New Co and Mn Catalysts Bearing ONO Ligands Containing Nucleophile for the Coupling of CO2 and Propylene Oxide

A series of novel ONO ligands bearing an ionic pendant-armed (hereinafter indicated as ONONu, where Nu corresponds to an anionic nucleophile) were synthesized, characterized, and successfully coordinated to cobalt and manganese precursors. New air-stable cobalt (III) complexes (1–6) and manganese (II) complexes (7 and 8) were obtained and characterized. Single crystal X-ray diffraction analysis of the Co(III) compound 5 confirmed the presence of two quaternized ligands coordinated to the metal and iodide as counterion. These novel complexes were revealed to be active catalysts in the coupling reaction of carbon dioxide and propylene oxide (PO) in different degrees of success. Among these, the manganese complex 8 afforded the best results towards the formation of propylene carbonate (PC) with a productivity of 256 kg PC/(kg cat·h), achieving a TON of 4860.