Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270106025157/gg3022sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270106025157/gg3022Isup2.hkl | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270106025157/gg3022IIsup3.hkl |
CCDC references: 296407; 296408
Compound (I), previously prepared directly (Eisler et al., 2005; Hlavatý 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 [Pd(PPh3)2Cl2] (126 mg, 0.18 mmol) were added to Et3N (75 ml), and after the 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 purified 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, δ, p.p.m.): 1.09 (s, TIPS); 13C NMR (125 MHz, CDCl3, δ, p.p.m.): 90.2 (C≡C), 81.6 (C≡C), 18.6 (CH), 11.3 (CH3); IR (solid, ν, 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 4,4'-bis(biphenyl-4-ylethynyl)biphenyl. 4,4'-Dibromobiphenyl (233 mg, 1.00 mmol), CuCl (14.9 mg, 0.15 mmol) and [Pd(PPh3)2Cl2] (105 mg, 0.15 mmol) were added to Et3N (40 ml), and after the 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 filtered. The product was purified by column chromatography (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 ([M - PhC6H4CC]+); 1H NMR (400 MHz, CDCl3, δ, p.p.m.): 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, δ, p.p.m.): 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, ν, 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.
All H atoms were treated as riding, with C—H distances of 1.00 Å and with Uiso(H) = 1.2Ueq(C).
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 defined structures. Under Sonogashira conditions, reactions between terminal alkynes (RC≡CH) and aryl halides can give rise to diynes, RC≡C—C≡CR, as side-products (these most often arise from bromo precursors) (Sonogashira et al. 1975; Sonogashira 2002). Related reactions (Liu & Burton, 1997) or modified Sonogashira conditions (Rossi et al., 1985) have been used for the specific formation of diynes. Two molecular cores that we have investigated are hexakis[(triisopropylsilyl)ethynyl]benzene and 4,4'-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-di(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 4,4'-dibromobiphenyl led to the quantitative formation of (II). Compounds (I) and (II) have previously been reported (Eisler et al., 2005; Hlavatý et al., 2002; Ried & Saxena, 1970; Toda & Tokumaru, 1990), but have not, to our knowledge, been structurally characterized. Here, we report their single-crystal structures, which illustrate a number of facets of weak C—H···π 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).
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 Me3Si(C≡C)2SiMe3 (Carré et al., 2003) and iPr3Si(C≡ C)nSiiPr3 (n = 4, 5 or 6; Eisler et al., 2005), in contrast with the curved backbone of iPr3Si(C≡C)8SiiPr3 (Eisler et al., 2005). The C—Si—C 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 rows of SiCCCCSi chains is 5.8 Å. Adjacent chains are interlocked, with the packing being supported by close methyl C—H to alkyne π interactions (C8—H83···C1 = 2.9 Å and C8—H83···C2 = 3.1 Å). This leads to the presence of close (repulsive) H···H contacts (Me2C—H61···H61—CMe2 = 2.7 Å). A second set of C—H···π interactions operates between molecules within each row (Fig. 2b). Their evolution gives rise to short H···H 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 E—C≡ C—C≡ C–E unit (E is Si, Sn, Ge or Pb) gave only 14 hits (Brouty et al., 1980; Brunel et al., 2001; Carré et al., 1999, 2003; Dam et al., 1998; Neugebauer et al., 2000). Among these are two polymorphs of Me3SiC≡CC≡CSiMe3 (structures determined at 120 and 203 K; Carré 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 solid-state packing of iPr3Si(C≡ C)4SiiPr3 resembles that of (I), with molecules organized in offset rows, while for iPr3Si(C≡ C)5SiiPr3 and iPr3Si(C≡C)6SiiPr3, a herringbone assembly is observed. In iPr3Si(C≡C)8SiiPr3, the polyyne backbone is significantly 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 C—H···π interactions listed in Table 3. The basic motif in the solid state is a dimeric unit (Fig. 4a), in which both C—Haryl···πalkyne and C—Haryl···πaryl interactions are present (Table 3).
The dimers further assemble into layers (Fig. 4b), again with C—H···π interactions playing a role (Table 3). Stacking of planes of molecules into the three-dimensional lattice is also supported by C—H···π 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 herringbone arrangement. Whereas C—H···π contacts control the ring orientations and packing in (II), π-stacking interactions are important in 1,4-diphenylbuta-1,3-diyne. Also related to (II) is 4-ethynylbiphenyl (Mague et al., 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 significant intermolecular interactions", although inspection of the data indicate the presence of weak C—Halkyne···πaryl contacts.
In conclusion, we have investigated the solid-state structures of two simple diynes and in both cases find that weak C—H···π contacts control the molecular packing. In the case of 1,4-di(biphenyl-4-yl)buta-1,3-diyne, a combination of C—Haryl···πalkyne and C—Haryl···πaryl interactions operate at the expense of π-stacking interactions.
For both compounds, data collection: COLLECT (Nonius, 2001); cell refinement: 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 refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: CRYSTALS.
