Syntheses and crystal structures of strained planar silacyclynes containing a diacetylene unit

Article abstract of DOI:10.1016/S0022-328X(98)01102-4

The synthesis and structural characterization of three silicon diacetylenic heterocyclynes 1,1-diisopropyl-4,5:10,11-dibenzosilacyclotrideca-4,10 diene-2,6,8,12-tetrayne (4), 1,1-dimethyl-4,5:10,11-dibenzosilacyclotrideca-4,10-diene-2,6,8,12-tetrayne (5),

Full text of DOI:10.1016/S0022-328X(98)01102-4

Journal of Organometallic Chemistry 578 (1999) 43–54
Syntheses and crystal structures of strained planar silacyclynes
containing a diacetylene unit
Li Guo a, Joseph M. Hrabusa III a, Claire A. Tessier a, Wiley J. Youngs a,*, Robert Lattimer b
a Department of Chemistry, The Uni6ersity of Akron, Akron, OH 44325-3601, USA
b Ad6anced Technology Group, BF Goodrich, Brecks6ille, OH 44141-3289, USA
Received 8 May 1998
Dedicated to Professor Peter Jutzi on the occasion of his 60th birthday
Abstract
The synthesis and structural characterization of three silicon diacetylenic heterocyclynes 1,1-diisopropyl-4,5:10,11-dibenzosilacy-
clotrideca-4,10 diene-2,6,8,12-tetrayne (4), 1,1-dimethyl-4,5:10,11-dibenzosilacyclotrideca-4,10-diene-2,6,8,12-tetrayne (5), and 1-
methyl-1-n-octadecyl-4,5:10,11-dibenzosilacyclotrideca-4,10-diene-2,6,8,12-tetrayne (6) are reported. A dimer (7) and a cobalt
complex (9) of 4 have also been characterized. Deprotonation of 1,4-di-(o-ethynylphenyl)butadiyne with two equivalents of
n-BuLi resulted in the formation of the dianion. Addition of one equivalent of the appropriate dialkyldichlorosilane to a highly
diluted THF solution of the dianion resulted in the formation of compounds 4, 5, 6 and 7. These compounds were irradiated and
were annealed. Comparisons to related compounds are made. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Silicon; Diacetylene; Heterocyclyne; 1,4-Topological polymerization
1. Introduction
substituents on either end [2]. As an offshoot of our
studies on planar silacyclynes [8] and continuing inter-
est in diacetylenes [9], strained silacyclynes which con-
tain a diacetylene moiety have been synthesized. The
strained nature of these diacetylenes could induce poly-
merization in the solid state. The introduction of the
silyl group into such a system is of interest because
silicon containing polymers have novel optical and
electronic properties [10,11]. The incorporation of dif-
ferent substituents on silicon would be expected to alter
the properties of this monomer and thus its polymer.
Reported herein are the synthesis, structural characteri-
zation, spectroscopic results, and preliminary thermal
stability studies of the strained silacyclyne–diacetylene
compounds 4, 5 and 6, the silacyclyne–diacetylenic
dimer 7, and their precursor 3. We also report the
synthesis and structural characterization of 9, a cobalt
complex of 4.
Solid state 1,4-topological polymerization of conju-
gated diacetylenes, first reported by Wegner in 1969 [1],
has been a topic of considerable research interest. The
resulting polymer chains are parallel to each other. The
polymer crystals thus produced have optical, electrical
and mechanical properties with pronounced anisotropy
[2]. Extensive p-conjugation along the diacetylene back-
bones is responsible for their nonlinear optical (NLO)
properties [3,4]. Polydiacetylenes are well known for
their promising third-order nonlinear optical properties
[5]. However, the synthesis of polydiacetylenes is not
straightforward [6,7]. Most diacetylene monomers are
composed of linear diacetylene rods with a variety of
* Corresponding author.
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(98)01102-4

44
L. Guo et al. / Journal of Organometallic Chemistry 578 (1999) 43–54
Scheme 1.
˚
˚
2. Results and discussion
90.0334 A and 90.0467 A for 4 and 5, respectively.
The maximum deviations from the planes (Si, C1 to
C12) in 4 and 5 are the silicon atoms at −0.0633 and
The synthetic route to 4, 5 and 6 is outlined in
Scheme 1. Glaser coupling of o-iodophenylacetylene
with copper(II)acetate in pyridine/methanol at r.t. gave
1,4-di-o-iodophenylbutadiyne (1) in 90% isolated yield.
Palladium–copper catalyzed coupling of trimethysilyl-
acetylene with 1,4-di-o-iodophenylbutadiyne gave 1,4-
di-(o-trimethylsilylethynylphenyl)butadiyne (2) in 90%
yield. Compound 2 was readily desilylated with KF to
form 1,4-di-(o-ethynylphenyl)butadiyne (3) in quantita-
tive yield. The combination of 1,4-di-(o-ethynyl-
phenyl)butadiyne in THF with 2 equivalents of freshly
standardized n-butyl lithium resulted in a deep green
solution. The mixture was then introduced into a highly
dilute solution of dialkyldichlorosilane in THF to af-
ford the desired products. The isolated yields for com-
pound 4, 5 and 6 are 32, 30 and 66%, respectively. High
dilution (0.002 M) was used for the second step to
avoid polymer formation. The cyclic dimer 7 was iso-
lated in 13% yield as a crystalline solid. The cyclic
dimers related to compounds 5 or 6 were not observed.
Compounds 4, 5, 6 and 7 are white solids, very stable in
air at room temperature and crystallize readily from a
mixture of methylene chloride and hexane. The crystal
structures of compounds 4, 5 and 7 have been obtained.
Low temperature single-crystal X-ray crystallo-
graphic results reveal the structural details of com-
pound 4 and compound 5 (Fig. 1). They have quite
similar structures. The central pockets, which contain
silicon and the alkynes (Si, C1 to C12), are planar in
both compounds with deviations from planarity of
˚
−0.1671 A, respectively. The diacetylene portions are
bowed [12] with the four carbon atoms of the di-
acetylene (C5, C6, C7 and C8) deviating from linearity
by an average of 8.1° (ranging from 6.0 to 12.1°) in 4
and 8.5° (ranging from 6.9 to 11.1°) in 5. The angles at
the silicon atom in both molecules are very close to the
ideal tetrahedral angle, indicating that there is no angu-
lar strain on the silicon atoms. This differs from the
analogous single alkyne cyclyne 8, in which the internal
ꢀC–Si–Cꢀ is 100.1° [8b]. The dialkyne moiety widens
the internal angle of the silicon atom. The bond length
of silicon to alkyne carbons is 1.840 A on average,
compared to that of 1.822 A in 8. The average bond
length of all alkynes is 1.206 A for compound 4 and
1.198A for compound 5. Table 1 lists selected bond
˚
˚
˚
˚
lengths and angles for compounds 4, 5 and 9.
