Elektronenreiche Olefine, 2 Struktur und Elektrontransfer-Reaktivität des cyclisch σ/π-hyperkonjugierten Carbosilans 3,3,6,6-Tetrakis(trimethylsilyl)-1,4-cyclohexadien

Crystal and molecular structure analysis of the title compound 1, a most electron rich carbosilane, exhibits a shallow boat conformation for the cyclohexadiene ring which is shielded by four bulky Me Si groups. Multiple hyperconjugative interaction occurs between the two non-conjugated olefinic π systems and the four rather long (192 pm) carbon-silicon o bonds which form an angle of about 34° with the assumed π axis. The HOMO destabilization caused by this unique structural arrangement explains the energetically facile formation and subsequent reactivity of the cation radical 1+ which was found to undergo oxidative desilylation to the aromatic 1,4-bis(trimethylsilyl) benzene precursor in the single electron transfer reaction with TCNE.