(HEXAPHENYLTRIMETHYLENE)METHANE DICATION AND RELATED CARBOCATIONS

By ionization of the respective alkenediol (8a), the (hexaphenyltrimet hylene)methane dication (2) has been prepared and found stable in solu tion under superacidic stable ion conditions (FSO3H/SO2ClF) up to at l east -20 degrees C. The spectroscopic data and AM1 theoretical modelin g indicate that although the entire pi-system is twisted, phenyl group s stabilize the positive charges in 2 to a similar degree as those in the trityl cation. The hexa-p-CF3 derivative of 2 was also observable but only at very low temperatures (-90 degrees C). Disruption of the 3 -fold symmetry and reduction of the number of stabilizing phenyl rings even to five resulted in intramolecular allylation and subsequent for mation of the corresponding indenyl cations. In all the cases studied no evidence for ''Y-aromatic'' stabilization was found.