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 (F δ- ) closer in space to partially positive silicon (Si δ+ ). Therefore, the conformational preference of these systems is thought to be controlled primarily by sterics as well as hyperconjugative stabilization (σ C-Si → σ* C-F ). • A synthesis of 3-fluorosilinanes was developed to investigate their conformation. • By NMR, fluorine adopts an equatorial position in the two silinanes investigated. • Hyperconjugation is thought to be an important factor in these systems.