Synthesis and Structural Study of [5.5](2,6)Pyridinophanes and -cyclophanes Containing Silylene Units†
journal contributionposted on 21.05.1998 by Bernadette Rezzonico, Micheline Grignon-Dubois, Michel Laguerre, Jean-Michel Léger
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Four [5.5](2,6)pyridinophanes and -cyclophanes containing silylene units (2a,b, 3a,b) have been prepared by reacting dichlorosilanes with pyridine- or benzenedimethanol. X-ray structures of compounds 2a, 2b, and 3a have been determined. The diphenylsilylene pyridinophane 2b and dimethylsilylene cyclophane 3a were found to adopt an anti conformation in the solid state. In contrast, the dimethylsilylene pyridinophane 2a exhibits a syn arrangement. The conformational preference of these cyclophanes without the influence of the packing energy was analyzed by molecular mechanics calculations. The results show that all the derivatives preferentially adopt a syn conformation, whereas the anti geometry found in the solid state for 2b and 3a does not play a significant role in the conformational equilibrium at room temperature.