Synthesis and characterisation of new oligoacetylenic silanes

Article abstract of DOI:10.1039/b108510g

Synthetic routes to a series of novel oligoacetylenic silanes with or without (hetero)aromatic bridges have been developed. The compound Me₃SiC≡CSi(Ph)₂C≡CSiMe₃ was first prepared, which was selectively desilylated with CaCO₃ in methanol at room temperature to afford the mono-protected bis(alkynyl) silane Me₃SiC≡CSi(Ph)₂C≡CH in moderate yield. Treatment of this mono-protected species with ⁿBuLi, followed by silylation with Ph₂SiCl₂, gives a good yield of Me₃SiC≡CSi(Ph)₂C≡CSi(Ph)₂ C≡CSi(Ph)₂C≡CSiMe₃, with alternating silicon and acetylene units. A range of linear silicon-linked oligoalkynes containing phenylene, bithienylene and anthrylene rings, HC≡CRC≡CSi(Ph)₂C≡CRC≡CH and HC≡CRC≡CSi(Ph)₂C≡CRC≡CSi(Ph)₂ C≡CRC≡CH (R = 1,4-phenylene, 5,5′-bithienylene or 9,10-anthrylene), were synthesised by condensation reactions of Ph₂SiCl₂ with the components obtained in situ from a HC≡CRC≡CH-ⁿBuLi mixture in THF and the products were isolated by chromatography on silica. All these new compounds have been characterised by IR, ¹H and ¹³C NMR and UV/VIS spectroscopies and mass spectrometry. The single-crystal X-ray structure of HC≡C(p-C₆H₄)C≡CSi(Ph)₂C≡C (p-C₆H₄)C≡CSi(Ph)₂C≡C(p-C ₆H₄C≡CH has been determined, showing that two silicon atoms and six acetylene units constitute the backbone of the molecule.

Full text of DOI:10.1039/b108510g

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Synthesis and characterisation of new oligoacetylenic silanes
Wai-Yeung Wong,* Albert W.-M Lee,* Chun-Kin Wong, Guo-Liang Lu, Hongkui Zhang,
Tian Mo and Kwun-Ting Lam
Department of Chemistry, Hong Kong Baptist University, Waterloo Road, Kowloon Tong,
Hong Kong, P.R. China. E-mail: rwywong@hkbu.edu.hk
Received (in Montpellier, France) 21st August 2001, Accepted 20th November 2001
First published as an Advance Article on the web 19th February 2002
Synthetic routes to a series of novel oligoacetylenic silanes with or without (hetero)aromatic bridges
:
have been developed. The compound Me3SiC CSi(Ph)2C CSiMe3 was first prepared, which was selectively
:
desilylated with CaCO3 in methanol at room temperature to afford the mono-protected bis(alkynyl) silane
:
n
Me3SiC CSi(Ph)2C CH in moderate yield. Treatment of this mono-protected species with BuLi, followed by
:
:
:
:
:
silylation with Ph2SiCl2 , gives a good yield of Me3SiC CSi(Ph)2C CSi(Ph)2C CSi(Ph)2C CSiMe3 ,
with alternating silicon and acetylene units. A range of linear silicon-linked oligoalkynes
:
containing phenylene, bithienylene and anthrylene rings, HC CRC CSi(Ph)2C CRC CH and
:
:
:
0
:
:
:
:
:
:
HC CRC CSi(Ph)2C CRC CSi(Ph)2C CRC CH (R ¼ 1,4-phenylene, 5,5 -bithienylene or 9,10-anthrylene),
were synthesised by condensation reactions of Ph2SiCl2 with the components obtained in situ from a
:
n
HC CRC CH– BuLi mixture in THF and the products were isolated by chromatography on silica. All these
:
new compounds have been characterised by IR, H and 13C NMR and UV=VIS spectroscopies and mass
1
:
spectrometry. The single-crystal X-ray structure of HC C(p-C6H4)C CSi(Ph)2C C(p-C6H4)C CSi(Ph)2C C
:
:
:
:
:
(p-C6H4)C CH has been determined, showing that two silicon atoms and six acetylene units constitute the
backbone of the molecule.
The molecular design and synthesis of linear, cyclic or dendritic
systems composed of silicon atoms and acetylene units has
aroused considerable interest.1–5 These carbon-rich acetylene-
based scaffolds have been demonstrated to exhibit intriguing
electrical, electronic, optical and structural properties.1–5 The
lower ionisation energy of the silicon atom compared with
carbon is expected to enhance the through-bond interaction
of ethynyl units along the backbone.6,7 In this context, the
chemistry of linear inorganic polymers containing alternating
arrangements of silylene and p-electron moieties represents an
important area of current active research because they possess
good potential as functional materials such as semiconductors,8
hole-transporting9–11 and heat-resistant materials,12–14 photo-
resists15,16 and ceramic precursors.1,17 The unusual electrical
and optical properties associated with these materials are
generally attributed to the delocalisation of electrons through
the silylene linkages via p–dSi interactions18,19 or s–p con-
jugation.6,20 Among these, p-conjugated systems incorporating
phenylene, anthrylene or oligothienylene bridges along with Si
residues in the main chain have been extensively investigated
regarding their applications to electro- and optical devices.21–28
However, to our knowledge, reports on the synthesis of
linear oligoacetylenic silanes have been scarce and related
problems in this area remain relatively unexplored.5,29,30
Alkynylsilane-based short-chain oligomers are not only key
intermediates in the preparation of their polymeric or cyclic
compounds but also useful alternative materials with poten-
tially enhanced performance by limiting the conjugation length
of the polymer.31,32 In this respect, oligo(phenylene vinylene)s
represent one of the best examples that have recently drawn
considerable attention.31–33 Investigation of well-defined
p-conjugated oligomers can provide an insight into the elec-
tronic, emissive and structural properties of the related poly-
meric materials.31 These oligoacetylenic silanes are also
attractive building blocks for molecular architectures, but their
syntheses have been largely hampered by the limited avail-
ability of suitable difunctionalised silyl compounds by the
ready polymerisation of the starting silylacetylene pre-
cursors.34–37 We have recently described a systematic approach
to the synthesis of some oligoacetylenic sulfides,38,39 and the
fruitful results prompted us to prepare a new series of linear
:
oligoacetylenic silanes containing Ph2SiC C units. Based on
our experience in the preparation of oligoacetylenic sulfides
and related compounds in organic synthesis,40 we report here
the first synthesis of a novel class of well-defined oligo(alk-
ynylsilane)s, with or without (hetero)aromatic groups, and a
description of their spectroscopic, optical and structural
properties is also presented.