C22H42Si2 | Z = 1 |
Mr = 362.75 | F(000) = 202 |
Triclinic, P1 | Dx = 1.006 Mg m−3 |
Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
a = 7.2397 (4) Å | Cell parameters from 3524 reflections |
b = 7.8151 (5) Å | θ = 3–30° |
c = 10.9548 (5) Å | µ = 0.15 mm−1 |
α = 86.680 (5)° | T = 173 K |
β = 80.485 (4)° | Plate, colourless |
γ = 78.542 (4)° | 0.30 × 0.16 × 0.14 mm |
V = 598.90 (6) Å3 |
Nonius KappaCCD area-detector diffractometer | 2019 reflections with I > 3σ(I) |
Graphite monochromator | Rint = 0.069 |
φ and ω scans | θmax = 30.0°, θmin = 3.2° |
Absorption correction: multi-scan DENZO and SCALEPACK (Otwinowski & Minor, 1997) | h = −10→10 |
Tmin = 0.98, Tmax = 0.98 | k = −10→10 |
29988 measured reflections | l = −15→15 |
3478 independent reflections |
Refinement on F | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.050 | H-atom parameters constrained |
wR(F2) = 0.054 | Method, part 1, Chebychev polynomial, (Watkin, 1994; Prince,
1982)
[weight] = 1.0/[A0T0(x) + A1T1(x) ··· + An-1Tn-1(x)],
where Ai are the Chebychev coefficients listed below and x = F /Fmax Method = robust weighting (Prince, 1982) W = [weight][1-(ΔF/6σF)2]2 Ai are 1.89 -0.168 1.21 |
S = 1.09 | (Δ/σ)max = 0.007 |
2019 reflections | Δρmax = 0.93 e Å−3 |
109 parameters | Δρmin = −0.64 e Å−3 |
0 restraints |
C22H42Si2 | γ = 78.542 (4)° |
Mr = 362.75 | V = 598.90 (6) Å3 |
Triclinic, P1 | Z = 1 |
a = 7.2397 (4) Å | Mo Kα radiation |
b = 7.8151 (5) Å | µ = 0.15 mm−1 |
c = 10.9548 (5) Å | T = 173 K |
α = 86.680 (5)° | 0.30 × 0.16 × 0.14 mm |
β = 80.485 (4)° |
Nonius KappaCCD area-detector diffractometer | 3478 independent reflections |
Absorption correction: multi-scan DENZO and SCALEPACK (Otwinowski & Minor, 1997) | 2019 reflections with I > 3σ(I) |
Tmin = 0.98, Tmax = 0.98 | Rint = 0.069 |
29988 measured reflections |
R[F2 > 2σ(F2)] = 0.050 | 0 restraints |
wR(F2) = 0.054 | H-atom parameters constrained |
S = 1.09 | Δρmax = 0.93 e Å−3 |
2019 reflections | Δρmin = −0.64 e Å−3 |
109 parameters |
x | y | z | Uiso*/Ueq | ||
C1 | 0.9569 (2) | 0.4465 (2) | 0.54262 (17) | 0.0297 | |
C2 | 0.8806 (3) | 0.3535 (3) | 0.61763 (18) | 0.0325 | |
C3 | 0.4976 (3) | 0.2698 (3) | 0.7054 (2) | 0.0410 | |
C4 | 0.4047 (4) | 0.4570 (4) | 0.7391 (3) | 0.0594 | |
C5 | 0.4776 (4) | 0.2384 (4) | 0.5727 (3) | 0.0573 | |
C6 | 0.8595 (3) | −0.0168 (3) | 0.68257 (19) | 0.0388 | |
C7 | 1.0699 (4) | −0.0721 (4) | 0.6943 (3) | 0.0610 | |
C8 | 0.7444 (5) | −0.1499 (3) | 0.7470 (3) | 0.0674 | |
C9 | 0.7757 (4) | 0.2751 (4) | 0.8877 (2) | 0.0596 | |
C10 | 0.6525 (5) | 0.1876 (4) | 0.9890 (2) | 0.0615 | |
C11 | 0.9605 (7) | 0.2834 (8) | 0.9147 (3) | 0.1148 | |
Si1 | 0.75346 (8) | 0.21347 (8) | 0.72851 (5) | 0.0297 | |
H31 | 0.4287 | 0.1908 | 0.7629 | 0.0483* | |
H41 | 0.4181 | 0.4768 | 0.8264 | 0.0670* | |
H42 | 0.4688 | 0.5396 | 0.6820 | 0.0670* | |
H43 | 0.2663 | 0.4776 | 0.7313 | 0.0670* | |
H51 | 0.5388 | 0.1153 | 0.5510 | 0.0709* | |
H52 | 0.5419 | 0.3206 | 0.5153 | 0.0709* | |
