Low-Temperature Kinetic NMR Studies on the Insertion of a Single Olefin Molecule into a Zr—C Bond: Assessing the Counterion-Solvent Interplay

摘要

The insertion of an olefin molecule into a metal-carbon bond is the fundamental step of Ziegler-Natta olefin polymerization that occurs, in homogeneous phase, through the initial association of an olefin molecule with a metal cation of the catalytic ion pair. Not surprisingly, the insertion reaction is strongly affected by the counterion and solvent, the interplay of which determines the type of ion pair. "Sticky" counterions and low polar solvents favor inner sphere ion pairs (ISIPs), where the counterion is located in the first coordination sphere of the catalyst, whereas weakly coordinating counterions and more polar and coordinating solvents lead to outer sphere ion pairs (OSIPs), where the counterion is located in the second coordination sphere.