Synthesis and Reactivity of the Methylene Arenium Form of a Benzyl Cation, Stabilized by Complexation

Benzyl cations are unstable intermediates involved in various chemical and biological processes. Two extreme resonance forms of these cations include positive charge localization at the methylene carbon or delocalization in the ring, the latter, nonaromatic form, termed “methylene arenium”. The preparation of the discrete methylene arenium compound, stabilized by coordination to a metal (palladium) center, is described. It was fully characterized, including by X-ray diffraction. Reactivity patterns, resulting from charge distribution in the ring, were observed. Upon controlled release of the methylene arenium compound into solution, it demonstrates aromatic benzyl cation reactivity.