Ligand Coordination Driven by Monomer and Polymer Chain: The Intriguing Case of Salalen–Ti Catalyst for Propene Polymerization

Salalen−Ti systems for propene polymerization catalysis were originally developed under the assumption of a “directional site epimerization promoted electronically” strategy and allowed the synthesis of polypropylene samples with extraordinarily high isotacticities. Our DFT calculations revealed an alternative and more intriguing interpretation of polymerization behavior of such systems. Ligand coordination around the metal center driven by the monomer and the polymer chain dictates the formation of active species different from the ones expected from X-ray structures of precursors. The “synergic” role of R1 and R3 substituents is responsible of the extraordinarily high isotacticities reported in propene polymerization.