ml) gave 15b (0.44
Addition of PhMe2SiLi (6.0 mmol) to complex 22
(1.14 g, 5.0 mmol) followed by quenching the reaction
mixture with trifluoroacetic acid (0.5 ml) produced 23a
(0.58 g, 2.55 mmol, 51%) and 23b (0.19 g, 0.85 mmol,
17%) as a colorless liquid. Compound 23b rearranged to
an unidentified mixture of silyl compounds upon stand-
ing at room temperature for ca. 20 h, and only 1H-NMR
and 13C-NMR data could be obtained immediately after
column separation. Only 23a could be isolated as a pure
compound. Compound 23a: IR (CH2Cl2) 3676, 3376,
1
g, 1.62 mmol, 32%) as a colorless liquid. H-NMR (400
MHz, CDCl3) d 7.52 (m, 2H), 7.31 (m, 3H), 5.11 (m,
2H), 2.00 (m, 4H), 1.68 (s, 3H), 1.60 (s, 3H), 1.62 (m,
5H), 0.30 (s, 6H); 13C-NMR (100.4 MHz, CDCl3) d
133.6, 128.9, 127.7, 124.6, 119.6, 39.9, 27.3, 26.8, 25.6,
17.6, 15.7, ꢁ3.4.
/
2989, 1607, 1427, 1083 cmꢁ1 1H-NMR (400 MHz,
;
4.1.8. 1-Deutero-2-methyl-4-dimethyl(phenyl)silylbut-1-
ene (17)
CDCl3) d 7.51 (m, 2H), 7.33 (m, 3H), 6.14 (m, 1H), 5.88
(m, 2H), 2.35 (m, 4H), 1.79 (m, 2H), 0.35 (s, 6H); 13C-
NMR (50 MHz, CDCl3) d 145.68, 138.55, 135.53,
134.78, 134.11, 128.90, 127.74, 126.04, 32.93, 32.58,
Addition of PhMe2SiLi (3.75 mmol) to complex 14a
(0.39 g, 1.88 mmol) followed by quenching the reaction
mixture with CF3COOD (0.29 ml) produced 17 (0.15 g,
1
27.27, ꢁ
3.43; MS (20 eV) m/e 228 [Mꢀ, 60], 213 (96),
185 (31), 168 (50), 145 (34), 137 (97), 135 (49); HRMS
(EI) m/e Calc. for C15H20Si: 228.1334; Found, 228.1323.
/
0.75 mmol, 40%) as a colorless liquid. H-NMR (400
MHz, CDCl3) d 7.53 (m, 2H), 7.36 (m, 3H), 5.17 (t, Jꢂ
8.6 Hz, 1H), 1.68 (s, 3H), 1.63 (d, Jꢂ8.6 Hz, 2H), 1.50
(s, 2H), 0.26 (s, 6H).
/
/
4.1.12. 1-Dimethyl(phenyl)silylcyclohepta-1,3-diene
(23b)
1H-NMR (400 MHz, CDCl3) d 7.44 (m, 5H), 5.76 (m,
4H), 2.33 (m, 3H), 1.94 (m, 1H), 1.83 (m, 1H), 0.30 (s,
6H); 13C-NMR (100.4 MHz, CDCl3) d 138.06, 135.22,
133.87, 133.05, 128.99, 127.73, 125.62, 123.25, 35.19,
4.1.9. Addition of PhMe2SiLi to complex 19a followed by
acid quenching generated dienylsilanes 6 and 20
Addition of PhMe2SiLi (6.0 mmol) to complex 19a
(1.07 g, 5.0 mmol) followed by quenching the reaction
mixture with trifluoroacetic acid (0.5 ml) gave 6 (0.54 g,
2.5 mmol, 50%) liquid and 20 (0.13 g, 0.60 mmol, 12%)
both as colorless liquid. The analytical data of 6
obtained from this addition is identical to that of the
previous result obtained from quenching the anion
intermediate 4b with benzoyl chloride. Attempts to
obtain pure compound 20 were not successful. Com-
plexation of the impure material with Fe2(CO)9 in
refluxing ether produced complex 3a (0.04 g) after flash
column chromatography of the crude mixture. The
analytical data are consistent with that of complex 3a
obtained from addition/quenching process as mentioned
in Eq. (1).
31.86, 27.88, ꢁ
/
3.78, ꢁ4.54.
/
Acknowledgements
This work was supported by grants from National
Taiwan Normal University (ORD91-1) and the Na-
tional Science Council (NSC 90-2113-M-003-008).
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