Highly Isospecific Polymerization of Ortho-Methoxystyrene and Its Derivatives by Bis(aminophenyl)amido-Pincer Rare-Earth Metal Catalysts.

The highly isoselective polymerization of styrenyl monomers is highly desired but faces great challenge, partly because of the limited optional items in the catalyst toolbox. In this study, we synthesized a series of bis(aminophenyl)amido-pincer yttrium and lutetium complexes, and upon activation with a borate, these complexes exhibited high isoselectivity (>99% mmmm) in the polymerization of ortho-methoxystyrene (oMOS) with a notable polar group activation effect. Additionally, these catalytic systems efficiently polymerized oMOS derivatives containing fluoro- and methoxy groups, yielding the corresponding highly isospecific (>99% mmmm) polymers. Density functional theory (DFT) calculations indicated that the C2 symmetry of the ligand skeleton plays a critical role in the lutetium-catalyzed highly isoselective polymerization of oMOS. The resultant polymers can serve as effective building blocks for the synthesis of isotactic polystyrene derivatives.