1,4-Bis(triisopropylsilyl)buta-1,3-diyne and 1,4-bis(biphenyl-4-yl)buta-1, 3-diyne

Article abstract of DOI:10.1107/S0108270106025157

We report the single crystal structures of 1,4-bis(triisopropylsilyl)buta- l,3-diyne, C₂₂H₄₂Si₂, and l,4-bis(biphenyl-4- yl)buta1,3-diyne, C₂₈H₁₈, the packing in both of which illustrates the versatil

Full text of DOI:10.1107/S0108270106025157

organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
Â
et al., 2005; Hlavaty et al., 2002; Ried & Saxena, 1970; Toda &
Tokumaru, 1990), but have not, to our knowledge, been
structurally characterized. We report here their single-crystal
structures, which illustrate a number of facets of weak CÐ
HÁ Á Áꢀ interactions in dictating solid-state structures. Such
hydrogen bonds are now well established as important
components in solid-state supramolecular assemblies
(Desiraju, 2002, 2005; Desiraju & Steiner, 1999; Nishio, 2004;
Nishio et al., 1998; Steiner, 2002), and their role in organic
reactions has recently been assessed (Nishio, 2005).
ISSN 0108-2701
1,4-Bis(triisopropylsilyl)buta-1,3-diyne
and 1,4-bis(biphenyl-4-yl)buta-1,3-
diyne
Edwin C. Constable, Deborah Gusmeroli, Catherine E.
Housecroft,* Markus Neuburger and Silvia Schaffner
Department of Chemistry, University of Basel, Spitalstrasse 51, CH-4056 Basel,
Switzerland
Correspondence e-mail: catherine.housecroft@unibas.ch
Received 2 June 2006
Accepted 29 June 2006
Online 22 July 2006
We report the single crystal structures of 1,4-bis(triisopropyl-
silyl)buta-1,3-diyne, C22H42Si2, and 1,4-bis(biphenyl-4-yl)buta-
1,3-diyne, C28H18, the packing in both of which illustrates the
versatility of weak CÐHÁ Á Áꢀ supramolecular interactions in
dictating the overall solid-state structures.
Comment
We have been interested in the development of polyalkyne-
based stars and dendrimers and their reactions with Co2(CO)8
to produce organometallic cluster-decorated architectures
(Constable et al., 2006). We have used Sonogashira palladium-
catalysed cross-coupling reactions (Sonogashira et al., 1975;
Sonogashira, 2002) for the divergent assembly of polyalkynes
containing rigid frameworks with well-de®ned structures.
Under Sonogashira conditions, reactions between terminal
alkynes (RC CH) and aryl halides can give rise to diynes
(RC CÐC CR) as side-products (these most often arise
from bromo precursors) (Sonogashira et al. 1975; Sonogashira
2002). Related reactions (Liu & Burton, 1997) or modi®ed
Sonogashira conditions (Rossi et al., 1985) have been used for
the speci®c formation of diynes. Two molecular cores that we
have investigated are hexakis[(triisopropylsilyl)ethynyl]-
benzene and 4,40-bis(biphenyl-4-ylethynyl)biphenyl. During
attempts to synthesize these compounds, we found that 1,4-
bis(triisopropylsilyl)buta-1,3-diyne, (I), and 1,4-bis(biphenyl-
4-yl)buta-1,3-diyne, (II), could be produced quantitatively.
With the aim of preparing C6(C CSiiPr3)6, we treated C6I6
with six equivalents of iPr3SiC CH under Sonogashira cross-
coupling conditions. Instead of the desired product, compound
(I) was formed quantitatively under the conditions shown in
the scheme. This was also the case when C6Br6 was used as the
precursor. Similarly (see scheme), the palladium-catalysed
cross-coupling reaction between 4-ethynylbiphenyl and 4,40-
dibromobiphenyl led to the quantitative formation of (II).
Compounds (I) and (II) have been reported previously (Eisler
.
