Thermochemistry of Silaethylene and Methylsilylene from Experiment and Theory

Article abstract of DOI:10.1021/ja00209a003

Fourier transform ion cyclotron resonance spectroscopy has been used to examine the deprotonation energetics of the methylsilyl cation, CH3SiD2⁺, to yield silaethylene and methylsilylene proton affinities of 205 +/- 3 and 215 +/- 4 kcal/mol, respectively.These values combined with the known heat of formation of methylsilyl cation, yield ΔH^o_{f 298}(CH2SiH2) = 43 +/- 3 kcal/mol and ΔH^o_{f 298}(CH3SiH) = 53 +/- 4 kcal/mol.These results are corroborated by ab initio generalized valence bond-configuration interaction calculations which indicate that silaethylene is more stable than methylsilylene by 11.6 kcal/mol, in excellent agreement with the experimental difference (10 +/- 3 kcal/mol).The adiabatic ionization potential of methylsilylene is calculated to be 8.22 eV, which is lower than the value of 8.85 eV determined for silaethyene using photoelectron spectroscopy.