A STUDY ON THE REDUCING ABILITIES OF TRIS(ALKYLTHIO)SILANES

Tris(methylthio)silane and tris(isopropylthio)silane effectively reduce a variety of organic substrates via free radical mechanisms. These silanes can also be used as hydrosilylating agents for alkenes having electron-donating substituents. The bond dissociation energy of the Si-H bonds have been measured by photoacoustic calorimetry and found to be around 83 kcal mol-1. The absolute rate constants for the reaction of the tert-butoxyl radical with (RS)3SiH have been measured by a laser flash photolysis technique and the optical absorption spectra of the corresponding radicals have been obtained. Multiple scattering X(alpha) calculations showed that the dominant absorption detected in the UV-vis region was due to sigma(Si-S)(e) --> SOMO and SOMO --> sigma*(Si-S)(e) transitions.