Synthesis of bis(1,2,3-substituted cyclopentadienyl)zirconium dichloride derivatives and their use in ethylene polymerization

Abstract

Catalytic Pauson–Khand reaction products with norbornadiene could be effectively transformed to trisubstituted cyclopentadienes, which have been used to synthesize a series of unbridged bis(1-R′-2-R-3-R′-trisubstituted cyclopentadienyl)zirconium dichlorides 3 (R=R′=Ph), 4(R=Ph, R′=Me), 21(R= n-Bu, R′=Me), 22(R= t-Bu, R′=Me), 23(R=(CH 2) 4OMe), R′=Me), and 24(R= n-Bu, R′=Ph). The crystal structure of 24 was determined by X-ray crystallography. These zirconium complexes in the presence of methylaluminoxane (MAO) show activities for the polymerization of ethylene. The activities are in the following order: 21> 4> 22∼ 23∼Cp 2ZrCl 2> 3∼ 24. The activity of 21 is four times higher than that of Cp 2ZrCl 2 under similar conditions.