Non-degenerate 1,2-silyl shift in silyl substituted alkyltrimethylcyclopentadienes

Article abstract of DOI:10.1016/j.jorganchem.2004.09.081

The five new silanes C₅Me₃RSiMe_nCl _{3 - n} (n = 3, R = i-Pr (5); n = 2, R = i-Pr (6); n = 2, R = s-Bu (7); n = 2, R = cyclohexyl (8); and n = 3, R = t-Bu (9)) were synthesized by reaction of 1-alkyl-2,3,4-trimethylcyclopentadienyl lithium salts with appropriate chlorosilane and characterized by NMR, MS, and IR spectra. At elevated temperatures (250-360 K), all the silanes undergo a non-degenerate sigmatropic silyl rearrangement, which generates non-equivalent structures a and b. The presence of minor structure c was observed in compounds 5 and 7 only. The Diels-Alder cycloaddition of 5 with strong dienophiles tetracyanoethylene (TCNE), and dimethylacetylenedicarboxylate (DMAD) provides compounds 10 and 11, which confirmed isomers a and b, respectively. The free energy of activation of b → a isomerization for compounds 5-8 evaluated from variable temperature NMR spectra show only marginal influence of group R on the 1,2-silyl shift rate. Moreover, in compounds 5 and 7, the process b → a was found significantly faster than b → c process in the above-mentioned temperature range.

Full text of DOI:10.1016/j.jorganchem.2004.09.081

Journal of Organometallic Chemistry 690 (2005) 731–741
www.elsevier.com/locate/jorganchem
Non-degenerate 1,2-silyl shift in silyl substituted
alkyltrimethylcyclopentadienes
a
Jirı Pinkas , Jirı Kubista , Robert Gyepes , Jirı Cejka , Philippe Meunier ,
a
b
a
c
ˇ
ˇ´
ˇ´
ˇ´
ˇ
´
a,
*
Karel Mach
a
´ ˇ
J. Heyrovsky Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Dolejskova 3, 182 23 Prague 8, Czech Republic
b
Department of Inorganic Chemistry, Charles University, Hlavova 2030, 128 40, Prague 2, Czech Republic
´
c
` ` ´ ´ ´
Laboratoire de Synthese et Electrosynthese Organometalliques Associe au CNRS (UMR 5188), Faculte des Sciences, Universite de Bourgogne,
6 boulevard Gabriel, 21000 Dijon, France
Received 23 June 2004; accepted 14 September 2004
Abstract
The five new silanes C5Me3RSiMenCl3 ꢀ n (n = 3, R = i-Pr (5); n = 2, R = i-Pr (6); n = 2, R = s-Bu (7); n = 2, R = cyclohexyl (8);
and n = 3, R = t-Bu (9)) were synthesized by reaction of 1-alkyl-2,3,4-trimethylcyclopentadienyl lithium salts with appropriate chlo-
rosilane and characterized by NMR, MS, and IR spectra. At elevated temperatures (250–360 K), all the silanes undergo a non-
degenerate sigmatropic silyl rearrangement, which generates non-equivalent structures a and b. The presence of minor structure
c was observed in compounds 5 and 7 only. The Diels–Alder cycloaddition of 5 with strong dienophiles tetracyanoethylene (TCNE),
and dimethylacetylenedicarboxylate (DMAD) provides compounds 10 and 11, which confirmed isomers a and b, respectively. The
free energy of activation of b ! a isomerization for compounds 5–8 evaluated from variable temperature NMR spectra show only
marginal influence of group R on the 1,2-silyl shift rate. Moreover, in compounds 5 and 7, the process b ! a was found significantly
faster than b ! c process in the above-mentioned temperature range.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: Substituted cyclopentadienes; Silatropic shift; Dynamic NMR spectroscopy; Diels–Alder cycloaddition; X-ray crystallography
1. Introduction
In (trimethylsilyl)cyclopentadiene both degenerate
1,2-silatropic and non-degenerate 1,2-prototropic shift
occur at ambient temperature, but the latter is 106
slower than the former one [11]. The molecule exists
mainly (up to 90%) as an allylic isomer and the remain-
ing two vinylic isomers were proved by trapping with
strong dienophiles [11,12]. A step-wise replacement of
methyl groups bonded to silicon atom by more electro-
negative chlorine atoms led to a decrease in allylic/viny-
lic isomer ratio, and an increase in free energy value
(e.g., 15.2 kcal/mol for SiMe3 and 16.3 kcal/mol for
SiCl3) [13]. In silyl substituted pentamethylcyclopenta-
dienes, however, the trend for free energy of activation
was found to be quite opposite (e.g., 15.3 kcal/mol for
SiMe3 and 13.1 kcal/mol for SiCl3) [14]. NMR
Fluxional behaviour of cyclopentadienyl-like frame-
works with r-bonded main group elements [1] is induced
by two main processes: 1,2-metallotropic and 1,2-proto-
tropic shift. The rate of both depends on the nature of
main group element, substituents bonded to this ele-
ment, and on the effect of other groups substituted on
cyclopentadienyl [2], isodicyclopentadienyl [3], indenyl
[4–7], fluorenyl [8] and higher benzannulated rings
[9,10].
*
Corresponding author. Tel.: +420 2 8658 5367; fax: +420 2 8658
2307.
E-mail address: mach@jh-inst.cas.cz (K. Mach).
0022-328X/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.09.081

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J. Pinkas et al. / Journal of Organometallic Chemistry 690 (2005) 731–741
1
ondary or tertiary alkyl group. According to H NMR
investigations of chiral silylcyclopentadienes at different
temperatures proved that 1,2-silyl migration proceeds
with retention of configuration on silicon atom [15,16].
Compounds with general formula C5(SiMe3)nH6 ꢀ n
show fluxional behavior for n = 1–3, but the compound
for n = 4 possesses only 2,3,5,5-isomer in the normal
range of temperatures [2].
Although chemistry of cyclopentadienes and methyl-
cyclopentadienes bearing organosilyl groups was widely
investigated, only a few examples of cyclopentadienes
with other non-migrating group(s) beside silyl group(s)
were published. A non-degenerate exchange process
between 1,2-(SiMe3)2-4-(t-Bu)C5H3 and 2-(t-Bu)-5,5-
(SiMe3)2C5H3 isomers was described in t-butyl-bis(tri-
methylsilyl)cyclopentadiene [17]. A fluxional behavior
of a compound resulting from introduction of one tri-
methylsilyl group on 1,4-bis(t-butyl)cyclopentadiene
was assigned by Jutzi and coworkers to a degenerate
1,2-silyl shift [18] and by Royo and coworkers to a
non-degenerate 1,3-shift [19].
spectra all the prepared cyclopentadienes contained
predominantly isomers with two protons in allylic posi-
tion (up to 91% in 1, 85% in 2, 90% in 3, and 66% in
4).
