Phenylfluorenyl cation

The following represent the resonance forms of the phenylfluorenyl cation ... 

Of the 16 resonance forms of the triphenylmethyl cation shown in the solution for Problem 3(g), no two resonance forms place the positive charge on adjacent atoms. However, when looking at the 16 resonance forms of the phenylfluorenyl cation shown in the solution for Problem 3(h), there are multiple pairs of resonance forms (one of which is shown below) where the positive charge may be placed on adjacent atoms. This is a disfavored electronic relationship and is destabilizing to the cation itself. Thus, through charge distribution and delocalization, because the phenylfluorenyl cation possesses partial positive charges on two adjacent atoms, the triphenylmethyl cation [Problem 3(g)] is more stable. 

In the cationic polymerisation of a-methylstyrene by trityl salts the 9-phenylfluorenyl cation is the major product... 

In weaker acid systems, other reactions involving the triplet state supervene to the exclusion of dimerization. Photolysis of 85 in 3-3% sulfuric acid, 96-5% acetic acid, and 0-2% water gave as products tri-phenylmethane (93), 9-phenylfluorene (94), 6is-9-phenylfluorenyl peroxide (95) and benzophenone (96). When benzene was present, tetra-phenylmethane (97) was also formed in addition to the other products. When the triphenylmethyl cation is irradiated in 3-3% H2SO4, 80 1% HOAc, 16-4% toluene, and 0-2% H2O, the products observed were... 

Apparently 9-phenylfluorenyl is not only a good anion but also a bad cation. The chloride probably shares in some of the resonance stabilization of the anion while the cation does not. Another example of a connection between the resonance of an anion and the properties of a related covalent compound is provided by the hydrocarbon triphenyl-methylcyclopentadiene, which has an unusually high dipole moment although it does not conduct in liquid sulfur dioxide.180... 

Cozens and co-workers found that the xanthyl cation was spontaneously generated by adsorption of 9-xanthenoI within several acidic zeolites [33]. The cation was characterized spectroscopically and was found to be stable over a long period of time. Diffuse reflectance spectra of the zeolite composites exhibited absorption bands similar to those for the xanthyl cation in solution [10]. Fluorescence spectra also corresponded to cation solution spectra. The 9-phenylxanthyl, 9-phenylfluorenyl, and triphenylmethyl carbocations are similarly formed and readily detectable on dry montmorillonite clay minerals [34]. 

In perchloro-9-phenylfluorenyl radical, anion and cation, the great steric repulsions between the two 9-phenyl o-chlorine pairs and the fluorene 1- and... 

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