Synthesis Of Diimide Nickel And Cobalt Transition Metal Complexes And Their Catalytic Properties For Ethylene Polymerization

Polyethylene plastic has good mechanical properties,chemical stability,corrosion resistance,harmlessness,recyclability and reprocessing properties,and can be widely used in industry,agriculture,medical treatment and daily life.As a typical example of late-transition metal catalyst,α-diimine type catalyst system catalyzes ethylene polymerization by“chain walking”method.Polymerized ethylene into medium branched,high branched,and other new polyethylene.Since the Brookhart group reportedα-diimide-nickel（II）and-palladium（II）complexes,the search forα-diimide catalysts has never stopped.It was found that the change of the structure ofα-diimine has a critical effect on the activity and properties of the synthesized polymers.In this thesis,we designed and synthesizedα-diimine nickel complex catalyst and pyridine cobalt metal complex catalyst for ethylene polymerization,and discussed the effects of different substituents and reaction conditions on ethylene polymerization.It mainly includes the following four chapters:Chapter 1:Introduction.The present situation of polyethylene and catalysts for ethylene polymerization were described,with emphasis onα-diimine Ni-Pd catalyst and N,N,N-tridentate pyridine Fe-Co catalyst.Chapter 2:In order to improve thermal stability ofα-diimine nickel catalyst,this chapter synthesized symmetrical 1,2-bis（2,6-bis（bis（4-alkylphenyl）methyl）-4-tert-butylphenylimide）acenaphthene-nickel compounds.In general,under the activation of MMAO,all nickel bromide complexes show high activity and generate polyethylene with high molecular weight.In particular,these catalysts have high thermal stability.Especially for the catalysts Ni-H,Ni-Me and Ni-OMe,they still show good activity at 100℃,respectively 1.98×10⁶g（mol,h）^-1、1.64×10⁶g（mol,h）^-1、1.39×10⁶g（mol,h）^-1.Chapter 3:In order to improve the catalytic activity and product performance of the N,N,N-tridentate pyridine cobalt catalyst,this chapter introduced methoxy into the large steric hindrance group diphenylmethyl and synthesized asymmetric 2-（1-（2,6-bis（4,4’-dimethoxydiphenylmethyl）-4-methylaniline）ethyl）-6-（1-（arylaminine）eth yl）pyridine cobalt and symmetric 2,6-bis（1-（2,6-bis（4,4’-dimethoxydiphenylmethyl）-4-methylaniline）ethyl）pyridine cobalt.Under the activation of MAO or MMAO,the asymmetric pyridine cobalt complex has high activity,generates high molecular weight polyethylene and narrow molecular weight distribution.However,symmetrical pyridine cobalt complex showed poor activity.Chapter 4:Summary.