The new, bright red compounds [DBS][B(C6F5)4], [DBS][BCl(C6F5)3], [DBS][B(C6F5)3–OH⋯H2O–B(C6F5)3] and [DBS][B(CH2CMe3)(C6F5)3] (DBS = C15H11, dibenzosuberenyl, dibenzotropylium, dibenzo[a,e]tropylium or dibenzo[a,d]cycloheptenocarbonium) have been synthesized and characterized spectroscopically and, except for [DBS][B(CH2CMe3)(C6F5)3], crystallographically. The crystal structures show that the DBS+ carbocation is planar and suggest pronounced delocalization of the positive charge over part of the seven-membered ring, in particular the CH carbon and the carbon atoms α and β to it. The electrophilic DBS+ carbocation activates alkene polymerization catalyst precursors of the type Cp′2ZrMe2, its efficacy being comparable to that of the well known but sterically more hindered trityl carbocation, Ph3C+. As with the Ph3C+ ion, DBS+ does not initiate carbocationic polymerization of isobutene in dichloromethane directly, but rather by reacting with trace amounts of water to generate protons.
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