H53 | 0.3393 | 0.2586 | 0.5645 | 0.0709* | |
H61 | 0.8522 | −0.0164 | 0.5922 | 0.0438* | |
H71 | 1.1419 | 0.0169 | 0.6516 | 0.0681* | |
H72 | 1.0841 | −0.0815 | 0.7839 | 0.0681* | |
H73 | 1.1219 | −0.1879 | 0.6553 | 0.0681* | |
H81 | 0.6071 | −0.1104 | 0.7378 | 0.0764* | |
H82 | 0.7563 | −0.1599 | 0.8369 | 0.0764* | |
H83 | 0.7942 | −0.2662 | 0.7083 | 0.0764* | |
H91 | 0.7203 | 0.4029 | 0.8872 | 0.0746* | |
H101 | 0.5256 | 0.1890 | 0.9637 | 0.0758* | |
H102 | 0.6338 | 0.2519 | 1.0677 | 0.0758* | |
H103 | 0.7177 | 0.0641 | 1.0019 | 0.0758* | |
H111 | 1.0319 | 0.3429 | 0.8443 | 0.1414* | |
H112 | 0.9478 | 0.3494 | 0.9921 | 0.1414* | |
H113 | 1.0317 | 0.1616 | 0.9263 | 0.1414* |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0239 (8) | 0.0318 (10) | 0.0326 (9) | −0.0062 (7) | −0.0017 (7) | 0.0007 (7) |
C2 | 0.0277 (9) | 0.0334 (10) | 0.0354 (10) | −0.0081 (8) | 0.0000 (7) | 0.0021 (8) |
C3 | 0.0278 (9) | 0.0357 (11) | 0.0566 (13) | −0.0100 (8) | 0.0054 (9) | 0.0002 (9) |
C4 | 0.0435 (13) | 0.0436 (14) | 0.0807 (19) | 0.0029 (11) | 0.0084 (12) | −0.0058 (13) |
C5 | 0.0394 (12) | 0.0649 (17) | 0.0713 (17) | −0.0095 (12) | −0.0187 (12) | −0.0064 (14) |
C6 | 0.0429 (11) | 0.0323 (10) | 0.0345 (10) | −0.0028 (9) | 0.0057 (8) | 0.0043 (8) |
C7 | 0.0546 (15) | 0.0534 (16) | 0.0620 (16) | 0.0157 (13) | −0.0053 (12) | 0.0055 (13) |
C8 | 0.088 (2) | 0.0300 (12) | 0.0721 (18) | −0.0165 (12) | 0.0280 (15) | −0.0034 (11) |
C9 | 0.0759 (18) | 0.0780 (19) | 0.0339 (11) | −0.0474 (16) | 0.0060 (11) | −0.0040 (11) |
C10 | 0.083 (2) | 0.0739 (19) | 0.0320 (11) | −0.0399 (16) | 0.0080 (12) | −0.0008 (11) |
C11 | 0.131 (4) | 0.199 (5) | 0.0512 (18) | −0.116 (4) | −0.018 (2) | 0.000 (2) |
Si1 | 0.0289 (3) | 0.0302 (3) | 0.0291 (3) | −0.0106 (2) | 0.00341 (18) | 0.00170 (18) |
C1—C1i | 1.373 (3) | C7—H71 | 1.000 |
C1—C2 | 1.204 (2) | C7—H72 | 1.000 |
C2—Si1 | 1.8432 (18) | C7—H73 | 1.000 |
C3—C4 | 1.523 (3) | C8—H81 | 1.000 |
C3—C5 | 1.523 (4) | C8—H82 | 1.000 |
C3—Si1 | 1.873 (2) | C8—H83 | 1.000 |
C3—H31 | 1.000 | C9—C10 | 1.524 (3) |
C4—H41 | 1.000 | C9—C11 | 1.432 (5) |
C4—H42 | 1.000 | C9—Si1 | 1.876 (2) |
C4—H43 | 1.000 | C9—H91 | 1.000 |
C5—H51 | 1.000 | C10—H101 | 1.000 |
C5—H52 | 1.000 | C10—H102 | 1.000 |
C5—H53 | 1.000 | C10—H103 | 1.000 |
C6—C7 | 1.523 (3) | C11—H111 | 1.000 |
C6—C8 | 1.530 (3) | C11—H112 | 1.000 |
C6—Si1 | 1.873 (2) | C11—H113 | 1.000 |
C6—H61 | 1.000 | ||
C1i—C1—C2 | 179.6 (3) | H72—C7—H73 | 109.5 |
C1—C2—Si1 | 177.18 (18) | C6—C8—H81 | 109.4 |
C4—C3—C5 | 109.7 (2) | C6—C8—H82 | 109.5 |
C4—C3—Si1 | 112.72 (17) | H81—C8—H82 | 109.5 |
C5—C3—Si1 | 111.02 (15) | C6—C8—H83 | 109.5 |
C4—C3—H31 | 107.5 | H81—C8—H83 | 109.5 |
C5—C3—H31 | 109.3 | H82—C8—H83 | 109.5 |
Si1—C3—H31 | 106.4 | C10—C9—C11 | 114.6 (3) |
C3—C4—H41 | 109.4 | C10—C9—Si1 | 112.41 (18) |
C3—C4—H42 | 109.5 | C11—C9—Si1 | 119.0 (2) |
H41—C4—H42 | 109.5 | C10—C9—H91 | 107.6 |
C3—C4—H43 | 109.5 | C11—C9—H91 | 98.7 |
H41—C4—H43 | 109.5 | Si1—C9—H91 | 101.9 |
H42—C4—H43 | 109.5 | C9—C10—H101 | 109.6 |
