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^–).