Results and discussion
Syntheses
The preparation of the silylacetylene oligomer 3 starts with
the synthesis of a mono-protected bis(alkynyl) silane 2.
n
Treatment of trimethylsilylacetylene with BuLi at À78 ꢀC
yielded the corresponding lithium salt, which reacted in situ
a
:
white solid, Me3SiC C-
with Ph2SiCl2 to provide
:
:
Si(Ph)2C CSiMe3 , 1, in 72% yield based on Me3SiC CH
(Scheme 1). The desired mono-protected bis(acetylene) silane
2 was obtained as a colourless liquid in moderate yield when
1 was desilylated with CaCO3 in MeOH at room tempera-
ture. 2 was found to be slightly unstable in air, especially
when concentrated, which precluded satisfactory elemental
analysis. It is noteworthy that mono-desilylation of 1 to
produce 2 did not occur under commonly used desilylation
conditions (e.g., K2CO3–MeOH or KF–MeOH).38,39,41–43
Careful mono-desilylation of 1 with a CaCO3–MeOH mix-
ture should be conducted under anhydrous condition and
354
New J. Chem., 2002, 26, 354–360
DOI: 10.1039/b108510g
This journal is # The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2002

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n
Scheme 1 (i) BuLi, À20 ꢀC, Ph2SiCl2 , THF; (ii) CaCO3–MeOH, r.t.
:
:
:
:
close monitoring with TLC. When HC CSi(Ph)2C CH star-
ted to appear, the reaction was quenched by water. Work-up
and flash column chromatography gave 2 in 42% yield.
Although the yield of 2 was not very high, the recovered 1
could be reused to prepare 2. Freshly prepared 2 was then
treated with nBuLi followed by silylation with Ph2SiCl2 in
THF to furnish, on chromatography, 3 as a colourless oily
substance with a yield of 65%. The chain length was doubled
in this synthetic procedure. Attempts have also been made to
extend the chain length through further mono-desilylation of
3 followed by silylation with Ph2SiCl2 . Unfortunately, only a
complicated mixture was obtained in this way.
cules is outlined in Scheme 2. When HC CRC CH was trea-
ted with 1 equiv. of nBuLi or freshly prepared (Me3Si)2NLi
(as a base) in THF followed by 0.5 equiv. of Ph2SiCl2 at
ꢀ
:
:
:
:
À78 C, a mixture of HC CRC CSi(Ph)2C CRC CH and
:
:
:
:
:
:
HC CRC CSi(Ph)2C CRC CSi(Ph)2C CRC CH (R ¼ 1,4-
phenylene, 5,50-bithienylene or 9,10-anthrylene) was formed
along with small amounts of their higher oligomers and the
recovered starting diethynyl compounds. Purification of 4–6
was effected by preparative TLC on silica, leading to the iso-
lation of the products as white (4a and 4b), pale yellow (5a and
5b) and orange-yellow (6a and 6b) solids in moderate to good
yields. Compounds 4–6 are generally stable as solids in air at
room temperature and dissolve readily in common organic
solvents such as CH2Cl2 and CHCl3 . However, 5 and 6
decompose slightly when kept in solution for a prolonged
period of time or under light and do not melt below their
decomposition temperatures. All the new compounds in this
In the pursuit of more stable oligoacetylenic silanes with
tunable physical and optical properties, it seemed an attractive
goal to us to synthesise new silylacetylene compounds con-
taining a range of aromatic and heteroaromatic moieties along
the backbone. The synthetic route leading to the target mole-
n
Scheme 2 (i) BuLi, À20 ꢀC, Ph2SiCl2 , THF.
New J. Chem., 2002, 26, 354–360
355

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the extent of bathochromic shifts induced by the increased
chain length is less pronounced with increasing number of
study were satisfactorily characterised by common spectro-
1
scopic methods (IR, MS, H and 13C NMR).
repeat units. The fact that the polymeric homologues of 4 and
:
:
:
6, [–C CSi(Ph)2C CRC C–]n , display very similar lowest
energy peaks at 303 (R ¼ 1,4-phenylene) and 450 (R ¼ 1,10-
anthrylene) nm as those of 4b and 6b, respectively, suggest that
there would probably be little benefit in increasing the number
of repeating units above three in the control of spectral
properties of these diphenylsilylene materials.36,45
Spectroscopic properties
All the spectroscopic data of compounds 1–6 are consistent
with their structures (Experimental section). The IR spectra of
these oligoacetylenic species display strong nC C absorption
:
bands in the range 2040–2159 cmÀ1 28,38,43
The terminal acet-
.
ylenic C–H signal also appears around 3275–3305 cmÀ1 for 2, 4,
5 and 6. In all cases, 1H NMR resonances arising from the
protons of the organic fragments were observed, and all the
phenyl, phenylene, bithienylene and anthrylene carbon atoms
were clearly identified in the aromatic region of the 13C-{1H}
NMR spectra. Notably, there are four and six distinct13C
NMR signals for all the individual sp carbons in 4a–6a and
4b–6b, respectively, in accordance with their formulations.
