Formation of C 6H nSi + ( n = 5–8) from phenylsilane: an experimental and theoretical study

Abstract

The metastable ion decomposition (MID) spectra of C 6H n Si + ( n = 6–8) generated by electron ionization of phenylsilane were obtained using mass-analyzed ion kinetic energy spectrometry (MIKES). H and H 2 losses were the main channels in the MID of C 6H 8Si + ( 1). The dominant product ion in the MIDs of C 6H 7Si + ( 2) and C 6H 6Si + ( 3) was C 6H 5Si + ( 4) formed by H 2 and H losses, respectively. Density functional theory calculations were performed to investigate isomerizations and dissociations of 1– 3 at the B3LYP/6-311++G(d,p) level. RRKM model calculations were performed to understand their dissociation kinetics. These theoretical results predict that the consecutive dissociation 1 → 3 (+ H 2) → 4 + H dominates at low energies, while 1 → 2 (+ H ) → 4 + H 2 at high energies. It has been found that several isomers of 1– 3 including ion–molecule complexes, C 6H 6·SiH x + ( x = 0–2), play important roles in the dissociation of 1. Reaction mechanisms are proposed for the formation of several isomers of 1– 4 from the phenylsilane molecular ion.