C3—C5—H51 | 109.4 | C9—C10—H102 | 109.6 |
C3—C5—H52 | 109.4 | H101—C10—H102 | 109.5 |
H51—C5—H52 | 109.5 | C9—C10—H103 | 109.2 |
C3—C5—H53 | 109.6 | H101—C10—H103 | 109.5 |
H51—C5—H53 | 109.5 | H102—C10—H103 | 109.5 |
H52—C5—H53 | 109.5 | C9—C11—H111 | 109.7 |
C7—C6—C8 | 111.1 (2) | C9—C11—H112 | 110.1 |
C7—C6—Si1 | 113.98 (18) | H111—C11—H112 | 109.5 |
C8—C6—Si1 | 113.26 (15) | C9—C11—H113 | 108.6 |
C7—C6—H61 | 106.4 | H111—C11—H113 | 109.5 |
C8—C6—H61 | 107.4 | H112—C11—H113 | 109.5 |
Si1—C6—H61 | 104.0 | C9—Si1—C6 | 116.94 (13) |
C6—C7—H71 | 109.5 | C9—Si1—C3 | 109.87 (12) |
C6—C7—H72 | 109.4 | C6—Si1—C3 | 110.38 (10) |
H71—C7—H72 | 109.5 | C9—Si1—C2 | 106.99 (10) |
C6—C7—H73 | 109.4 | C6—Si1—C2 | 105.97 (9) |
H71—C7—H73 | 109.5 | C3—Si1—C2 | 106.00 (9) |
Symmetry code: (i) −x+2, −y+1, −z+1. |
C28H18 | F(000) = 744 |
Mr = 354.45 | Dx = 1.230 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2yn | Cell parameters from 10543 reflections |
a = 6.6723 (2) Å | θ = 1–30° |
b = 11.0320 (3) Å | µ = 0.07 mm−1 |
c = 26.0094 (7) Å | T = 173 K |
β = 91.2833 (14)° | Block, colourless |
V = 1914.04 (9) Å3 | 0.27 × 0.22 × 0.20 mm |
Z = 4 |
Nonius KappaCCD area-detector diffractometer | 2992 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.081 |
φ and ω scans | θmax = 30.1°, θmin = 1.6° |
Absorption correction: multi-scan DENZO and SCALEPACK (Otwinowski & Minor, 1997) | h = −9→9 |
Tmin = 0.98, Tmax = 0.99 | k = −15→15 |
21205 measured reflections | l = −36→36 |
5625 independent reflections |
Refinement on F | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.040 | H-atom parameters constrained |
wR(F2) = 0.047 | Method = modified Sheldrick (Reference ),
w = 1/[σ2(F2) + (0.03P)2], where P = [max(Fo2,0) + 2Fc2]/3 |
S = 0.99 | (Δ/σ)max = 0.004 |
2992 reflections | Δρmax = 0.13 e Å−3 |
253 parameters | Δρmin = −0.18 e Å−3 |
0 restraints |
C28H18 | V = 1914.04 (9) Å3 |
Mr = 354.45 | Z = 4 |
Monoclinic, P21/n | Mo Kα radiation |
a = 6.6723 (2) Å | µ = 0.07 mm−1 |
b = 11.0320 (3) Å | T = 173 K |
c = 26.0094 (7) Å | 0.27 × 0.22 × 0.20 mm |
β = 91.2833 (14)° |
Nonius KappaCCD area-detector diffractometer | 5625 independent reflections |
Absorption correction: multi-scan DENZO and SCALEPACK (Otwinowski & Minor, 1997) | 2992 reflections with I > 2σ(I) |
Tmin = 0.98, Tmax = 0.99 | Rint = 0.081 |
21205 measured reflections |
R[F2 > 2σ(F2)] = 0.040 | 0 restraints |
wR(F2) = 0.047 | H-atom parameters constrained |
S = 0.99 | Δρmax = 0.13 e Å−3 |
2992 reflections | Δρmin = −0.18 e Å−3 |
253 parameters |
x | y | z | Uiso*/Ueq | ||
C1 | −0.5927 (2) | 0.68368 (12) | −0.28227 (5) | 0.0404 | |
C2 | −0.7262 (2) | 0.74412 (13) | −0.31455 (6) | 0.0443 | |
C3 | −0.8638 (2) | 0.82376 (13) | −0.29479 (6) | 0.0473 | |
C4 | −0.8675 (2) | 0.84263 (14) | −0.24233 (6) | 0.0469 | |
C5 | −0.7337 (2) | 0.78279 (13) | −0.20981 (6) | 0.0417 | |
C6 | −0.5927 (2) | 0.70190 (12) | −0.22909 (5) | 0.0360 | |
C7 | −0.44585 (19) | 0.63912 (12) | −0.19488 (5) | 0.0348 | |
