Generation of perfluorinated 1-alkylbenzocyclobuten-1-yl and 1-alkylindan-1-yl cations. On paradoxical stabilizing influence of an electron-withdrawing perfluoroisopropyl group on the relative stabilities of the cations

Abstract

When perfluoro-1-alkylbenzocyclobutenes and -indanes were dissolved in an excess of SbF5, perfluorinated alkylbenzocycloalken-1-yl cations containing a fluorine atom or a perfluoroalkyl group in the cationic centre were generated. Contrary to expectations, a number of stable long‐lived perfluoro-1-isopropylbenzocycloalken-1-yl cations containing an electron-withdrawing perfluoroisopropyl group in the cationic centre have been obtained. The DFT (B3LYP/6-31G*) calculations showed that the relative stabilities of isomeric cations containing a fluorine atom or a perfluoroalkyl group in the cationic centre change in favor of cations containing a perfluoroalkyl group in the cationic center when going from a CF3 to a CF(CF3)2 group.This is in accordance with the experimental data.