ALPHA-SILYL-SUBSTITUENT STABILIZATION OF CARBANIONS AND SILYL ANIONS

The electron affinities for a series of cr-silyl-substituted silyl and carbon radicals have been measured. These electron affinities (kcal/mol) include the following: EA((Me(3)Si)(2)CH) = 36.0 +/- 0.2, EA(Me(2)HSiSiMe(2)) = 32.3 +/- 0.8, EA((Me(3)Si)(2)SiH) = 44.7 +/- 1.9, and EA((Me(3)Si)(3)Si) = 46.8 +/- 2.0. The electron affinity of the dimethylsilyl radical was also determined to be 24.7 +/- 0.5 kcal/mol. From these electron affinities and the bond dissociation energies, we derive the gas-phase acidities for these compounds. These quantities allow us to compare the stabilization in carbon and silyl anions by or-silyl groups. Ab initio calculations aid in understanding the stabilization mechanism.