Effective and Robust Oxido-Molybdenum(V) Corrole Catalysts for Carbon Dioxide Utilization under Environmentally Benign Conditions

Oxido-molybdenum(V) corrole complexes, Mo(O)DMPC (Mo-1) and Mo(O)DMPCBr₁₄ (Mo-2), were synthesized and characterized using various spectroscopic techniques. The oxidation state of molybdenum(V) in Mo-1 and Mo-2 was confirmed by electron paramagnetic resonance (EPR) spectroscopy, revealing an axial compression with a dxy¹ configuration. These complexes were utilized as catalysts for the cycloaddition of CO₂ with various epoxides to produce the corresponding cyclic carbonates under solvent-less conditions in the presence of tetrabutylammonium bromide (TBAB) as a cocatalyst. These catalysts exhibited high turnover frequencies (TOFs) ranging from 4675 to 6332 h⁻¹, with 73-99% yields and >99% product selectivity. Notably, Mo-2 expressed a relatively high catalytic performance, achieving a TOF of 6332 h⁻¹ in the reaction with styrene epoxide and other derivatives. The superior catalytic activity of Mo-2, as compared to that of Mo-1, is attributed to the electron-withdrawing effect of the bromo substituents, as supported by cyclic voltammetry and DFT studies. To the best of our knowledge, this is an initial report on the catalytic activity of oxido-molybdenum(V) corroles for CO₂ cycloaddition, demonstrating their potential as efficient catalysts for converting CO₂ into value-added chemicals.