X-ray quality crystals of (I) were grown from a CH2Cl2
solution. Fig. 1 shows the structure of the centrosymmetric
molecule of (I). The carbon backbone is linear, as observed for
i
Â
Me3Si(C C)2SiMe3 (Carre et al., 2003) and Pr3Si(C C)n-
SiiPr3 (n = 4, 5 or 6; Eisler et al., 2005), in contrast with the
curved backbone of Pr3Si(C C)8SiiPr3 (Eisler et al., 2005).
i
The CÐSiÐC bond angles lie in the range 105.97 (9)±
116.94 (13)ꢀ.
Molecules of (I) pack in rows (Fig. 2a), such that the
distance between the least-squares planes containing adjacent
Ê
rows of SiCCCCSi chains is 5.8 A. Adjacent chains are inter-
locked, with the packing being supported by close methyl CÐ
Ê
HÁ Á Á(alkyne ꢀ) interactions (C8ÐH83Á Á ÁC1 = 2.9 A and C8Ð
Acta Cryst. (2006). C62, o505±o509
DOI: 10.1107/S0108270106025157
# 2006 International Union of Crystallography o505

organic compounds
i
solid-state packing of Pr3Si(C C)4SiiPr3 resembles that of
(I), with molecules organized in offset rows, while for
Ê
H83Á Á ÁC2 = 3.1 A). This leads to the presence of close
(repulsive) HÁ Á ÁH contacts (Me2CÐH61Á Á ÁH61ÐCMe2
=
i
Ê
2.7 A). A second set of CÐHÁ Á Áꢀ interactions operates
between molecules within each row (Fig. 2b). Their evolution
gives rise to short HÁ Á ÁH contacts between pairs of molecules.
The structures of a number of molecules closely related to
(I) have been determined and comparisons of the solid-state
packing are instructive. A search of the Cambridge Structural
Database (CSD, Version 5.2.7; Allen, 2002; Bruno et al., 2002)
for molecules containing an EÐC CÐC CÐE unit (E is
Si, Sn, Ge or Pb) gave only 14 hits (Brouty et al., 1980; Brunel
iPr3Si(C C)5SiiPr3 and Pr3Si(C C)6SiiPr3, a herring-bone
Â
et al., 2001; Carre et al., 1999, 2003; Dam et al., 1998; Neuge-
bauer et al., 2000). Among these are two polymorphs of
Me3SiC CC CSiMe3 (structures determined at 120 and
Â
203 K; Carre et al., 2003). The packing of the molecules in both
polymorphs differs from that in (I). Although the molecules
are interlocked by virtue of the close approach of SiMe3
and alkyne groups, molecules in both polymorphs of
Me3SiC CC CSiMe3 form grid-like assemblies, in contrast
with the parallel alignment of molecules observed in the solid
state of (I).
Compound (I) is a member of a family of polyynes,
iPr3Si(C C)nSiiPr3 (n = 4, 5, 6 and 8; Eisler et al., 2005). The
Figure 1
Figure 2
(a) The packing of molecules of (I), showing parts of two offset rows.
The molecular structure of (I), showing the atom-numbering scheme.
Displacement ellipsoids are drawn at the 30% probability level and H
atoms are shown as small spheres of arbitary radii. Unlabelled atoms and
C1i are generated by the symmetry operator ( x + 2, y + 1, z + 1).
(b) CÐHÁ Á Áꢀ interactions between adjacent molecules in a row (C2iÁ Á Á
ii
i
ii
ii
Ê
Ê
Ê
H53 = 3.2 A, C1 Á Á ÁH53 = 2.9 A and C1Á Á ÁH53 = 3.1 A). [Symmetry
codes: (i) x + 2, y + 1, z + 1; (ii) 1 x, 1 y, 1 z.]
Figure 3
The molecular structure of (II), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are
shown as small spheres of arbitary radii.
ꢁ
o506 Constable et al.
