Allyl Radical Nature of a Phenylcyclopentadienyl Radical Annelated with Two Homoadamantene Frameworks

1-Phenylcyclopentadiene fused with two homoadamantene units at the 2,3- and 4,5-positions (4) was deprotonated with KH to lead to the quantitative formation of the corresponding cyclopentadienyl (Cp) anion 3–. This anion was oxidized by AgCl to afford an orange crystalline solid consisting of Cp radical 3• and cyclopentadiene 4. The ESR spectrum in hexane exhibited approximately 15 lines, demonstrating that the two homoadamantene frameworks were equivalent and that the C1–C2(Ph)–C3 moiety of the five-membered ring formed a symmetrical allyl-like radical in agreement with the prediction by DFT calculation. The reaction of the Cp radical 3• with an oxygen molecule in the presence of Ag+SbF6– afforded the SbF6– salt of a phenylpyrylium ion annelated with two homoadamantene frameworks (8+SbF6–).