Assignment of these 13C resonances was made on the basis of
peak intensities and by analogy with results of other similar
acetylide compounds.28,38,43,44 For 4–6, the 13C chemical shifts
remain relatively unshifted for the outermost acetylene carbons
In the solution state, compounds 4–6 are luminescent at
room temperature and the emission peaks range from 339 to
484 nm. There is a slight bathochromic shift in the emission
wavelength upon going from compounds a to b within each
series incorporating a particular R group. We also note that
the position of the absorption maximum depends on the nat-
ure of the aromatic unit R. For the series 4a–6a, the lmax of the
low-energy band increases from 290 nm for 4a to 365 nm for
5a and a significant red-shift of the absorption maximum is
observed for 6a (438 nm) when a more electron-rich unit such
as anthracene is introduced.
A similar trend was also
encountered for the group 4b–6b. It has been suggested for
some conjugated aromatic copolymers that the position of the
absorption maximum is related to the degree of destabilisation
of the HOMO and stabilisation of the LUMO.47 The presence
of the electron-rich anthracene residue in 6a and 6b tends to
reduce the energy gap between these frontier levels, and gives
rise to a bathochromic shift of the absorption and emission
compared to the other two groups of molecules having
phenylene and bithienylene moieties.
:
:
as compared to the free ligand HC CRC CH whereas the
innermost acetylene carbons in close proximity to Si appear at
more downfield positions. For comparison, while the sp car-
bons of 5,50-diethynyl-2,20-bithiophene resonate at d 76.66
43
:
:
(C CH) and 82.68 (C CH), those for 5a appear at d 76.58
and 82.77 for the outermost carbons and at d 93.46 and 101.03
for the innermost C C units close to the SiPh2 group. The 13C
:
NMR spectrum of 5b shows six resonances of sp carbon atoms.
The nearly unaltered chemical shift values at d 76.58 and 82.76
in 5b correspond to the two outer carbons, while the lower field
signals at d 93.46, 93.62, 101.00 and 101.05 are ascribed to the
middle and innermost acetylene carbons. The 29Si NMR che-
mical shifts of 4 and 6 do not differ significantly from those for
the longer chain homologues,45 in line with the UV=VIS spec-
tral data (vide infra). These results indicate that there is a
diminishing effect on the degree of electronic conjugation with
increasing number of Si residues in the backbone. The formulae
of these oligoacetylenic silanes were successfully confirmed by
EI and positive FAB mass spectrometry and the respective
molecular ion peaks were detected in each case.
Crystal structure analysis
The crystallographically determined structure of 4b by an
X-ray diffraction experiment serves to identify the oligomeric
nature of the product unequivocally. A perspective drawing of
compound 4b is shown in Fig. 1, which includes the atom
numbering scheme. The principal bond lengths and angles are
listed in Table 1. There is a crystallographic centrosymmetry at
the central phenylene ring such that two halves of the molecule
are related by an inversion centre at the centroid of the C(25)–
C(26)–C(27A)–C(25A)–C(26A)–C(27) plane. In the solid state,
The optical properties of our new compounds have been
investigated in CH2Cl2 solutions. The electronic absorption
and emission data are given in the Experimental section.
Trimethylsilyl-capped Si-containing tetrayne 3 shows ca. 50
nm red-shifted absorption bands in comparison with 1, prob-
ably due to the extended conjugation through Si as the chain
length is doubled. The absorption spectra of 4a and 4b are
dominated by p–p* transitions of the bridging units in the
near-UV region, and a notable bathochromic shift in lmax with
increased extinction coefficients is observed upon going from
1,4-diethynylbenzene (260, 273 nm) to 4a (274, 290 nm) and 4b
(274, 289, 303 nm). Both 5a and 5b exhibit strong p–p* tran-
sitions in the near-UV range with a similar absorption pattern,
attributable to the bithienyl moiety.43 The lowest energy band
red-shifts from 353 (5,50-diethynyl-2,20-bithiophene)43 to 365
(5a) and 370 nm (5b). The polymeric analogue of 5 with a
:
:
4b possesses three –C C(p-C6H4)C C– moieties alternately
connected by two SiPh2 units in a linear fashion. There are a
:
total of six C C units in the entire molecule. The C C bond
:
+
lengths lie within the narrow range of 1.197(2)–1.206(3) A and
:
the C CH bond shows a slight shortening of bond length
+
[1.164(4) A] due to the libration effect.48 The Si–C(sp) single
+
+
bond lengths are 1.810(2)–1.822(2) A [ave. 1.816(2) A], which
are slightly shorter than those observed in related silylacetylene
compounds such as the two silapericyclyne conformers
+
[1.83(2)–1.836(3) A],49 the cis-trans and all-trans isomers
of 1,2,5,6-tetramethyl-1,2,5,6-tetraphenyl-1,2,5,6-tetrasilacyclo-
octa-3,7-diyne [1.841(5)–1.843(5), 1.828(6)–1.836(6) A, respec-
+
tively]35 and the 1G-dendrimer with 10 silicon atoms and 9
+
acetylene units [1.827(5)–1.851(5) A].5 These data, together
:
with the slightly shorter C–C(ring) bond [ca. 1.427(3)–
1.436(2) A], are consistent with a partial conjugation effect
+
:
:
:
single thiophene group [–C CSi(Ph)2C C(2,5-C4H2S)C C–]n
shows its lowest energy absorption at 304 nm in the same
solvent.45 The UV=VIS spectra of 6a and 6b are characterised
by intense absorption bands with fine structure most likely
arising from transitions similar to those for anthracene.46 With
reference to the bands in anthracene (326, 342, 359, 378 nm),
those for 6a and 6b are red-shifted by ca. 50–80 nm, the
bathochromic shift being greater than for 9,10-diethynyl-
anthracene (lmax 361, 380, 402, 426 nm).28 The corresponding
absorption peaks in 6b with a longer chain length are further
red-shifted with respect to those in 6a. These properties are
suggestive of the presence of through-Si conjugation along the
backbone in these oligomeric organosilicon systems. However,
along the molecular backbone. The linearity of the acetylene
units is evident from the bond angles of Si–C(sp)–C(sp) and
C(sp)–C(sp)–C(sp2), and the unusually small Si(1)–C(10)–C(9)
bond angle [172.7(2)ꢀ] is presumably caused by the solid-state
packing effect in the crystal lattice. All the aromatic rings are
nearly planar with normal bond parameters.
