Unexpected Selective Methyl Group Abstractions from SiMe3 Moieties of CH2SiMe3 Ligands To Give New Cationic Titanium Complexes

The synthesis of the alkylated pentafulvene titanium complex Cp*Ti(CH2SiMe3)(π‐η5:σ‐η1‐C5H4=CR2) (CR2=adamantylidene) is described. The coordination mode of the pentafulvene ligand in this complex allowed for the subsequent synthesis of a series of nitrile‐insertion products. By reacting these neutral compounds with the strong Lewis acid B(C6F5)3, unprecedented selective methyl‐group ions from the SiMe3 moieties under formation of novel cationic titanium complexes with the corresponding MeB(C6F5)3− anion are demonstrated. The proposed silylium ion intermediates of these reactions are directly stabilized by either the exocyclic carbon atom of the pentafulvene ligand or by the lone pairs of the nitrogen atoms of the chelating Cp,N‐ligands. In addition, a titanium enamine complex and its reaction with B(C6F5)3 is reported, which results in the formation of a betaine. A titanium pentafulvene complex and Cp,N‐chelated derivatives thereof with CH2SiMe3 substituents are employed for the synthesis of a variety of novel cationic titanium complexes by unprecedented selective ions of one methyl group from the SiMe3 moieties by B(C6F5)3. One complex reacts with B(C6F5)3 through formation of a betaine (see scheme).