The structure of compound 7, as shown by X-ray
crystallography, consists of a 26-membered ring of
psuedo-hexagonal geometry (Fig. 2). Compound 7
adopts a chair conformation as dictated by the tetrahe-
dral geometry requirement of two silicon atoms as well
as the spatial repulsion of four isopropyl groups. Both
diacetylenes in 7 show small deviations from linearity
with the CꢀC–C angles ranging from C4–C5–C6
177.4(4)° to C6–C7–C8 179.4(4)°. The two opposing
diacetylenes are 8.416 A (X1A to X1B) away from each
other. The mean bond length of all eight alkynes is
1.199 A which corresponds to that in a normal alkyne
bond. The valence angles of silicon ꢀC–Si–Cꢀ
˚
˚

L. Guo et al. / Journal of Organometallic Chemistry 578 (1999) 43–54
45
(104.0(2)° and 104.3(2)°) are smaller than tetrahedral
values. The acetylene carbons adjacent to the silicon
atoms are bent slightly inward with deviations
from linearity ranging from 169.1(3)° at Si2–C13–
C14 to 176.9(3)° at Si1–C24–C23. Similar results
have been found in dodecamethyl(6)pericyclynosilane,
(Me2SiCꢀC)6, where CꢀC–Si angles range from
174.8(5) to 176.7(6)° [13,14]. Selected bond lengths and
angles of 7 are listed in Table 2.
similar coupling patterns for the aromatic protons in
their 1H-NMR and their UV-vis show an absorbance at
similar wave numbers. In order to understand the UV-
vis spectrum of the cyclic silane compounds 4, 5 and 6,
it is useful to compare the spectra of these compounds
to that of 8 [8b]. In 8, there is no diacetylene in the
heterocyclyne, instead a single alkyne replaces the di-
acetylenic moiety between the two benzo groups (Fig.
1). The long wavelength UV-vis absorption maxima of
compounds 4, 5 and 6 occur at ca. 366 nm, m=3.1×
104 to 4.0×104 (Table 3), whereas the corresponding
peak of 8 appears at 334 nm, m=3.2×104. This
bathochromic shift of 32 nm in going from compound
8 to 4 reveals the enhancement of conjugation in com-
pound 4 derived from the diacetylenic moiety. In other
bent diacetylenes, it is believed that the bending distor-
tion of the diacetylene is not responsible for the
Table 3 lists the IR (CꢀC stretch), UV-vis, and
1H-NMR in the aromatic region for compounds 4, 5, 6,
7 and 8. All compounds in comparison have very
bathochromic
shift
[15,16].
The
substantial
bathochromic shift in 4 and 5 is probably due to
homoconjugation rather than strain. This conclusion
was drawn based on a strained cyclotetradeca-1,3-diyne
[17] and its unstrained reference compound di-tert-
butyl-1,3-butadiyne that share the same UV absorption
maxima. The UV-vis spectrum of compound 7 shows
only one strong peak at 240 nm. The long wavelength
maximum in the spectrum of compound 7 appears only
as a small shoulder at 354 nm of the peak at 240 nm.
The weakness of the absorption is presumably due to
the nonplanar nature of compound 7, and the resulting
lack of conjugation throughout the ring.
In order to make reactivity comparisons of mono-
and diacetylenic heterocyclynes, a cobalt complex, 9, of
ligand 4 was synthesized as described in Equation 1.
Compound 4 was combined with an excess of dicobal-
toctacarbonyl (2.4 equivalents) in 15 ml of hexane at
room temperature and stirred overnight. Workup and
crystallization from a solvent mixture of hexane and
diethyl ether resulted in dark red crystals.
(1)
An X-ray crystal structure of complex 9 was obtained
at low temperature. It crystallizes in the monoclinic
space group P21/c with one molecule per asymmetric
unit. The thermal ellipsoid labeling diagram of complex
9 is shown in Fig. 3. Fig. 4 shows the structure of the
ligand moiety in the complex.
The crystal structure of complex 9 clearly reveals that
one dicobalthexacarbonyl moiety is coordinated with
one alkyne of the diacetylene and that the other di-
cobalthexacarbonyl moiety is coordinated to one
Fig. 1. Thermal ellipsoid plots of 4, 5 and 8 drawn at 50% probabil-
ity.

46
L. Guo et al. / Journal of Organometallic Chemistry 578 (1999) 43–54
Table 1
˚
Selected bond lengths (A) and angles (°) for compounds 4, 5 and 9
Bond lengths
4
5
9
Bond angles
4
5
9
Si–C1
1.837(2)
1.842(2)
1.209(2)
1.440(2)
1.432(2)
1.203(3)
1.374(2)
1.204(2)
1.430(2)
1.443(2)
1.209(2)
1.419(2)
1.419(2)
1.826(2)
1.826(2)
1.201(3)
1.434(3)
1.412(3)
1.197(3)
1.364(3)
1.192(3)
1.420(3)
1.429(3)
1.201(3)
1.415(3)
1.416(3)
1.843(9)
1.855(9)
1.34(1)
1.45(1)
1.45(1)
1.20(1)
1.39(1)
1.35(1)
1.46(1)
1.46(1)
1.20(1)
1.44(1)
1.39(1)
C1–Si–C12
Si–C1–C2
108.26(8)
178.2(2)
176.4(2)
119.2(2)
117.4(2)
167.9(2)
173.4(2)
174.0(2)
172.3(2)
118.3(2)
119.0(2)
175.2(2)
176.1(2)
107.13(10)
176.2(2)
177.0(2)
119.1(2)
118.3(2)
168.9(2)
173.1(2)
172.6(2)
171.4(2)
118.4(2)
119.4(2)
176.6(2)
173.4(2)
106.6(4)
146.2(7)
145.2(8)
123.2(8)
120.1(8)
169(1)
Si–C12
C1–C2
C2–C3
C4–C5
C5–C6
C6–C7
C7–C8
C8–C9
C10–C11
C11–C12
C3–C4
C9–C10
C1–C2–C3
C2–C3–C4
C3–C4–C5
C4–C5–C6
C5–C6–C7
C6–C7–C8
C7–C8–C9
C8–C9–C10
C9–C10–C11
C10–C11–C12
C11–C12–Si
172(1)
152.3(9)
143.0(8)
123.5(8)
122.9(8)
173.3(9)
179.6(9)
Fig. 2. Two views of the crystal structure of 7. Hydrogen atoms are omitted for clarity. On the left is the thermal ellipsoid plot drawn at 50%
probability. The chair conformation of 7 is shown on the right.
