Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536802022870/bt6216sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S1600536802022870/bt62162sup2.hkl |
CCDC reference: 204674
Key indicators
- Single-crystal X-ray study
- T = 178 K
- Mean (C-C) = 0.003 Å
- R factor = 0.042
- wR factor = 0.115
- Data-to-parameter ratio = 24.9
checkCIF results
No syntax errors found ADDSYM reports no extra symmetry
Compound (1) was metallated with n-butyllithium in THF in the presence of tetramethylethylenediamine and the resulting dianion was then quenched with trimethylsilylchloride (Stamm, 1992). Recrystallization of (2) from pentane afforded single crystals.
Methyl H atoms were identified in difference syntheses, idealized and then refined using rigid methyl groups (C—H = 0.98 Å and H—C—H = 109.5°) being allowed to rotate but not tip.
Data collection: P3 (Nicolet, 1987); cell refinement: P3; data reduction: XDISK (Nicolet, 1987); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP (Siemens, 1994); software used to prepare material for publication: SHELXL97.
C16H30Si2 | Z = 1 |
Mr = 278.58 | F(000) = 154 |
Triclinic, P1 | Dx = 0.986 Mg m−3 |
a = 6.363 (2) Å | Mo Kα radiation, λ = 0.71073 Å |
b = 8.963 (2) Å | Cell parameters from 50 reflections |
c = 9.157 (3) Å | θ = 10–11.5° |
α = 70.76 (2)° | µ = 0.18 mm−1 |
β = 72.13 (2)° | T = 178 K |
γ = 83.41 (2)° | Prism, colourless |
V = 469.2 (2) Å3 | 0.70 × 0.25 × 0.15 mm |
Nicolet R3 diffractometer | Rint = 0.015 |
Radiation source: fine-focus sealed tube | θmax = 27.6°, θmin = 3.4° |
Graphite monochromator | h = 0→8 |
ω scans | k = −11→11 |
2355 measured reflections | l = −11→11 |
2162 independent reflections | 3 standard reflections every 147 reflections |
1613 reflections with I > 2σ(I) | intensity decay: none |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.042 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.115 | H-atom parameters constrained |
S = 1.02 | w = 1/[σ2(Fo2) + (0.056P)2 + 0.1101P] where P = (Fo2 + 2Fc2)/3 |
2162 reflections | (Δ/σ)max < 0.001 |
87 parameters | Δρmax = 0.29 e Å−3 |
0 restraints | Δρmin = −0.21 e Å−3 |
C16H30Si2 | γ = 83.41 (2)° |
Mr = 278.58 | V = 469.2 (2) Å3 |
Triclinic, P1 | Z = 1 |
a = 6.363 (2) Å | Mo Kα radiation |
b = 8.963 (2) Å | µ = 0.18 mm−1 |
c = 9.157 (3) Å | T = 178 K |
α = 70.76 (2)° | 0.70 × 0.25 × 0.15 mm |
β = 72.13 (2)° |
Nicolet R3 diffractometer | Rint = 0.015 |
2355 measured reflections | 3 standard reflections every 147 reflections |
2162 independent reflections | intensity decay: none |
1613 reflections with I > 2σ(I) |
R[F2 > 2σ(F2)] = 0.042 | 0 restraints |
wR(F2) = 0.115 | H-atom parameters constrained |
S = 1.02 | Δρmax = 0.29 e Å−3 |
2162 reflections | Δρmin = −0.21 e Å−3 |
87 parameters |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane) 0.4358 (0.0072) x − 6.8427 (0.0071) y + 3.2746 (0.0099) z = 1.3751 (0.0083) * −0.0006 (0.0005) C1 * 0.0018 (0.0016) C2 * −0.0007 (0.0006) C3 * −0.0006 (0.0005) C5 Rms deviation of fitted atoms = 0.0010 5.2707 (0.0040) x + 4.1904 (0.0062) y + 6.7925 (0.0053) z = 6.0327 (0.0022) Angle to previous plane (with approximate e.s.d.) = 88.49 (0.08) * 0.0009 (0.0005) Si * 0.0013 (0.0007) C3 * −0.0035 (0.0018) C4 * 0.0012 (0.0006) C4_1 Rms deviation of fitted atoms = 0.0020 |
