Novel and efficient palladium complexes with β-ketoiminate ligands for the polymerization of norbornene

A series of the noble palladium complexes containing β-ketoiminate ligands with internal bases, [Pd(η³-allyl)(β-ketoiminate)], [Pd(Me)(PPh₃)(β-ketoiminate)] and [Pd(Me)(β-ketoiminate)], have been successfully prepared. Crystallographically determined structures showed that these complexes are distorted square planar and pendant bases of the β-ketoiminate ligands fail to coordinate to the metal in the first two classes of complexes while bases do coordinate in the 3^rd class complexes. These complexes are active towards norbornene polymerization on activation with H(OEt₂)₂BAr'₄ (Ar' = 3,5-bistrifluoromethylphenyl) and modified methylalumioxane (MMAO). MMAO is more efficient for the activation for polymerization. Generally, the polymerization activity increases with the following order; [Pd(allyl)(β-ketoiminate)] < [Pd(Me)(PPh₃)(β-ketoiminate)] < [Pd(Me)(β-ketoiminate)].