A series of novel nickel complexes (1−4) bearing anilido−imine ligands, [(Ar1NCHC6H4NAr2)NiBr]2 (Ar1 = Ar2 = 2,6-dimethylphenyl, 1; Ar1 = 2,6-dimethylphenyl, Ar2 = 2,6-diisopropylphenyl, 2; Ar1 = Ar2 = 2,6-diisopropylphenyl, 3; Ar1 = 2,6-diisopropylphenyl, Ar2 = 2,6-dimethylphenyl, 4), have been synthesized and characterized. The solid-state structures of the complexes 1, 2, and 4 were confirmed by X-ray single-crystal analyses to be in the form of a dinuclear and bromine-bridged structure. However, there is an equilibrium that shifts between the monomer and dimer in solution, which has been monitored using 1H NMR and UV−vis spectrophotometry. The themodynamic parameters for the equilibriums were calculated to be ΔH = +13.68 kJ/mol and ΔS = 40.32 J/(mol K) for 1 and ΔH = +8.35 kJ/mol and ΔS = 15.21 J/(mol K) for 3. All nickel complexes show low activities for ethylene oligomerization with MAO as cocatalyst but high catalytic activities for norbornene polymerization in the presence of MAO.

Cobalt complexes 1-4 bearing N,O-chelate ligands based on condensation products of 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone with aniline, o-methylaniline, a-naphthylamine, and p-nitroaniline, respectively, were synthesized, and the structures of 1 and 4 were characterized by single-crystal X-ray diffraction analyses. The bis(b-ketoamine) cobalt complexes could act as moderately active catalyst precursors for norbornene polymerization with the activation of methylaluminoxane. This catalytic reaction proceeded mainly through a vinyl-type polymerization mechanism. 1 H NMR and IR showed that in all cases, a small amount of double bonds raised from ring-opening metathesis polymerization (ROMP) was present in the polymerization products. The variation of the polymerization conditions affected the ROMP unit ratio in the polynorbornenes. V V C 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5535-5544, 2005

Late transition metal (nickel, cobalt) complexes (1, 2) with β-ketoamine ligand (L) based on the pyrazolone derivative are synthesized by condensing 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone with p-fluoroaniline, and then treating the β-ketoamine (L) produced with the respective metal halide. The bis(β-ketoamine)metal complexes can act as catalyst precursors for norbornene polymerization with activation by methylaluminoxane. The effects of the central metal variation in the complex on catalyst activities and polymer microstructure are described.

A series of nickel complexes with β-ketoamine ligands based on pyrazolone derivatives were synthesized by condensing pyrazolone with aniline, 2-chloroaniline or naphthylamine and then reacting the produced β-ketoamine with nickel halide. The solid-state structures of these three complexes were determined by single-crystal X-ray diffraction. The bis(β-ketoamine)nickel complexes are all air-stable and can act as highly active catalyst precursors for styrene polymerization with activation of methylaluminoxane under mild reaction conditions. The activity of the catalyst for styrene polymerization is as high as 2.10 × 10 5 g polymer/mol Ni h. Both steric and electronic effects were found to be important and influential for catalytic activity.

A new β-ketoimine ligand was prepared through traditional condensation of 2-acetylcyclohexanone with 1-naphthylamine. Consequently, the new moisture-and air-stable bis(β-ketoamino)nickel(II) complex Ni[2-CH 3 C(O)C 6 H 8 ( NAr)] 2 (Ar = naphthyl) was synthesized and characterized. The solidstate structures of the ligand and complex have been determined by single-crystal X-ray diffraction. Additionally, the new complex is a highly active catalyst precursor for polymerization of norbornene in combination with methylaluminoxane.