Trimethylsilyl or chlorodimethylsilyl substituted
cyclopentadienes 5–9 were obtained by the reaction of
1-alkyl-2,3,4-trimethylcyclopentadienyl lithium salts
with an excess of chlorotrimethylsilane or dichlorodi-
methylsilane, respectively, in THF (Scheme 1).
2.2. Temperature-dependent NMR spectroscopic studies
of 5–9
1
The H NMR spectra of compounds 5–9 were meas-
ured in the temperature range 200–360 K. The shape of
1H NMR spectra of compounds 5–8 in toluene-d8
strongly depended on the temperature, whereas the
changes in the spectrum of 9 were rather marginal.
The temperature-dependent spectra can be explained
by assuming a non-degenerate [1,5] sigmatropic rear-
rangement due to trimethylsilyl 1,2-shift (Scheme 2).
Cooling to temperatures below 240 K slowed down
this process on the NMR time scale and gave rise to sets
of signals representing ‘‘frozen’’ isomers a and b for
compounds 6 and 8, or isomers a, b and c for com-
pounds 5 and 7. The isomers b predominate (60–72%)
in all cases, presumably due to the absence of steric
repulsion between the bulky secondary alkyl group
and the silyl group. Abundances of isomer c in com-
pounds 5 and 7 are only 6% and 4%, respectively. The
signals of allylic and vinylic protons broadened with
increasing temperature, and showed coalescence at
about 330 K for 6 and 8, at 340 K for 7, and at 360 K
for 5 (Fig. 1). The further increase in temperature above
350 K resulted in merging the signals to a single reso-
nance at 4.94 ppm for 6, 4.80 ppm for 7, and 4.93
ppm for 8. The proportion between isomers a, b (and
c in compounds 5 and 7) is unaffected by increase in
the temperature, and it indicates the absence of other
Here, we report the synthesis of five new ((alkyl)tri-
methylcyclopentadienyl)silanes with sterically demand-
ing alkyls, their dynamic NMR study showing thermal
dependence of the silyl migration rate, and an evidence
for isomer structures involved in the fluxional process.
2. Results and discussion
2.1. Synthesis of silyl substituted
alkyltrimethylcyclopentadienes
1-Alkyl-2,3,4-trimethylcyclopentadienes (mixture of
isomers, where alkyl = i-Pr (1), s-Bu (2), cyclohexyl
(3), t-Bu (4)) were prepared by the reaction of appro-
priate alkyl Grignard (or lithium) reagent with a
mixture of 2,3,4-trimethylcyclopent-2-en-1-one and
3,4,5-trimethylcyclopent-2-en-1-one [20], followed by
hydrolysis, and an iodine catalyzed dehydration. The
cyclopentadienes were obtained in rather low yields
(36–47%), presumably due to a steric hindrance of sec-
Scheme 1. Preparation of silanes 5–9.

J. Pinkas et al. / Journal of Organometallic Chemistry 690 (2005) 731–741
733
Scheme 2. Non-degenerate silyl group rearrangement in silyl substituted (alkyl)trimethylcyclopentadienes.
fluxional processes. The migration of trimethylsilyl
group in compound 9 was evidenced by the shift of viny-
lic proton signal from 5.86 ppm at 280 K to an averaged
signal positioned at 5.82 ppm at 370 K. This estimates
the content of isomer b to be higher than 99%. This cir-
cumstance precludes the evaluation of relevant activa-
tion parameters for 9.
groups by electron-attracting chlorine atoms (e.g., 14.8
kcal/mol for C5Me5SiMe3, and 13.8 kcal/mol for C5Me5-
SiMe2Cl) [14].
2.3. Diels–Alder reaction of 5 with dienofiles
In order to confirm the isomers assumed from low
temperature 1H and 13C {1H} NMR measurements,
compound 5 was reacted with strong dienophiles: tetra-
cyanoethylene (TCNE), and dimethylacetylenedicarb-
oxylate (DMAD) (Scheme 3). The reaction with less
reactive DMAD [21,22] independently of the reaction
temperature (25 and 140 ꢁC) gave only one product. A
typical proton bridgehead signal of relative intensity 1
at 3.67 ppm, together with only one downfield shifted
methyl signal at 1.64 ppm (due to the methyl group at-
tached to the double bond) is compatible with structure
10. The orientation of 7-positioned trimethylsilyl group
in exo position towards the dimethylethenediylcarboxy-
late bridge was deduced from NOESY experiment show-
ing a strong through-space interaction of SiMe3 protons
with the methyl group placed on the double bound.
On the other hand, the reaction of 5 with TCNE at 25
ꢁC afforded product 11 arising from isomer 5a. The pro-
ton NMR spectrum of 11 showed the bridging proton
signal at 1.51 ppm, and two signals at 1.31 and 1.45
ppm of methyl groups placed on double bond, showing
a mutual homoallylic interaction (5JHH = 1.0 Hz). The
structure of 11 was also confirmed by X-ray diffraction
analysis (vide infra).
The careful band-shape analysis of recorded spectra
(for details see Section 3) provided the rate constants
for b ! a and b ! c processes. The simulation of exper-
imental spectra excluded a ! c (due to 1,3-silyl shift)
process in the range of studied temperatures. In com-
pounds 5 (Fig. 2) and 7, the silyl migration b ! a was
found significantly faster than b ! c (evaluated rate
constants kba are about 20 times higher than kbc). Acti-
vation parameters (free energy of activation DGz300, free
enthalpy DHà, and entropy DSà) for b ! a and for
b ! c (in compounds 5 and 7) generated from Eyring
plots are summarised in Table 1. The obtained DG3z00
values show only marginal influence of bulky alkyl
groups on free energy of rearrangement b ! a in com-
pounds 5–8, or b ! c in compounds 5 and 7. Signifi-
cantly higher DGz300 values for b ! c process compared
to DGz300 values for b ! a in compounds 5 and 7 can
be attributed to steric repulsion between silyl and methyl
groups during the transition state formation. A slightly
higher DGz300 for b ! a in 5 compared to 6 is in rough
agreement with previously reported lowering of DG3z00
in a series of C5Me5SiMenCl3 ꢀ n (for n = 0–3) com-
pounds upon replacing of electron-donating methyl

734
J. Pinkas et al. / Journal of Organometallic Chemistry 690 (2005) 731–741
Fig. 1. Dynamic 1H NMR spectra of 5 in the temperature range 233–360 K.
These results can be accounted for by different steric
talline 11 resulted in its decomposition above 122 ꢁC.
