Interaction between Cationic Zirconium Alkyl Complexes and Fluorine-Substituted BPh4 Anions in Ion-Pair Metallocene Catalyst Systems

Abstract

Stability of various fluorinated BPh⁴ anions in ion-pair metallocene catalyst systems has been studied. XPS measurement shows that the incorporation of electron-withdrawing fluorine substiuents decreases the electron density of boron drastically. The anions can be classified into three types according to the reactivity associated with its Lewis basisity, i. e., the number of fluorine substituents: (1) the anion without any fluorine substituent that reacts with Cp₂ZrR with phenyl group transfer, (2) those with 1-3 fluorine substituents that react with trialkyl aluminium, and (3) those with 4 and 5 fluorine substituents that undergo no side reactions. Practically, the stability of the anion is one of the most important requirements for the application of the ion-pair (non-MAO) metallocene catalyst.