Carbon dioxide conversion into valuable chemicals has received much attention since it has potential applications as an abundant, nontoxic and renewable C1 source. The most widely studied area in the activation of CO₂ is its coupling reaction with various epoxides to produce industrially important commodity chemicals such as, polycarbonate and cyclic carbonate. Herein, we are trying to understand aluminum and iron complexes in parallel, by comparing the difference in selectivity of the iron and aluminum catalyst based on an imino-tris(phenolate) ligand. While generating polycarbonate and cyclic carbonate in the catalytic cycle, a metal oxide complex is possible, in which the metal center is coordinated to an oxygen atom of ring-opened epoxide. A following metal carbonate intermediate is generated by insertion of CO₂. To investigate the intermediates, we are striving to directly synthesize metal oxide and carbonate complexes with aluminum and iron. An aluminum complex, {(NO₃)Al}₂, was synthesized and has been well characterized by various spectroscopic techniques and X-ray crystallography. Sodium isopropoxide, which possesses an analogous structure of ring-opened propylene oxide, was added to {(NO₃)Al}₂ to synthesize {(NO₃)Al(OⁱPr)}Na, the expected intermediate-like aluminum isopropoxide. Following insertion of CO₂ possibly generates the carbonate intermediate, {(NO₃)Al(OC(=O)OⁱPr)}Na. An iron complex, {(NO₃)Fe(THF)}₂, was synthesized and well characterized by various spectroscopic techniques and X-ray crystallography. In a similar way, two kinds of the iron complex intermediate could possibly be prepared: {(NO₃)Fe(OⁱPr)}Na and {(NO₃)Fe(OC(=O)OⁱPr)}Na. By comparing the aluminum and iron complexes in a parallel way, we expect to better understand the intermediates of the aluminum and iron complexes and might suggest a plausible reason for the selective behavior.