Concluding remarks
The present work provides a convenient entry to a new series
of oligoacetylenic silanes. The results here indicate through-Si
conjugation along the backbone of these molecules and
356
New J. Chem., 2002, 26, 354–360

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Fig. 1 A perspective drawing of 4b with the atom numbering scheme.
+
Table 1 Selected bond lengths (A) and angles (ꢀ) for compound 4b
mmol) was added in one portion and the reaction mixture was
stirred for 2h at this temperature. The solution was then
allowed to warm up to room temperature and stirred for an
additional 3 h. The crude material was partitioned between
NH4Cl solution and diethyl ether. The aqueous layer was
extracted with ether and the organic phase was dried over
Na2SO4 , filtered and concentrated. The title product was
purified by column chromatography on silica, eluting with
petroleum ether–CH2Cl2 (4 : 1, v=v). The product was
obtained as a white solid in 72% yield (3.76 g). m.p.: 65–67 ꢀC.
C(1)–C(2)
C(6)–C(9)
Si(1)–C(10)
Si(1)–C(13)
C(11)–C(12)
1.164(4)
1.427(3)
1.810(2)
1.855(2)
1.197(2)
C(2)–C(3)
1.433(3)
1.206(3)
1.822(2)
1.855(2)
1.436(2)
C(9)–C(10)
Si(1)–C(11)
Si(1)–C(19)
C(12)–C(25)
C(1)–C(2)–C(3)
Si(1)–C(10)–C(9)
C(10)–Si(1)–C(11)
177.3(3)
172.7(2)
109.44(9)
C(6)–C(9)–C(10)
Si(1)–C(11)–C(12)
C(11)–C(12)–C(25)
176.7(2)
178.0(2)
178.1(2)
IR (KBr): 2109 cmÀ1 (nC C). 1H NMR (CDCl3): d 0.22 (s, 18H,
:
Me), 7.36–7.39 (m, 6H, Ph) and 7.70–7.73 (m, 4H, Ph). 13C-
1
:
{ H} NMR (CDCl3): d À0.16 (Me), 106.10, 118.90 (C C),
attempts have been made to evaluate how the nature of
the linking unit R and the chain length of this type of oligo-
mers would influence their optical and spectroscopic proper-
ties. We are currently extending these studies to higher
generations and further investigations of other properties (such
as conducting properties) of these p-electronic systems are now
in progress.
127.86, 129.99, 134.69 (aromatic CH) and 132.73 (aromatic
quaternary C). 29Si NMR (CDCl3): d À17.58 and 0.00. EI MS:
m=z 376 (Mþ). UV=VIS (cyclohexane): lmax=nm (e  104 dm3
molÀ1 cmÀ1) 211 (3.0) and 224 (2.8). Calcd for C22H28Si3: C,
70.14; H, 7.49. Found: C, 69.89; H, 7.20%.
:
:
Me3SiC CSi(Ph)2C CH, 2. To a solution of 1 (132mg,
0.35 mmol) in MeOH (10 cm3) was added CaCO3 (35 mg). The
reaction mixture was stirred at room temperature for 5 h and
the course of the reaction was monitored closely by spot TLC.
Experimental
:
:
When HC CSi(Ph)2C CH started to appear, the reaction was
subsequently quenched by water and the mixture extracted
with CH2Cl2 . The resulting organic extract was dried over
Na2SO4 , filtered and concentrated. The concentrate was then
subjected to flash column chromatography on silica using
petroleum ether–CH2Cl2 (6 : 1, v=v) as eluent to give 2 as a
colourless liquid (45 mg, 42%). This compound can be used
for the following preparation without further purification.
IR (CH Cl ): 3283 (n:CH) and 2040 cmÀ1(nC C). 1H NMR
General
All reactions were conducted under an atmosphere of dry
nitrogen with the use of standard Schlenk techniques. Solvents
for preparative work were dried and distilled before use. IR
spectra were recorded on a Nicolet FTIR-550 spectrometer.
