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Octahedral Group 4 Metal Complexes That Contain Amine, Amido, and Aminopyridinato Ligands:  Synthesis, Structure, and Application in α-Olefin Oligo- and Polymerization

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journal contribution
posted on 06.11.1996, 00:00 by Hans Fuhrmann, Simon Brenner, Perdita Arndt, Rhett Kempe
The reaction of trimethylsilyl-substituted 2-aminopyridines with mixed chloro(dialkylamido)metal complexes (titanium and zirconium) leads via amine elimination to octahedral group 4 metal complexes that contain amine, amido, and aminopyridinato ligands. The X-ray crystal structure analyses of (4-Me-TMS-APy)(NMe2)(HNMe2)TiCl2 (1) (crystallographic data:  P21/c (No. 14), monoclinic, a = 16.754(2) Å, b = 14.395(2) Å, c = 17.890(3) Å, β = 110.28(1)°, Z = 8) and (6-Me-TMS-APy)(NEt2)(HNEt2)ZrCl2 (2) (crystallographic data:  P21/n (No. 14) monoclinic, a = 10.125(1) Å, b = 16.331(1) Å, c = 15.276(2) Å, β = 93.90(1), Z = 4) prove the compounds to be mononuclear with a cisoid arrangement of the two chloro ligands embedded in a reactive pocket determined by the steric demand of the three nitrogen containing ligands. Oligo- and polymerization studies with propene and 1-butene reveal the following results. First, 1 is a remarkably active precatalyst in contrast to the very low activity of 2. Second, MAO, a 1:1 mixture of i-Bu3Al/B(C6F5)3 (homogeneous polymerization) and ethylaluminum sesquichloride (if 1 is incorporated in a MgCl2-matrix) have shown to be the most active cocatalysts. Third, the polymers and oligomers are atactic.