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A novel potassium complex, [K2L2(H2O)MeOH]n (1), was prepared by reacting KOH and a substituted tetrazolyl ligand LH (LH = 1-[5-(2-hydroxyphenyl)-2H-tetrazol-2-yl]-2-methyl-2-propanol). The prepared complex was characterized by infrared spectroscopy and mass analysis and its solid-state structure was determined to be a high dimensional coordination polymer by X-ray crystallography. The synthesized potassium coordination polymer 1 was used as a catalyst for the cycloaddition of CO2 to propylene oxide and is the first potassium coordination polymer to be used for this purpose. The prepared catalyst provided high selectivity toward cyclic propylene carbonate (>99%) and showed considerable activity despite the heterogeneous reaction condition.

Cobalt complexes containing a salen-type pyridoxal ligand with pyridine were synthesized as a new Co(III) catalytic system for the cycloaddition of carbon dioxide. Two cobalt(III) complexes possessing a salen-type pyridoxyl ligand were synthesized by the reaction of pyridoxal ligands (pyr2en = (N,N′-bis(pyridoxylideneiminato)ethylene) and pyr2cy = (N,N′-bis(pyridoxylideneiminato)cyclohexane)) and Co(OAc)2 and characterized by various analytical methods, including infrared spectroscopy and high-resolution mass analysis. Single-crystal X-ray crystallography analysis confirmed that the cobalt pyr2en complex had a distorted octahedral structure: the tetradentate Schiff base ligand binds the cobalt metal in one plane, and the metal center adopts an octahedral geometry by the additional coordination of acetate and dimethyl sulfoxide. The synthesized complexes were used as catalysts in the cycloaddition of carbon dioxide (CO2) to propylene oxide. The catalysts showed high activity for cycloaddition between CO2 and epoxides, even at a low loading (0.5 mol%), in the presence of various cocatalysts.