Synthesis and Characterization of Nickel (II) Complexes Bearing 2-(Imidazol-2-yl)pyridines or 2-(pyridin-2-yl)phenanthroimidazoles/oxazoles and Their Polymerization of Norbornene

Abstract Series of 2-R 1 -6-(1-R 2 -4,5-diphenyl-1H-imidazol-2-yl)pyridine (R 1  = R 2  = H, L1 ; R 1  = Me, R 2  = H, L2 ; R 1  = H, R 2  = Me, L3 ; R 1  = R 2  = Me, L4 ), 2-(6-R 1 -pyridin-2-yl)-1H-phenanthro[9,10-d]imidazole (R 1  = H, L5 ; R 1  = Me, L6 ) and 2-(pyridin-2-yl)phenanthro[9,10-d]oxazole ( L7 ) were synthesized and used to prepare their corresponding dihalonickel complexes ( C1 – C9 ). All organic compounds and nickel complexes were characterized by elemental and spectroscopic analyses. Molecular structures of C1 , C4 , C5 and C8 were confirmed by the single-crystal X-ray diffraction analysis. The single-crystal X-ray analysis revealed complex C1 as a distorted octahedral geometry, complex C4 as a distorted square pyramidal geometry, complex C5 as a distorted trigonal bipyramidal configuration, and complex C8 as a tetrahedral geometry. Upon activation with methylaluminoxane (MAO), the nickel complexes showed good activity towards norbornene polymerization through main additional and minor ring-opening metathesis. The reaction parameters such as norbornene concentration, reaction temperature and different coordinate environments caused by the ligands affected their catalytic performances.