The easy dissociation of 11 was corroborated by its
EI-MS spectra showing the ionised products of retro
Diels–Alder reaction only.
crowding in 5a and 5b isomers with respect to entering
dienophiles. Whereas a mutual steric congestion of iso-
propyl and methylcarboxylate groups disfavours the ap-
proach of DMAD to isomer 5a, the reaction of DMAD
with 5b is possible. For TCNE, the reaction with ‘‘more
hindered’’ isomer 5a took place only to give 11 as a
kinetically preferred product. Our attempts to obtain
an expected thermodynamic product at 140 ꢁC gave a
number of unidentifiable products, and heating of crys-
2.4. Crystal structure of 11
The structure of Diels–Alder adduct 11 was corrobo-
rated by X-ray diffraction analysis (Fig. 3). The selected
bond lengths and angles are given in Table 2. The most

J. Pinkas et al. / Journal of Organometallic Chemistry 690 (2005) 731–741
735
kba kbc
[s-1] [s-1]
T
[K]
360 3142 168
350 1862 106
340 904 55
330 629 30
320 367 18
310 209 10
300 107
8
2
250
7
6.0
5.5
5.0
4.5
ppm
4.0
3.5
3.0
2.5
Hc
Ha
Hb
SiMe3
Hb
Hc
i-Pr
Ha
i-Pr
i-Pr
kab
kba
kbc
kcb
SiMe3
SiMe3
5a
5b
5c
Fig. 2. Expanded region of experimental (upper) and simulated (lower) 1H NMR spectra for 5 in toluene-d8 in the temperature range 250–360 K. The
simulated signals are denoted Ha–c, and their assignment is depicted in the attached scheme.
Table 1
Activation parameters obtained from an Eyring plot for b ! a and b ! c rearrangements in compounds 5–8
Compound
b ! a
b ! c
DGz300 (kcal/mol)
DHà (kcal/mol)
DSà (cal/K/mol)
DGz300 (kcal/mol)
DHà (kcal/mol)
DSà (cal/K/mol)
ꢀ15.3 0.6
5
6
7
8
14.8 0.1
14.5 0.3
14.2 0.2
14.1 0.2
11.2 0.1
6.2 0.3
10.3 0.1
9.9 0.1
ꢀ12.1 0.4
ꢀ27.5 1.1
ꢀ13.0 0.6
ꢀ13.9 0.7
16.6 0.2
12.0 0.1
Not observed
15.9 0.3
Not observed
11.4 0.1
ꢀ14.9 0.9
˚
dimethylfulvene (1.601 and 1.607 A) [24], isodicyclo-
˚
pentadiene (1.591 and 1.600 A) [25], and (trimethylsi-
important factor indicating the stability of 11 towards
the retro-Diels–Alder reaction is the length of new C–
˚
C bonds. Whereas the C3–C4 value (1.608(2) A) lies in
the range typical for new formed bonds in other
Diels–Alder adducts of TCNE with, e.g., chlorocyclo-
˚
pentadiene (1.604 and 1.607 A) [23], chloropentamethyl-
˚
cyclopentadiene (1.602 and 1.603 A) [23], 6,6-
˚
lyl)indene (1.582(2) and 1.593(8) A) [7], the C1–C2
˚
length of 1.628(2) A is significantly longer, apparently
due to a steric hindrance of neighbouring iso-propyl
group. These structural data are in agreement with a fac-
ile decomposition of 11 to starting materials as it was

736
J. Pinkas et al. / Journal of Organometallic Chemistry 690 (2005) 731–741
SiMe3
H
H
i-Pr
i-Pr
H
i-Pr
SiMe3
SiMe
3
5a
5b
5c
Me3Si
H
Me3Si
7
7
i-Pr
2
H
CN
CN
CN
i-Pr
5
1
6
5
COOMe
4
3
4
3
1
6
2
CN
COOMe
11
10
Scheme 3. Reaction of 5 with TCNE and DMAD.
molecule, as evidenced by remarkably larger Si–C7–C1
angle compared to Si–C7–C4
(120.44(10)ꢁ)
(113.77(10)ꢁ).
3. Experimental
3.1. General procedures
All reactions with moisture- and air-sensitive com-
pounds were carried out under an atmosphere of ar-
gon. Solvents were dried by potassium benzophenone
(tetrahydrofuran, diethylether), LiAlH4 (xylene), and
CaH2 (dichloromethane), and freshly distilled prior to
use. A mixture of trimethylcyclopentenones was pre-
pared according to the literature procedure [26]. Cyclo-
hexylbromide, iso-propylchloride, sec-butylchloride,
dichlorodimethylsilane, chlorotrimethylsilane, tetracy-
anoethylene (TCNE), and dimethylacetylenedicarb
oxylate (DMAD) were obtained from Aldrich and
used as received. 1H NMR (500 MHz) and 13C
Fig. 3. Molecular structure of 11 (30% probability thermal motion
ellipsoids) showing the atom numbering scheme. The hydrogen atoms
are omitted for clarity.
NMR (125 MHz) were measured on
a Bruker
Table 2
DRX500 spectrometer in benzene-d6 solution at 300
K, or in toluene-d8 for temperature-dependent experi-
ments in the temperature range 200–360 K. EI-MS
spectra were measured on a KRATOS Concept 32S
˚
Selected bond lengths (A) and angles (ꢁ) for 11
Si–C7
1.935(2)
1.628(2)
1.553(2)
1.608(2)
1.525(2)
C–Na
1.141(2)–1.146(2)
1.539(2)
1.600(2)
C1–C2
C1–C7
C3–C4
C4–C5
C1–C6
C2–C3
C4–C7
C5–C6
1.551(2)
1.337(2)
´
instrument (Centre de Spectroscopie Moleculaire de
´
lÕUniversite de Bourgogne) at 70 eV, or on a VG-
7070E mass spectrometer at 70 eV. GC–MS analyses
were carried out on a Hewlett–Packard gas chromato-
graph (5890 series II; capillary column SPB-1 (Supe-
lco)) interfaced to a mass spectrometric detector
(5791 A). Infrared spectra were recorded on a Nicolet
Avatar FT-IR spectrometer in the range 400–4000
cmꢀ1. Melting points were measured on a Koffler
block and were uncorrected.
Si–C7–C(1) 120.44(10)
C–C–Nb
Si–C7–C4 113.77(10)
176.33(17)–178.65(16)
a
Range of C–N bond lengths in four carbonitrile groups.
Range of angles in four carbonitrile groups.
b
observed by EI-MS. The steric hindrance of iso-propyl
group is also responsible for declination of trimethylsilyl
group from the iso-propyl-substituted side of the

J. Pinkas et al. / Journal of Organometallic Chemistry 690 (2005) 731–741
737
3.2. Preparation of 1-iso-propyl-2,3,4-trimethyl-
cyclopenta-1,3-diene (1)
(C5Me3); 12.96 (CH2Me); 21.83 (CHMe); 31.44
(C2Me); 34.99 (CHMe); 42.39 (CH2, Me3(s-Bu)C5H2);
131.94, 136.06, 136.14, 141.39 (Cq, Me3(s-Bu)C5H2).
