A catalyst system comprising (i) a bulky ligand catalyst compound; and (ii) a novel borate activator is active for olefin polymerization. The novel borate contains at least one chelating (divalent) ligand and contains at least one fluorine atom. Preferred borate activators are provided as anilinium or carbonium salts. Highly preferred borate salts contain two perfluorinated alkoxy chelating ligands. The catalyst system may be used to produce polyethylene for "end use" applications such as polyethylene film and molded polyethylene goods.