To conclude, we described the synthesis and polymerization studies of a series of α-diimine Ni(II) and Pd(II) complexes bearing different substituents on the acenaphthyl backbone. Very little difference was observed for the Ni(II) complexes in ethylene polymerization, except for the sterically bulky complex Ni-5. Ni-5 generated polyethylene with much higher molecular weight and much lower branching density than the classic complex Ni-6 and the rest of the nickel complexes. In contrast, the backbone substituents have some dramatic effects on the Pd(II)-catalyzed ethylene polymerization and copolymerization with methyl acrylate. Again, the sterically bulky complex Pd-5 generated polyethylene and copolymer with much higher molecular weight than the classic complex Pd-6. This provides an alternative strategy to modify the ligand structures in the α-diimine framework and correspondingly influence the polymerization and copolymerization processes..
