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

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)(NMe(2))(HNMe(2))TiCl(2) (1) (crystallographic data: P2(1)/c (No. 14), monoclinic, a = 16.754(2) Å, b = 14.395(2) Å, c = 17.890(3) Å, beta = 110.28(1) degrees, Z = 8) and (6-Me-TMS-APy)(NEt(2))(HNEt(2))ZrCl(2) (2) (crystallographic data: P2(1)/n (No. 14) monoclinic, a = 10.125(1) Å, b = 16.331(1) Å, c = 15.276(2) Å, beta = 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-Bu(3)Al/B(C(6)F(5))(3) (homogeneous polymerization) and ethylaluminum sesquichloride (if 1 is incorporated in a MgCl(2)-matrix) have shown to be the most active cocatalysts. Third, the polymers and oligomers are atactic.