Table 2
˚
Selected bond length (A) and angles (°) for compound 7
7
Si1–C1
Si1–C24
Si2–C12
Si2–C13
C1–C2
1.842(3)
1.833(4)
1.833(4)
1.844(3)
1.198(4)
1.201(6)
C7–C8
1.196(6)
1.210(5)
1.198(5)
1.198(5)
1.193(5)
C1–Si1–C24
C12–Si2–C13
Si1–C1–C2
C5–C6–C7
C6–C7–C8
104.3(2)
104.0(2)
169.9(3)
178.4(4)
179.4(4)
Si2–C12–C11
Si2–C1C–C14
C17–C18–C19
C18–C19–C20
Si1–C24–C23
174.4(3)
169.1(3)
178.3(4)
179.1(4)
176.9(3)
C11–C12
C13–C14
C17–C18
C19–C20
C5–C6
Table 3
Spectral data for compounds 4, 5, 6, 7 and 8
IR w(CꢀC) (cm−1
)
UV-vis umax (nm) and m (×10−4
)
1H-NMR of aromatic protons
l(ppm) in C6D6
4
5
6
7
8
2152 (s)
2157 (s)
2157 (s)
2160 (s)
2153 (s)
2211 (w)
2209 (w)
2211 (w)
(w)
366
364
366
354
334
4
7.25
7.28
7.30
7.47
7.44
6.97
6.97
6.99
7.20
7.34
6.64
6.64
6.64
7.09
6.77
3.8
3.1
weak
3.2

L. Guo et al. / Journal of Organometallic Chemistry 578 (1999) 43–54
47
alkyne adjacent to silicon. After reviewing the cobalt
chemistry of analogous silicon cyclyne ligands
SiPh2(OBET) and Ge(OBET)2 [18], we have concluded
that dicobalthexacarbonyl selectively complexes
strained alkynes. In the series of compounds (4, 5 and
6) in which diacetylene is incorporated in the silicon
cyclyne ring, the most strained alkyne is one of the
diacetylenes. Therefore, one alkyne in the diacetylene in
ligand 4 is coordinated with dicobalthexacarbonyl. Ap-
parently, this complexation shields the second alkyne in
the diacetylene from reacting with dicobaltoctacarbonyl
because it is part of a ring. The rest of the dicobalt-
octacarbonyl reacted with one of the alkynes next to
silicon atom. The 1H- and the 13C-NMR spectral results
show that the bulk sample contains one complex and
the number of peaks is consistent with the X-ray struc-
ture. There are reports that both alkynes in bis-
trimethylsilylbutadiyne react with an excess of
dicobaltoctacarbonyl [19]. Pannell reported that either
one or both of the alkynes in bis-trimethylsilybutadiyne
coordinated with dicobalt carbonyl. There are at least
two reported X-ray crystal structures of complexes in
which both alkynes in a diacetylene moiety are coordi-
nated to dicobalthexacarbonyl [20,21]. Corriu reported
the high yield reactions of poly[(silylene)diacetylenes]
and its analogs with dicobaltoctacarbonyl to form com-
plexes in which only one of the alkynes in the di-
acetylene moiety was coordinated with cobalt carbonyl
[10].
Selected bond lengths and angles for complex 9 are
listed with its free ligand 4 in Table 1. The coordinated
˚
alkyne bond lengths are 1.34(2) and 1.33(2) A for
C1ꢀC2 and C7ꢀC8, respectively. The bond length of
˚
C1–Si is 1.85(2) A, whereas C12–Si which is uncoordi-
˚
nated to cobalt is 1.86(2) A. They are not significantly
˚
longer than those in the free ligand, which is 1.840(2) A
on average. Among the four alkyne carbons in the
diacetylene moiety of free ligand, the smallest angle is
167.9(2)° at C4–C5–C6. This angle C4–C5–C6 be-
comes 170.9(14)° upon complexation of the adjacent
alkyne with dicobalthexacarbonyl. Among the four co-
ordinated alkyne carbons, the average value is
147.2(28)° ranging from 144.1(12)° at C2 to 151.5(14)°
at C7. Fig. 4 demonstrates that the planarity of the
central frame is dramatically distorted at C1ꢀC2, but
not at C7ꢀC8. This distortion is also observed in
SiPh2(OBET)(Co2(CO)6)2 and Ge(OBET)2(Co2(CO)6)2.
Ortho(bisethynyl)tolane (OBET) is similar to com-
pound 3 but has only one alkyne between the benzo
groups instead of a diacetylenic moiety. Unlike these
two cobalt complexes, the inner angle of silicon, C1–
Si–C12, is decreased from 108.26(28)° in the free ligand
4 to 105.8(6)° in its complex 9. Crystal and data
collection parameters for all the diacetylenic heterocy-
clynes are listed in Table 4.
It is well known that 1,3-butadiynes undergo topo-
logical polymerization in their crystalline states on ex-
posure to heat, UV light or g radiation. The crystal of
a monomer 1,3-butadiyne acts as a preformed lattice
for the polymer crystal. The monomers will polymerize
if the diyne ‘rods’ are stacked parallel to each other in
their crystal structures [2]. During the polymerization,
successive diyne molecules tilt toward the stacking axis
so that the terminal acetylenic carbons of adjacent
molecules move within bonding range (Fig. 5). Reactiv-
ities are dependent on the stacking pattern of the
monomers in the crystal. If s is defined as the perpen-
dicular distance between two adjacent diyne rods, d is
the distance between the centers of two adjacent alky-
nes, and r is the angle between the diacetylene rod and
the stacking axis, then s=d (sin r). Baughman [22] and
Wegner [23] specified that for significant reactivity, s
Fig. 3. Molecular structure of complex 9 with thermal ellipsoids
drawn at 50% probability. Hydrogen atoms are omitted for clarity.
