Highly active Mn(III) meso-tetrakis(2,3-dichlorophenyl)porphyrin catalysts for the cycloaddition of CO2 with epoxides
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A new free-base porphyrin, meso-tetrakis(2,3-dichlorophenyl)porphyrin, (H2T2,3-DCPP) and the respective manganese(III) complexes [MnIII(T2,3-DCPP)X] with six different axial ligands (NO3−, AcO−, IO3−, Br−, Cl−, HO−) were synthesized and characterized. The molecular structure of [MnIII(T2,3-DCPP)Cl] was also confirmed by single crystal X-ray diffraction. The complexes, when combined with tetrabutylammonium halides as nucleophile source cocatalysts, were highly active catalysts in the solvent-free cycloaddition reactions of carbon dioxide with styrene oxide, selectively producing the respective cyclic carbonate. The complex [MnIII(T2,3-DCPP)Cl] was used to evaluate a series of parameters in the system and efficiently catalyzed the transformation of various epoxides using TBAI as cocatalyst, 30 bar of CO2 at 100 °C, producing nearly quantitative conversions in most of the cases. Remarkable TON values of 500,000 and 434,780 were achieved, respectively, for propylene oxide and styrene oxide using [MnIII(T2,3-DCPP)Cl] as catalyst. Recycling experiments were conducted and the system maintains high conversion rates after eight runs, which indicated a high stability and reusability of the catalyst.
Carbon dioxide, Cyclic carbonate, Metalloporphyrins, Manganese complexes, Homogeneous catalysis
MILANI, Jorge Luiz Sônego et al. Highly active Mn(III) meso-tetrakis(2,3-dichlorophenyl)porphyrin catalysts for the cycloaddition of CO2 with epoxides. Journal of CO2 Utilization, Amsterdam, v. 30, p. 100-106, 2019. DOI: 10.1016/j.jcou.2018.12.017. Disponível em: https://www.sciencedirect.com/science/article/abs/pii/S2212982018308771?via%3Dihub. Acesso em: 20 nov. 2023.