Novel highly active binuclear neutral nickel and palladium complexes as precatalysts for norbornene polymerization

A series of binuclear neutral nickel and palladium complexes [(XC6H2CHNC6H3-iPr2)MRL]24b–f (X = NO2, M = Ni, R = Ph, L = PPh3, 4b; X = H, M = Pd, R = Me, L = PPh3, 4c; X = H, M = Pd, R = Me, L = Py, 4d; X = NO2, M = Pd, R = Me, L = PPh3, 4e; X = NO2, M = Pd, R = Me, L = Py, 4f) and [(C10H7CHNC6H3-iPr2)MRL]28a–c (M = Ni, R = Ph, L = PPh3, 8a; M = Pd, R = Me, L = PPh3, 8b; M = Pd, R = Me, L = Py, 8c) have been synthesized and characterized. The structures of complexes 4e and 8b have also been confirmed by X-ray crystallographic analysis. With modified methylaluminoxane (MMAO) as cocatalysts, these complexes and complex [(C6H3CHNC6H3-iPr2)NiPh(PPh3)]24a are capable of catalyzing the addition polymerization of norbornene (NBE) with the high activity up to 2.3 × 108 g PNBE/(molM h). The structure of complexes affects considerably catalytic activity towards norbornene polymerization. The polymers obtained with nickel complexes are soluble, while those obtained with palladium complexes are insoluble. Palladium complexes 4c, 4e and 8b bearing PPh3 ligands exhibit much higher activities than the corresponding complexes 4d, 4f and 8c bearing pyridine ligands under the same conditions.

A series of binuclear neutral nickel and palladium complexes [(XC6H2CHNC6H3-iPr2)MRL]24b–f (X = H or NO2, M = Ni or Pd, R = Ph or Me, L = PPh3 or Py) and [(C10H7CHNC6H3-iPr2)MRL]28a–c (M = Ni or Pd, R = Ph or Me, L = PPh3 or Py) have been synthesized and characterized, and were shown to be highly active catalysts for vinylic polymerization of norbornene. Figure optionsDownload as PowerPoint slide