x | y | z | Uiso*/Ueq | ||
Si | 0.54749 (9) | 0.25475 (6) | 0.30629 (6) | 0.03061 (17) | |
C1 | −0.1248 (3) | 0.1335 (2) | 0.7153 (3) | 0.0415 (5) | |
H1A | −0.1267 | 0.0854 | 0.6339 | 0.050* | |
H1B | −0.1934 | 0.2390 | 0.6915 | 0.050* | |
H1C | −0.2072 | 0.0675 | 0.8224 | 0.050* | |
C2 | 0.1105 (3) | 0.1468 (2) | 0.7125 (2) | 0.0317 (4) | |
C3 | 0.2782 (3) | 0.1071 (2) | 0.6064 (2) | 0.0298 (4) | |
C4 | 0.4466 (3) | 0.08035 (19) | 0.4915 (2) | 0.0270 (4) | |
C5 | 0.1435 (4) | 0.2093 (3) | 0.8380 (2) | 0.0450 (5) | |
H5A | 0.3017 | 0.2111 | 0.8260 | 0.054* | |
H5B | 0.0688 | 0.1407 | 0.9461 | 0.054* | |
H5C | 0.0815 | 0.3167 | 0.8235 | 0.054* | |
C6 | 0.5172 (4) | 0.2187 (3) | 0.1249 (2) | 0.0434 (5) | |
H6A | 0.3600 | 0.2153 | 0.1344 | 0.052* | |
H6B | 0.5883 | 0.1176 | 0.1169 | 0.052* | |
H6C | 0.5873 | 0.3041 | 0.0280 | 0.052* | |
C7 | 0.8426 (3) | 0.2927 (2) | 0.2743 (3) | 0.0429 (5) | |
H7A | 0.9292 | 0.1948 | 0.2757 | 0.052* | |
H7B | 0.8549 | 0.3300 | 0.3606 | 0.052* | |
H7C | 0.8990 | 0.3734 | 0.1697 | 0.052* | |
C8 | 0.3795 (4) | 0.4324 (2) | 0.3365 (3) | 0.0426 (5) | |
H8A | 0.4428 | 0.5265 | 0.2476 | 0.051* | |
H8B | 0.3798 | 0.4443 | 0.4390 | 0.051* | |
H8C | 0.2275 | 0.4199 | 0.3386 | 0.051* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Si | 0.0334 (3) | 0.0273 (3) | 0.0284 (3) | −0.00164 (19) | −0.0086 (2) | −0.00493 (19) |
C1 | 0.0378 (11) | 0.0394 (11) | 0.0430 (11) | 0.0052 (9) | −0.0068 (9) | −0.0138 (9) |
C2 | 0.0382 (10) | 0.0243 (8) | 0.0285 (9) | 0.0026 (7) | −0.0054 (8) | −0.0079 (7) |
C3 | 0.0355 (10) | 0.0240 (8) | 0.0288 (9) | −0.0001 (7) | −0.0102 (7) | −0.0060 (7) |
C4 | 0.0313 (9) | 0.0246 (8) | 0.0252 (8) | −0.0006 (7) | −0.0085 (7) | −0.0075 (7) |
C5 | 0.0558 (13) | 0.0409 (11) | 0.0388 (11) | −0.0024 (10) | −0.0058 (10) | −0.0198 (9) |
C6 | 0.0505 (13) | 0.0463 (12) | 0.0303 (10) | −0.0032 (10) | −0.0115 (9) | −0.0073 (9) |
C7 | 0.0396 (11) | 0.0379 (10) | 0.0463 (12) | −0.0063 (9) | −0.0108 (9) | −0.0062 (9) |
C8 | 0.0483 (12) | 0.0286 (9) | 0.0467 (12) | 0.0010 (9) | −0.0151 (10) | −0.0056 (8) |
Si—C6 | 1.861 (2) | C5—H5A | 0.9800 |
Si—C7 | 1.863 (2) | C5—H5B | 0.9800 |
Si—C8 | 1.864 (2) | C5—H5C | 0.9800 |
Si—C4 | 1.8834 (18) | C6—H6A | 0.9800 |
C1—C2 | 1.507 (3) | C6—H6B | 0.9800 |
C1—H1A | 0.9800 | C6—H6C | 0.9800 |
C1—H1B | 0.9800 | C7—H7A | 0.9800 |
C1—H1C | 0.9800 | C7—H7B | 0.9800 |
C2—C3 | 1.309 (2) | C7—H7C | 0.9800 |
C2—C5 | 1.510 (3) | C8—H8A | 0.9800 |
C3—C4 | 1.314 (2) | C8—H8B | 0.9800 |
C4—C4i | 1.501 (3) | C8—H8C | 0.9800 |
C6—Si—C7 | 109.49 (10) | C2—C5—H5C | 109.5 |
C6—Si—C8 | 109.11 (10) | H5A—C5—H5C | 109.5 |
C7—Si—C8 | 108.70 (10) | H5B—C5—H5C | 109.5 |
C6—Si—C4 | 110.50 (9) | Si—C6—H6A | 109.5 |
C7—Si—C4 | 110.35 (9) | Si—C6—H6B | 109.5 |
C8—Si—C4 | 108.66 (9) | H6A—C6—H6B | 109.5 |
C2—C1—H1A | 109.5 | Si—C6—H6C | 109.5 |
C2—C1—H1B | 109.5 | H6A—C6—H6C | 109.5 |
H1A—C1—H1B | 109.5 | H6B—C6—H6C | 109.5 |
