Examining the silicon-fluorine gauche effect in 3-fluoro silacyclohexanes

Two 3-fluorosilinanes featuring different substitution at silicon were synthesized and their conformations analyzed by NMR and DFT. Based on the results, both compounds prefer a conformation wherein the fluorine atom is oriented equatorial rather than axial, which would have placed the partially negative fluorine (Fδ-) closer in space to partially positive silicon (Siδ+). Therefore, the conformational preference of these systems is thought to be controlled primarily by sterics as well as hyperconjugative stabilization (σC-Si → σ*C-F).