C22H42Si2 and C28H18
Acta Cryst. (2006). C62, o505±o509

organic compounds
i
assembly is observed. In Pr3Si(C C)8SiiPr3, the polyyne
1997). As in (II), the biphenyl unit of 4-ethynylbiphenyl is
non-planar. The authors (Mague et al., 1997) describe the
structure as containing `no signi®cant intermolecular inter-
actions', although inspection of the data indicate the presence
of weak CÐHalkyneÁ Á Áꢀaryl contacts.
backbone is signi®cantly curved and the molecular packing is
less readily compared with that of the smaller polyynes (Eisler
et al., 2005).
Crystals of (II) were grown from a CH2Cl2 solution, and the
molecular structure is shown in Fig. 3. The molecule is slightly
bowed and the aryl rings are twisted with respect to one
another, so that the angles between the least-squares planes of
the rings containing atoms C6 and C7, atoms C7 and C22, and
atoms C22 and C23 are 28.70 (7), 61.07 (6) and 44.22 (6)ꢀ,
respectively. The origin of these ring orientations can be
traced to the intermolecular CÐHÁ Á Áꢀ interactions listed in
Table 3. The basic motif in the solid state is a dimeric unit
(Fig. 4a), in which both CÐHarylÁ Á Áꢀalkyne and CÐHarylÁ Á Áꢀaryl
interactions are present (Table 3).
In conclusion, we have investigated the solid-state struc-
tures of two simple diynes and in both cases ®nd that weak
CÐHÁ Á Áꢀ contacts control the molecular packing. In the case
of 1,4-bis(biphenyl-4-yl)buta-1,3-diyne, a combination of CÐ
HarylÁ Á Áꢀalkyne and CÐHarylÁ Á Áꢀaryl interactions operate at the
expense of ꢀ-stacking interactions.
Experimental
Compound (I), previously prepared directly (Eisler et al., 2005;
The dimers further assemble into layers (Fig. 4b), again with
CÐHÁ Á Áꢀ interactions playing a role (Table 3). Stacking of
planes of molecules into the three-dimensional lattice is also
supported by CÐHÁ Á Áꢀ contacts (Table 3) . The molecular
structure of (II) shows interesting contrasts with that of 1,4-
diphenylbuta-1,3-diyne (Fronczek & Erickson, 1995; Surette et
al., 1994). Molecules of the latter are planar in the solid state
and pack in a herring-bone arrangement. Whereas CÐHÁ Á Áꢀ
contacts control the ring orientations and packing in (II), ꢀ-
stacking interactions are important in 1,4-diphenylbuta-1,3-
diyne. Also related to (II) is 4-ethynylbiphenyl (Mague et al.,
Â
Hlavaty et al., 2002), was the product of an unsuccessful attempt to
prepare C6(CCSiiPr3)6. C6I6 (1.00 g, 1.20 mmol), CuCl (17.8 mg,
0.18 mmol) and [PdCl2(PPh3)2] (126 mg, 0.18 mmol) were added
to Et3N (75 ml) and, after addition of iPr3SiC CH (2.13 ml,
9.60 mmol), the mixture was stirred at 333 K for 12 h under argon.
