ELECTRON-SPIN RESONANCE STUDIES OF ARYL-SUBSTITUTED CYCLOPOLYSILANE ANION-RADICALS

Several aryl-substituted cyclopolysilanes have been reduced to anion-radicals and have been studied by ESR spectroscopy. Compounds investigated were Si5Me9X (X phenyl, biphenyl, p-Me3SiC6H4, p-MeC6H4) and p-MeC6H4) and Si5Me9SiMe2X (X phenyl, p-Me3SiC6H4 and p-Me2NC6H4). The species have ESR spectra typical of delocalized cyclopentasilane anion-radicals except for biphenylnonamethylcyclopentasilane, which gives an ESR pattern indicating that the unpaired electron is mainly associated with the biphenyl ring system. An analysis of 1H and 13C hyperfine coupling constants for Si5Me9X-. suggests that the principal effect of the aryl substituents is inductive. The anion-radicals of Si5Me9SiMe2X decay to Si5Me9H-., and the electronic nature of the aryl substituent has no major effect on the stability of the parent radical. © 1979.