GC–MS, m/z (relative abundance): 165 (6), 164 (M+Å;
32), 149 ([M ꢀ Me]+; 14), 136 (22), 135 ([M ꢀ Et]+;
100), 121 (12), 120 (16), 119 (34), 107 (20), 105 (28), 93
(24), 91 (39), 79 (16), 77 (21), 65 (12), 41 (24). IR (neat,
cmꢀ1): 2960 (vs), 2917 (vs), 2872 (vs), 1655 (vw), 1453
(s), 1377 (s), 1332 (vw), 1311 (w), 1286 (vw), 1228
(vw), 1168 (m), 1123 (w), 1089 (w), 1057 (vw), 988 (w),
952 (vw), 859 (vw), 693 (vw), 513 (w).
A solution of iso-propylchloride (23.5 g, 300 mmol) in
diethyl ether (80 ml) was added drop-wise to a mixture
of magnesium turnings (9.4 g, 400 mmol) with a small
amount (ca. 0.1 g) of iodine in diethyl ether (50 ml) at
a rate maintaining a mild reflux. After the reaction
ceased the mixture was refluxed for additional 30 min.
After cooling, a mixture of trimethylcyclopentenones
(24.8 g, 200 mmol) in 50 ml of diethyl ether was slowly
added and the reaction mixture was refluxed for 2 h.
Resulting grey-green mixture was poured onto crushed
ice (ca. 50 g) and the product was extracted with diethyl
ether (4 · 100 ml). Volume of combined organic phases
was reduced to ca. 100 ml and a few crystals of iodine
were added to induce dehydration of the obtained alco-
hol. The mixture was left standing overnight, while a
water layer separated. The resulting brown mixture
was washed subsequently with saturated aqueous so-
dium thiosulphate solution (2 · 40 ml), water (20 ml)
and dried over sodium sulphate. The solvent was re-
moved on a rotary evaporator and the crude product
was distilled at reduced pressure (11 mmHg). The prod-
uct distilled at 72–74 ꢁC as a colorless liquid. Yield: 10.7
g (36%).
3.4. Preparation of 1-cyclohexyl-2,3,4-trimethyl-
cyclopenta-1,3-diene (3)
The above-described procedure was used. A Grig-
nard reagent prepared from cyclohexylbromide (21.5 g,
130 mmol) was reacted with a mixture of trimethylcyclo-
pentenones (14.9 g, 120 mmol) to give a magnesium
alcoholate which afforded after hydrolysis, iodine-cata-
lyzed dehydration, and distillation at 75–78 ꢁC/2 mmHg
compound 3 as a slightly yellow liquid. Yield: 10.4 g
(46%).
1H NMR (C6D6): 1.15–1.32 (m, 6H, b-CH2 and c-
CH2, cyclohexyl); 1.62–1.79 (partially overlapped by a
stronger signal of methyl protons, m, 4H, a-CH2, cyclo-
hexyl); 1.73, 1.77, 1.85 (3 · s, 3 · 3H, C5Me3); 2.50 (tt,
3
1H NMR (C6D6): 1.03 (d, JHH = 6.9 Hz, 6H,
4
CHMe2); 1.71, 1.74, 1.84 (3 · s, 3 · 3H, C5Me3); 2.59
3JHH = 11.4 Hz, JHH = 3.3 Hz, 1H, CH, cyclohexyl);
3
(br s, 2H, Me3(i-Pr)C5H2); 2.82 (septuplet, JHH = 6.9
2.62 (br s, 2H, Me3(cyclohexyl)C5H2). 13C {1H}
(C6D6): 10.87, 10.91, 13.34 (C5Me3); 23.58, 26.97,
33.91 (CH2, cyclohexyl); 37.85 (CH, cyclohexyl); 43.13
(CH2, Me3(cyclohexyl)C5H2); 131.55, 134.58, 135.84,
141.91 (Cq, Me3(cyclohexyl)C5H2). GC–MS, m/z (rela-
tive abundance): 190 (M+Å; 26), 175 ([M ꢀ Me]+; 10),
147 (29), 134 (13), 133 (13), 121 (9), 119 (26), 109 (9),
108 (37), 107 (14), 105 (16), 93 (26), 91 (32), 79 (12),
77 (15), 65 (9), 55 (22), 53 (11), 41 (100), 39 (32). IR
(neat, cmꢀ1): 2923 (vs), 2852 (vs), 1653 (vw), 1448 (s),
1380 (s), 1333 (w), 1299 (vw), 1262 (w), 1243 (vw),
1162 (m), 1122 (w), 1085 (m), 1043 (w), 1026 (w), 990
(w), 949 (w), 889 (m), 850 (w), 781 (vw), 692 (vw), 510
(m).
Hz, 1H, CHMe2). 13C {1H} (C6D6): 11.23, 11.26, 13.58
(C5Me3); 23.60 (CHMe2); 27.59 (CHMe2); 42.28 (CH2,
Me3(i-Pr)C5H2); 131.61, 134.67, 136.06, 142.66 (Cq,
Me3(i-Pr)C5H2). GC–MS, m/z (relative abundance):
151 (8), 150 (M+Å; 41), 136 (17), 135 ([M ꢀ Me]+; 100),
120 (13), 119 (28), 108 (7), 107 (16), 105 (14), 93 (19),
91 (26), 79 (9), 77 (11), 65 (6), 41 (7), 39 (7). IR (neat,
cmꢀ1): 2959 (vs), 2924 (s), 2869 (s), 1656 (vw), 1625
(vw), 1444 (m), 1382 (m), 1360 (w), 1309 (w), 1235
(w), 1171 (w), 1123 (w), 1088 (w), 1050 (w), 853 (w),
693 (w).
3.3. Preparation of 1-sec-butyl-2,3,4-trimethyl-
cyclopenta-1,3-diene (2)
3.5. Preparation of 1-tert-butyl-2,3,4-trimethyl-
cyclopenta-1,3-diene (4)
The above-described procedure was used. A Grig-
nard reagent prepared from sec-butylchloride (22.2 g,
240 mmol) was reacted with a mixture of trimethylcyclo-
pentenones (19.8 g, 160 mmol) to give a magnesium
alcoholate which afforded after hydrolysis, iodine-cata-
lyzed dehydration and distillation at 71–74 ꢁC/7 mmHg
compound 2 as a colorless liquid. Yield: 10.0 g (38%).
A slightly modified procedure was used. A pentane
solution of t-BuLi (55 ml, 1.7 M, 93 mmol) was reacted
with a mixture of trimethylcyclopentenones (10.5 g, 85
mmol) in pentane (100 ml) to give after hydrolysis, io-
dine-catalyzed dehydration and distillation at 80–82
ꢁC/5 mmHg compound 4 as a colorless liquid. Yield:
6.5 g (47%).
