PROBING THE UNUSUAL KINETIC-BEHAVIOR OF SI2C2-COMPOUNDS( REACTIONS WITH UNSATURATED AND AROMATIC)

The unusual non-first-order kinetic behavior of Si2C2+ ions produced b y direct laser vaporization in a Fourier transform ion cyclotron reson ance mass spectrometer was probed using a variety of experimental tech niques to specify the energy content of these ions. The ions apparentl y are formed with at least 0.8 eV of excess energy in an excited elect ronic state, possibly as isomers of the ground state. Reactions with a variety of substituted benzenes and unsaturated hydrocarbons were als o investigated. The results of the substituted benzene reactions displ ay a number of similarities to the reactions of Si+ with benezene or N O2, proceeding through adduct formation for the former and producing s ilicon oxides in the latter. Carbon-13 labeling of Si2C2+ in the react ions with 2- and 3-carbon unsaturated neutrals reveals the detailed me chanism of these reactions. The C3H4 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-carb on bonds is important.