Synthesis and Characterization of Nickel(II) and Palladium(II) Complexes based on Tridentate [N–NP] and [N–NS] Ligands and Their Applications in Norbornene Polymerization

The series of anilido-imine N–NP and N–NS tridentate nickel and palladium complexes [(ArNHC6H4CHNPh-2-XPh)­MCl] (X = PPh, Ar = 2,6-Me2C6H3, M = Ni (2a), X = PPh, Ar = 2,6-Et2C6H3, M = Ni (2b); X = PPh, Ar = 2,6-i-Pr2C6H3, M = Ni (2c); X = S, Ar = Ph, M = Ni (2d); X = S, Ar = 2,6-Me2C6H3, M = Ni (2e); X = S, Ar = 2,6-i-Pr2C6H3, M = Ni (2f); X = PPh, Ar = 2,6-Me2C6H3, M = Pd (3a); X = PPh, Ar = 2,6-Et2C6H3, M = Pd (3b); X = PPh, Ar = 2,6-i-Pr2C6H3, M = Pd (3c)) were synthesized. All the complexes were fully characterized by IR, NMR and elemental analyses. X-ray diffraction analyses on complexes 2a,c and 3a revealed an almost square-planar coordination of the central metal. After activation with methylaluminoxane (MAO), the nickel­(II) complexes 2a–f can be used as catalysts for norbornene polymerization to produce vinyl addition type polynorbornene (PNB) with high catalytic activities, up to 5.82 × 107 g of PNB (mol of Ni)−1 h–1, while poor catalytic activities are found for the palladium complexes 3a–c.