1H NMR (C6D6): 1.19 (s, 9H, CMe3); 1.68, 1.82, 1.88
(3 · s, 3 · 3H, C5Me3); 2.59 (br s, 2H, Me3(t-Bu)C5H2).
13C {1H} (C6D6): 11.05, 13.14, 13.26 (C5Me3); 30.75
3
1H NMR (C6D6): 0.79 (t, JHH = 7.5 Hz, 3H,
3
CH2Me); 1.02 (d, JHH = 7.0 Hz, 3H, CHMe); 1.28–
1.45 (m, 2H, CH2Me); 1.71, 1.74, 1.84 (3 · s, 3 · 3H,
C5Me3); 2.50–2.55 (m, 1H, CHMe); 2.56–2.60 (m, 2H,
Me3(s-Bu)C5H2). 13C {1H} (C6D6): 11.39, 11.55, 13.69

738
J. Pinkas et al. / Journal of Organometallic Chemistry 690 (2005) 731–741
(CMe3); 32.93 (CMe3); 45.51 (CH2, Me3(t-Bu)C5H2);
130.78, 134.34, 136.71, 143.82 (Cq, Me3(t-Bu)C5H2).
GC–MS, m/z (relative abundance): 165 (6), 164 (M+Å;
37), 150 (13), 149 ([M ꢀ Me]+; 100), 134 (22), 133 (21),
119 (15), 108 (57), 93 (54), 91 (37), 79 (13), 77 (17), 57
(22), 41 (17). IR (neat, cmꢀ1): 2962 (vs), 2909 (vs),
2868 (vs), 1653 (m), 1624 (w), 1447 (s), 1382 (s), 1326
(w), 1294 (vw), 1253 (m), 1213 (w), 1188 (m), 1124
(w), 1081 (w), 1044 (w), 1014 (w), 856 (w), 793 (w),
748 (vw), 696 (vw), 510 (w).
3.7. Preparation of 6
A hexane solution of n-butyllithium (17.5 ml, 1.6 M,
28 mmol) was slowly dropped at 0 ꢁC to a solution of 1
(4.17 g, 28 mmol) in diethyl ether (80 ml). The reaction
mixture was allowed to warm to room temperature and
stirred overnight. The resulting white precipitate was fil-
tered, washed three times with 20 ml of diethyl ether and
suspended in THF (60 ml). The THF suspension was
transferred to an excess of dichlorodimethylsilane (6.1
g, 56 mmol) in the same solvent previously cooled to
ꢀ78 ꢁC. The reaction mixture was allowed to warm to
room temperature and then stirred for additional 14 h.
Volatiles were removed in vacuum, and an oily residue
was dissolved in pentane (30 ml), and filtered to remove
LiCl. The pentane was evaporated in vacuum to leave
compound 6 (a mixture of isomers) as a slightly yellow
liquid. Yield: 5.57 g (82%).
EI-MS, m/z (relative abundance): 244 (29), 243 (16),
242 (M+Å; 80), 229 (42), 228 (21), 227 ([M ꢀ Me]+;
100), 207 ([M ꢀ Cl]+;13), 149 ([M ꢀ SiMe2Cl]+; 48),
135 (15), 134 (18), 133 (80), 119 (27), 105 (14), 95 (31),
93 ([SiMe2Cl]+; 94), 91 (20), 79 (7), 77 (8). IR (neat,
cmꢀ1): 2961 (vs), 2927 (s), 2869 (s), 1615 (vw), 1544
(vw), 1456 (m), 1403 (w), 1383 (m), 1362 (w), 1316
(vw), 1252 (vs), 1200 (vw), 1171 (vw), 1147 (w), 1122
(w), 1072 (w), 1030 (w), 988 (w), 959 (vw), 922 (vw),
843 (vs), 811 (vs), 787 (vs), 726 (vw), 687 (w), 665 (m),
584 (vw), 544 (w), 499 (m), 471 (s), 423 (vw).
3.6. Preparation of 5
To a stirred solution of 1 (6.2 g, 41 mmol) in THF
(350 ml) was slowly dropped butyllithium solution in
hexane (21 ml, 2.5 M, 52 mmol). A voluminous white
precipitate formed after several minutes. After stirring
for additional 5 h, chlorotrimethylsilane (7.0 ml, 57
mmol) was added in one portion, and the mixture was
then stirred overnight. Volatiles were removed at a re-
duced pressure, and the residue was fractionally distilled
in vacuum. The core fraction distilled at 60–61 ꢁC (0.5
mmHg) as a slightly yellow liquid (a mixture of isomers).
Yield: 3.3 g (37%).
GC–MS, m/z (relative abundance): 223 (10), 222
(M+Å; 46), 208 (6), 207 ([M ꢀ Me]+; 31), 149 (12), 148
(42), 147 (6), 134 (10), 133 (46), 119 (16), 105 (8), 91
(9), 75 (5), 74 (8), 73 ([SiMe3]+; 100), 59 (6), 45 (11).
IR (neat, cmꢀ1): 2958 (vs), 2927 (s), 2867 (s), 1658
(vw), 1614 (vw), 1547 (vw), 1513 (vw), 1453 (m), 1404
(w), 1381 (w), 1361 (w), 1260 (m), 1248 (vs), 1147 (w),
1119 (w), 1069 (w), 1027 (w), 983 (w), 837 (vs), 798
(m), 751 (m), 684 (m), 624 (m).
3.7.1. Isomer 6a: chloro(2-iso-propyl-3,4,5-
trimethylcyclopenta-2,4-dien-1-yl)dimethylsilane
1H NMR (toluene-d8, 233 K): 0.20, 0.21 (2 · s,
2 · 3H, SiMe2Cl); 1.20, 1.32 (2 · d, 2 · 3JHH = 7.0 Hz,
2 · 3H, CHMe2); 1.71, 1.88, 1.93 (3 · s, 3 · 3H,
C5Me3); 2.77 (septuplet, JHH = 7.0 Hz, 1H, CHMe2);
2.93 (br s, 1H, Me3(i-Pr)(SiMe2Cl)C5H).
3
3.6.1. Isomer 5a: (2-iso-propyl-3,4,5-trimethylcyclo-
penta-2,4-dien-1-yl)trimethylsilane
1H NMR (toluene-d8, 233 K): 0.04 (s, 9H, SiMe3);
1.25, 1.36 (2 · d, 2 · 3JHH = 7.0 Hz, 2 · 3H, CHMe2);
1.81, 1.92, 1.98 (3 · s, 3 · 3H, C5Me3); 2.55–2.65 (m,
1H, CHMe2); 2.71 (br s, 1H, Me3(i-Pr)(SiMe3)C5H).
