Reactivity of zirconium complexes incorporating asymmetrically substituted ansa ligands and their use as catalysts in olefin polymerization.: X-ray crystal structures of [Me2Si(η5-C5Me4)(η5-C5H3R)]ZrCl2 (R = Et, iPr)

The synthesis and use of the ansa-zirconocene complexes [Me2Si(eta(5)-C5Me4)(eta(5)-C5H3R)]ZrCl2 (R = H (5), Me (6), Et (7), Pr-i (8), Bu-t (9), SiMe3 (10)) as catalysts in the polymerization of ethylene and propylene has been studied. The alkyl complexes [Me2Si(eta(5)-C5Me4)(eta(5)-C5H3R)]-ZrMe2 (R = H (11), Me (12), Et (13), Pr-i (14), Bu-t (15), SiMe3 (16)) have also been prepared. The reaction of 11-16 with B(C6F5)(3) gave the cationic species [{Me2Si(eta(5)-C5Me4)(eta(5)-C5H3R)}-ZrMe](+) (R = H (17), Me (18), Et (19), Pr-i (20), Bu-t (21), SiMe3 (22)). In the absence of cocatalyst, 17-22 have been shown to act as catalysts in the polymerization of ethylene. The molecular structures of 7 and 8 have been determined by single-crystal X-ray diffraction studies.