NMR spectra were recorded in CDCl3 on a JEOL JNM-EX
270, Varian Inova 400 MHz or Bruker 600 MHz FT-NMR
spectrometer. Electron impact (EI) and fast atom bombard-
ment (FAB) mass spectra were recorded on a Finnigan-SSQ
710 spectrometer. Electronic absorption and luminescence
spectra were measured in appropriate solvents with a Varian
Cary 100 UV=VIS spectrophotometer and a Perkin–Elmer
LS50B luminescence spectrometer, respectively. Unless other-
wise stated, all reagents were from commercial sources
and used as received. The starting diethynyl compounds
:
2
2
:
(CDCl3): d 0.22 (s, 9H, Me), 2.70 (s, 1H, C CH), 7.38–7.41 (m,
6H, Ph) and 7.72–7.74 (m, 4H, Ph). 13C-{1H} NMR (CDCl3): d
:
:
À0.33 (Me), 83.91, 105.24 and 119.52 (C C), 96.96 (C CH),
128.07, 130.36, 134.76 (aromatic CH) and 131.99 (aromatic
quaternary C). 29Si NMR (CDCl3): d À49.77 and À17.27. EI
MS: m=z 304 (Mþ). A satisfactory elemental analysis was not
obtained, probably due to contamination by a trace amount of
0
:
:
: :
HC CSi(Ph)2C CH.
HC CRC CH (R ¼ 1,4-phenylene, 5,5 -bithienylene or 9,10-
anthrylene) were prepared according to the reported proce-
dures.41,43,44,50 Separation of products was accomplished by
column chromatography on silica or preparative silica TLC
plates (Merck, Kieselgel 60).
:
:
:
:
Me3SiC CSi(Ph)2C CSi(Ph)2C CSi(Ph)2C CSiMe3 , 3. Com-
pound 2 (48 mg, 0.16 mmol) was dissolved in dry THF (10 cm3)
in a Schlenk flask. After cooling the flask to À78 ꢀC, nBuLi was
added dropwise to the stirred solution. After stirring for 1 h at
À78 ꢀC, Ph2SiCl2 (20 mg, 0.08 mmol) was added dropwise. The
resulting mixture was stirred at À78 ꢀC for 2h and then
warmed at room temperature for another 0.5 h. The crude
material was extracted between NH4Cl solution and CH2Cl2 .
The organic layer was dried over Na2SO4 and filtered. Con-
centration of the filtrate followed by silica column chromato-
graphy using petroleum ether–CH2Cl2 (6 : 1, v=v) as eluent
Synthetic procedures
Me3SiC CSi(Ph)2C CSiMe3 , 1. nBuLi (13 cm3, 20.8 mmol,
1.6 M solution in hexane) was added dropwise to a solution of
trimethylsilylacetylene (1.96 g, 20.0 mmol) in dry diethyl ether
(40 cm3) at À78 ꢀC under a nitrogen atmosphere. After the
mixture was stirred at À78 ꢀC for 1 h, Ph2SiCl2 (2.53 g, 10.0
:
:
New J. Chem., 2002, 26, 354–360
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afforded 3 as a colourless oil in 65% yield (41 mg). IR (KBr):
2040 cmÀ1 (nC C). 1H NMR (CDCl3): d 0.22 (s, 18H, Me),
mg, 25%) and 5b (Rf ¼ 0.27, 18 mg, 10%), all as pale yellow
solids. 5a: m.p.: 90–92 ꢀC (dec.). IR (KBr): 3284 (n:CH), 2139
:
7.34–7.43 (m, 18H, Ph) and 7.75–7.79 (m, 12H, Ph). 13C-{1H}
and 2098 cmÀ1(nC C). 1H NMR (CDCl3): d 3.42(s, H2 ,
:
3
C CH), 7.04 (d, JH–H ¼ 1.6 Hz, 2H, thienyl), 7.05 (d, 3JH–H
¼
:
NMR (CDCl3): d À0.33 (Me), 105.31, 110.39, 111.97, 119.69
:
(C C), 128.06, 128.07, 130.29, 130.44, 134.87, 134.98 (aro-
1.6 Hz, 2H, thienyl), 7.17 (d, 3JH–H ¼ 4.0 Hz, 2H, thienyl), 7.27
matic CH), 132.08 and 134.76 (aromatic quaternary C). 29Si
NMR (CDCl3): d À50.48, À27.31 and À17.28. EI MS: m=z 788
(Mþ). UV=VIS (cyclohexane): lmax=nm (e  104 dm3 molÀ1
cmÀ1) 256 (1.9), 262 (2.4), 266 (2.5) and 273 (2.0). A satisfac-
tory analytical analysis was not obtained due to contamination
(d, JH–H ¼ 4.0 Hz, 2H, thienyl), 7.43–7.48 (m, 6H, Ph) and
3
7.81–7.84 (m, 4H, Ph). 13C–{1H} NMR (CDCl3): d 82.77
:
:
(C CH), 76.58, 93.46, 101.03 (C C), 123.97, 124.04, 128.21,
130.52, 133.99, 134.88, 134.94 (aromatic CH), 121.53, 121.56,
132.01, 137.97 and 138.92 (aromatic quaternary C). 29Si NMR
(CDCl3): d À47.78. FAB MS: m=z 608 (Mþ). UV=VIS
(CH2Cl2): lmax=nm (e  104 dm3 molÀ1 cmÀ1) 229 (2.5), 259
(1.4) and 365 (5.3). Emission (CH2Cl2 , lexcitation ¼ 365 nm):
409 nm. Calcd for C36H20SiS4: C, 71.01; H, 3.31. Found: C,
:
:
by a trace amount of HC CSi(Ph)2C CH that was present in
the previous step.
