Synthesis and characterization of alkenyl and alkyl substituted group 4 metallocene dichloride complexes: Applications in ethylene polymerization

The alkenyl substituted zirconocene complexes, [Zr(η5-C5H4{CMeRCH2CH2CH = CMe2})2Cl2] (R = Me (1), Ph (2) were prepared from the reaction of the lithium derivative Li(C5H4{CMeRCH2CH2CH = CMe2}) (R = Me, Ph) with zirconium tetrachloride. The bulky alkyl substituted cyclopentadienyl ligand precursor was prepared as its fulvene derivative (C5H4) = CMeCH2CHMe2 (3) via the reaction of cyclopentadiene with 4-methyl-2-pentanone and then converted to Li(C5H4{CMe2CH2CHMe2}) (4) via nucleophilic attack of LiMe. The reaction of 4 with [TiCl4(THF)2] and ZrCl4 gave the metallocene complexes [M(η5-C5H4{CMe2CH2CHMe2})2Cl2] (M = Ti (5), Zr (6)), respectively. The ansa-ligand precursor, SiMe2(C5HMe4)(C5H4{CMe2CH2CHMe2}) (7), was prepared via the reaction of 4 with SiMe2(C5HMe4)Cl and subsequently converted to its dilithium derivate, Li2(Me2Si(C5Me4)(C5H3{CMe2CH2CHMe2})) (8), using n-butyllithium. The ansa-zirconocene complex, [Zr{Me2Si(η5-C5Me4)(η5-C5H3{CMe2CH2CHMe2})}Cl2] (9), was synthesized by the reaction of 8 with zirconium tetrachloride. Compounds 1–9 were characterized by 1H and 13C{1H} NMR spectroscopy. In addition, the molecular structures of 5, 6 and 9 were determined by single crystal X-ray diffraction studies. The metallocene complexes have been tested as catalyst (with co-catalyst MAO) in the polymerization of ethylene where the substituents on the cyclopentadienyl ligand have a direct influence on the catalytic activity.