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

Abstract

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 3rd 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)].