13C {1H} (toluene-d8 233 K): ꢀ1.04 (SiMe3); 11.62,
13.28, 15.25 (C5Me3); 22.20, 23.35 (CHMe2); 29.76
(CHMe2); 55.49 (CH, Me3(i-Pr)(SiMe3)C5H); 132.24,
133.52, 136.96, 143.54 (Cq, Me3(i-Pr)(SiMe3)C5H).
3.7.2. Isomer 6b: chloro(4-iso-propyl-1,2,3-
trimethylcyclopenta-2,4-dien-1-yl)dimethylsilane
1H NMR (toluene-d8, 233 K): 0.03, 0.24 (2 · s,
2 · 3H, SiMe2Cl); 1.05, 1.16 (2 · d, 2 · 3JHH = 7.0 Hz,
2 · 3H, CHMe2); 1.37 (s, 3H, C(SiMe2Cl)Me); 1.78,
1.91 (2 · s, 2 · 3H, 2 · @CMe); 2.50 (septuplet,
3JHH = 7.0 Hz, 1H, CHMe2); 5.81 (s, 1H, @CH).
3.6.2. Isomer 5b: (4-iso-propyl-1,2,3-trimethylcyclo-
penta-2,4-dien-1-yl)trimethylsilane
3.8. Preparation of 7
1H NMR (toluene-d8, 233 K): ꢀ0.04 (s, 9H, SiMe3);
1.16, 1.25 (2 · d, 2 · 3JHH = 7.0 Hz, 2 · 3H, CHMe2);
1.26 (s, 3H, C(SiMe3)Me); 1.83, 1.87 (2 · s, 2 · 3H,
2 · =CMe); 2.55–2.65 (m, 1H, CHMe2); 5.90 (s, 1H,
@CH). 13C {1H} (toluene-d8 233 K): ꢀ2.66 (SiMe3);
11.30, 12.40, 14.48 (C5Me3); 22.57, 24.02 (CHMe2);
27.62 (CHMe2); 51.23 (Cipso); 127.94 (@CH); 137.57,
142.54, 151.93 (Cq, Me3(i-Pr)(SiMe3)C5H).
The above procedure for obtaining 6 was used. The
lithium salt prepared from 2 (5.57 g, 34 mmol) and n-
butyllithium hexane solution (21.3 ml, 1.6 M, 34 mmol)
was reacted with an excess of dichlorodimethylsilane
affording 7 as a yellow liquid (a mixture of isomers).
Yield: 5.70 g (66%).
EI-MS, m/z (relative abundance): 258 (11), 257 (6),
256 (M+Å; 30), 229 (16), 228 (8), 227 ([M ꢀ Et]+; 44),

J. Pinkas et al. / Journal of Organometallic Chemistry 690 (2005) 731–741
739
163 ([M ꢀ SiMe2Cl]+; 9), 135 (17), 134 (19), 133 (26),
3.9.2. Isomer 8b: chloro(4-cyclohexyl-1,2,3-
trimethylcyclopenta-2,4-dien-1-yl)dimethylsilane
119 (30), 105 (14), 95 (60), 94 (14), 93 ([SiMe2Cl]+;
100), 91 (16), 79 (11), 78 (13), 77 (11), 67 (14), 65 (40),
63 (25). IR (neat, cmꢀ1): 2962 (vs), 2928 (s), 2872 (s),
1615 (vw), 1542 (vw), 1455 (m), 1377 (m), 1252 (vs),
1196 (vw), 1145 (w), 1118 (w), 1074 (w), 1025 (w), 989
(m), 961 (w), 843 (vs), 812 (vs), 787 (vs), 666 (m), 544
(w), 499 (m), 474 (s).
1H NMR (toluene-d8, 233 K): ꢀ0.01, 0.21 (2 · s,
2 · 3H, SiMe2Cl); 1.10–1.31 (m, 6H, b-CH2 and c-
CH2, cyclohexyl); 1.33 (s, 3H, C(SiMe2Cl)Me); 1.66–
1.78 (m, a-CH2, cyclohexyl); 1.75, 1.86 (2 · s, 2 · 3H,
2 · @CMe); 2.08–2.18 (m, 1H, CH, cyclohexyl); 5.74
(s, 1H, @CH).
3.10. Preparation of 9
3.8.1. Isomer 7a: (2-(sec-butyl)-3,4,5-
trimethylcyclopenta-2,4-dien-1-yl)chlorodimethylsilane
1H NMR (toluene-d8, 233 K): 0.14, 0.19 (2 · s,
The above procedure for obtaining 6 was used. The
lithium salt prepared from 4 (2.30 g, 14 mmol) and n-
butyllithium hexane solution (8.8 ml, 1.6 M, 14 mmol)
was reacted with an excess of chlorotrimethylsilane
yielding 9 as a yellow liquid. Yield: 2.40 g (73%).
EI-MS, m/z (relative abundance): 237 (11), 236 (M+Å;
44), 222 (11), 221 ([M ꢀ Me]+; 50), 180 (10), 163
([M ꢀ SiMe3]+; 11), 162 ([M ꢀ SiMe3H]+; 35), 148
(21), 147 (97), 133 (17), 119 (8), 105 (13), 91 (15), 77
(8), 75 (20), 74 (33), 73 ([SiMe3]+; 100), 59 (14), 45
(32), 43 (17), 41 (21). IR (neat, cmꢀ1): 2954 (vs), 2926
(s), 2902 (s), 2867 (s), 1602 (vw), 1477 (w), 1456 (w),
1382 (w), 1360 (m), 1283 (vw), 1259 (m), 1247 (vs),
1213 (w), 1200 (w), 1155 (w), 1111 (vw), 1070 (w),
1038 (vw), 1009 (w), 839 (vs), 801 (m), 751 (m), 687
(m), 622 (w), 550 (vw), 416 (w).
3
2 · 3H, SiMe2Cl); 0.78 (t, JHH = 6.5 Hz, 3H, CH2Me);
0.99 (d, JHH = 6.0 Hz, 3H, CHMe); 1.20–1.55 (m, 2H,
3
CH2Me); 1.67, 1.83, 1.90 (3 · s, 3 · 3H, C5Me3); 2.38–
2.48 (m, 1H, CHMe); 2.80 (s, 1H, Me3(s-
Bu)(SiMe2Cl)C5H).
3.8.2. Isomer 7b: (4-(sec-butyl)-1,2,3-
trimethylcyclopenta-2,4-dien-1-yl)chlorodimethylsilane
1H NMR (toluene-d8, 233 K): ꢀ0.01, 0.21 (2 · s,
3
2 · 3H, SiMe2Cl); 0.88 (t, JHH = 7.0 Hz, 3H, CH2Me);
1.08 (d, JHH = 6.5 Hz, 3H, CHMe); 1.20–1.55 (m, 2H,
3
CH2Me); 1.31 (s, 3H, C(SiMe2Cl)Me); 1.73, 1.85
(2 · s, 2 · 3H, 2 · =CMe); 2.21–2.30 (m, 1H, CHMe);
5.80 (s, 1H, @CH).
