Cyclic diynes with tetramethyldisilyl groups in the bridges. Syntheses and properties

Abstract

A series of cyclic diynes (8–15) with tetramethyldisilyl groups as bridging units have been synthesized from α,ω-bis(chloromethyl)diynes and 1,2-dichloro-1,1,2,2-tetramethyldisilane with lithium in the presence of catalytic amounts of biphenyl. X-Ray investigations of single crystals of 8–14 reveal a twisted-chair conformation for 9–11 and 14, and a twisted half-chair conformation for 8 and 12, whereas 13 adopts a twisted-boat conformation in the solid state. The He(I) photoelectron spectra of 8–14 reveal ionization energies between 8.5–10 eV for the ionization processes from the π-orbitals.