Transition metal complexes with pyrazine amine ligand: Preparation, structure and carbon dioxide copolymerization behavior

Three complexes [Fe(L)2](ClO4)2 (1)、[Ni(L)2](ClO4)2 (2) and [Co(L)2](ClO4)2 (3) were synthesized by the reaction of N,N'-(4-methylpyridin-2-yl)pyrazine-2,6-diamine (L) with Fe(ClO4)2·6H2O, (Ni(ClO4)2·6H2O or Co(ClO4)2·6H2O) at room temperature, respectively. They were characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffraction. The catalytic behavior of the complexes for the synthesis of propylene carbonate from propylene oxide and carbon dioxide were studied. The results show that all of them showed excellent catalytic activities with TOF as high as 2104 h-1, 2824 h-1 and 2605 h-1, respectively. Complex 2 that exhibit higher catalytic activity was taken to explore the influence of time, pressure and temperature to optimize the reaction condition in detail.