Design And Synthesis Of Bifunctional And Bimetallic Trivalent Cobalt Catalyst

Polycarbonates can widely be used in engineering thermoplastics, medical equipment and packaging materials as a biodegradable polymer. Polycarbonates can be prepared by CO2/epoxides copolymerization. The environmentally-friendly method has the advantage of inexpensive raw materials and high atom economy compared to traditional synthetic process. Thus, the selective synthesis of high carbonate content and high molecular weight polymers become a target. The most challenging task is to control the stereoselectivity to obtain stereoregularity and crystalline polycarbonates. Based on the recognition of copolymerization mechanism and synergistic catalytic of "electrophilic-nucleophilic", we developed a series of biphenyl-based bimetallic trivalent cobalt catalyst. The paper focuses on exploring the stereoselective ring of epoxides to carry out the research works as follow:1. A novel biphenyl-based bifunctional and bimetallic trivalent cobalt catalyst was synthesized by acylation, quaternary ammoniation and so on. The catalyst can solve the asymmetric alternating copolymerization of CO2/cyclohexene. We explore the influence of axial ions, quaternary ammonium ions and reaction condition. Quaternary ammonium salt(Y-) and axial ion(X') have great influence on the selectivity of polymerization reaction. Conversion of cyclohexene is 19.8% under the condition of X-= Y-= OAc-, T= 25?, P= 1.2 MPa. Substitute2,4-dinitrophenol anion to acetate resulting in better activity and lower selectivity.2. We gain a binaphthyl-based bifunctional and bimetallic trivalent cobalt catalyst through changing bridging group. The catalysts have high asymmetric splitting capability on rac-epoxides, Which can be used to prepare stereoregularity polyether. If we choose toluene as solvent, the conversion of cyclohexene is 15.8% under the condition of X= Y= OAc-, T= 25?. The less hindrance of quaternary ammonium cations (n-butylammonium) may resulting in poor activity.