3.9. Preparation of 8
3.10.1. Isomer 9b: (4-tert-butyl-1,2,3-
trimethylcyclopenta-2,4-dien-1-yl)trimethylsilane
1H NMR (C6D6): 0.09 (s, 9H, SiMe3); 1.22 (s, 3H,
C(SiMe3)Me); 1.28 (s, 9H, CMe3); 1.76, 2.00 (2 · s,
2 · 3H, 2 · =CMe); 5.90 (s, 1H, @CH). 13C {1H}
(C6D6): ꢀ2.65 (SiMe3); 12.16, 13.93 (2 · @CMe);
14.18 (C(SiMe3)Me); 30.44 (CMe3); 32.99 (CMe3);
45.84 (C(SiMe3)Me); 129.76 (br, @CH); 133.33,
144.01, 153.47 (Cq).
The above-described procedure was used. The lith-
ium salt prepared from 3 (3.30 g, 17.4 mmol) and n-
butyllithium hexane solution (10.9 ml, 1.6 M, 17.4
mmol) was reacted with excess dichlorodimethylsilane
to give 8 (a mixture of isomers) as a yellow liquid. Yield:
3.40 g (69%).
EI-MS, m/z (relative abundance): 284 (18), 283 (14),
282 (M+Å; 55), 239 (7), 200 (13), 189 ([M ꢀ SiMe2Cl]+;
26), 147 (6), 145 (9), 133 (21), 119 (10), 105 (14), 95
(39), 94 (10), 93 ([SiMe2Cl]+; 98), 91 (19), 65 (22), 55
(18), 43 (100), 42 (71), 41 (91), 40 (14), 39 (60). IR (neat,
cmꢀ1): 2919 (vs), 2850 (vs), 1614 (w), 1541 (vw), 1448 (s),
1403 (m), 1385 (m), 1344 (w), 1251 (vs), 1223 (w), 1190
(vw), 1179 (vw), 1147 (m), 1124 (m), 1078 (m), 1027 (m),
993 (s), 959 (w), 929 (w), 889 (s), 846 (vs), 810 (vs), 787
(vs), 754 (m), 671 (s), 638 (w), 535 (m), 502 (s), 470 (s),
432 (w).
3.11. Preparation of 5-iso-propyl-1,6,7-trimethyl-7-
trimethylsilyl-bicyclo[2.2.1]hepta-2,5-diene-2,3-
dicarboxylic acid dimethyl ester (10)
At 140 ꢁC: To a xylene solution (20 ml) of preequili-
brated (by reflux for 20 min) silanes 5 (636.0 mg, 2.86
mmol) DMAD (407.0 mg, 2.86 mmol) was added by syr-
inge. The reaction mixture was refluxed with stirring for
additional 2 h, and the main part of the solvent was
evaporated at a reduced pressure. An orange oily resi-
due was diluted by minimum amount of hexane (5
ml), and the solution was cooled to ꢀ78 ꢁC. A brownish
precipitate was separated, washed by cold hexane (3 · 2
ml), and dried in vacuum. Yield: 810.0 mg (78%).
At 25 ꢁC: The mixture of isomers 5 (320.0 mg, 1.44
mmol) was diluted by dichloromethane (15 ml), and
DMAD (205.0 mg, 1.44 mmol) was added. The reaction
3.9.1. Isomer 8a: chloro(2-cyclohexyl-3,4,5-
trimethylcyclopenta-2,4-dien-1-yl)dimethylsilane
1H NMR (toluene-d8, 233 K): 0.15, 0.18 (2 · s,
2 · 3H, SiMe2Cl); 0.98–1.20 (m, 6H, b-CH2 and c-
CH2, cyclohexyl); 1.66–1.78 (m, a-CH2, cyclohexyl);
1.67, 1.81, 1.88 (3 · s, 3 · 3H, C5Me3); 2.25–2.35 (m,
1H, CH, cyclohexyl); 2.87 (s, 1H, Me3(cyclohexyl)
(SiMe2Cl)C5H).
1
mixture was stirred in the dark for 30 h. A H NMR

740
J. Pinkas et al. / Journal of Organometallic Chemistry 690 (2005) 731–741
spectroscopy of resulting yellow solution revealed the
same product as in the above-described case.
147 (5), 134 (9), 133 (44), 128 ([(CN)2C@C(CN)2]+; 21),
119 (12), 105 (8), 103 (6), 91 (11), 77 (7), 76 (24), 75
(12), 74 (25), 73 ([SiMe3]+; 100), 59 (16), 45 (30), 41
(12). IR (KBr, cmꢀ1): 3000 (m), 2981 (s), 2950 (s), 2926
(m), 2900 (m), 2856 (m), 2245 (vw), 1651 (vw), 1471
(m), 1455 (m), 1395 (m), 1385 (m), 1344 (vw), 1300
(vw), 1256 (vs), 1228 (m), 1181 (w), 1130 (vw), 1101
(vw), 1078 (w), 1059 (w), 1041 (w), 1000 (vw), 943 (vw),
918 (w), 860 (vs), 844 (vs), 789 (vw), 768 (m), 753 (m),
688 (w), 669 (vw), 655 (vw), 622 (vw), 439 (vw).
M.p. 77–79 ꢁC. 1H NMR (C6D6): ꢀ0.07 (s, 9H,
SiMe3); 0.83, 1.05 (2 · d, 2 · 3JHH = 7.0 Hz, 2 · 3H,
CHMe2); 1.11 (s, 3H, C(7)Me); 1.20 (s, 3H, C(1)Me);
3
1.64 (s, 3H, C(6)Me); 2.57 (septuplet, 1H, JHH = 7.0
Hz, CHMe2); 3.39, 3.49 (2 · s, 2 · 3H, COOMe); 3.67
(s, 1H, C(4)H). 13C {1H} (C6D6): 0.10 (SiMe3); 10.97
(C(1)Me); 11.78 (C(6)Me); 16.69 (C(7)Me); 20.58,
20.85 (CHMe2); 27.64 (CHMe2); 51.25, 51.34
(2 · COOMe); 58.76 (C(4)H); 69.81, 78.67 (Cq(1) and
Cq(7)); 145.94 (Cq(6)); 148.34 (Cq(5)); 152.77, 158.62
(Cq(2) and Cq(3)); 164.98, 167.56 (2 · COOMe). EI-
MS, m/z (relative abundance): 365 (3), 364 (M+Å; 10),
349 ([M ꢀ Me]+; 13), 333 ([M ꢀ OMe]+; 5), 317 (6),
305 ([M ꢀ COOMe]+; 9), 291 ([M ꢀ SiMe3]+; 16), 290
(12), 289 (6), 275 (10), 260 (11), 259 (23), 258 (9), 245
(12), 233 (10), 232 (17), 231 (34), 229 (12), 222 ([Me3(i-
Pr)SiMe3C5H]+; 25), 217 (29), 215 (12), 207 (12), 201
(24), 199 (12), 178 (14), 173 (14), 171 (14), 157 (11),
149 (8), 148 (30), 134 (10), 133 (14), 119 (9), 91 (11),
89 (18), 75 (11), 74 (16), 73 ([SiMe3]+; 100), 59
([COOMe]+; 25), 45 (27), 41 (10). IR (KBr, cmꢀ1):
2953 (s), 2933 (m), 2901 (m), 2872 (m), 1727 (s), 1708
(vs), 1624 (s), 1468 (m), 1456 (m), 1429 (s), 1404 (vw),
1383 (m), 1373 (w), 1311 (s), 1277 (vs), 1249 (vs), 1209
(s), 1170 (w), 1142 (m), 1106 (m), 1071 (w), 1042 (s),
991 (w), 969 (vw), 934 (w), 905 (vw), 866 (s), 833 (s),
803 (w), 793 (vw), 777 (w), 763 (w), 752 (m), 684 (w),
631 (vw), 604 (vw), 560 (vw).
