Synthesis Of Novel Late-transition Metal Catalysts And Homopolymerization Of Butadiene And Norbornene

This work focuses on designing and synthesis of late-transition metal complexes used as catalysts for catalytic polymerization of norbornene and butadiene. Two types of ligands, imino or amido pyridyl alcohol ligands, were used in the preparation of late-transition metal complexes. Upon activation with Al-based cocatalysts, their catalytic properties were detailedly investigated and discussed. Three parts are included in this work as follows:Part one:The progresses of catalysts, especially late-transition metal complexes used in the polymerization of norbornene and butadiene are summarized, respectively.Part two:A series of (imino)pyridyl alcohol ligands were synthesized and characterized by elemental analysis, FT-IR,1H NMR and13C NMR. Then these ligands reacted with NiCl2-6H2O, NiBr2, Ni(OAc)2-6H2O or PdCl2to yield the corresponding nickel and palladium complexes bearing tridentate [NNO] ligands. These complexes were sufficiently characterized by elemental and spectroscopic analysis along with X-ray diffraction analysis. The X-ray diffraction demonstrated that five-coordinated nickel halide complexes and six-coordinated nickel acetate complex were prepared, and cationic palladium complexes formed with the [PdCl4]2-counterion. On treatment with excess methylaluminoxane (MAO), all nickel complexes displayed high catalytic activities more than106g(PNB)·mol-1(cat)·h-1for vinyl polymerization of norbornene, while the activities reached1.883×107g(PNB)·mol-1(cat)·h-1for palladium complexes. All the vinyl-type PNBs obtained by these complexes had high molecular weights and relatively narrow molecular weight distributions. The parameters of reaction conditions, the type of metals and steric effects of coordinative ligands had influences on the catalytic properties.Part three:On the basis of previous studies, a series of imino-or amino-pyridyl alcohol ligands were synthesized and characterized by elemental analysis, FT-IR,1H NMR and13C NMR. Then these ligands reacted with COCI2·6H2O or NiCl2·6H2O to yield corresponding cobalt(II) and nickel(Ⅱ) complexes with tridentate [NNO] ligands. Theses complexes were characterized by elemental and spectroscopic analysis along with X-ray diffraction analysis. The X-ray diffraction demonstrated that all the complexes adopted distorted trigonal bipyramidal configuration with the equatorial plane formed by the pyridyl nitrogen atom and two chlorine atoms. On activation with ethylaluminum sesquichloride (EASC), the cobalt complexes displayed high catalytic activity for the polymerization of1,3-butadiene to yield cis-1,4-polybutadiene with high selectivity (>96%) under the Al/Co molar ratio of40at25℃. The conversion of butadiene, microstructure and molecular weight of the resulting polymers were affected by the reaction parameters and ligand environment. However, in comparison with the corresponding cobalt complexes, the nickel complexes obtained relatively lower catalytic activity, cis-1,4content and molecular weight under the similar reaction conditions.