GAS-PHASE GENERATION AND CHARACTERIZATION OF NEUTRAL AND IONIZED HSIOH, H2SIO, H2SIOH, AND H3SIO BY COLLISIONAL ACTIVATION AND NEUTRALIZATION REIONIZATION MASS-SPECTROMETRY

Results of mass spectrometric measurements are reported which characterize the chemical bonding in the stable ions HSiOH.+, H2SiO.+, H2SiOH+, and H3SiO+ and provide evidence for the existence of the corresponding neutral molecules HSiOH, H2SiO, H2SiOH., and H3SiO., in the gas phase. The experiments were performed with a modified four-sector ZAB mass spectrometer with a BEBE configuration and collision cells mounted in the intermediate field-free regions B(1)/E(1), E(1)/B(2), and B(2)/E(2). Observed collisional-activation (CA) mass spectra of the ions [H2,Si,O].+ and [H3,Si,O]+ generated from electron impact of tetramethoxysilane are most compatible with the connectivities HSiOH.+ and H2SiOH+, respectively. Neutralization-reionization (NRMS) experiments and CA experiments with the "recovery" signals established identical connectivities for the corresponding neutral species. Charge-reversal (CR) experiments with the negative ions [H2,Si,O].- and [H3,Si,O]- generated from C6H5SiH3 by chemical ionization in the presence of N2O were used to provide evidence for isomeric ions with the connectivities H2SiO.+ and H3SiO+ while neutralization-reionization (-NR+) experiments showed that the connectivities of the negative ions were carried forward to the corresponding neutral species. Theoretical predictions suggest that the H3SiO+, which was observed experimentally, is in its triplet state.