Ligands Bis(imino)aryl NCN Pincer Cobalt Complex: Synthesis, Characterization, Property And Disproportionation

Pincer ligands have attracted great attention from the chemical community due to their excellent and stable chemical structure,and have attracted many researchers'research and development.Nowadays,Rh,Ir and other transition metal Pincer complexes have been extensively studied.In contrast,cobalt Pincer complexes have been studied less frequently.To this end,we synthesized three types of Cobalt metal complexes based on NCN Pincer ligands to investigate the properties of Cobalt metal complexes.In chapter two of this paper,some characterization methods and experimental preparations are mainly introduced.In Chapter 3,the synthesis of three types of Cobalt metal complexes is explained:these three types of complexes are mainly synthesized by using conventional lithium-halide exchange reactions.Since the three types of cobalt complexes are paramagnetic compounds,we mainly performed infrared and elemental analysis on them.At the same time,1d-LiBr,1d-CoCl2,2b,2d,3a,and 4d crystals were grown by slow evaporation in glove box,and the crystal structures were analyzed by X-ray diffraction.In the last paragraph of Chapter 3,the detailed mechanisms of the disproportionation reaction were proposed.Cobalt?II?was stabilized by experimentally adding PMe₃,and 3a,3b,3c,and 3d cobalt complexes were prepared.In Chapter 4,we explored the properties of the three types of complexes in catalyzing the polymerization of isoprene,and characterizing the polymers by nuclear magnetic resonance and gpc.We prepared 10 cobalt metal complexes to catalyze the polymerization of isoprene with various types of alkyl aluminum as cocatalysts.It was found that when the cocatalyst was diethylaluminum chloride or sesquiethyl aluminum chloride,Most of the catalysts have good catalytic effects.Within 2 hours,most of the catalysts can achieve a catalytic yield of more than 75%on the polymerization of isoprene.Among them,1d is the best and can be used in milder conditions.The polymerization can be completed in 1h.