:
:
:
:
:
:
HC CRC CSi(Ph)2C CRC CH, 4a, and HC CRC C-
70.81; H, 3.42%. 5b: m.p.: 53–54 ꢀC (dec.). IR (KBr): 3285
:
:
:
:
Si(Ph)2C CRC CSi(Ph)2C CRC CH, 4b (R ¼ 1,4-pheny-
lene). To a chilled solution of 1,4-diethynylbenzene (200 mg,
1.59 mmol) in dried THF (20 cm3) at À20 ꢀC, (Me3Si)2NLi
(266 mg, 1.59 mmol) freshly prepared from (Me3Si)2NH and
nBuLi in THF (20 cm3) or nBuLi (1.0 cm3, 1.60 mmol, 1.6 M in
hexane) was added dropwise under a nitrogen purge. The
mixture was stirred for 30 min at this temperature and then 2h
at room temperature. The resulting solution was again cooled
to À20 ꢀC and a solution of Ph2SiCl2 (201 mg, 0.80 mmol) in
THF (10 cm3) was added dropwise over 30 min. The reaction
mixture was stirred for a further 30 min at À20 ꢀC prior to
stirring at room temperature for 3 h. The volatile components
were evaporated and the residue was extracted with CH2Cl2 .
The organic extract was dried over Na2SO4 and filtered. The
filtrate was concentrated and subjected to preparative TLC
isolation using silica plates and hexane–CH2Cl2 (3 : 1, v=v) as
eluent. From the second (Rf ¼ 0.55) and third (Rf ¼ 0.45)
bands, compounds 4a and 4b were obtained as white solids
with yields of 52(179 mg) and 17% (67 mg), respectively,
based on 1,4-diethynylbenzene. The starting 1,4-diethy-
nylbenzene was also recovered in a pure form from the top
band (40 mg, 20%), which can be employed as a precursor for
the synthesis of more 4a and 4b. 4a: m.p.: 96–98 ꢀC. IR (KBr):
(n:CH), 2142 and 2100 cmÀ1(nC C). H NMR (CDCl3): d 3.42
1
:
3
:
(s, 2H, C CH), 7.04 (d, JH–H ¼ 1.6 Hz, 2H, thienyl), 7.05 (d,
3JH–H ¼ 1.6 Hz, 2H, thienyl), 7.06 (d, JH–H ¼ 3.6 Hz, 2H,
3
thienyl), 7.17 (d, 3JH–H ¼ 3.6 Hz, 2H, thienyl), 7.26 (t, 3JH–H
¼
4.0 Hz, 4H, thienyl), 7.42–7.48 (m, 12H, Ph) and 7.81–7.83 (m,
:
13
1
8H, Ph). C-{ H} NMR (CDCl3): d 82.76 (C CH), 76.58,
:
93.46, 93.62, 101.00, 101.05 (C C), 123.98, 124.05, 124.14,
128.21, 130.52, 133.99, 134.89, 134.91, 134.95 (aromatic CH),
121.55, 121.56, 121.74, 132.00, 137.98, 138.85 and 138.93
(aromatic quaternary C). 29Si NMR (CDCl3): d À47.79. FAB
MS: m=z 1002(M þ). UV=VIS (CH2Cl2): lmax=nm (e  104 dm3
molÀ1 cmÀ1) 230 (2.9), 260 (1.5) and 370 (7.2). Emission
(CH2Cl2 , lexcitation ¼ 370 nm): 412nm. Calcd for C 60H34Si2S6:
C, 71.82; H, 3.42. Found: C, 71.45; H, 3.21%.
:
HC CRC CSi(Ph)2C CRC CH, 6a, and HC CRC C-
:
:
:
:
:
:
:
:
:
Si(Ph)2C CRC CSi(Ph)2C CRC CH, 6b (R ¼ 9,10-anthry-
lene). These anthryl-substituted oligoalkynes were similarly
synthesised as described for 4a and 4b from 9,10-diethynyl-
anthracene (288 mg, 1.27 mmol). The resulting brown-yellow
suspension was then purified by silica TLC separation, eluting
with hexane–CH2Cl2 (3 : 1, v=v) to give three major yellow
bands identified as 9,10-diethynylanthracene (Rf ¼ 0.73, 72mg,
25%), 6a (Rf ¼ 0.54) and 6b (Rf ¼ 0.44). Further purification of
the desired products 6a and 6b was accomplished by another
TLC separation using the same solvent mixture, followed by
recrystallisation to afford orange-yellow solids of 6a and 6b in
27 (109 mg) and 10% (44 mg) yield, respectively. 6a: m.p.:
3276 (n:CH) and 2157 cmÀ1(nC C). 1H NMR (CDCl3): d 3.24 (s,
:
:
2H, C CH), 7.47–7.52(m, 10H, Ph), 7.58–7.60 (m, 4H, C 6H4)
and 7.89–7.94 (m, 4H, C6H4) 13C-{1H} NMR (CDCl3): d 79.43
:
:
(C CH), 83.02, 89.62, 107.98 (C C), 128.17, 130.42, 131.97,
132.00, 134.89 (aromatic CH), 122.69, 122.95 and 132.44
(aromatic quaternary C). 29Si NMR (CDCl3): d À47.88. FAB
MS: m=z 432(M þ). UV=VIS (CH2Cl2): lmax=nm (e  104 dm3
molÀ1 cmÀ1) 228 (3.1), 274 (9.0) and 290 (1.1). Emission
(CH2Cl2 , lexcitation ¼ 290 nm): 339 nm. Calcd for C32H20Si: C,
88.85; H, 4.66. Found: C, 88.59; H, 4.40%. 4b: m.p.: 180–
155–156 ꢀC (dec.). IR (KBr): 3303 (n:CH) and 2131 cmÀ1(nC C).
:
1
:
H NMR (CDCl3): d 4.10 (s, 2H, C CH), 7.50–7.56 (m, 4H,
anthryl), 7.57–7.67 (m, 10H, Ph), 8.09–8.20 (m, 4H, anthryl),
8.57–8.67 (m, 4H, anthryl) and 8.69–8.79 (m, 4H, anthryl).
