2‑Methoxyethylamino-bis(phenolate)yttrium Catalysts for the Synthesis of Highly Isotactic Poly(2-vinylpyridine) by Rare-Earth Metal-Mediated Group Transfer Polymerization

Highly isotactic poly­(2-vinylpyridine) (P2VP) was synthesized by the group transfer polymerization of the prochiral 2-vinylpyridine (2VP) with 2-methoxyethylamino­bis­(phenolate)yttrium complexes. Isotacticities of up to P_m = 0.92, narrow molecular weight distributions, and high molecular weights were achieved by steric modifications of the variable bisphenolate ligand structure. The resulting polymer samples were characterized by thermoanalysis (DSC, TGA), GPC, and ¹³C NMR. The origin of the isotactic microstructure was attributed to an enantiomorphic site control mechanism based on ¹³C NMR mechanistic studies and allowed new insights into ¹³C pentad assignments.