C8 | −0.4883 (2) | 0.61167 (12) | −0.14374 (5) | 0.0383 | |
C9 | −0.3502 (2) | 0.55329 (13) | −0.11215 (5) | 0.0392 | |
C10 | −0.1630 (2) | 0.51991 (12) | −0.13049 (5) | 0.0380 | |
C11 | −0.1186 (2) | 0.54662 (13) | −0.18163 (5) | 0.0425 | |
C12 | −0.2573 (2) | 0.60554 (13) | −0.21262 (5) | 0.0411 | |
C13 | −0.0158 (2) | 0.46191 (13) | −0.09803 (5) | 0.0403 | |
C14 | 0.1134 (2) | 0.41480 (13) | −0.07189 (5) | 0.0400 | |
C15 | 0.2629 (2) | 0.36037 (13) | −0.04304 (5) | 0.0402 | |
C16 | 0.3953 (2) | 0.31275 (13) | −0.01812 (5) | 0.0399 | |
C17 | 0.8892 (2) | 0.24459 (13) | 0.04483 (5) | 0.0378 | |
C18 | 0.7385 (2) | 0.30587 (13) | 0.01827 (5) | 0.0388 | |
C19 | 0.5507 (2) | 0.25203 (13) | 0.01075 (5) | 0.0364 | |
C20 | 0.5180 (2) | 0.13698 (13) | 0.03093 (5) | 0.0396 | |
C21 | 0.6690 (2) | 0.07580 (13) | 0.05649 (5) | 0.0386 | |
C22 | 0.8591 (2) | 0.12755 (12) | 0.06373 (5) | 0.0341 | |
C23 | 1.02184 (19) | 0.05969 (12) | 0.09049 (5) | 0.0344 | |
C24 | 1.1465 (2) | 0.11595 (13) | 0.12693 (5) | 0.0395 | |
C25 | 1.2975 (2) | 0.05167 (14) | 0.15205 (6) | 0.0449 | |
C26 | 1.3293 (2) | −0.06874 (14) | 0.14039 (6) | 0.0469 | |
C27 | 1.2081 (2) | −0.12579 (14) | 0.10409 (6) | 0.0475 | |
C28 | 1.0551 (2) | −0.06251 (13) | 0.07936 (5) | 0.0418 | |
H11 | −0.4944 | 0.6259 | −0.2972 | 0.0483* | |
H21 | −0.7229 | 0.7300 | −0.3525 | 0.0530* | |
H31 | −0.9601 | 0.8674 | −0.3182 | 0.0563* | |
H41 | −0.9674 | 0.8999 | −0.2277 | 0.0561* | |
H51 | −0.7379 | 0.7976 | −0.1719 | 0.0500* | |
H81 | −0.6214 | 0.6349 | −0.1298 | 0.0458* | |
H91 | −0.3846 | 0.5346 | −0.0758 | 0.0470* | |
H111 | 0.0141 | 0.5229 | −0.1957 | 0.0508* | |
H121 | −0.2224 | 0.6248 | −0.2489 | 0.0492* | |
H171 | 1.0221 | 0.2848 | 0.0506 | 0.0453* | |
H181 | 0.7641 | 0.3889 | 0.0044 | 0.0465* | |
H201 | 0.3829 | 0.0985 | 0.0268 | 0.0473* | |
H211 | 0.6428 | −0.0072 | 0.0702 | 0.0463* | |
H241 | 1.1268 | 0.2037 | 0.1350 | 0.0473* | |
H251 | 1.3838 | 0.0926 | 0.1787 | 0.0535* | |
H261 | 1.4399 | −0.1146 | 0.1582 | 0.0560* | |
H271 | 1.2309 | −0.2131 | 0.0957 | 0.0571* | |
H281 | 0.9675 | −0.1046 | 0.0533 | 0.0500* |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0450 (8) | 0.0379 (8) | 0.0385 (8) | −0.0012 (7) | 0.0038 (7) | 0.0022 (7) |
C2 | 0.0514 (9) | 0.0410 (8) | 0.0404 (8) | −0.0040 (8) | −0.0010 (7) | 0.0055 (7) |
C3 | 0.0480 (9) | 0.0390 (8) | 0.0545 (10) | −0.0006 (7) | −0.0062 (8) | 0.0082 (8) |
C4 | 0.0441 (9) | 0.0401 (8) | 0.0565 (10) | 0.0040 (7) | 0.0017 (8) | −0.0011 (8) |
C5 | 0.0429 (9) | 0.0405 (8) | 0.0419 (8) | −0.0009 (7) | 0.0044 (7) | −0.0037 (7) |
C6 | 0.0368 (8) | 0.0337 (7) | 0.0374 (8) | −0.0059 (6) | 0.0019 (6) | −0.0001 (6) |
C7 | 0.0367 (8) | 0.0322 (7) | 0.0354 (7) | −0.0022 (6) | 0.0010 (6) | −0.0033 (6) |
C8 | 0.0382 (8) | 0.0397 (8) | 0.0370 (8) | −0.0023 (7) | 0.0044 (6) | −0.0039 (7) |
C9 | 0.0458 (9) | 0.0389 (8) | 0.0330 (7) | −0.0021 (7) | 0.0018 (6) | −0.0016 (6) |
C10 | 0.0426 (9) | 0.0323 (7) | 0.0390 (8) | −0.0019 (7) | −0.0044 (7) | −0.0039 (6) |
