咪唑基卡宾-膦/Ni(Ⅱ)配合物/一氯二乙基铝催化乙烯选择性二聚OA

A series of imidazolyl-carbene-phosphine bidentate ligands were designed and synthesized,and their structures were characterized using nuclear magnetic resonance(NMR)spectroscopy in the current study.The reaction of these imida-zolyl-carbene-phosphine ligands with NiBr2(DME)(nickel bromide ethylene glycol dimethyl ether)produced the corre-sponding carbene-phosphine/Ni(Ⅱ)complexes.These complexes exhibited high catalytic activity for ethylene dimerization and excellent selectivity for 1-butene in the presence of diethylaluminum chloride(DEAC)as a co-catalyst.Based on the imidazolyl-carbene-phosphine/Ni(Ⅱ)/DEAC catalytic system,the various effective factors for ethylene dimerization,such as the substituents at the nitrogen atom of the imidazolyl-carbene-phosphine ligand,the aluminum source,reaction tempera-ture,Al/Ni molar ratio,reaction time,and catalyst concentration,were systematically investigated.Experimental results demonstrated that the catalytic performance was optimal when the substituent on the nitrogen atom was an isopropyl group.Under the conditions of ethylene pressure at 1.0 MPa,Al/Ni molar ratio of 1 000∶1,and polymerization temperature at 30℃,the ethylene dimerization activity reached 2.58×107 g/(mol·h),with a butene selectivity of 86.77%(of which 1-butene selectivity was up to 75.62%).Finally,density functional theory(DFT)calculations were employed to simulate the structures of different imidazolyl-carbene-phosphine/Ni(Ⅱ)complexes,thus providing a theoretical explanation for the experimental results observed.