13
C-{ H} NMR (CDCl3): d 90.24 (C CH), 80.18, 101.26,
182 ꢀC. IR (KBr): 3287 (n:CH) and 2159 cmÀ1 (nC C). 1H NMR
:
1
:
:
(CDCl3): d 3.19 (s, 2H, C CH), 7.43–7.47 (m, 16H, aromatic),
7.52–7.54 (m, 8H, aromatic) and 7.83–7.85 (m, 8H, aro-
:
105.60 (C C), 126.98, 127.02, 127.08, 127.30, 128.32, 130.50,
135.01 (aromatic CH), 117.74, 118.34, 127.66, 132.35 and
132.62 (aromatic quaternary C). 29Si NMR (CDCl3): d À47.40.
FAB MS: m=z 632(M þ). UV=VIS (CH2Cl2): lmax=nm (e  104
dm3 molÀ1 cmÀ1) 228 (3.1), 270 (11.7), 390 (1.3), 412 (2.6) and
438 (3.4). Emission (CH2Cl2 , lexcitation ¼ 390 nm): 436 and 480
nm. Calcd for C48H28Si: C, 91.10; H, 4.46. Found: C, 90.84; H,
matic).13 C-{ H} NMR (CDCl3): d 79.44 (C CH), 83.01,
1
:
:
89.56, 90.00, 107.95, 108.00 (C C), 128.17, 130.43, 131.96,
132.17, 132.20, 134.89 (aromatic CH), 122.67, 122.93, 123.08
and 132.38 (aromatic quaternary C). 29Si NMR (CDCl3): d
À47.89. FAB MS: m=z 738 (Mþ). UV=VIS (CH2Cl2): lmax=nm
(e  104 dm3 molÀ1 cmÀ1) 228 (4.7), 274 (14.1), 289 (14.8) and
303 (11.3). Emission (CH2Cl2 , lexcitation ¼ 289 nm): 329, 399sh
nm. Calcd for C54H34Si2: C, 87.76; H, 4.64. Found: C, 87.52;
H, 4.31%.
4.28%. 6b: m.p.: 96–98 ꢀC (dec.). IR (KBr): 3290 (n:CH) and
2130 cmÀ1(nC C). H NMR (CDCl3): d 4.09 (s, 2H, C CH),
1
:
:
7.47–7.55 (m, 4H, anthryl), 7.56–7.72 (m, 20H, Ph), 8.06–8.23
(m, 8H, anthryl), 8.57–8.65 (m, 4H, anthryl) and 8.69–8.83 (m,
8H, anthryl). 13C-{ H} NMR (CDCl3): d 90.24 (C CH), 80.17,
1
:
:
:
:
:
:
:
HC CRC CSi(Ph)2C CRC CH, 5a, and HC0 CRC C-
:
101.20, 101.74, 105.55, 105.65 (C C), 126.98, 127.02, 127.07,
:
:
:
:
Si(Ph)2C CRC CSi(Ph)2C CRC CH, 5b (R ¼ 5,5 -bithieny-
lene). These compounds were prepared using the conditions
described above for 4a and 4b but 5,50-diethynyl-2,20-bithio-
phene (118 mg, 0.55 mmol) was used instead of 1,4-diethy-
nylbenzene. Elution using a 2: 1 hexane–CH 2Cl2 mixture gave
three yellow bands, from which three compounds were sepa-
rated. In order of elution, these compounds were 5,50-diethy-
nyl-2,20-bithiophene (Rf ¼ 0.68, 20 mg, 17%), 5a (Rf ¼ 0.50, 42
127.30, 127.38, 128.32, 130.52, 135.01, 135.16 (aromatic CH),
117.70, 118.34, 127.16, 130.78, 132.34, 132.63 and 132.65
(aromatic quaternary C). 29Si NMR (CDCl3): d À47.41. FAB
MS: m=z 1040 (Mþ). UV=VIS (CH2Cl2): lmax=nm (e  104 dm4
molÀ1 cmÀ1) 228 (6.4), 270 (16.7), 391 (1.6), 413 (3.1), 423 (2.9),
438 (3.6) and 450 (3.6). Emission (CH2Cl2 , lexcitation ¼ 413
nm): 454 and 484 nm. Calcd for C78H46Si2: C, 90.14; H, 4.46.
Found: C, 89.85; H, 4.14%.
358
New J. Chem., 2002, 26, 354–360

View Article Online
10 A. Adachi, J. Ohshita, T. Ohno, A. Kunai, S. A. Manhart,
Table 2 Summary of crystal structure data for compound 4b
K. Okita and J. Kido, Appl. Organomet. Chem., 1999, 13,
859.
11 S. A. Manhart, A. Adachi, K. Sakamaki, K. Okita, J. Ohshita,
T. Ohno, T. Hamaguchi, A. Kunai and J. Kido, J. Organomet.
Chem., 1999, 592, 52 .
12S. Ijadi-Maghsoodi and T. J. Barton, Macromolecules, 1990, 23,
4485.
13 M. Itoh, M. Mitsuzaka, K. Iwata and K. Inoue, Macromolecules,
1997, 30, 694.
14 J. Ohshita, A. Shinpo and A. Kunai, Macromolecules, 1999, 38,
5998.
15 M. Ishikawa and K. Nate, in Inorganic and Organometallic
Polymers, eds. M. Zeldin, K. J. Wynne and H. R. Allcock,
ACS Symposium Series 360, ACS, Washington, DC, 1988,
ch. 16.
