ABSTRACT
At room temperature in the presence of Na+ cations, the rearranging dianion is formed via homogeneous disporportionation, thermodynamically favored by ion pairing and kinetically supported by the fast follow-up reaction. When ion pairing is suppressed by application of low temperatures or the addition of sodium complexing 15-crown-5, the anion radical becomes persistent and the reactive dianion species has to be generated via heterogeneous ET at much more negative potentials. The same results are obtained when the bulky tetrabutylammonium ion is used as counterion [230]. Replacing 1,1,3-triphenylindene with l-methyl-1-phenylindene or 1,2-dihydro-l, 1 '-spiribiindene, the anion radical undergoes a quite unusual cleavage of the alkyl-aryl bond, whereas the dianion rearranges in the same manner as triphenylindcne [231 }.
