Arrhenius parameters for the system (CH&Si + D2⇄(CH3)3SiD + D. The (CH3)3Si - D Bond dissociation energy

Abstract

Quantitative investigation in silicon chemistry are handicapped by a lack of reliable bond dissociation energy values, but a few of these data have recently been obtained with chemical accuracy. Walsh and his group used Benson's iodination technique to determine the Si - H bond dissociation energy in trimethylsilane H;((CH,),Si - H) = 378 f 6 kJ mol-1. Davidson and coworkers have determined the Si - C and Si - Si bond dissociation energy in tetramethylsilane and hexamethyldisilane, obtaining 355 * 6 and 337 & 4 kJ mol-', respectively. Electron impact measurements on numerous silicon compounds including the series (CH,),Si - X (X = H, CH,, (CH,),Si) have been combined with a thermochemical bond energy scheme to give Hi((CH,),Si-H) = 372 ? 17, @((CH,),Si - CH,) = 355 f 17, H;((CH,),Si - Si(CH,),) = 313 f 35 kJ mol-' in reasonable agreement with the thermochemical and kinetic values quoted above. Earlier electron impact studies gave appearance potentials in generally good agreement with those in, discrepancies in the reported values of bond dissociation energies arising not from the basic experimental data but from erroneous ancillary data used to calculate the bond dissociation energies from the electron impact results.