(Z,Z)-1,4-Diiodo-1,4-bis(trimethylsilyl)buta-1,3-diene

The asymmetric unit of the title compound, C10H20I2Si2, contains two half-molecules. Both complete molecules are generated by crystallographic inversion centers located at the mid-points of the central C—C single bonds; the butadiene groups are planar, with a trans conformation about the central C—C bond. The molecules show short intramolecular H⋯I contacts of 2.89 and 2.92 Å. The crystal packing shows no short intermolecular contacts.

The asymmetric unit of the title compound, C 10 H 20 I 2 Si 2 , contains two half-molecules. Both complete molecules are generated by crystallographic inversion centers located at the mid-points of the central C-C single bonds; the butadiene groups are planar, with a trans conformation about the central C-C bond. The molecules show short intramolecular HÁ Á ÁI contacts of 2.89 and 2.92 Å . The crystal packing shows no short intermolecular contacts.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: SU2074).

S2. Experimental
The title compound was prepared as described by Yamaguchi et al. (1998), and recrystallized from n-hexane at 153 K.

S3. Refinement
H atoms were geometrically positioned and treated as riding atoms: C planar -H = 0.95 Å, C methyl -H=0.98 Å, with U iso (H)= 1.2U eq (C butene ) and = 1.5U eq (C methyl ).   The crystal packing of the title compound, viewed down the a axis (the displacement ellipsoids are drawn at the 50% probability level).

Crystal data
C 10 H 20 I 2 Si 2 M r = 450.24 Triclinic, P1 Hall symbol: -P 1 a = 6.3553 (17) Å b = 11.502 (2) Å c = 11.698 (2) Å α = 103.027 (13) where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.002 Δρ max = 1.12 e Å −3 Δρ min = −0.94 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.0130 (5) Special details 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 F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.