Aryl‐Substituted Cobalt (II) Dibenzoylmethane Catalysts for Ambient‐Pressure Fixation of CO 2 With Epoxides/Aziridines to Produce Cyclic Carbonates/Oxazolidinones

ABSTRACT The catalytic conversion of CO 2 into industrially relevant chemicals offers a sustainable pathway for carbon mitigation, yet most existing methods require harsh reaction conditions. In this work, a series of substituted cobalt (II) dibenzoylmethane complexes (Co(x‐dbm) 2 ) were applied to enable efficient CO 2 fixation with epoxides or aziridines at ambient pressure. Systematic substituent screening demonstrated that electron‐donating groups (CH 3 , t‐Bu) significantly enhanced the catalytic activity in both CO 2 /epoxide and CO 2 /aziridine systems. For epoxide coupling, the optimized catalyst achieves up to 96% epoxide conversion and > 99% selectivity for cyclic carbonates at 40°C with only 0.5 mol% catalyst loading. Parallel experiments highlighted that electron‐donating substituents simultaneously strengthen metal–ligand coordination and improve solubility, synergistically boosting catalytic efficiency. For aziridine coupling, 63% aziridine conversion with 92% oxazolidinone selectivity was attained at 40°C using tetrabutylammonium bromide (TBAB) as cocatalyst, whereas 86% aziridine conversion and 87% selectivity were achieved at 80°C with tetrabutylammonium chloride (TBAC) as cocatalyst. The balance between nucleophilicity (driving aziridine ring‐opening) and leaving‐group ability (facilitating ring‐closure of the intermediate carbamate salt to form the oxazolidinone) of the halide anions (XCl, Br, I) in tetrabutylammonium cocatalysts (TBAX) influenced both activity and selectivity, demonstrating the comparable rates of the ring‐opening and ring‐closing steps.