Half-sandwich β-diketonato complexes of zirconium and their application as catalysts to ethylene polymerization

The bis(β-diketonato) Zr complexes CpZr(acac)2Cl (acac = acetylacetonato) (1) and Cp*Zr(acac)2Cl (2) can be synthesized by the reac-tion of Cp′ZrCl3(Cp′ = Cp or Cp*) with 2 equiv of lith-ium acetylacetonate. CpZr(acac)2Cl (1) can be quan-titatively prepared by treatment of Cp2ZrCl2 with ex-cess acetylacetone. The tris(β-diketonato) Zr com-plex CpZr(tfac)3 (tfac = trisfluoroacetylacetonato) (3) has been prepared by treatment of CpZrCl3 with so-dium trisfluoroacetylacetonate. The replacement of both chlorine atoms and one Cp group from zir-conocene dichloride by nonfluorinated diketone,acetylacetone,readily occurs at room temperature in triethylamine medium,offering the tris(β-diketonato) Zr complex CpZr(acac)3 (4). The complexes were characterized by 1H NMR spectroscopic methods. In addition,the molecular structures of complexes 3 and 4 have been determined by X-ray diffraction methods. When activated by excess methylaluminoxane (MAO),these complexes were active for ethylene polymerization,offering polyethylenes with high mo-lecular weights and narrow molecular weight distribu-tions. Complex 4 showed a very high ethylene po-lymerization activity of up to 7100 kg PE/mol Zr·h at 5 atm. Complexes 1 and 2 were also active for ethyl-ene/1-hexene copolymerization.

Half-sandwich β-diketonato complexes of zirconium and their application as catalysts to ethylene polymerization

The bis(β-diketonato) Zr complexes CpZr(acac)₂Cl (acac = acetylacetonato) (1) and Cp*Zr(acac)₂Cl (2) can be synthesized by the reaction of Cp′ZrCl₃(Cp′ = Cp or Cp*) with 2 equiv of lithium acetylacetonate. CpZr(acac)₂Cl (1) can be quantitatively prepared by treatment of Cp₂ZrCl₂ with excess acetylacetone. The tris(β-diketonato) Zr complex CpZr(tfac)₃ (tfac = trisfluoroacetylacetonato) (3) has been prepared by treatment of CpZrCl₃ with sodium trisfluoroacetylacetonate. The replacement of both chlorine atoms and one Cp group from zirconocene dichloride by nonfluorinated diketone, acetylacetone, readily occurs at room temperature in triethylamine medium, offering the tris(β-diketonato) Zr complex CpZr(acac)₃ (4). The complexes were characterized by ¹H NMR spectroscopic methods. In addition, the molecular structures of complexes 3 and 4 have been determined by X-ray diffraction methods. When activated by excess methylaluminoxane (MAO), these complexes were active for ethylene polymerization, offering polyethylenes with high molecular weights and narrow molecular weight distributions. Complex 4 showed a very high ethylene polymerization activity of up to 7100 kg PE/mol Zr·h at 5 atm. Complexes 1 and 2 were also active for ethylene/1-hexene copolymerization.