Synthesis and characterization of catalytic active oxazolidine/Schiff complexes using 2-quinoline formaldehyde and tris-base for carbon dioxide chemical fixation

Catalytic chemical fixation of carbon dioxide to high value-added chemicals has attracted extensive attention and the discovery of new catalytic system has always been a research hotspot in carbon dioxide chemistry. Three complexes were synthesized by using 2-quinoline formaldehyde and tris-base precursor through Schiff base reaction and characterized. Compound Co[L1]2Cl2·2H2O (1) and compound Ni[L1]2Cl2·2H2O (2) are two mononuclear complex with derived schiff base ligand (L1 = 2-(hydroxymethyl)-2-((quinolin-2-ylmethylene)amino)propane-1,3-diol), while compound Cu2[L2]2Cl2∙2CH3OH (3) is a dinuclear complex containing derived deprontonated ligand (L2 = (2-(quinolin-2-yl)oxazolidine-4,4-diyl)dimethanol) The self-assembly process of these complexes were monitored by ESI-MS. The catalytic explore for the cycloaddition of CO2 and different reaction substrates and preliminary kinetic studies shows that all complexes are active and the reaction is an intramolecular Lewis acid-base catalytic mechanism. This is the first report of oxazolidine complex/ tetrabutylammonium halide catalyst in for cycloaddition of epoxides and CO2 reaction and the complex 3 is more active than the other two complexes, which provides new notions for the design and solicitation of Schiff base/oxazolidine catalysts.