Disclosed are polymerization catalyst activator complexes prepared from the reaction of a carbenium salt and Lewis base containing an aromatic group. Also disclosed are polymerization catalyst activator complexes prepared via the reaction of a Group 13 element containing salt including a Lewis base containing an aromatic group and a tritylhalide compound. Also disclosed are polymerization catalyst systems including the activator complex of the invention, and processes for polymerizing olefin(s) utilizing same.