Gas-phase association reactions of trimethylsilylium ((CH3)3Si+) with organic bases

Abstract

This article is a review of the gas-phase association reactions of (CH3)3Si+ with organic bases. The reactions are considered under the headings of the three pressure regimes under which they are studied. ICR and FTICR studies, carried out at pressures of 10−5 and lower, allow insights into the stabilizations, collisional and radiative, and decompositions of the nascent adducts. At pressures around 2 Torr, chemical ionization studies demonstrate the utility and limitations of (CH3)3Si+ as a reagent ion, whereas high-pressure mass spectrometric and flowing afterglow experiments yield information on the thermodynamics of the association reactions. Information is also obtained on the stabilization of alkyl and vinyl cations by a (CH3)3Si group in a position β to the charge site. High pressure (∼ 1 atmosphere) γ-radiolytic experiments give detailed information of the neutral products formed via the association reactions and also yield relative rate data for inter- and intramolecular processes that occur in the energy-rich adducts prior to collisional stabilization and neutralization. The ease of experimentation with R3Si+ in the gas phase is contrasted with the difficulty of its recognition and observation in the condensed phase. © 1997 John Wiley & Sons, Inc., Mass Spectrom Rev 16(1), 25–49, 1997