Density functional theory study of Fe(CO)5 and [Fe(CO)6]2+ complexes catalyzed the water gas shift reaction extended to the aqueous phase

Abstract

The WGSR with Fe(CO)5 and [Fe(CO)6]2+ complexes were investigated using DFT in both gaseous and aqueous phases. Thermodynamic analyses indicated that the high dielectric constant of water inhibits the activity of OH− and [Fe(CO)6]2+ ions, leading to a substantial decrease in the energy released during the nucleophilic attack of OH− on Fe(CO)5 and [Fe(CO)6]2+ in the aqueous phase. In addition, a potential low energy pathway has been discovered by designing new transition states for the final step of Fe(CO)5-catalyzed WGSR: 1 → 6 → 2 → 3 → 4 → 5(a) → 5(b) → 6. According to the results of the ESM, [Fe(CO)6]2+ possesses the highest gaseous phase TOF value (1.27×10−18 s–1), both Fe(CO)5 and [Fe(CO)6]2+ have higher TOF values in the gaseous phase compared to the aqueous phase, which increases with rising temperature. Therefore, these results suggest that [Fe(CO)6]2+ serves as the advantageous catalyst involved WGSR in the aqueous phase.