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More than 100 years after the cyclopentadienyl anion appeared in the literature, the first cyclopentadienyl cation, the pentamethyl derivative C5Me5+, has now been prepared in a single step as the tetrakis(pentafluorophenyl)borate salt. This material is crystalline and stable at room temperature for weeks. The crystal structure of C5Me5+ (see picture) reveals localized bonding.
Lambert et al. (Mon,) studied this question.
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