Nickel(II) and copper(II) complexes as catalysts for norbornene vinyl polymerization bearing tetradentate β-ketoiminato ligands

• Tetradentate [ONNO] β-ketoiminato nickel and copper complexes were synthesized.
• Nickel complexes were showed good activities in norbornene vinyl polymerzation.
• Vinyl typed polynorbornenes were obtained with high molecular weights.

The series of nickel(II) and copper(II) complexes (3a–f) bearing tetradentate [ONNO] β-ketoiminato ligands, N,N′-bis(2-benzoyl-3-oxobutylidene)-o-phenylenediamine 2a, N,N′-bis(2-benzoyl-3-oxobutylidene)-ethylenediamine 2b, N,N′-bis(2-benzoyl-3-oxobutylidene)-trans-1,2-cyclohexanediamine 2c, have been synthesized and characterized. X-ray crystal structures of complexes 3a–c and 3e–f reveal that each central metal adopts an almost square planar coordination geometry. Upon activation with methylaluminoxane (MAO), the nickel(II) complexes 3a–c display high catalytic activities for the vinyl polymerization of norbornene (NB), yielding high molecular weights of the polynorbornene (PNB), especially the complex 3b (24.46 × 105 gPNB/molNi h). While copper(II) complexes 3d–f only traces of PNB are generated. The catalytic system 3b/MAO is chosen for further investigations under various polymerization parameters.

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