The dramatic effect of NH3 co-ligation on the FE+-assisted activation of carbon dioxide in the gas phase: From bare metal ions to complexes
✍ Scribed by Paraskevas A. Karipidis; Constantinos A. Tsipis
- Publisher
- John Wiley and Sons
- Year
- 2008
- Tongue
- English
- Weight
- 687 KB
- Volume
- 29
- Category
- Article
- ISSN
- 0192-8651
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✦ Synopsis
Abstract
The catalytic efficiency of Fe^+^ ion over the CO~2~ decomposition in the gas phase has been extensively investigated with the help of electronic structure calculation methods. Potential‐energy profiles for the activation process Fe^+^ + CO~2~ → CO + FeO^+^ along two rival potential reaction paths, namely the insertion and addition pathways, originating from the end‐on κ^1^‐O and κ^2^‐O,O coordination modes of CO~2~ with the metal ion, respectively, have been explored by DFT calculations. For each pathway the potential energy surfaces of the high‐spin sextet (S = 5/2) and the intermediate‐spin quartet (S = 3/2) spin‐states have been explored. The complete energy reaction profile calculated by a combination of ab initio and density functional theory (DFT) computational techniques reveals a two‐state reactivity, involving two spin inversions, for the decomposition process and accounts well for the experimentally observed inertness of bare Fe^+^ ions towards CO~2~ activation. Furthermore, the coordination of up to three extra ancillary NH~3~ ligands with the Fe^+^ metal ion has been explored and the geometric and energetic reaction profiles of the CO~2~ activation processes Fe^+^ + n·NH~3~ + CO~2~ → [Fe(NH~3~)~n~(CO~2~)]^+^ → [Fe(NH~3~)~n~(O)(CO)]^+^ → CO + [Fe(O)(NH~3~)~n~]^+^ (n = 1, 2 or 3) have thoroughly been scrutinized for both the insertion and the addition mechanisms. Inter alia, the geometries and energies of the various states of the [Fe(NH~3~)~n~(CO~2~)]^+^ and [Fe(NH~3~)~n~(O)(CO)]^+^ complexes are explored and compared. Finally, a detailed analysis of the coordination modes of CO~2~ in the cationic [Fe(NH~3~)~n~(CO~2~)]^+^ (n = 0, 1, 2 and 3) complexes is presented. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2008