C11 | 0.0404 (8) | 0.0457 (9) | 0.0415 (8) | 0.0012 (7) | 0.0037 (7) | −0.0024 (7) |
C12 | 0.0426 (8) | 0.0466 (9) | 0.0342 (7) | 0.0003 (7) | 0.0039 (7) | 0.0007 (7) |
C13 | 0.0459 (9) | 0.0362 (8) | 0.0388 (8) | −0.0053 (7) | −0.0015 (7) | −0.0043 (7) |
C14 | 0.0448 (9) | 0.0380 (8) | 0.0373 (8) | −0.0038 (7) | −0.0001 (7) | −0.0037 (7) |
C15 | 0.0444 (9) | 0.0392 (8) | 0.0370 (8) | −0.0051 (7) | 0.0005 (7) | −0.0038 (7) |
C16 | 0.0435 (9) | 0.0412 (8) | 0.0350 (7) | −0.0047 (7) | 0.0032 (7) | −0.0053 (7) |
C17 | 0.0391 (8) | 0.0361 (8) | 0.0383 (8) | −0.0070 (7) | 0.0011 (6) | −0.0033 (6) |
C18 | 0.0455 (9) | 0.0346 (7) | 0.0363 (7) | −0.0039 (7) | 0.0003 (6) | −0.0013 (6) |
C19 | 0.0391 (8) | 0.0396 (8) | 0.0305 (7) | 0.0004 (7) | 0.0013 (6) | −0.0052 (6) |
C20 | 0.0368 (8) | 0.0429 (8) | 0.0392 (8) | −0.0062 (7) | 0.0017 (6) | −0.0023 (7) |
C21 | 0.0400 (8) | 0.0367 (8) | 0.0394 (8) | −0.0071 (7) | 0.0044 (7) | 0.0011 (6) |
C22 | 0.0381 (8) | 0.0350 (7) | 0.0293 (7) | −0.0026 (6) | 0.0033 (6) | −0.0039 (6) |
C23 | 0.0359 (8) | 0.0356 (8) | 0.0320 (7) | −0.0050 (6) | 0.0057 (6) | 0.0001 (6) |
C24 | 0.0398 (8) | 0.0382 (8) | 0.0405 (8) | −0.0048 (7) | 0.0034 (7) | −0.0014 (7) |
C25 | 0.0394 (9) | 0.0507 (9) | 0.0445 (8) | −0.0048 (7) | −0.0015 (7) | 0.0042 (7) |
C26 | 0.0408 (9) | 0.0504 (9) | 0.0496 (9) | 0.0051 (8) | 0.0083 (7) | 0.0118 (8) |
C27 | 0.0552 (10) | 0.0397 (8) | 0.0480 (9) | 0.0057 (8) | 0.0113 (8) | 0.0024 (7) |
C28 | 0.0472 (9) | 0.0387 (8) | 0.0397 (8) | −0.0024 (7) | 0.0071 (7) | −0.0023 (7) |
C1—C2 | 1.3815 (18) | C15—C16 | 1.2045 (18) |
C1—C6 | 1.3977 (18) | C16—C19 | 1.433 (2) |
C1—H11 | 1.000 | C17—C18 | 1.3834 (18) |
C2—C3 | 1.379 (2) | C17—C22 | 1.3977 (19) |
C2—H21 | 1.000 | C17—H171 | 1.000 |
C3—C4 | 1.381 (2) | C18—C19 | 1.3965 (18) |
C3—H31 | 1.000 | C18—H181 | 1.000 |
C4—C5 | 1.3834 (19) | C19—C20 | 1.393 (2) |
C4—H41 | 1.000 | C20—C21 | 1.3722 (18) |
C5—C6 | 1.3979 (18) | C20—H201 | 1.000 |
C5—H51 | 1.000 | C21—C22 | 1.3999 (18) |
C6—C7 | 1.4806 (18) | C21—H211 | 1.000 |
C7—C8 | 1.3994 (18) | C22—C23 | 1.4799 (18) |
C7—C12 | 1.3995 (19) | C23—C24 | 1.3929 (17) |
C8—C9 | 1.3803 (18) | C23—C28 | 1.3975 (19) |
C8—H81 | 1.000 | C24—C25 | 1.3838 (18) |
C9—C10 | 1.3968 (19) | C24—H241 | 1.000 |
C9—H91 | 1.000 | C25—C26 | 1.380 (2) |
C10—C11 | 1.4006 (19) | C25—H251 | 1.000 |
C10—C13 | 1.431 (2) | C26—C27 | 1.381 (2) |
C11—C12 | 1.3767 (18) | C26—H261 | 1.000 |
C11—H111 | 1.000 | C27—C28 | 1.3835 (19) |
C12—H121 | 1.000 | C27—H271 | 1.000 |
C13—C14 | 1.2041 (18) | C28—H281 | 1.000 |
C14—C15 | 1.373 (2) | ||
C2—C1—C6 | 121.20 (14) | C14—C15—C16 | 179.36 (15) |
C2—C1—H11 | 119.4 | C15—C16—C19 | 177.96 (15) |
C6—C1—H11 | 119.4 | C18—C17—C22 | 121.24 (12) |
C1—C2—C3 | 120.43 (14) | C18—C17—H171 | 119.4 |
C1—C2—H21 | 119.8 | C22—C17—H171 | 119.4 |
C3—C2—H21 | 119.8 | C17—C18—C19 | 120.12 (13) |
C2—C3—C4 | 119.41 (14) | C17—C18—H181 | 119.9 |
C2—C3—H31 | 120.3 | C19—C18—H181 | 119.9 |
