Probing the unusual kinetic behavior of Si 2C +2 reactions with unsaturated and aromatic compounds

Abstract

The unusual non-first-order kinetic behavior of Si 2C + 2 ions produced by direct laser vaporization in a Fourier transform ion cyclotron resonance mass spectrometer was probed using a variety of experimental techniques to specify the energy content of these ions. The ions apparently are formed with at least 0.8 eV of excess energy in an excited electronic state, possibly as isomers of the ground state. Reactions with a variety of substituted benzenes and unsaturated hydrocarbons were also investigated. The results of the substituted benzene reactions display a number of similarities to the reactions of Si + with benezene or NO 2, proceedings through adduct formation for the former and producing silicon oxides in the latter. Carbon-13 labeling of Si 2C + 2 in the reactions with 2- and 3-carbon unsaturated neutrals reveals the detailed mechanism of these reactions. The C 3H 4 isomers (allene and propyne) both appear to react by insertion into single bonds, leading to different products in these two cases. This is in contrast to the reactions with ethylene and acetylene, where insertion into the multiple carbon—carbon bonds is important