C2—C1—H1C | 109.5 | Si—C7—H7A | 109.5 |
H1A—C1—H1C | 109.5 | Si—C7—H7B | 109.5 |
H1B—C1—H1C | 109.5 | H7A—C7—H7B | 109.5 |
C3—C2—C1 | 121.97 (17) | Si—C7—H7C | 109.5 |
C3—C2—C5 | 121.48 (18) | H7A—C7—H7C | 109.5 |
C1—C2—C5 | 116.55 (16) | H7B—C7—H7C | 109.5 |
C2—C3—C4 | 174.86 (18) | Si—C8—H8A | 109.5 |
C3—C4—C4i | 121.56 (19) | Si—C8—H8B | 109.5 |
C3—C4—Si | 116.38 (13) | H8A—C8—H8B | 109.5 |
C4i—C4—Si | 122.06 (16) | Si—C8—H8C | 109.5 |
C2—C5—H5A | 109.5 | H8A—C8—H8C | 109.5 |
C2—C5—H5B | 109.5 | H8B—C8—H8C | 109.5 |
H5A—C5—H5B | 109.5 | ||
C6—Si—C4—C3 | −117.95 (15) | C6—Si—C4—C4i | 62.6 (2) |
C7—Si—C4—C3 | 120.81 (16) | C7—Si—C4—C4i | −58.6 (2) |
C8—Si—C4—C3 | 1.73 (18) | C8—Si—C4—C4i | −177.68 (18) |
Symmetry code: (i) −x+1, −y, −z+1. |
Experimental details
Crystal data | |
Chemical formula | C16H30Si2 |
Mr | 278.58 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 178 |
a, b, c (Å) | 6.363 (2), 8.963 (2), 9.157 (3) |
α, β, γ (°) | 70.76 (2), 72.13 (2), 83.41 (2) |
V (Å3) | 469.2 (2) |
Z | 1 |
Radiation type | Mo Kα |
µ (mm−1) | 0.18 |
Crystal size (mm) | 0.70 × 0.25 × 0.15 |
Data collection | |
Diffractometer | Nicolet R3 diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 2355, 2162, 1613 |
Rint | 0.015 |
(sin θ/λ)max (Å−1) | 0.651 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.042, 0.115, 1.02 |
No. of reflections | 2162 |
No. of parameters | 87 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.29, −0.21 |
Computer programs: P3 (Nicolet, 1987), P3, XDISK (Nicolet, 1987), SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), XP (Siemens, 1994), SHELXL97.
C2—C3 | 1.309 (2) | C4—C4i | 1.501 (3) |
C3—C4 | 1.314 (2) | ||
C2—C3—C4 | 174.86 (18) | C3—C4—Si | 116.38 (13) |
C3—C4—C4i | 121.56 (19) | C4i—C4—Si | 122.06 (16) |
Symmetry code: (i) −x+1, −y, −z+1. |
As the cumulogues of conjugated dienes, conjugated bisallenes are of interest for preparative (e.g. as partners in cycloaddion reactions; Sankararaman et al., 2000) and structural reasons. The structure of the parent system 1,2,4,5-hexatetraene in solution and in the gas phase has been described (Christensen et al., 1973; cf. Traetteberg et al., 1973). Since structural data for this class of hydrocarbons are still scarce, we decided to prepare 2,7-dimethyl-4,5-bis(trimethylsilyl)-octa-2,3,5,6-tetraene, (2), a fully substituted bis-allene, and investigate it by X-ray structural analysis. As a precursor we used 2,7-dimethyl-octa-2,4,5,6-tetraene, (1), whose solid-state structure we have reported recently (Jones et al., 2002).
The structure of (2) is shown in Fig. 1. The molecule possesse a crystallographic inversion centre at the midpoint of the C4—C4i bond. Bond lengths and angles [e.g. the allenic bond lengths of 1.309 (2) and 1.314 (2) Å] may be considered normal [cf. 1.3067 (16) and 1.3126 (16) Å in (1); Jones et al., 2002]. The planes C1/2/3/5 and Si/C3/4/4i are mutually perpendicular [interplanar angle 88.49 (8)°].
The packing (Fig. 2) is unexceptional. The shortest H···H contacts are H6A···H8A(1 − x, 1 − y, −z) = 2.53 Å and H7B···H8C(1 + x, y, z) = 2.52 Å.