Isotactic-specific polymerization of propene by a Cs-symmetric zirconium(IV) complex bearing a dianionic tridentate [-NNN-] amidomethylpyrrolidepyridine ligand

The synthesis and characterization of a new tridentate amidomethylpyrrolidepyridine ligand (LigH2) and of the corresponding LigZr(NMe2)2 complex (1) are described. Characterization of 1 by singlecrystal X-ray diffraction analysis showed a slightly distorted square-pyramidal geometry. Variable-temperature NMR analysis suggested that 1 adopts a Cs-symmetric structure in solution. Complex 1 in combination with AliBu2H and methylalumoxane afforded a highly active single-site catalyst for the polymerization of ethylene and propene, producing ultrahigh molecular weight linear polyethylene and isotactic polypropylene via an “enantiomorphic sites” mechanism of steric control.