5,5′-Bis[(trimethylsilyl)methyl]-2,2′-bipyridine

The molecule of the title compound, C18H28N2Si2, occupies a special position on an inversion centre. The Si—CH2—C(ipso) plane is approximately orthogonal to the plane of the pyridine rings, the corresponding dihedral angle being 82.0 (2)°.

The molecule of the title compound ( Fig.1) occupies a special position in the inversion centre. The SiMe 3 groups are trans disposed relative to the plane of the two pyridyl rings giving the molecule a zigzag shape (Fig. 2). The dihedral angle between the plane of the bipyridyl rings, and that of trimethylsilylmethyl substituent, as defined by Si1-C6-C4, is 82.0 (2)°.
The molecules in crystal show stacking arrangement with methylenetrimethylsilyl groups of the adjacent molecules oriented in the same direction (Fig. 2).

Experimental
A solution of LDA, prepared from n-BuLi (1.9 M, 1.42 ml, 2.7 mmol), and dry diisopropylamine (0.42 ml, 3.0 mmol) in dry THF (8 ml) was cooled to −78° C and a solution of 5,5'-dimethyl-2,2'-bipyridine (100 mg, 0.54 mmol) and dry HMPA (1.13 ml, 6.5 mmol) in dry THF (5 ml) was added dropwise, resulting in a deep red/brown opaque reaction mixture. This was stirred for 2 h, then trimethylsilyl chloride (217 mg, 2.0 mmol) was added, and the stirring was continued for 0.5 h more at −78° C. The resulting transparent red solution was quenched with 2 ml of absolute ethanol. Fortuitously, this solution precipitated crystals of (I) suitable for X-ray structure determination when its volume was reduced by rotary evaporation. To the remaining material, saturated NaHCO 3 (10 ml) was added and the product was extracted with ethyl acetate (3 × 40 ml).
The combined organic fractions were dried over anhydrous Na 2 SO 4 and the solvent removed under vacuum. The resulting solid was purified by chromatography on deactivated silica gel, affording (I) as a greasy white solid (142 mg, 80%

Refinement
All aromatic and methylene H atoms were located in the difference map and refined with isotropic thermal parameters  Fig. 1. ORTEP (Burnett and Johnson (1996), Farrugia (1997)) drawing of (I) with displacement ellipsoids shown at 50% probability level. Only the non-hydrogen atoms in the asymmetric unit are labelled; unlabelled atoms are derived from the corresponding labelled atoms by means of the (1 − x, 3 − y, −z) transformation.

Data collection
Bruker SMART 1000 CCD area-detector diffractometer 2057 independent reflections Refinement. An empirical absorption correction determined with SADABS (Sheldrick, 1996) was applied to the data. The data integration and reduction were undertaken with SAINT and XPREP (Bruker, 2001). The data reduction included the application of Lorentz and polarization corrections. The reflection data were merged including Fridel opposites. The structure was solved in the space group P-1 by direct methods with SHELXS97 (Sheldrick, 1997) within the WinG-X (Farrugia, 1999) interface and extended and refined with SHELXL97 (Sheldrick 1997). Anisotropic thermal parameters were refined for the non-hydrogen atoms. All aromatic and methylene H atoms were located and refined with isotropic thermal parameters. Methyl H atoms were constrained as riding atoms, fixed to the parent C atom with a distance of 0.96 Å. U iso values were set to 1.5 U eq of the parent C atom.
Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional Rfactors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating Rfactors(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.