Metastable Ion Study of Organosilicon Compounds Part II-Hexamethyldisiloxane

Article abstract of DOI:10.1002/oms.1210250109

Unimolecular reactions of the metastable silicenium ion (CH3)3SiOSi(CH3)2+ generated by dissociative ionization of hexamethyldisiloxane were investigated by mass-analysed ion kinetic energy (MIKE) spectrometry.The characteristic fragmentations observed were losses of CH4 and (CH3)2Si=O molecules.Complete scrambling of all methyl groups prior to these reactions was found by investigating the MIKE spectra of deuterium labelled analogues (CD3)3SiOSi(CH3)2+ and (CH3)3SiOSi(CD3)2+.The loss of methane was accompanied by a large kinetic energy release (T_0.5 = 482 meV).The MIKE spectra of silicenium ions were compared with those of their carbon analogues.The most predominant reaction of metastable (CH3)3COC(CH3)2+ ion was the loss of CH2=C(CH3)2 leading to protonated acetone.Significant differences between the ion fragmentation characteristics of silicon and carbon compounds were found.