Organosilicon chemistry. Part XIV. Insertion of 1,2,2-trifluoroethylidene into C–H bonds of tetra-alkylsilanes: a novel alkyl group rearrangement

Abstract

1,2,2-Trifluoroethylidene, generated by pyrolysis of trifluoro-(1,1,2,2-tetrafluoroethyl)silane, inserts (10–30%) into various C–H bonds in the alkyl groups of alkyltrimethylsilanes, RSiMe₃(R = Et, Prⁿ, Prⁱ, Buⁿ, Buⁱ, Bu^s, isopentyl, and cyclopentyl), but does not insert into the primary C–H bonds in tetramethylsilane. The ease of insertion into the C–H bonds is tertiary > secondary > primary, and C–H bonds α to silicon are somewhat deactivated as compared with those further removed from silicon. In general the α-insertion products are unstable under the reaction conditions and decompose to give fluorotrimethylsilane; other insertion products are stable. Insertion is also observed into the primary C–H bonds of hexamethyldisilane and hexamethyldisiloxane (ca. 5%). A novel rearrangement of the s-butyl group to the n-butyl group occurs during the reaction of trichloro-(s-butyl)-silane with methylmagnesium bromide.