C4—C3—H31 | 120.3 | C16—C19—C18 | 120.75 (13) |
C3—C4—C5 | 120.44 (14) | C16—C19—C20 | 120.37 (13) |
C3—C4—H41 | 119.8 | C18—C19—C20 | 118.87 (13) |
C5—C4—H41 | 119.8 | C19—C20—C21 | 120.73 (13) |
C4—C5—C6 | 121.03 (13) | C19—C20—H201 | 119.6 |
C4—C5—H51 | 119.5 | C21—C20—H201 | 119.6 |
C6—C5—H51 | 119.5 | C20—C21—C22 | 121.20 (13) |
C5—C6—C1 | 117.48 (12) | C20—C21—H211 | 119.4 |
C5—C6—C7 | 121.64 (12) | C22—C21—H211 | 119.4 |
C1—C6—C7 | 120.87 (12) | C21—C22—C17 | 117.79 (12) |
C6—C7—C8 | 121.81 (12) | C21—C22—C23 | 120.67 (12) |
C6—C7—C12 | 120.88 (12) | C17—C22—C23 | 121.54 (12) |
C8—C7—C12 | 117.31 (12) | C22—C23—C24 | 121.02 (12) |
C7—C8—C9 | 121.34 (13) | C22—C23—C28 | 120.58 (12) |
C7—C8—H81 | 119.3 | C24—C23—C28 | 118.40 (13) |
C9—C8—H81 | 119.3 | C23—C24—C25 | 120.68 (14) |
C8—C9—C10 | 120.66 (13) | C23—C24—H241 | 119.7 |
C8—C9—H91 | 119.7 | C25—C24—H241 | 119.7 |
C10—C9—H91 | 119.7 | C24—C25—C26 | 120.23 (14) |
C9—C10—C11 | 118.60 (12) | C24—C25—H251 | 119.9 |
C9—C10—C13 | 121.56 (13) | C26—C25—H251 | 119.9 |
C11—C10—C13 | 119.83 (13) | C25—C26—C27 | 119.88 (14) |
C10—C11—C12 | 120.12 (13) | C25—C26—H261 | 120.1 |
C10—C11—H111 | 120.0 | C27—C26—H261 | 120.0 |
C12—C11—H111 | 119.9 | C26—C27—C28 | 120.17 (14) |
C7—C12—C11 | 121.96 (13) | C26—C27—H271 | 119.9 |
C7—C12—H121 | 119.0 | C28—C27—H271 | 119.9 |
C11—C12—H121 | 119.0 | C23—C28—C27 | 120.62 (13) |
C10—C13—C14 | 177.56 (15) | C23—C28—H281 | 119.7 |
C13—C14—C15 | 178.75 (15) | C27—C28—H281 | 119.7 |
Experimental details
(I) | (II) | |
Crystal data | ||
Chemical formula | C22H42Si2 | C28H18 |
Mr | 362.75 | 354.45 |
Crystal system, space group | Triclinic, P1 | Monoclinic, P21/n |
Temperature (K) | 173 | 173 |
a, b, c (Å) | 7.2397 (4), 7.8151 (5), 10.9548 (5) | 6.6723 (2), 11.0320 (3), 26.0094 (7) |
α, β, γ (°) | 86.680 (5), 80.485 (4), 78.542 (4) | 90, 91.2833 (14), 90 |
V (Å3) | 598.90 (6) | 1914.04 (9) |
Z | 1 | 4 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 0.15 | 0.07 |
Crystal size (mm) | 0.30 × 0.16 × 0.14 | 0.27 × 0.22 × 0.20 |
Data collection | ||
Diffractometer | Nonius KappaCCD area-detector | Nonius KappaCCD area-detector |
Absorption correction | Multi-scan DENZO and SCALEPACK (Otwinowski & Minor, 1997) | Multi-scan DENZO and SCALEPACK (Otwinowski & Minor, 1997) |
Tmin, Tmax | 0.98, 0.98 | 0.98, 0.99 |
No. of measured, independent and observed reflections | 29988, 3478, 2019 [I > 3σ(I)] | 21205, 5625, 2992 [I > 2σ(I)] |
Rint | 0.069 | 0.081 |
(sin θ/λ)max (Å−1) | 0.703 | 0.706 |
Refinement | ||
R[F2 > 2σ(F2)], wR(F2), S | 0.050, 0.054, 1.09 | 0.040, 0.047, 0.99 |
No. of reflections | 2019 | 2992 |
No. of parameters | 109 | 253 |
H-atom treatment | H-atom parameters constrained | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.93, −0.64 | 0.13, −0.18 |
Computer programs: COLLECT (Nonius, 2001), DENZO and SCALEPACK (Otwinowski & Minor, 1997), DENZO and SCALEPACK, SIR92 (Altomare et al., 1994), CRYSTALS (Betteridge et al., 2003), ORTEP-3 (Farrugia, 1997), CRYSTALS.
