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

Abstract

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.