Vinyl-addition polymerizations of norbornene and methyl methacrylate by the palladium(II) complexes ligated by 2-iminomethylquinoline and 2-iminomethylpyridine derivatives

Abstract

Novel Pd(II) complexes, namely, [LnPdCl2] (Ln = LA and LB), where LA is (E)-3-methoxy-N-(quinolin-2-ylmethylene)propan-1-amine and LB is (E)-N-(pyridin-2-ylmethylene)hexan-1-amine, were synthesized and characterized. X-ray diffraction studies revealed distorted square planar geometries around the Pd(II) center in [LnPdCl2] (Ln = LA and LB). The catalytic capabilities of the synthesized complexes were tested in vinyl addition polymerization of norbornene (NB) in the presence of the cocatalyst modified methylaluminoxane (MMAO), displaying high activities with conversions ≥ 94% in chlorobenzene at 25 °C. The complex [LBPdCl2] displayed the highest activity of up to 4.40 × 106 gPNBmolPd−1h−1 at 25 °C, generating insoluble polynorbornene (PNB) at an NB/Al/Pd ratio of 8,000:500:1. In addition, preliminary methyl methacrylate (MMA) polymerization studies of the [LnPdCl2]/MMAO system demonstrated that the activities toward polar vinyl monomer production were in the range of 8.00 × 104 to 8.20 × 104gPMMAmolPd−1h−1 at 60 °C, yielding a high-molecular-weight syndiotactic poly(methyl methacrylate) (PMMA, Mw = 1.89 × 106gmol−1).