Mechanistic Studies of Oxygen-Atom Transfer (OAT) in the Homogeneous Conversion of N<sub>2</sub>O by Ru Pincer Complexes
As the overall turnover-limiting step (TOLS) in the homogeneous conversion of N<sub>2</sub>O, the oxygen-atom transfer (OAT) from an N<sub>2</sub>O to an Ru-H complex to generate an N<sub>2</sub> and Ru-OH complex has been comprehensively investigated by density f...
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MDPI AG
2022-05-01
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| Online Access: | https://www.mdpi.com/2304-6740/10/6/69 |
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| author | Guangchao Liang Min Zhang Charles Edwin Webster |
| author_facet | Guangchao Liang Min Zhang Charles Edwin Webster |
| author_sort | Guangchao Liang |
| collection | DOAJ |
| description | As the overall turnover-limiting step (TOLS) in the homogeneous conversion of N<sub>2</sub>O, the oxygen-atom transfer (OAT) from an N<sub>2</sub>O to an Ru-H complex to generate an N<sub>2</sub> and Ru-OH complex has been comprehensively investigated by density functional theory (DFT) computations. Theoretical results show that the proton transfer from Ru-H to the terminal N of endo N<sub>2</sub>O is most favorable pathway, and the generation of N<sub>2</sub> via OAT is accomplished by a three-step mechanism [N<sub>2</sub>O-insertion into the Ru-H bond (TS-1-2, 24.1 kcal mol<sup>−1</sup>), change of geometry of the formed (Z)-O-bound oxyldiazene intermediate (TS-2-3, 5.5 kcal mol<sup>−1</sup>), and generation of N<sub>2</sub> from the proton transfer (TS-3-4, 26.6 kcal mol<sup>−1</sup>)]. The Gibbs free energy of activation (ΔG<sup>‡</sup>) of 29.0 kcal mol<sup>−1</sup> for the overall turnover-limiting step (TOLS) is determined. With the participation of potentially existing traces of water in the THF solvent serving as a proton shuttle, the Gibbs free energy of activation in the generation of N<sub>2</sub> (TS-3-4-OH<sub>2</sub>) decreases to 15.1 kcal mol<sup>−1</sup> from 26.6 kcal mol<sup>−1</sup> (TS-3-4). To explore the structure–activity relationship in the conversion of N<sub>2</sub>O to N<sub>2</sub>, the catalytic activities of a series of Ru-H complexes (C1–C10) are investigated. The excellent linear relationships (R<sup>2</sup> > 0.91) between the computed hydricities (ΔG<sub>H</sub><sup>−</sup>) and ΔG<sup>‡</sup> of TS-3-4, between the computed hydricities (ΔG<sub>H</sub><sup>−</sup>) and the ΔG<sup>‡</sup> of TOLS, were obtained. The utilization of hydricity as a potential parameter to predict the activity is consistent with other reports, and the current results suggest a more electron-donating ligand could lead to a more active Ru-H catalyst. |
| first_indexed | 2024-03-09T23:29:51Z |
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| spelling | doaj.art-07c1cb44816f460789ac22bd01d528042023-11-23T17:10:21ZengMDPI AGInorganics2304-67402022-05-011066910.3390/inorganics10060069Mechanistic Studies of Oxygen-Atom Transfer (OAT) in the Homogeneous Conversion of N<sub>2</sub>O by Ru Pincer ComplexesGuangchao Liang0Min Zhang1Charles Edwin Webster2Academy of Advanced Interdisciplinary Research, Xidian University, Xi’an 710071, ChinaDepartment of Pharmacy, Medical School, Xi’an International University, Xi’an 710077, ChinaDepartment of Chemistry, Mississippi State University, Starkville, Mississippi State, MS 39762, USAAs the overall turnover-limiting step (TOLS) in the homogeneous conversion of N<sub>2</sub>O, the oxygen-atom transfer (OAT) from an N<sub>2</sub>O to an Ru-H complex to generate an N<sub>2</sub> and Ru-OH complex has been comprehensively investigated by density functional theory (DFT) computations. Theoretical results show that the proton transfer from Ru-H to the terminal N of endo N<sub>2</sub>O is most favorable pathway, and the generation of N<sub>2</sub> via OAT is accomplished by a three-step mechanism [N<sub>2</sub>O-insertion into the Ru-H bond (TS-1-2, 24.1 kcal mol<sup>−1</sup>), change of geometry of the formed (Z)-O-bound oxyldiazene intermediate (TS-2-3, 5.5 kcal mol<sup>−1</sup>), and generation of N<sub>2</sub> from the proton transfer (TS-3-4, 26.6 kcal mol<sup>−1</sup>)]. The Gibbs free energy of activation (ΔG<sup>‡</sup>) of 29.0 kcal mol<sup>−1</sup> for the overall turnover-limiting step (TOLS) is determined. With the participation of potentially existing traces of water in the THF solvent serving as a proton shuttle, the Gibbs free energy of activation in the generation of N<sub>2</sub> (TS-3-4-OH<sub>2</sub>) decreases to 15.1 kcal mol<sup>−1</sup> from 26.6 kcal mol<sup>−1</sup> (TS-3-4). To explore the structure–activity relationship in the conversion of N<sub>2</sub>O to N<sub>2</sub>, the catalytic activities of a series of Ru-H complexes (C1–C10) are investigated. The excellent linear relationships (R<sup>2</sup> > 0.91) between the computed hydricities (ΔG<sub>H</sub><sup>−</sup>) and ΔG<sup>‡</sup> of TS-3-4, between the computed hydricities (ΔG<sub>H</sub><sup>−</sup>) and the ΔG<sup>‡</sup> of TOLS, were obtained. The utilization of hydricity as a potential parameter to predict the activity is consistent with other reports, and the current results suggest a more electron-donating ligand could lead to a more active Ru-H catalyst.https://www.mdpi.com/2304-6740/10/6/69nitrous oxideRu-Hoxygen-atom transferDFT mechanism |
| spellingShingle | Guangchao Liang Min Zhang Charles Edwin Webster Mechanistic Studies of Oxygen-Atom Transfer (OAT) in the Homogeneous Conversion of N<sub>2</sub>O by Ru Pincer Complexes Inorganics nitrous oxide Ru-H oxygen-atom transfer DFT mechanism |
| title | Mechanistic Studies of Oxygen-Atom Transfer (OAT) in the Homogeneous Conversion of N<sub>2</sub>O by Ru Pincer Complexes |
| title_full | Mechanistic Studies of Oxygen-Atom Transfer (OAT) in the Homogeneous Conversion of N<sub>2</sub>O by Ru Pincer Complexes |
| title_fullStr | Mechanistic Studies of Oxygen-Atom Transfer (OAT) in the Homogeneous Conversion of N<sub>2</sub>O by Ru Pincer Complexes |
| title_full_unstemmed | Mechanistic Studies of Oxygen-Atom Transfer (OAT) in the Homogeneous Conversion of N<sub>2</sub>O by Ru Pincer Complexes |
| title_short | Mechanistic Studies of Oxygen-Atom Transfer (OAT) in the Homogeneous Conversion of N<sub>2</sub>O by Ru Pincer Complexes |
| title_sort | mechanistic studies of oxygen atom transfer oat in the homogeneous conversion of n sub 2 sub o by ru pincer complexes |
| topic | nitrous oxide Ru-H oxygen-atom transfer DFT mechanism |
| url | https://www.mdpi.com/2304-6740/10/6/69 |
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