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

The series of nickel(II) and copper(II) complexes (3a-f) bearing tetradentate [ONNO] beta-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 x 10(5) g(PNB)/mol(Ni) 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. (C) 2013 Elsevier B.V. All rights reserved.