FOURIER-TRANSFORM ION-CYCLOTRON RESONANCE SPECTROMETRIC STUDIES OF LEWIS ACID-BASE CHEMISTRY IN MONOCHLOROSILANE

Fourier transform ion cyclotron resonance spectrometry is used to dete rmine reaction pathways and rate constants for the reactions of the Le wis acids, SiHnCl3-n+ (n = 1-3), with SiH3Cl. SiH2Cl+ is observed to p articipate in both an H- transfer reaction and a disproportionation re action with SiH3Cl. The ions SiH3+ and SiHCl2+ are observed to partici pate in only H- transfer reactions with SiH3Cl. The H- affinity of SiH 2Cl+ is determined to be 1.4 +/- 0.3 kcal mol(-1) greater than that of SiHCl2+. Within experimental uncertainty, the values of the H- affini ties of the chlorosilyl ions Lie within 1.7 kcal mol-l of each other a nd decrease in the order SiH2Cl+ approximate to SiCl3+ > SiHCl2+. The disilylchloronium ion, (SiH3Cl+, is proposed to be an intermediate com plex in the reaction of SiH3+ with SiH3Cl. Here, (SiH3Cl+ is formed th rough the reaction of protonated SiH3Cl with SiH3Cl. It is stable at r oom temperature at least on the order of tenths of seconds. By use of previously reported thermochemical data, the ionization potential of S iH2Cl and the hydride affinity of SH2Cl+ are derived to be 7.66 +/- 0. 23 eV and 251.2 +/- 5.1 kcal mol(-1), respectively.