Novel diphenyl thioether-bridged binuclear metallocenes of Ti and Zr for synthesis of polyethylene with broad molecular weight distribution
Abstract
Two diphenyl thioether-bridged binuclear metallocenes of Ti and Zr, [(C5H5)Cl2MC5H4CH2(p-C6H4)]2S [M = Ti (1) and Zr (2)], have been synthesized by treating the dilithium salts of the corresponding ligand [(C5H5CH2(p-C6H4)]2S with two equivalents of C5H5TiCl3 and C5H5ZrCl3(DME), respectively, in toluene at 0°C. Both new complexes have been characterized by 1H-NMR spectroscopy and elemental analysis. Homogeneous ethylene polymerization using both complexes was performed in the presence of methylaluminoxane (MAO). The influences of molar ratio of [MAO]/[Cat], concentration of the catalysts, time, and temperature have been studied systematically. The catalytic activity of 1 is higher than that of the corresponding oxygen-bridged catalyst [(C5H5)Cl2TiC5H4CH2(p-C6H4)]2O. The catalytic activity of 2 is at least two times higher than that of 1 under any tested polymerization conditions. The melting points of polyethylene (PE) produced by 1 and 2 are higher than 130°C, indicating a highly linear and highly crystalline PE. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
