Collision-induced dissociation of the phenylsilane molecular ion

The high-energy collision-induced dissociation of the phenylsilane molecular ion generated by electron ionization has been investigated using tandem mass spectrometry (MS/MS). It was observed that the dissociation of the molecular ion (M⁺) occurs mainly via [M-H]⁺ [M-2H]⁺, and [M-3H]⁺, followed by two consecutive losses of C₂H₂. The structures of the precursors for the [M-CH₃]⁺, [M-SiH]⁺, and [M-SiH₂]^+. ions are proposed. The data suggest that the molecular ion undergoes rearrangements to several isomers prior to dissociation, including the ion containing a five-membered carbon ring. Reaction mechanisms are proposed for the dissociations via the isomeric molecular ions.