Synthesis of the heptamethylbenzenium cation in zeolite-β:: in situ NMR and theory

We synthesized the heptamethylbenzenium cation on zeolite-beta by co-feeding excess methanol and benzene into a flow rector at 250 degreesC. Experimental isotropic (1)3C chemical shifts are in excellent agreement with theoretical (GIAO-MP2/tzp/dz) values calculated for the theoretical (B3LYP/6-311G*) structure of the cation. These results, along with a previous study of the pentamethylbenzenium cation on HZSM-5, afford an example of zeolite topology controlling the substitution pattern of persistent carbenium ions.