Synthesis of chiral unbridged zirconocene complexes: Applications in the polymerization of ethylene and propylene

The lithium derivatives of the chiral substituent bearing cyclopentadienyl ligands, Li{C5H4(CHRR′)} (R = Pri, R′ = Me (1); R = Pri, R′ = Ph (2); R = But, R′ = Me (3); R = But, R′ = Ph (4)), were prepared via the reaction of alkyllithium compounds with the corresponding fulvene reagent. The mixed cyclopentadienyl zirconocene complexes [Zr(η5-C5H5)(η5-C5H4{CHRR′})Cl2] (R = Pri, R′ = Me (5); R = Pri, R′ = Ph (6); R = But, R′ = Me (7); R = But, R′ = Ph (8)) were prepared via the reaction of the lithium precursors 1–4 with [Zr(η5-C5H5)Cl3]. The symmetrical zirconocene complexes, [Zr(η5-C5H4{CHRR′})2Cl2] (R = Pri, R′ = Me (9); R = Pri, R′ = Ph (10); R = But, R′ = Me (11); R = But, R′ = Ph (12)), were synthesized from the reaction of two molar equivalents of 1–4 with ZrCl4. When the mono(cyclopentadienyl) complexes [Zr(η5-C5H4{CHRR′})Cl3] (R = Pri, R′ = Me (17); R = Pri, R′ = Ph (18); R = But, R′ = Me (19); R = But, R′ = Ph (20)) were reacted with Li(C9H7) the zirconocene derivatives, [Zr(η5-C9H7)(η5-C5H4{CHRR′})Cl2] (R = Pri, R′ = Me (21); R = Pri, R′ = Ph (22); R = But, R′ = Me (23); R = But, R′ = Ph (24)), were obtained. The molecular structure of 11 has been determined by single-crystal X-ray diffraction studies. 5–12 and 21–24 have been tested as catalysts in the polymerization of ethylene and propylene. Isotactic polypropylene with [mmmm] pentads between 20 and 40% were obtained and their tacticity can be related directly to the structure of the catalyst.

The preparation and characterization of new unbridged zirconocene complexes containing chiral substituents and their catalytic activity and selectivity in the polymerization of ethylene and propylene are described. Figure optionsDownload as PowerPoint slide