3.13. Evaluation of activation parameters from variable
temperature NMR spectra
1H NMR spectra were acquired under conditions of
slow and moderate exchange. The resultant band-shape
of allylic and vinylic protons was then iteratively simu-
lated and fitted by WINDNMR-Pro program [27] as
two spin (for 6 and 8), or three spin (for 5 and 7) system.
Activation parameters were obtained from modified
Eyring equation: ln(k/T) = ꢀDHà/RT + (23.76 + DSà/R)
using least-squares fit to linear plot ln(k/T) versus 1/T
[28].
3.14. X-ray crystallography
The slightly yellowish crystals of 11 were grown from
diethyl ether solution. All diffraction data were collected
Table 3
Crystallographic data, data collection and structure refinement data
for compound 11
3.12. Preparation of 1-iso-propyl-4,5,6-trimethyl-7-
trimethylsilyl-bicyclo[2.2.1]hept-5-ene-2, 2,3,3-
tetracarbonitrile (11)
Chemical formula
Molecular weight
Crystal system
Space group
T (K)
C20H26N4Si
350.54
Monoclinic
P21/c (No. 14)
150(2)
The mixture of isomers 5 (473.5 mg, 2.13 mmol) was
diluted by dichloromethane (40 ml), and TCNE (273.0
mg, 2.13 mmol) was added. The reaction mixture was
stirred for 30 h at 25 ꢁC, concentrated to ca. 5 ml, and
layered by hexane (30 ml). Light brown crystals sepa-
rated after several hours. Analytically pure slightly yel-
lowish crystals of 11 were obtained by double
recrystallization from diethyl ether (611.5 mg, 82%).
˚
a (A)
8.9573(2)
18.0626(4)
12.6512(3)
90.000
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
Z
94.2644(14)
90.000
4
Crystal size (mm3)
0.40 · 0.30 · 0.20
1.141
0.124
Dcalc (g cmꢀ3
)
1
M.p. 122 ꢁC (dec.). H NMR (C6D6): ꢀ0.40 (s, 9H,
l (Mo Ka) (mmꢀ1
F(000)
)
SiMe3); 1.03, 1.21 (2 · d, 2 · 3JHH = 7.5 Hz, 2 · 3H,
CHMe2); 1.22 (s, 3H, C(4)Me); 1.31, 1.45 (2 · q,
5JHH = 1.0 Hz, 2 · 3H, C(5)Me and C(6)Me); 1.51 (s,
752
h range (ꢁ)
hkl range
3.21–29.13
ꢀ12/12, ꢀ24/24, ꢀ17/17
5481
3
1H, C(7)H); 1.84 (septuplet, JHH = 7.5 Hz, 1H,
Unique diffractions
Observed diffractions
Parameters
CHMe2). 13C {1H} (C6D6): 0.64 (SiMe3); 11.29, 12.86
(C(5)Me and C(6)Me); 15.23 (C(4)Me); 20.16, 20.57
(CHMe2); 29.46 (CHMe2); 49.07, 66.03 (Cq(1) and
Cq(4)); 51.18, 52.08 (Cq(2) and Cq(3)); 55.98 (C(7)H);
111.71, 112.89, 113.14, 113.83 (4 · CN); 141.76, 143.08
((Cq(5) and Cq(6)). EI-MS, m/z (relative abundance):
350 (M+Å; not observed), 223 (7), 222 ([Me3(i-Pr)Si-
Me3C5H]+; 30), 208 (6), 207 (24), 149 (11), 148 (48),
4577
234
R, wRa[I>rI)]
R, wRa (all data)
Sb
0.0536, 0.1401
0.0655, 0.1478
1.057
ꢀ3
˚
Dqmax, min (e A
)
0.521, ꢀ0.546
P
P
P
2
a
RðF Þ ¼ kF oj ꢀ jF ck= jF oj; wRðF 2Þ ¼ ½ ðwðF o2 ꢀ F c2Þ Þ=
P
2
wðF 2oÞ Þꢁ
P
1=2
ð
.
2
1=2
b
S ¼ ½ ðwðF 2o ꢀ F c2Þ Þ=ðNdiffrs ꢀ NparamsÞꢁ
.

J. Pinkas et al. / Journal of Organometallic Chemistry 690 (2005) 731–741
741
[8] Y.X. Chen, M.D. Rausch, J.C.W. Chien, Organometallics 12
(1993) 4607.
on a Nonius KappaCCD diffractometer at 150 K. The
structures were solved by direct methods (SIR-97 [29])
and refined by weighted full-matrix least-squares on F2
[9] S.S. Rigby, H.K. Gupta, N.H. Werstiuk, A.D. Bain, M.J.
McGlinchey, Polyhedron 14 (1995) 2787.
(
SHELXL-97 [30]). All non-hydrogen atoms were refined
[10] S.S. Rigby, H.K. Gupta, N.H. Werstiuk, A.D. Bain, M.J.
McGlinchey, Inorg. Chim. Acta 251 (1996) 355.
[11] A.J. Ashe III, J. Am. Chem. Soc. 92 (1970) 1233.
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Crystallographic data, excluding structure factors,
have been deposited at the Cambridge Crystallographic
Data Centre (11: 241844). Copies of the data can be ob-
tained free of charge upon application to The Director,
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax:
+44 1223 336033; e-mail: deposit@ccdc.cam.ac.uk or
www: http://www.ccdc.cam.ac.uk).
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Acknowledgement
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J.P. thanks French Government (Grant for doctorate
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