(E)-1,2-Bis{4-[dimethyl(vinyl)silyl]phenyl}ethene

The molecule of the title compound, C32H34Si2, is situated about a centre of symmetry. The whole diphenylethene fragment is planar and the Car—Si—C3 group is rotated by ca 30° with respect to the plane of the benzene ring. The crystal structure is stabilized by some C—H⋯π contacts as well as van der Waals interactions.

The molecule of the title compound, C 32 H 34 Si 2 , is situated about a centre of symmetry. The whole diphenylethene fragment is planar and the C ar -Si-C 3 group is rotated by ca 30 with respect to the plane of the benzene ring. The crystal structure is stabilized by some C-HÁ Á Á contacts as well as van der Waals interactions.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: TK2222). The synthesis of {(E)-1,2-bis(4-(dimethyl(vinyl)silyl)phenyl)}ethene, (I), consisted of two steps. During first step, the well know metathesis reaction of 4-bromostyrene was applied to obtain {(E)-1,2-bis(4-bromophenyl)}ethene which was used as a substrate for the second step, the typical reaction between an aryl-halide derivative of an olefin, a Grignard reagent generated in situ and vinylchlorosilane. This kind of vinylsilane-stilbene can be used as a very efficient monomer for the synthesis of arylene-silylene-vinylene polymers, polycarbosilanes or co-polymers with suitable aromatic olefin via silylative coupling polycondensation (SCP) or polyhydrosilylation reactions (Majchrzak et al., 2005(Majchrzak et al., , 2007Maciejewski et al., 2003).
The molecule of (I) is centrosymmetric with the mid-point of the central C41?C41A bond lying on a centre of symmetry ( Fig. 1). The phenyl rings (planar within 0.0046 (14) Å) are, from symmetry, co-planar. As the C41 and Si1 atoms are almost co-planar with these rings (deviation from the least-squares plane = 0.009 (3)Å and 0.054 (3) Å, respectively), the whole diphenylethene fragment is planar. The C(ar)-Si-C 3 group is rotated by ca 30° with respect to to the plane of the phenyl ring, as can be seen from the values of C2-C1-Si-C(X) torsion angles: 28.5 (2)° for X = 13, -92.5 (2)° for X = 12, and 148.0 (2)° for X = 11. The crystal structure is stabilized by some relatively directional C-H···π contacts as well as van der Waals interactions.

First
Step: A solution of 4-bromostyrene (6.095 g, 33.30 mmol) in THF (35 ml) was placed in a 50 ml glass two-neck mini reactor which was fitted with a condenser connected with an inert gas line. The Hoveyda-Grubbs catalyst 1 st generation (10 mg, 0.017 mmol) was added and the reaction mixture was heated at 316-318 K and left for 5 h. The crude product was precipitated partially from solution. After the reaction was completed, the mixture was cooled to room temperature and the excess of organic solvent was evaporated under high vacuum. The mix of yellowish crystals was recovered by filtration and washed with cold hexane (3 x 10 ml). The residue was recrystallized from ethanol to provide

S3. Refinement
Hydrogen atoms were found in difference Fourier maps and freely refined so that the range of C= H = 0.88 (3) to 1.09 (4) Å.

Figure 1
Molecular structure of (I) showing displacement ellipsoids at the 50% probability level and the atom numbering scheme.

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.