REACTIONS OF METHYL CATIONS WITH METHYLSILANES

The gas-phase reactions of CH3+ with (CH3)4-nSiHn (n = 0, 1, 2, 3) have been studied in a tandem mass spectrometry apparatus. Reaction cross sections at 1 -eV kinetic energy in the laboratory system have been determined by direct comparison with the known cross section for hydride ion transfer from SiH4 to CH3+. Relative cross sections have been determined as a function of kinetic energy in the range of 1 -10 eV in order to determine whether reactions were endothermic or exothermic. The major reactions are hydride and methide (CH3-) transfer from the silane to CH3+, with methide transfer becoming dominant for (CH3)3SiH and (CH3)4Si. Isotopic studies show only very minor incorporation of l3C atoms and D atoms in the ionic products when CH3+ reactant ions are replaced by 13CH3 and CD3+. This is interpreted as indicating that the reactions do not proceed through pentavalent collision complexes but rather are of the direct type. Copyright © 1979, American Chemical Society. All rights reserved.