The solvent was removed and the residue was extracted with 30%
CH2Cl2 in hexanes (200 ml). The product was puri®ed by column
chromatography (alumina, hexanes) and (I) was collected as a dark-
yellow solid (1.74 g, 100%; m.p. 369 K). FAB±MS m/z: 362 ([M]+), 319
([M iPr], base peak); 1H NMR (400 MHz, CDCl3): ꢁ 1.09 (s, TIPS);
13C NMR (125 MHz, CDCl3): ꢁ 90.2 (C C), 81.6 (C C), 18.6 (CH),
11.3 (CH3); IR (solid, ꢂ, cm 1): 2943 (s), 2866 (s), 2050 (s), 1458 (s),
1383 (s), 1365 (s), 1230 (m), 1011 (s), 991 (s), 881 (vs), 663 (vs), 625
(vs). Crystals were grown from a solution in CH2Cl2. The route to
compound (II) was optimized during attempts to prepare 4,40-
bis(biphenyl-4-ylethynyl)biphenyl. 4,40-Dibromobiphenyl (233 mg,
1.00 mmol), CuCl (14.9 mg, 0.15 mmol) and [PdCl2(PPh3)2] (105 mg,
0.15 mmol) were added to Et3N (40 ml) and, after addition of
4-ethynylbiphenyl (Foroozesh et al., 1997) (196 mg, 1.10 mmol), the
mixture was stirred at 333 K for 18 h under argon. The solvent was
removed, the residue was redissolved in hexanes (150 ml) and the
mixture was ®ltered. The product was puri®ed by column chroma-
tography (alumina, hexanes±CH2Cl2 1:4) to yield (II) as a yellow solid
(195 mg, 100%; m.p. 513 K). FAB±MS m/z: 354 ([M]+, base peak), 177
1
([M PhC6H4CC]+); H NMR (400 MHz, CDCl3): ꢁ 7.60 [m, 12H,
H(B2,B3,A2)], 7.46 [m, 4H, H(A3)], 7.38 [t, 2H, H(A4)]; 13C NMR
(125 MHz, CDCl3): ꢁ 141.9 [C(1A/1B)], 140.0 [C(1B/1A)], 132.9
[C(3B)], 128.9 [C(3A)], 127.9 [C(4A)], 127.1 [C(2A)], 127.0 [C(2B)],
120.6 [C(4B)], 81.8 [C(ArC C)], 74.6 [C(ArC C); IR (solid, ꢂ,
cm 1): 3059 (w), 3036 (w), 2133 (w), 1599 (m), 1481 (s), 1448 (s), 839
(vs), 762 (vs), 721 (vs), 696 (vs). Crystals of (II) were grown from a
solution in CH2Cl2.
Compound (I)
Crystal data
3
Ê
C22H42Si2
V = 598.90 (6) A
Z = 1
Mr = 362.75
Triclinic, P1
a = 7.2397 (4) A
3
Dx = 1.006 Mg m
Mo Kꢃ radiation
Ê
Ê
1
b = 7.8151 (5) A
ꢆ = 0.15 mm
T = 173 K
Ê
Figure 4
c = 10.9548 (5) A
ꢃ = 86.680 (5)ꢀ
ꢄ = 80.485 (4)ꢀ
ꢅ = 78.542 (4)ꢀ
(a) The dimeric motif in the solid-state structure of (II). [Symmetry code
(i) 1 x, 1 y, z.] (b) The packing of molecules of (II) into layers. Two
dimeric units are shown in the middle of the ®gure.
Plate, colourless
0.30 Â 0.16 Â 0.14 mm
ꢁ
Acta Cryst. (2006). C62, o505±o509
Constable et al. C22H42Si2 and C28H18 o507

organic compounds
Data collection
Table 3
ꢀ
Ê
Important intermolecular CÐHÁ Á Áꢀ contacts (A, ) in compound (II).
Cg1 is the centroid of ring C1±C6, Cg2 of ring C7±C12, Cg3 of ring C17±C22
and Cg4 of ring C23±C28.
