In this study, new complexes LNiCl(1), LNiBr(2), LNiI(3), and LPdCl(4) (L ¼ 4,6-di-tert-butyl-2-(N-(quinolin-8-yl)iminomethyl)phenolato) have been synthesized and characterized. X-ray diffraction studies on Complexes 1 and 4 revealed that N, N, O, and halogen atoms coordinated to metal, with a nearly square planar geometries in all cases. All these complexes are robust and exhibit high activities for the addition polymerization of norbornene (NB) with methylaluminoxane as cocatalyst [up to 47.62 kg PNB(mmol of Ni)and also lead to various activities and molecular weights of polynorbornenes under different reaction conditions. It is noteworthy that Complexes 1 and 4 show better activity under higher reaction temperature of 80 C. However, Complex 2 showed lower activity, and Complex 3 was found nearly inert toward NB polymerization, probably, because of thermal instability.
A series of different steric hindrance nickel(II) complexes 1-6 bearing 2,6-bis(imino)pyridine ligands have been synthesized and characterized. The molecular structures of the complexes 3-5 were determined by X-ray diffraction analysis. The coordination geometry around the nickel center of the complexes is either square pyramid for complexes 3 and 4 or trigonal bipyramid for complex 5. All of the nickel complexes exhibit high catalytic activity for norbornene polymerization in the presence of MAO, although low activity for ethylene oligomerization and polymerization. The effects of the Al/Ni ratio, halogen, monomer concentration, temperature, and reaction time on activity of catalyst for norbornene polymerization and polymer microstructure were investigated.
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