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)(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.