Cyclic polysilanes : XIX. A temperature study of redistribution equilibria between permethylcyclopolysilanes

Abstract

Equilibria among the cyclic compounds (Me 2Si) n where n = 5, 6 and 7 have been studied between 30–58°C. Thermodynamic values for the redistribution reactions between pairs of compounds are, for n = 5 → 6, Δ H = −18 kcal/mole, Δ S = −20 cal/deg. mole; for n = 7 → 6, Δ H −3, Δ S +33; for n = 7 → 5, Δ H +18, Δ S + 51. The enthalpies indicate that the stabilities of the rings increase in the order (Me 2Si) 5 < (Me 2Si) 7 < (Me 2Si) 6. The differences are smaller than corresponding differences among the cycloalkanes, probably because the silicon compounds are less affected by steric repulsions and angle strain.