Journal of Molecular Catalysis A-Chemical, Vol.208, No.1-2, 73-81, 2004
Tritylpyridinium tetrakis(pentafluorophenyl)borate as an efficient activator for "constrained-geometry'' catalysts in ethylene polymerization
Ethylene polymerization with linked amido-cyclopentadienyl or "constrained-geometry" titanium catalysts, Ti(eta(5):eta(1)-(C5Me4SiMe2NBu)-Bu-t)X-2 (X = Me, Bz, Cl), activated by tritylpyridinium tetrakis(entafluorophenyl)borate, [Ph3C(NC5H5)] [B(C6F5)(4)], and silica-supported tritylpyridinium tetrakis(entafluorophenyl)borate (PySTB) was found to proceed with high activity. H-1 NMR spectra in CD2Cl2 suggest that ([Ti(eta(5):eta(1)-(CMe4)-Me-5,(SiMe2NBu)-Bu-t)Me (NC5H5)](+) is formed as the main cationic species. Using the heterogeneous cocatalyst PySTB in hexane, unexpectedly high ethylene polymerization activity was achieved, giving high molecular weight polyethylenes with excellent morphology and high bulk density (up to 0.46 g/cm(3)). (C) 2003 Elsevier B.V. All rights reserved.