Various energy minima and corresponding fragmentation processes: Alkylsilanes

Fragmentation of alkylsilanes, in particular trimethylethylsilane, were studied by mass-analysed ion kinetic energy (MIKE) and collision-induced decomposition MIKE techniques. Ab initio and semi-empirical molecular orbital calculations were applied to explain the main fragmentation processes. These calculations indicate that more than one minimum can be located on the potential energy surface of a given ground-state molecule ion. These differ from each other mainly in the length of the silicon-carbon bonds. The structures can be adequately described as complexes of a trivalent silyl ion and an alkyl radical. Each of these complexes fragments by the loss of the weakly bound alkyl radical. The calculated energetics of these reactions were found to be in good agreement with the observed energy dependence of the mass spectra.