Thermostable α-Diimine Nickel Complexes with Substituents on Acenaphthequinone-backbone for Ethylene Polymerization

In order to promote the thermostability of a-diimine nickel complex by ligand backbone structure,a series of α-diimine nickel complexes with substituents on acenaphthequinone backbone were synthesized and used as catalysts for ethylene polymerization.When the hydroxyethyl phenoxyl group was introduced to the acenaphthequinone-backbone,the thermal stability and activity of the catalyst could be significantly improved.The catalytic activity of complex C2[5-(4-(2-hydroxyethyl)phenoxyl)-N,N-bis(2,6-diisopropyl)acenaphthylene-1,2-diimine]nickel(Ⅱ)dibromide with isopropyl substituents on N-aryl reached 8.2×10^6g/(molNi·h)at 70℃and 2 MPa.The activity of[5-(4-(2-hydroxyethyl)phenoxyl)-N,N-bis(2,6-dibenzhydryl-4-menthylphenyl)acenaphthylene-1,2-diimine]nickel(Ⅱ)dibromide(C3)still maintained at 6.7×10^5 g/(molNi·h)at 120℃.Compared with C3 containing bulky dibenzhydryl substituents,the activity of C2 was sensitive to the change of the polymerization pressure.However,the polyethylenes obtained from complex C3 had lower branching density.Meanwhile,the molecular weight could reach 971 kg/mol,which is almost 5 times as much as that of the polyethylene obtained from complex C2.

Linear/branched Block Polyethylene Produced by a-Diimine Nickel(Ⅱ)Catalyst and Bis(phenoxy-imine)Zirconium Binary Catalyst System in the Presence of Diethyl Zinc

In order to promote development of linear/branched block polyethylenes based on new catalytic systems,we synthesized a novel a.dimine nickel(Ⅱ)complex with isopropyl substituents on ortho-N-aryl and hydroxymethyl phenyl substituents on para-Naryl structures.The activity of a-dimine nickl(Ⅱ)catalyst was 3.02x10^(6)g-mol_(ni)^(-1)·h^(-1) at 70℃,and resultant polyethylene possessed 135/1000C branches.The linear/branched block polyethylenes were synthesized from ethylene polymerization catalyzed by the a-dimine nicke(Ⅱ)complex/bis(phenoxy-imine)zirconium in the presence of diethyI zinc.With the addition of ZnEtz(from 0 to 400),the melting peak of resultant polyethylene changed from a single melting peak to bimodal melting peaks.The molecular weights of resultant polyethylene ranging from 26.8 kg/mol to 17.1 kg/mol and PDI values varying gradually from 24.4 to 15.2 were obtained vla adjusting ZnEt;equiv.and molar ratio of two catalysts.In addition,the branching degree of the polyethylene increased from 13/1000C to 56/1000 with the increase of the proportion of a dimine nickel(Ⅱ)catalyst.Using this binary catalyst system,the reaction temperature of chain shutting polymerization can be carried out at 70℃,which is more conducive to industrial application.