˚
should be about 3.4–4.0 A and r about 45°. Huntsman
[2] has examined monomeric diacetylenes and found
that reactive diynes in general satisfy these requirments,
but that some diacetylenes still showed reactivity to-
ward polymerization when their packing parameters
deviated from the expected limits. The outer limits are
˚
observed as r=41–60°, d=4.35–5.34 A and s=3.94–
Fig. 4. The side view of the ligand 4 in complex 9.

48
L. Guo et al. / Journal of Organometallic Chemistry 578 (1999) 43–54
Table 4
Crystal and data collection parameters for compounds 3, 4, 5, 7 and 9
Compound
3
4
5
7
9
Formula
Molecular weight
Cryst. color
C20H10
250.28
Colorless
0.15 0.25 0.40
C26H22Si
362.53
Colorless
0.30 0.40 0.40
P21/c
14.279(2)
9.1397(13)
15.661(2)
90
91.212(10)
90
2043.4(5)
1.178
C22H14Si
306.42
Colorless
0.20 0.40 0.60
P21/c
5.272(1)
20.239(4)
15.180(3)
90
90.89(3)
90
1619.5(5)
1.257
C
725.1
52H44Si2
C38H22Co4O12Si
934.37
Deep red
0.30 0.40 0.60
P21/c
19.67(2)
12.478(8)
17.45(2)
90
115.39(6)
90
3869(6)
1.604
Colorless
0.25 0.40 0.40
P21/c
20.116(4)
11.461(2)
18.532(4)
90
100.75(3)
90
4197.6(14)
1.147
Cryst size (mm)
Space group
(
P1
˚
a (A)
7.264(1)
7.378(1)
7.391(1)
74.93(3)
74.03(3)
64.33(3)
338.68(8)
1.227
˚
b (A)
˚
c (A)
h (°)
i (°)
k (°)
3
˚
V (A )
zcalcd (g cm−3
)
Z
1
4
4
4
4
T (K)
141
100
147
100
140
Reflections (indep.)
Reflections (obs.)
Parameters refined
R1 (%)
1092
830
91
4.72(I\2|(I))
6.84
3591
2977
244
3.63(I\2|(I))
4.95
2627
2109
208
4.46(I\2|(I))
5.971
7380
4298
491
5.65(F\4|(F))
1.21
6754
3292
496
5.68(I\2s(I))
1.16
R2[%](all data)
˚
3.50 A among the examples in the paper. Due to the
difficulties of actually running the polymerizations, Pa-
ley et al. [6] reported that computer modeling could
predict the potential polymerizability of monomers.
Statistically, all of the compounds which are known to
polymerize readily in the solid state tend to have d=5–
and the stacking axis fall outside of the limits derived
from calculations for diacetylenes that are reactive in
the solid state. The packing diagrams suggest that
intermolecular spatial repulsions of isopropyl groups
prevent the diyne units from moving into favorable
bonding orientations. With this in mind, we synthesized
its analog 5 in which smaller methyl groups are at-
tached to the silicon atom instead of isopropyl groups.
Its packing parameters indeed exhibit adjacent di-
acetylene rods stacked closer to each other having
˚
6.5 A and r=45–67°. In conclusion, no matter what
the packing parameters are for the topological polymer-
ization to occur, the overall orientation should favor
new bond formation between two adjacent diacetylenes
in the process of 1,4-addition.
˚
d=5.27 A. The angle r=42.9° is much more favorable
The thermal ellipsoid labeling diagram of compound
3 is shown in Fig. 6. Selected bond lengths and angles
for compound 3 are listed in Table 5. Packing diagrams
of compounds 3, 4 and 5 are displayed in Fig. 7. They
are packed parallel to each other in their solid state for
all three crystal structures. Their packing parameter
calculations are shown in Fig. 8 with results listed in
Table 6. The perpendicular distance s for compound 4
is within the optimum limit. However the stacking
than that of compound 4. Even though compound 3
˚
distance d=9.14 A between the monomers in the array
and the angle r=23.3° between the diacetylene rods
Fig. 5. 1,4-Addition of diacetylene: d is the distance between the
centers of two alkynes; r is the angle between the diacetylene rod and
the stacking axis and s is the perpendicular distance between two
adjacent diacetylene rods.
Fig. 6. Thermal ellipsoid plot of 3 drawn at 50% probability.

L. Guo et al. / Journal of Organometallic Chemistry 578 (1999) 43–54
49
1
Table 5
The H-NMR of the brown irradiated 5 showed that it
was principally the unreacted monomer, and the low
temperature X-ray diffraction results of radiated crys-
tals of 3 revealed that it was principally the same as its
starting monomer. This indicates that the polymeriza-
tion is only occurring at the surface with these
compounds.
The thermal behavior of compounds 3, 4, 5 and 6 in
the solid state has been studied by differential scanning
calorimetry (DSC) and thermogravimetric analysis
(TGA). The DSC and TGA of compound 4 show a
large exothermic transition and 10% weight loss at
160°C. An exothermic transition for compound 5 oc-
curs at 125° with a 10% weight loss. Due to the poor
solubility of these annealed compounds, they have not
yet been characterized. Compound 6 melts at 71°C and
has a exothermic transition at 132°C without weight
loss until the temperature reaches 390°C. Compound 3
exploded to form a black powder in the process of
measurements. It has a exothermic peak at about 136°C
and its weight loss is about 35%.
˚
Selected bond length (A) and angles (°) for compound 3
3
C1–C2
C2–C3
C3–C8
C8–C9
C9–C10
C10–C10A
1.184(3)
1.430(3)
1.421(3)
1.431(3)
1.204(3)
1.370(4)
C1–C2–C3
C2–C3–C8
C3–C8–C9
C8–C9–C10
C9–C10–C10A
178.4(2)
120.3(2)
120.1(2)
179.4(2)
179.3(3)
has all the stacking parameters outside the optimum
limit, it is the most unstable species of all. At room
temperature its crystals gradually turn from colorless to
dark brown on exposure to light. Compound 3 is stable
when it is kept in a solution of hexane or methylene
chloride in the dark.
Diacetylene polymerization can be induced by expo-
sure to ultraviolet or X-ray radiation or heat annealing.
