Half-zirconocene anilide complexes: synthesis, characterization and catalytic properties for ethylene polymerization and copolymerization with 1-hexene

A number of half-zirconocene anilide complexes of the type Cp*ZrCl2[N(2,6-(R2C6H3)-C-1)R-2] [R-1 = Pr-i (1, 3), Me (2); R-2 = Me (1, 2), Bn (3)] and Cp*ZrCl[N(2,6-Me2C6H3)Me](2) (4) (Cp* = pentamethylcyclopentadienyl) were synthesized from the reactions of Cp*ZrCl3 with the lithium salts of the corresponding anilide in diethyl ether at room temperature. All new zirconium complexes were characterized by H-1 and C-13 NMR and elemental analysis. Molecular structures of complexes 1, 2 and 4 were determined by single crystal X-ray diffraction analysis. Upon activation with Al'Bu-3 and Ph3CB(C6F5)(4), complexes 1-4 exhibit good catalytic activity for ethylene polymerization, and produce polyethylene with a moderate molecular weight. Among these zirconium complexes, complex 1 shows the highest catalytic activity while complex 4 shows the lowest catalytic activity for ethylene polymerization. Complexes 1-3 also exhibit moderate catalytic activity for copolymerization of ethylene with 1-hexene, and produce copolymers with relatively high molecular weight and reasonable 1-hexene incorporation. In addition, the activation procedure of these catalyst systems were studied by H-1 NMR spectroscopy.