Synthesis and ethylene polymerization behavior of {MeB(3-Ph-pyrazolyl)3}TiCl3 |
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Authors: | Changle Chen |
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Institution: | Department of Chemistry, The University of Chicago, 5735 South Ellis Avenue, Chicago, IL 60637, USA |
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Abstract: | The new methyl-tris(pyrazolyl)borate reagents LiMeTpPh] (1) MeTpPh]− = MeB(3-Ph-pyrazolyl)3−) and TlMeTpPh] (2) react with TiCl4 to afford (MeTpPh)TiCl3 (3) in 77% and 81% yield respectively. 2 reacts with ZrCl4 and HfCl4 to yield mixtures of products. The reaction of 1 with TiCl3(THF)3 proceeds with B-N bond cleavage to afford TiCl3(3-Ph-pyrazole)(THF)2 as the major product (30%). The reaction of 3 with MeLi (3 equiv) yields 1 (60%) and reduced Ti species, via apparent displacement of MeTpPh]− and generation of unstable TiCl4Me4−x species. Under MAO activation conditions (MAO = methylalumoxane), 3 polymerizes ethylene to linear polyethylene. 3/MAO is significantly more active in ethylene polymerization than the hydrido-tris(pyrazolyl)borate analogue {HB(3-Ph-pyrazolyl)3}TiCl3/MAO. |
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Keywords: | tris(pyrazolyl)borate methyl-tris(pyrazolyl)borate methyl-tris(3-Ph-pyrazolyl)borate titanium ethylene polymerization |
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