Abstract
New unsymmetrical (α-diimine)nickel(II)|catalysts having different pendent groups at theortho positions on aromatic rings were synthesized and subjected to propylene polymerizations with MAO (methylaluminoxane). Structural analyses of the resulting polypropylenes by1H and13C NMR showed that the ortho substituents on aromatic rings of (α-diimine)nickel(II)|catalyst affected significantly the polypropylene microstructure. While Cs symmetric catalyst afforded a syndiotactic polypropylene (rr triad content=66%)|due to the syndiospecific chain end control, C1 symmetric catalysts produced much less stereoregular polypropylenes (rr triads content <50%), presumably because of collision of the isospecific site control with the syndiospecific chain end control.
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