Nonius KappaCCD area-detector
diffractometer
' and ! scans
Absorption correction: multi-scan
(DENZO and SCALEPACK;
Otwinowski & Minor, 1997)
Tmin = 0.98, Tmax = 0.98
29988 measured re¯ections
3478 independent re¯ections
2019 re¯ections with I > 3ꢇ(I)
Rint = 0.069
ꢈmax = 30.0ꢀ
Distance
Angle
Within the dimer (Fig. 4a)
H181Á Á ÁC14i
2.9
3.0
3.1
2.8
3.5
H181Á Á ÁC15i
Re®nement
H171Á Á ÁC13i
Re®nement on F
R[F > 2ꢇ(F)] = 0.050
wR(F) = 0.054
S = 1.09
2019 re¯ections
109 parameters
H-atom parameters constrained
w = [1 ꢂFo Fc†2/36ꢇ2ꢂF†/
1:89T0ꢂx† 0:168T1ꢂx†
+ 1:21T2ꢂx†], where Ti are the
Chebychev polynomials and
x ˆ Fc=Fmax (Watkin, 1994;
Prince, 1982)
C24ÐH241Á Á ÁCg2i
C25ÐH251Á Á ÁCg1i
147
174
Other interactions within a layer (Fig. 4b)
C3ÐH31Á Á ÁCg2ii
(Á/ꢇ)max = 0.007
2.9
3.4
148
170
3
Ê
Áꢉmax = 0.93 e A
C26ÐH261Á Á ÁCg1iii
3
Ê
0.64 e A
Áꢉmin
=
Interactions between layers
C1ÐH11Á Á ÁCg4iv
2.9
3.1
3.4
2.9
151
127
136
121
C8ÐH81Á Á ÁCg3v
C11ÐH111Á Á ÁCg1vi
Table 1
Selected geometric parameters (A, ) for (I).
ꢀ
Ê
C20ÐH201Á Á ÁCg4vii
3
2
1
2
5
2
1
Symmetry codes: (i) 1 x; 1 y; z; (ii)
x; 12 ‡ y;
z; (iii)
1
‡ x,
y,
2
z; (vii)
C1ÐC1i
C1ÐC2
C2ÐSi1
1.373 (3)
1.204 (2)
1.8432 (18)
C3ÐSi1
C6ÐSi1
C9ÐSi1
1.873 (2)
1.873 (2)
1.876 (2)
1
2
3
2
1
2
1
2
1
2
‡ z; (iv)
‡ x; 12 y;
‡ z; (v) x; 1 y; z; (vi)
x;
‡ y,
2
1 ‡ x; y; z.
C1iÐC1ÐC2
179.6 (3)
C1ÐC2ÐSi1
177.18 (18)
Ê
All H atoms were treated as riding, with CÐH = 1.00 A and
Uiso(H) = 1.2Ueq(C).
Symmetry code: (i) x ‡ 2; y ‡ 1; z ‡ 1.
For both compounds, data collection: COLLECT (Nonius, 2001);
cell re®nement: DENZO and SCALEPACK (Otwinowski & Minor,
1997); data reduction: DENZO and SCALEPACK; program(s) used
to solve structure: SIR92 (Altomare et al., 1994); program(s) used to
re®ne structure: CRYSTALS (Betteridge et al., 2003); molecular
graphics: ORTEP-3 (Farrugia, 1997); software used to prepare
material for publication: CRYSTALS.
Compound (II)
Crystal data
C28H18
Mr = 354.45
Monoclinic, P21=n
Z = 4
Dx = 1.230 Mg m
Mo Kꢃ radiation
ꢆ = 0.07 mm
T = 173 K
Block, colourless
0.27 Â 0.22 Â 0.20 mm
3
1
Ê
a = 6.6723 (2) A
Ê
b = 11.0320 (3) A
The authors thank the Swiss National Science Foundation
and the University of Basel for ®nancial support.
Ê
c = 26.0094 (7) A
ꢄ = 91.2833 (14)ꢀ
3
Ê
V = 1914.04 (9) A
Data collection
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: GG3022). Services for accessing these data are
described at the back of the journal.
Nonius KappaCCD area-detector
diffractometer
' and ! scans
Absorption correction: multi-scan
(DENZO and SCALEPACK;
Otwinowski & Minor, 1997)
Tmin = 0.98, Tmax = 0.99
21205 measured re¯ections
5625 independent re¯ections
2992 re¯ections with I > 2ꢇ(I)
Rint = 0.081
ꢈmax = 30.1ꢀ
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C22H42Si2 and C28H18
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Constable et al. C22H42Si2 and C28H18 o509