To induce the 1,4-addition polymerization of com-
pounds 5 and 3, their colorless crystals were placed on
a watch glass and irradiated with a medium pressure
mercury lamp for 4 days. While irradiating, the crystals
of 5 turned brown and those of 3 turned metallic black.
In many of the reports the polymer itself was not
characterized, and the development of a deep red or
blue color upon heating or irradiation serves as the
evidence for the occurrence of the polymerization [2].
2.1. Experimental procedure
2.1.1. Materials
All chemicals were purchased from Aldrich Chemical
and used as received unless otherwise stated. Solvents
for reactions were dried and distilled before use. Te-
trahydrofuran (THF) was predried with sodium hy-
droxide and distilled over sodium benzophenone ketyl
to which a small amount of tetraethylene glycol
dimethylether was added. All the dichlorosilanes were
purchased from Gelest. Dimethyldichlorosilane and di-
isopropyldichlorosilane were treated with anhydrous
potassium carbonate for at least a day and distilled
from this reagent before use. Methyl-n-octade-
cyldichlorosilane was used after being pumped on un-
der vacuum. n-Butyllithium in hexane (1.6 M) was
purchased from Aldrich and was freshly standardized
with diphenylacetic acid before use [24]. o-Iodophenyl-
acetylene was synthesized by standard procedures [25].
All reactions were carried out under nitrogen using
standard Schlenk techniques unless otherwise noted
[26,27].
1,4-Di-(o-iodophenyl)butadiyne (1): o-Iodophenyl-
acetylene (16 g, 70.2 mmol) was added to a mixture of
pyridine (350 ml), methanol (350 ml) and cupric acetate
(331.9 g, 175.5 mmol) and stirred for 1 day. Ice and
diethylether followed by a mixture of sulfuric acid and
ice were added to the mixture. The water layer was
extracted with ether, and the combined ether extracts
were washed with dilute sulfuric acid, water, and
sodium carbonate solution, and dried over magnesium
sulfate. Removal of the volatiles and recrystallization
from hexane gave 1 as a white solid product (14 g) in
1
Fig. 7. Stacking pattern of compounds 3, 4 and 5.
90% yield. H-NMR (300 MHz, CDCl3) l 7.84 (d, 2H),

50
L. Guo et al. / Journal of Organometallic Chemistry 578 (1999) 43–54
Fig. 8. Packing parameter calculations of compounds 4, 5 and 3.
7.54 (d, 2H), 7.31 (t, 2H), 7.04 (t, 2H); 13C-NMR (75
MHz, C6D6) l 138.8, 133.9, 130.3, 128.5, 127.8, 100.9,
84.3, 77.1; IR (CꢀC stretch) 2212 cm−1(s).
1,4-Di-(o-trimethylsilylethynylphenyl)butadiyne (2):
Excess trimethylsilylacetylene (TMSA) was added to
1,4-di-o-iodophenylbutadiyne (6 g, 13.2 mmol), bis(ben-
zonitrile)dichloropalladium(II) (0.506 g, 1.32 mmol),
diyne melts at 120°C, but it explodes at ca. 125°C and
turns into a black powder. 1H-NMR (300 MHz,
CDCl3) l 7.52 (m, 4H), 7.31 (m, 4H), 3.37 (s, 2H);
13C-NMR (75 MHz, CDCl3) l 133.4, 133.0, 129.2,
128.9, 125.9, 125.2, 82.0, 81.8, 81.0, 72.8; IR (CꢀC
stretch) 2252, 2214, 2158, 2140, 2109 cm−1(s).
copper(I)
iodide
(0.251
g,
1.32mmol),
and
2.2. General procedure for the synthesis of silacyclynes
triphenylphosphine (0.693 g, 2.64 mmol) in 50 ml of
diisopropylamine and 150 ml benzene. After stirring for
12 h the mixture was filtered, the solvent removed
under reduced pressure and the residue chro-
matographed on silica gel with hexane to afford 2 in
90% yield. 1H-NMR (300 MHz, CDCl3) l 7.46 (m, 4H),
7.26 (m, 4H), 0.279 (s, 18H); 13C-NMR (75 MHz,
CDCl3) l 132.8, 132.1, 128.9, 128.4, 127.1, 125.3, 103.2,
100.0, 81.2, 78.1, 0.2. Anal. Calc. for Si2C26H22: C
79.13%; H 6.64%; found C 79.20% H 6.59%; IR (CꢀC
stretch) 2158 cm−1(s).
2.2.1. Synthesis of 1,1-diisopropyl-4,5:10,11dibenzosila-
cyclotrideca-4,10 diene-2,6,8,12-tetrayne (4)
and its dimer (7)
To
a
100 ml flask charged with 1,4-di-(o-
ethynylphenyl)butadiyne9 (300 mg, 1.2 mmol) in 40 ml
of THF was added n-butyl lithium (1.37 ml, 2.4 mmol).
The solution turned a deep green immediately. After 4
h, the mixture was transferred by cannula into a solu-
Table 6
1,4-Di-(o-ethynylphenyl)butadiyne (3): 1,4-Di-(o-
trimethylsilylethynylphenyl)butadiyne (0.651 g, 1.65
mmol), KF (0.274 g, 4.71 mmol), and water (0.17 ml,
9.41 mmol) were stirred in THF/MeOH (10/40 ml) at
r.t. for 12 h. Extraction with CH2Cl2, drying over
magnesium sulfate and removal of solvent gave com-
pound 3 in (97% yield). 1,4-Di-(o-ethynylphenyl)buta-
Packing parameters of compounds 3, 4 and 5
4
5
3
˚
s (A)
3.62
23.3
9.14
3.59
42.9
5.27
4.71
39.6
7.39
r (°)
˚
d (X1A–X1B) (A)

L. Guo et al. / Journal of Organometallic Chemistry 578 (1999) 43–54
51
1
tion of diisopropyldichlorolsilane (222.2 mg, 1.2 mmol)
in 560 ml of THF. After stirring at 70°C for 12 h the
reaction mixture was opened to air and worked up by
removal of the volatiles at reduced pressure, extraction
with CH2Cl2/H2O, and drying of the organic phase over
magnesium sulfate. The volatiles were removed under
vacuum. Chromatography on silica gel eluting with
hexane gave 32% yield of compound 4 and 13% yield of
its cyclic dimer 7 as white solids. Crystals suitable for
X-ray diffraction were grown from a hexane and
methylene chloride mixture by slow evaporation of
long needle like crystals. H-NMR (300 MHz, C6D6) l
7.30 (d, 2H), 6.99 (d, 2H), 6.64 (multiplet, 4H), 1.72 (m,
2H), 1.30 (d, 30H),.92 (m, 5H), 0.46 (s,3H); 13C-NMR
(75 MHz, C6D6) l 131.5, 129.8, 129.8, 128.9, 128.6,
126.2, 104.6, 96.8, 85.6, 81.5, 33.4, 32.3, 30.2, 30.2
(these last two peaks are very wide), 30.1, 30.1, 29.8,
29.7, 24.2, 23.1, 16.0, 14.4, −1.8; H{29Si}NMR (60
1
MHz, C6D6) l −36.2. FDMS, m/z 544 (M+), 272
(M+ +); Anal. Calc. for SiC39H48: C 85.97%; H 8.88%;
found C 79.89% H 8.79%; IR (CꢀC stretch) 2157
cm−1(s) and 2211 cm−1(w).
