Selectivity in propylene polymerization with group 4 Cp-amido catalysts

Article abstract of DOI:10.1021/om9609628

Mono-Cp-amido complexes [η⁵:η¹-Cp′SiMe₂(NR)]MCl ₂ (M=Ti, Zr) have been synthesized by metathesis and amine elimination routes in low to moderate yields (5-50%). Two optically active examples based on (S)-(-)-(α)-methylbenzylamine are presented, and the molecular structure of (+)-(R)-[η⁵:η¹-(Ind)SiMe ₂-(S)-NCHMePh]TiCl₂ (4) has been determined by X-ray crystallography. These complexes are active in the presence of methylaluminoxane for propylene polymerization and yield high molecular weight atactic polymers with slight syndiotactic enrichment. Productivities, molecular weights, and tacticities are dependent on Cp′ and NR. Incorporation of a chiral amine into the ligand framework has little effect on stereospecificity. Polypropylenes derived from the titanium catalysts show significant amounts of 2,1-monomer insertion (2-5%).