Reactions of Ph(ClCH2)SiH2 with fluoride ion sources: Formation of fluorine‐terminated siloxanes

Abstract

AbstractThe fluoride ion‐induced rearrangement of Ph(ClCH2)SiH2 was expected to provide either PhMeSiHF (migration of hydride) or (PhCH2)SiH2F (migration of phenyl). However, when Bu4N+F− (commercial TBAF) is added to Ph(ClCH2)SiH2, a mixture of fluorine‐terminated siloxanes, FPhMeSiO(PhMeSiO)xSiMePhF, is obtained. The presence of the Me group suggests a rapid anion‐induced migration of hydride to produce PhMeSiHF which reacts further with water present in TBAF samples. When the reaction mixture is cooled to 0°C or is monitored at the early stage of the reaction, the major products are PhMeSiF2, PhMeSi(OH)F, PhMeSi(OH)2, and FPhMeSiOSiMePhF which are proposed as the building blocks for the siloxanes. When dried CsF in CH3CN is used, the major products are PhMeSiF2 and PhMeSiH2 which are assumed to form from the fluoride ion‐induced disproportionation of PhMeSiHF. The reaction chemistry is rationalized in terms of hypervalent intermediates. The fluoride ion‐induced reactions of PhMeSiH2 and PhMeSiCl2 are also described and compared to those of Ph(ClCH2)SiH2.