Empirical formula
M
Crystal system
C54H34Si2
738.99
Triclinic
P1
-
Space group
+
a=A
+
8.0001(7)
9.4959(9)
14.769(1)
80.960(2)
74.773(2)
82.454(2)
1064.4(2)
1
b=A
+
c=A
a=ꢀ
b=ꢀ
g=ꢀ
+
U=A3
Z
m (Mo-Ka)=mmÀ1
No. reflections collected
0.119
6216
16 J. Ohshita and M. Ishikawa, in Polymeric Materials Encyclopedia,
ed. J. C. Salamone, CRC Press, New York, 1996, pp. 892and
references therein.
17 M. Birot, J.-P. Pillot and J. Dunogues, Chem. Rev., 1995, 95, 1443,
and references therein.
Unique reflections
Rint
Observed reflections [I > 2s(I)]
R1
wR2 [I > 2s(I)]
R1
wR2 (all data)
4519
0.0188
4519
0.0583
0.1741
0.0695
0.1890
18 H. Sakurai, H. Sugiyama and M. Kira, J. Phys. Chem., 1990, 94,
1837.
19 H. Sakurai, J. Organomet. Chem., 1980, 200, 261.
20 J. Yao and D. Y. Son, Organometallics, 1999, 18, 1736.
21 M. Kira and S. Tokura, Organometallics, 1997, 16, 1100.
22 F. Garten, A. Hilberer, F. Cacialli, Y. van Dam, B. Schlatmann,
R. H. Friend, T. M. Krapwijk and G. Hadziioannou, Adv. Mater.,
1997, 9, 127.
P
P
P
P
R1 ¼ jjFoj À jFcjj= jFoj, wR2 ¼ [ w(jFo j À jFc j)2= wjFo j ]
.
2
2
2 2 1=2
Crystallography
23 E. R. Silcoff and T. Sheradsky, Macromolecules, 1998, 31,
9116.
24 K. Yoshino, A. Fujii, H. Nakayama, S. Lee, A. Naka and
M. Ishikawa, J. Appl. Phys., 1999, 85, 414.
25 M. Kakimoto, H. Kashihara, T. Kashiwagi, T. Takiguchi,
J. Ohshita and M. Ishikawa, Macromolecules, 1997, 30, 7816.
26 A. Kunai, T. Ueda, K. Horata, E. Toyoda, I. Nagamoto,
J. Ohshita and M. Ishikawa, Organometallics, 1996, 15, 2000.
27 K. Boyer-Elma, F. H. Carre, R. J.-P. Corriu and W. E. Douglas,
J. Chem. Soc., Chem. Commun., 1995, 1, 725.
28 W. E. Douglas, D. M. H. Guy, A. K. Kar and C. Wang, Chem.
Commun., 1998, 2125.
29 U. Kruerke, J. Organomet. Chem., 1970, 21, 83.
30 H. Li, D. R. Powell, T. K. Firman and R. West, Macromolecules,
1998, 31, 1093.
31 K. Mullen and G. Wegner, Electronic Materials: T he Oligomer
Approach, Wiley-VCH, Weinheim, 1998.
32P. F. van Hutten, V. V. Krasnikov and G. Hadziioannou, Acc.
Chem. Res., 1999, 32, 257.
Colourless crystals of 4b suitable for X-ray diffraction analysis
were grown by evaporation of its solution in a hexane–CH2Cl2
mixture. Geometric and intensity data were collected using
graphite-monochromated Mo-Ka radiation (l ¼ 0.71073 A)
+
on a Bruker AXS SMART CCD area detector. The collected
frames were processed with the software SAINT51 and an
absorption correction was applied (SADABS52) to the col-
lected reflections. The structure was solved by direct methods
(SHELXTL53) in conjunction with standard difference Fourier
techniques and subsequently refined by full-matrix least-
squares analyses. All non-hydrogen atoms were assigned with
anisotropic displacement parameters. Hydrogen atoms were
generated in their idealised positions and allowed to ride on the
respective carbon atoms. Crystallographic and other experi-
mental details are collected in Table 2.
CCDC
www.rsc.org=suppdata=nj=b1=b108510g for crystallographic
reference
number
177961.
See
http:==
33 S. Wang, W. J. Oldham, Jr., R. A. Hudack, Jr. and G. C. Bazan,
J. Am. Chem. Soc., 2000, 122, 5695 and references cited therein.
34 J. Ohshita, A. Takata, A. Kunai, M. Kakimoto, Y. Harima,
Y. Kunugi and K. Yamashita, J. Organomet. Chem., 2000, 611,
537.
data in CIF or other electronic format.
35 M. Ishikawa, T. Hatano, Y. Hasegawa, T. Horio, A. Kunai,
A. Miyai, T. Ishida, T. Tsukihara, T. Yamanaka, T. Koike and
J. Shioya, Organometallics, 1992, 11, 1604.
36 R. J. P. Corriu, W. E. Douglas, Z.-X. Yang, F. Garnier and
A. Yassar, J. Organomet. Chem., 1991, 417, C50.
37 M. Ishikawa, Y. Hasegawa, A. Kunai and T. Yamanaka,
J. Organomet. Chem., 1990, 381, C51.
Acknowledgements
We thank the Hong Kong Research Grants Council (HKBU
2048=97P) and the Hong Kong Baptist University (FRG=98-
99=II-77) for financial support.
38 A. W. M. Lee, A. B. W. Yeung, M. S. M. Yuen, H. Zhang,
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39 H. Zhang, A. W. M. Lee, W.-Y. Wong and M. S. M. Yuen,
J. Chem. Soc., Dalton T rans., 2000, 3675.
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