An ESR Study of a Tetrasilaspirobiindane Anion Radical. Stereoelectronic ElectronAccepting Effects of Trialkylsilyl Groups

ESR spectra of a tetrasilaspirobiindane anion radical (1) showed a doublet of doublet hfs pattern at low temperatures and significant line-width alternation, indicating that there is remarkable difference in the electron-accepting effects between two silyl substituents at the benzene ring with the unpaired electron due to the ring conformation.