Synthesis and catalytic applications of C1 symmetric group 4 ansa-metallocene complexes

The group 4 ansa-metallocene complexes with chiral substituent bearing cyclopentadienyl ligands, [M{Me2Si(η5-C5Me4)(η5-C5H3{CHRR′})}Cl2] (R = Pri, R′ = Me (9); R = Pri, R′ = Ph (10); R = But, R′ = Me (11); R = But, R′ = Ph (12); M = Zr (a), Hf (b)), were synthesized by the reaction of the dilithium compounds, Li2{Me2Si(C5Me4)(C5H3{CHRR′})} (R = Pri, R′ = Me (5); R = Pri, R′ = Ph (6); R = But, R′ = Me (7); R = But, R′ = Ph (8)), with the tetrachloride salts of the transition metal. The molecular structures of 11a and 12a have been determined by single-crystal X-ray diffraction studies. The catalytic behaviour of 9–12 in the polymerization of ethylene and propylene has been studied. Isotactic polypropylene with [mmmm] pentads of the order of 60% were obtained with the C1 symmetric ansa-zirconocene catalysts.

Graphical abstractThe preparation and characterization of new group 4 ansa-metallocene complexes containing chiral substituents and their role as catalysts in ethylene and propylene polymerization are described. Figure optionsDownload full-size imageDownload as PowerPoint slide