1
solvents. Data for compound 4: H-NMR (300 MHz,
C6D6) l 7.25 (d, 2H), 6.97 (d, 2H), 6.64 (pentet, 4H),
1.30 (d, 12H), 1.26 to 1.14 (m, 2H); 13C-NMR (75
MHz, C6D6) l 131.9, 130.2, 130.1, 129.2, 128.9, 126.9,
106.1, 94.9, 85.8, 81.9, 18.4, 13.0. FDMS, m/z 362
(M+); Anal. Calc. for SiC26H22: C 86.14%; H 6.12%;
found C 79.78% (the sample burned at 980°C when
being measured) H 6.81%; IR (CꢀC stretch) 2152
cm−1(s) and 2212cm−1(w). Data for compound 7:
1H-NMR (300 MHz, C6D6) l 7.47 (d, 4H), 7.20 (m,
8H), 7.09 (t, 4H), 1.22 (d, 24H), 1.20 (m, buried under
Me peaks); 13C-NMR (75 MHz, CDCl3) l 132.9, 132.5,
128.4, 128.4, 126.6, 125.5, 104.8, 93.3, 81.1, 78.5, 18.0,
12.7. FDMS, m/z 724 (M+); Anal. Calc. for Si2C52H44:
C 86.14%; H 6.12% found C 85.30% H 6.28%; IR: n
(CꢀC) 2160 cm−1(s).
2.2.4. Synthesis of 9, a cobalt complex of 4
To a solution of 4 (65mg, 0.179 mmmol) in 15 ml of
hexane was added 2.4 equivalents of Co2(CO)8 (153.3
mg, 0.430 mmol) in hexane. After stirring for 12 h at
r.t. the volatiles were removed under vacuum. The
residue was dissolved in diethyl ether and hexane,
filtered and recrystallized. 1H-NMR (300 MHz, C6D6) l
7.66 (d, 1H), 7.57 (q, 2H), 7.40 (d, 1H), 6.88 (t, 2H),
6.77 (q, 2H), 1.54 (m, 2H), 1.29 (d, 12H); 13C-NMR (75
MHz, C6D6) l 200.1, 198.9, 140.4, 139.6, 136.2, 134.3,
132.7, 132.4, 129.9, 129.7, 128.2, 127.9, 123.8, 122.2,
108.1, 106.0, 102.7, 99.1, 98.0, 87.0, 76.7, 71.4, 19.3,
18.7, 14.9.
Table 7
Atomic coordinates [×104] and equivalent isotropic displacement
2
3
a
˚
parameters [A ×10 ] for compound 4
x/a y/b
1297(1) 1974(1)
2.2.2. Synthesis of 1,1-dimethyl-4,5:10,11-
dibenzosilacyclotrideca-4,10-diene-2,6,8,12-tetrayne (5)
Using the procedure described for 4 above 1,4-di-o-
ethynylphenylbutadiyne (250 mg, 1 mmol), two molar
equivalents of n-butyl lithium (1.31 ml, 2 mmol),
dimethyldichlorolsilane (129.1 mg, 1.0 mmol) and 500
ml THF were used to prepare compound 5. Chro-
matography on silica gel eluting with hexane/methylene
chloride (8:1) gave 30% yield of compound 5 as a white
z/c
7676(1)
U(eq)
Si
16(1)
20(1)
20(1)
19(1)
19(1)
21(1)
21(1)
21(1)
20(1)
19(1)
18(1)
19(1)
20(1)
22(1)
25(1)
24(1)
22(1)
22(1)
22(1)
22(1)
21(1)
21(1)
17(1)
27(1)
34(1)
26(1)
24(1)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
2198(1)
2785(1)
3527(1)
4336(1)
4354(1)
4207(1)
3941(1)
3630(1)
3152(1)
2263(1)
1887(1)
1634(1)
3474(1)
4207(1)
5008(1)
5072(1)
3537(1)
3060(1)
2187(1)
1789(1)
1253(1)
159(1)
560(2)
−385(2)
−1440(2)
−1054(2)
368(2)
7834(1)
7916(1)
8029(1)
8521(1)
8906(1)
9160(1)
9403(1)
9582(1)
9728(1)
9326(1)
8774(1)
8321(1)
7670(1)
7775(1)
8237(1)
8611(1)
10247(1)
10365(1)
9980(1)
9469(1)
6512(1)
8072(1)
5968(1)
6218(1)
7928(1)
9017(1)
1587(2)
2968(2)
4151(2)
5500(2)
5715(2)
4584(2)
3583(2)
−2832(2)
−3817(2)
−3422(2)
−2051(2)
6593(2)
7897(2)
8104(2)
7022(2)
2460(2)
1240(2)
1124(2)
3105(2)
2297(2)
819(2)
1
solid. H-NMR (300 MHz, C6D6) l 7.28 (d, 2H), 6.97
(d, 2H), 6.64 (pentet, 4H), 0.397 (s, 6H), 13C-NMR (300
MHz, C6D6) l 131.6, 129.8, 129.7, 128.9, 128.6, 126.2,
104.2, 97.3, 85.6, 81.5, −0.4. 13C-NMR (75MHz,
CDCl3) l 131.7, 129.7, 129.4, 129.0, 128.8, 125.9, 103.6,
96.9, 85.1, 80.6, -0.1; FDMS, m/z 306 (M+); Anal.
