Synthesis and Characterization of Cobalt(II/II) and Cobalt(II/III) Macrocyclic Complexes and Their Application in the Copolymerization of Epoxides and CO2

The synthesis and characterization of six dinuclear cobaltcomplexesbearing a conjugated macrocyclic ligand are reported. The condensationof 2,6-diformylphenol and o-phenylenediamine ledto semi-hydrogenated macrocycles A-C. The ligandprecursor A reacted with Co(OAc)(2)center dot 4H(2)O and generated the Co(II/II) complex 1, anda conjugated macrocyclic ligand was formed during the complexation.The partial oxidation of 1 with air resulted in mixed-valenceCo(II/III) complexes 2 and 3 bearing differentanionic ligands. Analogous Co(II/III) complexes 4-6 of Cl- and F-substituted ligand backbones were also synthesized.Structural characterization and charge determination of all complexeswere achieved through X-ray diffraction analysis and X-ray photoelectronspectroscopy. These complexes were applied in the copolymerizationof CO2 and cyclohexene oxide (CHO), and the mixed valenceCo(II/III) complex 2 showed good reactivity and selectivity(>99% polycarbonate).