AN ELECTRON-SPIN-RESONANCE STUDY OF SILACYCLOPENTYL AND RELATED RADICALS

Silacyclopentyl radicals, prepared by γ-irradiation of silacyclopentane in an adamantane matrix, exist at low temperatures in two equivalent twist conformations, which interconvert at higher temperatures. The temperature variation of the ESR spectrum gives the barrier to interconversion as 21.3 kJ mol-1. Reversible hydrogen exchange with [ 2H]16adamantane takes place near room temperature but not at lower temperatures. 1-Methylsilacyclopentyl in solution or in adamantane appears to be similar, to silacyclopentyl at high temperatures, but there is some evidence that an envelope conformation may be preferred. 1-Deuteriosilacyclopentyl, 1-chlorosilacyclopentyl and 3,3-dichloro-3- silacyclopentyl radicals have also been studied.