C1—C1i | 1.373 (3) | C3—Si1 | 1.873 (2) |
C1—C2 | 1.204 (2) | C6—Si1 | 1.873 (2) |
C2—Si1 | 1.8432 (18) | C9—Si1 | 1.876 (2) |
C1i—C1—C2 | 179.6 (3) | C1—C2—Si1 | 177.18 (18) |
Symmetry code: (i) −x+2, −y+1, −z+1. |
C6—C7 | 1.4806 (18) | C15—C16 | 1.2045 (18) |
C10—C13 | 1.431 (2) | C16—C19 | 1.433 (2) |
C13—C14 | 1.2041 (18) | C22—C23 | 1.4799 (18) |
C14—C15 | 1.373 (2) | ||
C10—C13—C14 | 177.56 (15) | C14—C15—C16 | 179.36 (15) |
C13—C14—C15 | 178.75 (15) | C15—C16—C19 | 177.96 (15) |
Distance | Angle | |
Within the dimer (Fig. 4a) | ||
H181···C14i | 2.9 | |
H181···C15i | 3.0 | |
H171···C13i | 3.1 | |
C24—H241···Cg2i | 2.8 | 147 |
C25—H251···Cg1i | 3.5 | 174 |
Other interactions within a layer (Fig. 4b) | ||
C3—H31···Cg2ii | 2.9 | 148 |
C26—H261···Cg1iii | 3.4 | 170 |
Interactions between layers | ||
C1—H11···Cg4iv | 2.9 | 151 |
C8—H81···Cg3v | 3.1 | 127 |
C11—H111···Cg1vi | 3.4 | 136 |
C20—H201···Cg4vii | 2.9 | 121 |
Symmetry codes: (i) 1 - x, 1 - y, -z; (ii) -3/2 - x, 1/2 + y, -1/2 -z; (iii) -5/2 + x, 1/2 - y, -1/2 + z; (iv) -3/2 + x, 1/2 - y, -1/2 + z; (v) -x, 1 - y, -z; (vi) -1/2 - x, -1/2 + y, -1/2 - z; (vii) -1 + x, y, z. |
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 defined structures. Under Sonogashira conditions, reactions between terminal alkynes (RC≡CH) and aryl halides can give rise to diynes, RC≡C—C≡CR, as side-products (these most often arise from bromo precursors) (Sonogashira et al. 1975; Sonogashira 2002). Related reactions (Liu & Burton, 1997) or modified Sonogashira conditions (Rossi et al., 1985) have been used for the specific formation of diynes. Two molecular cores that we have investigated are hexakis[(triisopropylsilyl)ethynyl]benzene and 4,4'-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-di(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 4,4'-dibromobiphenyl led to the quantitative formation of (II). Compounds (I) and (II) have previously been reported (Eisler et al., 2005; Hlavatý et al., 2002; Ried & Saxena, 1970; Toda & Tokumaru, 1990), but have not, to our knowledge, been structurally characterized. Here, we report their single-crystal structures, which illustrate a number of facets of weak C—H···π 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).
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 Me3Si(C≡C)2SiMe3 (Carré et al., 2003) and iPr3Si(C≡ C)nSiiPr3 (n = 4, 5 or 6; Eisler et al., 2005), in contrast with the curved backbone of iPr3Si(C≡C)8SiiPr3 (Eisler et al., 2005). The C—Si—C 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 rows of SiCCCCSi chains is 5.8 Å. Adjacent chains are interlocked, with the packing being supported by close methyl C—H to alkyne π interactions (C8—H83···C1 = 2.9 Å and C8—H83···C2 = 3.1 Å). This leads to the presence of close (repulsive) H···H contacts (Me2C—H61···H61—CMe2 = 2.7 Å). A second set of C—H···π interactions operates between molecules within each row (Fig. 2b). Their evolution gives rise to short H···H 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 E—C≡ C—C≡ C–E unit (E is Si, Sn, Ge or Pb) gave only 14 hits (Brouty et al., 1980; Brunel et al., 2001; Carré et al., 1999, 2003; Dam et al., 1998; Neugebauer et al., 2000). Among these are two polymorphs of Me3SiC≡CC≡CSiMe3 (structures determined at 120 and 203 K; Carré 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 solid-state packing of iPr3Si(C≡ C)4SiiPr3 resembles that of (I), with molecules organized in offset rows, while for iPr3Si(C≡ C)5SiiPr3 and iPr3Si(C≡C)6SiiPr3, a herringbone assembly is observed. In iPr3Si(C≡C)8SiiPr3, the polyyne backbone is significantly 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 C—H···π interactions listed in Table 3. The basic motif in the solid state is a dimeric unit (Fig. 4a), in which both C—Haryl···πalkyne and C—Haryl···πaryl interactions are present (Table 3).
The dimers further assemble into layers (Fig. 4b), again with C—H···π interactions playing a role (Table 3). Stacking of planes of molecules into the three-dimensional lattice is also supported by C—H···π 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 herringbone arrangement. Whereas C—H···π contacts control the ring orientations and packing in (II), π-stacking interactions are important in 1,4-diphenylbuta-1,3-diyne. Also related to (II) is 4-ethynylbiphenyl (Mague et al., 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 significant intermolecular interactions", although inspection of the data indicate the presence of weak C—Halkyne···πaryl contacts.
In conclusion, we have investigated the solid-state structures of two simple diynes and in both cases find that weak C—H···π contacts control the molecular packing. In the case of 1,4-di(biphenyl-4-yl)buta-1,3-diyne, a combination of C—Haryl···πalkyne and C—Haryl···πaryl interactions operate at the expense of π-stacking interactions.