Identifying the origins of why catalysts fail to achieve high active-site counts is critical, especially for commercial polymerization catalysts such as (pyridylamido)hafnium olefin polymerization catalysts. Recently, it was experimentally reported that only 50% of the trityl-activated (pyridylamido)hafnium catalyst (L(R1R2)Hf(Me)2, R1 = 2-iPr-Ph, R2 = H) is active in the homopolymerization of 1-octene. Why is this the case? This presentation will show how the counteranion-catalyst interactions are responsible for deactivating one catalyst diastereomer over the other. Extensive sampling of the ion pair with molecular dynamics simulations reveals distinct preferred counteranion orientations, which are differentiated by the location of the bridgehead substituent. Olefin monomers will be shown to insert preferentially to one, but not the other, of the two potentially active catalysts. The free energy of these processes will be linked to the conformational flexibility of the diastereomers, giving new physical insight into design principles for highly active polymerization catalysts.

Elucidating the dynamic role of the counteranion in olefin polymerization catalysis

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.