Norbornene and methyl methacrylate polymerizations catalyzed by palladium(II) complexes bearing aminomethylpyridine and aminomethylquinoline derivatives

초록

A series of Pd(II) complexes, 1-4 bearing N,N-bidentate aminomethylpyridine and aminomethylquinoline derivatives were synthesized and characterized. Single crystal X-ray diffraction analysis demonstrated that tetra-coordinated Pd(II) complexes adopted distorted square planar geometries around the metal center. In the presence of modified methylaluminoxane (MMAO) as a co-catalyst, Pd(II) complexes 1-4 exhibited significant activities (up to 43.2 x 10(5) g(PNB) mol Pd-1 h(-1)) towards the addition polymerization of norbornene (NB) at 25 degrees C. Insoluble poly(norbornene) (PNB) was obtained by all the tested catalytic systems, i.e., 1-4/MMAO. The catalytic capabilities of synthesized Pd(II) complexes were also tested towards methyl methacrylate (MMA) in the presence of modified methyl aluminoxane MMAO. Complex 3 with quinoline/piperidine functionalities showed the highest catalytic activity of 8.83 x 10(4) g(PMMA) mol Pd-1 h(-1) at 60 degrees C and resulted in high molecular weight PMMA (M-w = 2.16 x 10(6) g mol(-1)). All the complexes yielded syndiotactic poly(methyl methacrylate) (PMMA) (rr = 0.70). Notably, the steric bulk and electronic properties of the ligand framework affect their activities towards NB and MMA polymerizations, whereas, for PMMA, the stereoselectivities remained unaffected. (C) 2022 Elsevier B.V. All rights reserved.

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