Calc. for SiC22H14: C 86.3%; H 4.6.%; Found C 83.56%
H 4.67%; IR (CꢀC stretch) 2157 cm−1(s) and 2209
cm−1(w).
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
2.2.3. Synthesis of 1-methyl-1-n-octadecyl-
4,5:10,11-dibenzosilacyclotrideca-4,10-diene-2,6,8,
12-tetrayne (6)
Using the procedure described for 4 above 1, 4-di-o-
ethynylphenylbutadiyne (375 mg, 1.5 mmol), two equiv-
975(1)
2185(1)
−663(1)
250(1)
alents of n-butyllithum (1.65 ml,
3
mmol),
methyl-n-octadecyldichlorosilane (551.3 mg, 1.5 mmol)
and a total of 750 ml of THF were used in the synthesis
of 6. Compound 6 was isolated in 66% yield as white
a U(eq) is defined as one third of the trace of the orthogonalized Uij
tensor.

52
L. Guo et al. / Journal of Organometallic Chemistry 578 (1999) 43–54
Table 8
sen. The structures were solved by direct methods
[28,29]. Hydrogen atoms were calculated and refined
using a riding model. Atom positions resulting from
Atomic coordinates [×104] and equivalent isotropic displacement
2
3
a
˚
parameters [A ×10 ] for compound 5
x/a y/b
−80(1) 1258(1)
z/c
U(eq)
Table 10
Atomic coordinates [×104] and equivalent isotropic displacement
2
3
a
˚
Si
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
1127(1)
1501(2)
1731(1)
2025(2)
2808(2)
3296(2)
3600(2)
3855(2)
3991(2)
4038(2)
3361(2)
2643(2)
2049(2)
1554(2)
1830(2)
2583(2)
3070(2)
4723(2)
4743(2)
4083(2)
3397(2)
195(2)
21(1)
25(1)
24(1)
24(1)
26(1)
28(1)
29(1)
28(1)
28(1)
25(1)
24(1)
23(1)
24(1)
28(1)
33(1)
34(1)
33(1)
32(1)
34(1)
33(1)
28(1)
30(1)
29(1)
parameters [A ×10 ] for 7
1920(4)
3127(4)
4450(4)
3677(4)
1713(5)
574(1)
99(1)
x/a
y/b
z/c
U(eq)
−481(1)
−797(1)
−504(1)
−176(1)
242(1)
Si(1)
Si(2)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
3412(1)
1811(1)
4103(2)
4520(2)
5004(2)
5094(2)
4730(2)
4437(2)
4119(2)
3838(2)
3489(2)
2827(2)
2519(2)
2259(2)
1217(2)
816(2)
−1499(1)
1198(1)
1075(1)
4189(1)
1872(2)
2425(2)
3095(2)
3668(2)
3596(2)
3561(2)
3528(2)
3499(2)
3442(2)
3594(2)
3823(2)
4003(2)
3321(2)
2755(2)
2086(2)
1516(2)
1569(2)
1586(2)
1617(2)
1648(2)
1693(2)
1566(2)
1381(2)
1246(2)
3192(2)
3837(2)
4402(2)
4319(2)
3222(2)
3145(2)
3277(2)
3497(2)
2007(2)
1374(2)
816(2)
20(1)
19(1)
24(1)
23(1)
22(1)
22(1)
24(1)
26(1)
25(1)
26(1)
24(1)
22(1)
21(1)
20(1)
23(1)
20(1)
21(1)
20(1)
23(1)
24(1)
24(1)
23(1)
21(1)
18(1)
19(1)
20(1)
29(1)
33(1)
32(1)
27(1)
30(1)
33(1)
28(1)
25(1)
24(1)
33(1)
33(1)
28(1)
26(1)
27(1)
28(1)
22(1)
25(1)
21(1)
23(1)
22(1)
34(1)
36(2)
44(2)
39(2)
50(2)
38(2)
28(1)
38(2)
51(5)
−1307(3)
−1345(3)
−1519(3)
−686(3)
381(3)
1298(4)
2365(3)
3287(3)
4382(3)
4437(3)
3404(3)
2526(3)
917(3)
932(3)
1134(3)
315(3)
−798(3)
−1734(3)
−2794(3)
−3707(3)
−4792(3)
−4825(3)
−3778(3)
−2893(3)
−2551(3)
−2772(3)
−1966(4)
−929(3)
5391(3)
6428(3)
6477(3)
5496(3)
2227(3)
2506(4)
1699(3)
614(3)
−1832(5)
−3432(5)
−5203(4)
−5218(4)
−3517(4)
−2080(4)
6425(4)
7605(5)
6810(5)
4873(5)
−6909(5)
−8595(5)
−8607(5)
−6938(4)
−2089(5)
1856(5)
C(8)
C(9)
644(1)
1170(1)
1651(1)
1582(1)
1490(1)
−746(1)
−1320(1)
−1639(1)
−1381(1)
1223(1)
1742(1)
2212(1)
2168(1)
966(1)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(22)
C(7)
C(8)
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
C(27)
C(28)
C(29)
C(30)
C(31)
C(32)
C(33)
C(34)
C(35)
C(36)
C(37)
C(38)
C(39)
C(40)
C(41)
C(42)
C(43)
C(44)
C(45)
C(46)
C(47)
C(48)
C(49)
C(50)
C(51)
C(52)
339(2)
190(2)
521(2)
788(2)
1969(1)
777(2)
a U(eq) is defined as one third of the trace of the orthogonalized Uij
tensor.
1111(2)
1400(2)
1762(2)
2430(2)
2752(2)
3024(2)
5374(2)
5822(2)
5912(2)
5552(2)
3784(2)
3432(2)
2775(2)
2475(2)
17(2)
−429(2)
−577(2)
−276(2)
1468(2)
1827(2)
2483(2)
2782(2)
2745(2)
3761(2)
1309(2)
2436(2)
2108(2)
2568(2)
4267(2)
4081(2)
1025(2)
738(2)
Table 9
Atomic coordinates [×104] and equivalent isotropic displacement
2
3
a
˚
parameters [A ×10 ] for 3
x/a
y/b
z/c
U(eq)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
C(10)
−437(4)
543(3)
8258(3)
7861(3)
7434(3)
6544(3)
6147(3)
6636(3)
7507(3)
7917(3)
8824(3)
9580(3)
2256(3)
3450(3)
4870(3)
6730(3)
8093(3)
7640(3)
5801(3)
4405(3)
2505(3)
909(3)
42(1)
33(1)
29(1)
37(1)
42(1)
38(1)
33(1)
27(1)
28(1)
28(1)
1736(3)
1165(4)
2328(4)
4064(4)
4677(3)
3522(3)
4143(3)
4683(3)
885(2)
−5822(3)
−6862(3)
−6880(3)
−5882(3)
−362(3)
−1575(3)
1517(3)
1890(2)
1962(2)
1831(2)
1633(2)
1056(2)
211(2)
4917(2)
4397(2)
498(2)
1820(2)
172(2)
104(2)
4855(3)
4938(2)
4468(2)
3810(2)
a U(eq) is defined as one third of the trace of the orthogonalized Uij
tensor.
