Weakly Coordinating Cations as Alternatives to Weakly Coordinating Anions

Abstract

Big is beautiful: Activation of fluorenyl-based zirconocenes with methylaluminoxane (MAO) effects a red shift in the visible λmax proportional to the size of the metallocene (see potential energy surfaces in picture). Polymerization activities correlate directly with color (λmax), suggesting that bulky zirconocenium catalysts are weakly coordinating cations which, like weakly coordinating anions, diminish cation–anion interactions.