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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 32, Number 6
BKCSDE 32(6)
June 20, 2011 

Steric and Electronic Effects of Tetradentate Nickel(II) and Palladium(II) Complexes toward the Vinyl Polymerization of Norbornene
Dong-Hwan Lee, Jung Hwan Lee, Geun Hee Eom, Hyo Geun Koo, Cheal Kim,*, Ik-Mo Lee*
Ni(II) and Pd(II) complexes, N4-type tetradentate ligands, Norbornene polymerization, Electronic effect, Steric effect
A series of Ni(II) and Pd(II) complexes bearing N4-type tetradentate ligands, [Ni(X1X2-6-Me2bpb) 1] and [Pd(X1X2-6-Me2bpb) 2]; 6-Me2bpb = N,N'-(o-phenylene)bis(6-methylpyridine-2-carboxamidate), X1 = Cl, H, or CH3, X2 = NO2, Cl, F, H, CH3, or OCH3) were designed, synthesized, and characterized to investigate electronic and steric effects of ligand on the norbornene polymerization catalysts. Using modified methylaluminoxanes as an activator, the complexes exhibited high catalytic activities for the polymerization of norbornene and the nickel complexes exhibited better catalytic activity the palladium complexes. Ni complex 1a with NO2 group on the benzene ring showed the highest catalytic activity of 4.9 × 106 g of PNBEs/molNi · h and molecular weight of 15.28 × 105 g/mol with PDI < 2.30. Complexes with electron-withdrawing groups are more thermally stable (> 100 °C), and tend to afford higher polymerization productivities than the ones having electron-donating groups. Amorphous polynorbornenes were obtained with good solubility in halogenated aromatic solvents. A vinyl addition mechanism has been proposed for the catalytic polymerization.
1884 - 1890
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