Nickel complexes bearing N,N,N-tridentate quinolinyl anilido–imine ligands: Synthesis, characterization and catalysis on norbornene addition polymerization

The N,N,N-tridentate quinolinyl anilido–imine ligands 2-(ArNC(H))C6H4–HNC9H6N (LaH, Ar = 2,6-Me2C6H3; LbH, Ar = 2,6-iPr2C6H3) and 2-(C9H6N)NC(H)C6H4–HNAr (LcH, Ar = 2,6-Me2C6H3; LdH, Ar = 2,6-iPr2C6H3) were synthesized and characterized. Reactions of these ligands with nBuLi and subsequent additions of NiCl2(DME) afford the N,N,N-tridentate nickel complexes [2-(ArNC(H))C6H4–NC9H6N]NiCl (Ar = 2,6-Me2C6H3 (1a), 2,6-iPr2C6H3 (1b)) and [2-(C9H6N)NC(H)C6H4–NAr]NiCl (Ar = 2,6-Me2C6H3 (2a), 2,6-iPr2C6H3 (2b)). All the complexes were fully characterized by NMR and elemental analyses. X-ray diffraction analyses of 1b and 2b revealed an almost square-planar geometry around the metal center. When activated with MAO, these nickel complexes can be used as catalysts for the vinyl addition polymerization of norbornene affording high molecular weight polymer.