Gas-Phase Reactions of Si+ with Ammonia and the Amines (CH3)xNH3-x (x-1-3): Possible Ion-Molecule Reaction Pathways toward SiH, SiCH, SiNH, SiCH3, SiNCH3, and H2SiNH

Article abstract of DOI:10.1021/ja00216a010

Rate constants and product distributions have been determined for gas-phase Si⁺(2P) ions with ammonia and the amines (CH3)_xNH_3-x (x=1-3) at 296+/-2 K with the selected-ion flow tube technique.All reactions were observed to be fast and can be understood in terms of Si⁺ insertion into N-H and C-N bonds to form ions of the type SiNR₁R₂⁺ (R₁, R₂ = H, CH3) proceeding in competition (in the case of the amines) with hydride ion transfer to form immonium ions of the type CH2NR₁R₂⁺ (R₁, R₂ =H, CH3).C-N bond insert ion appears more efficient than N-H bond insertion.The contribution if hydride ion transfer increases with increasing stability of the immonium ion.The latter reaction leads directly to SiH as a neutral product.Other minor reaction channels were seen which lead directly or indirectly to SiCH and SiCH3.Rapid secondary proton transfer reactions were observed for SiNH2⁺ and SiNHCH3⁺ to produce gas-phase SiNH and SiNCH3 molecules.With methylamine SiNH2⁺ also appears to produce H2SiNH2⁺ which may deprotonate to form the simplest silanimine, H2SiNH, or aminosilylene, HSiNH2.Reactions of this type are of interest in molecular synthesis and here are proposed to contribute to the formation of SiH, SiCH, SiNH, SiCH3, SiNCH3, and H2SiNH or HSiNH2 in partially ionized interstellar gas clouds containing silicon, ammonia, and methylamines.