Metallocene analogues containing bulky heteroallylic ligands and their use as new olefin polymerization catalysts

Joachim Richter, Frank T. Edelmann, Mathias Noltemeyer, Hans Georg Schmidt, Michal Shmulinson, Moris S. Eisen

Research output: Contribution to journalArticlepeer-review

104 Scopus citations

Abstract

A series of Ti and Zr metallocene analogues containing bulky benzamidinate ligands has been prepared and fully characterized. Treatment of TiCl4(THF)2 or ZrCl4(THF)2 with two equivalents of the appropriate benzamidinate anions affords the bis(benzamidinato) complexes [C6H5C(NC3H7)2]2MCl2 (M=Ti (1), Zr (2)) and [C6H5C(NC6H11)2]2MCl2 (M = Ti (3), Zr (4)). The zirconium complex 2 was structurally characterized by X-ray diffraction. In a similar manner the nonafluoromesityl derivative [(CF3)3C6H2C(NC6H11)2]2ZrCl2 (5) was synthesized from ZrCl4(THF)2 and Li[(CF3)3C6H2C(NC6H11)2]. Methylation of 4 with methyllithium yields the dimethyl complex [C6H5C(NC6H11)2]2ZrMe2 (6). The mixed-ligand metallocene analogues [C6H5C(NC3HT7)2](C5Me5)MCl2 (M = Ti (7), Zr (8)) and [C6H5C(NC6H11)2](C5Me5)TiCl2 (9) have been prepared by reacting (C5Me5)TiCl3 or (Cs5Me5)ZrCl3 with one equivalent of a lithium N,N'-dialkytbenzamidinate. The polymerization of ethylene and propylene has been studied by the catalytic precatalyst complexes I and 2 upon reaction of an excess of methylalumoxane to obtain the active cationic complexes. The polymerization activity of the complexes is comparable to other benzamidinate ancillary containing ligands although toward shorter amounts of time due to a competitive inhibition presumably obtained by a β-hydrogen elimination from the ligand. Polymerization activity is strongly dependent on catalyst and cocatalyst concentrations and on temperature.

Original languageEnglish
Pages (from-to)149-162
Number of pages14
JournalJournal of Molecular Catalysis A: Chemical
Volume130
Issue number1-2
DOIs
StatePublished - 12 Mar 1998
Externally publishedYes

Keywords

  • Heteroallylic ligands
  • Metallocene analogues
  • Olefin polymerization
  • Zirconium complexes

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