Study Of Neutral Nickel Catalysts Developed A New Dual-core And The Catalytic Performance

After Metallocene catalysts, late transition metal catalysts have been aroused extensive attention because of its lower oxophilicity and greater functional group tolerance to early metals, it makes them likely targets for the development of catalysts for the copolymerization of ethylene with polar comonomers under mild condition. Based on Grubbs type catalysts, a series of Schiff base Coordinated nickel complexes have been synthesized, and its polymerization properties for ethylene were studied detailed under different polymerization conditions.Two substituted salicyladimine ligands were prepared by alkylation, formulation and conden-sation, which were reacted with trans-[NiCl(Ph)(PPh3)2] to give the neutral nickel(Ⅱ) complex CYG1 {[[O-(3-Cy-clohexanyl) (5-CH3)C6H2-ortho-C(H)=N-2,6-C6H3(i-Pr)2]Ni(Ph3P) (Ph)]2CH2} and complex CYG2 {[[O-(3-Cyclohexanyl) (5-Cl)C6H2-ortho-C(H)=N-2,6-C6H3 (i-Pr)2]Ni(Ph3P)(Ph)]2CH2}. All intermediates and neutral complexes(9) and (10) were characterized by GC-MS, 1HNMR.Catalytic properties of two compounds (CYG1 and CYG2) in ethylene polymerization were studied detailed. High activity or distinctive catalytic properties of these catalysts systems were found. In the polymerization of (CYG1 or CYG2)/Ni(COD)2, the polymerization activity increases and reaches a maximum, then decreases, while the polymer's molecular weight decreases steadily with the increase of catalysts' concentration. Elevating reaction pressure, the catalytic activities and the polymer's molecular weight all increased. With prolongation of polymerization time, the catalytic activities first increase and reaches a maximum, then decreases, while the molecular weight of PE increases. Effect of temperature on the catalytic properties of these two catalysts systems was very distinct. Under normal temperature, the polymerization activities were very low. While increasing the reaction temperature to 45℃, the catalytic activities and the molecular weight reached climax. Above 60°C, the catalysts deactivated badly, therefore both the catalytic activities and the molecular weight declined rapidly. Under the optimal polymerization conditions, the activities of these two compounds can reach: 5.34×105gPE/(mol Ni hr), 5.74×105 g PE/(mol Ni hr) respectively, the products' molecular weight can reach: 5.26×104, 8.61×104 respectively, and the distribution of the products' molecular weight can reach: 2.39 and 2.81 respectively.In additions, catalytic properties of the compound CYG1 in bulk polymerization of MMA was studied detailed. High activity of the catalyst system was found. In the polymerization of CYG1/ Al(i-Bu)3, With prolongation of polymerization time, the monomer conversion and the polymer's molecular weight all increase. Elevating reaction temperature, the monomer conversion increases, while the polymer's molecular weight decreases. With the increase of Al/Cat, thepolymer's molecular weight decreases gradually, while the monomer conversion increases. The polymer's molecular weight first increases and reaches a maximum, then decreases, while the monomer conversion decreases with the increase of MMA/Cat.