−17(3)
2.3. Crystal structure determinations
−689(3)
−193(3)
−599(4)
−2758(3)
2756(3)
649(3)
−1204(3)
−82(3)
X-ray crystallographic data were collected using
graphite monochromated Mo Ka radiation (u=0.710
˚
73 A) on a Syntex P21 diffractometer updated to a
Siemens R3 m/6 and equipped with a Molecular Struc-
ture Corp. low temperature device. X-ray data were
collected using ꢀ scans. The cell dimensions were
refined with intensity data from 20°52q530°. System-
atic absences are consistent with the space groups cho-
2102(2)
2880(2)
a U(eq) is defined as one third of the trace of the orthogonalized Uij
tensor.

L. Guo et al. / Journal of Organometallic Chemistry 578 (1999) 43–54
53
Table 11
least-squares refinement [30] for compounds 3, 4, 5, 7
and 9 are listed in Tables 7–11.
Atomic coordinates [x 104] and equivalent isotropic displacement
parameters [A x 103] for 9a
2
˚
x
y
z
U(eq)
3. Conclusion
Co(1)
Co(2)
Co(3)
Co(4)
Si
2623(1)
−2950(1)
−3536(1)
1578(1)
4183(1)
5054(1)
3657(1)
4055(1)
4038(2)
3116(4)
5052(5)
2758(5)
6281(5)
5929(5)
3811(4)
2766(5)
2758(4)
5323(5)
3319(16)
2935(13)
3984(4)
5744(13)
5901(8)
4546(6)
3541(7)
4701(7)
3300(7)
5205(5)
5795(7)
5603(6)
4270(6)
5952(6)
3090(6)
3113(6)
4665(7)
5948(6)
3606(17)
3370(14)
4028(6)
5051(15)
5176(11)
5167(6)
4591(6)
4001(7)
3215(6)
2371(6)
2198(6)
2849(6)
3319(6)
6733(6)
7451(6)
7439(6)
6681(6)
1717(6)
904(7)
30(1)
32(1)
29(1)
31(1)
28(1)
44(2)
65(2)
61(2)
71(3)
52(2)
47(2)
62(2)
46(2)
48(2)
40(3)
40(3)
51(2)
49(3)
49(3)
27(2)
39(3)
48(3)
38(3)
22(2)
42(3)
34(3)
33(3)
22(2)
32(3)
37(3)
37(3)
28(2)
34(4)
34(4)
36(3)
35(4)
35(4)
30(2)
28(2)
29(2)
24(2)
29(2)
27(2)
28(2)
29(2)
34(2)
33(2)
31(2)
24(2)
36(2)
36(2)
42(3)
31(2)
32(2)
51(3)
47(3)
27(2)
39(3)
48(3)
1970(1)
4017(1)
3210(1)
1157(1)
2923(4)
4137(4)
1776(4)
1359(4)
3064(4)
690(4)
In conclusion, several new silicon diacetylenic hetero-
cyclynes have been synthesized and structurally charac-
terized. We attempted to induce solid state 1,4-addition
polymerizations on these silicon heterocyclynes. Com-
pounds 3 and 5 were irradiated for several days turning
a dark color. However, polymerization occured only on
the surface and not throughout the bulk of 3 and 5.
The heterocyclynes 3, 4, 5 and 6 were annealed but due
to poor solubility the products have not yet been
characterized.
2760(1)
−1137(2)
−1358(5)
−3896(6)
−4372(6)
−2983(6)
−5258(5)
−4770(5)
3158(5)
−357(5)
1362(5)
4711(12)
4600(10)
3195(5)
3272(18)
2903(12)
−2085(7)
−1962(7)
−3540(8)
−3787(8)
−2269(6)
−3234(8)
−4587(8)
−4278(7)
−1810(6)
2524(7)
O(1A)
O(1B)
O(1C)
O(2A)
O(2B)
O(2C)
O(3A)
O(3B)
O(3C)
O(4A)
O(4A%)
O(4B)
O(4C)
O(4C%)
C(1)
C(1A)
C(1B)
C(1C)
C(2)
C(2A)
C(2B)
C(2C)
C(3)
C(3A)
C(3B)
C(3C)
C(4)
C(4A)
C(4A%)
C(4B)
C(4C)
C(4C%)
C(5)
4548(4)
4130(4)
5311(4)
3515(13)
3192(10)
1713(4)
4333(12)
4146(8)
1943(5)
2810(5)
3553(6)
2100(5)
2610(5)
1571(6)
2644(6)
1193(6)
3206(5)
4337(5)
4090(5)
4813(5)
3557(5)
3418(16)
3182(13)
2303(5)
3909(14)
3786(9)
3316(5)
3222(5)
3209(5)
2912(5)
2285(5)
1658(5)
1553(5)
1400(5)
3479(5)
4046(5)
4358(5)
4119(5)
2338(5)
1761(5)
1136(5)
1087(5)
268(5)
Acknowledgements
We would like to thank the National Science Foun-
dation for financial support and Zhengjie Pi for acquir-
ing the 1H{29Si}NMR data for compound 6.
Supporting Information Available: tables of anisotropic
thermal parameters, bond lengths and angles, and hy-
drogen parameters for compounds 4, 5, 6, 7 and 9 are
available from the authors.
388(8)
1446(7)
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−797(6)
3933(17)
3911(14)
3021(7)
3153(23)
2866(15)
−187(7)
416(7)
1179(6)
1612(6)
1515(7)
874(7)
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C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
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C(26)
258(7)
−288(7)
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−918(7)
−384(7)
2130(7)
2087(7)
1458(8)
837(7)
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