Base-free transfer hydrogenation of carbonyl substrates catalysed by neutral ruthenium(salicylaldimine) complexes: Inhibitory effect of visible light
In this study, a series of neutral ruthenium salicylaldimine complexes were synthesized and evaluated as catalysts for the base-free transfer hydrogenation of carbonyl compounds, including acetophenone. Under base-free conditions, the complexes demonstrated high catalytic activity, achieving convers...
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Elsevier
2024-12-01
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| Series: | Results in Chemistry |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S2211715624005666 |
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| author | N. Visagie M.C. Joseph E.D. Maggott S.F. Mapolie |
| author_facet | N. Visagie M.C. Joseph E.D. Maggott S.F. Mapolie |
| author_sort | N. Visagie |
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| description | In this study, a series of neutral ruthenium salicylaldimine complexes were synthesized and evaluated as catalysts for the base-free transfer hydrogenation of carbonyl compounds, including acetophenone. Under base-free conditions, the complexes demonstrated high catalytic activity, achieving conversions of up to 79 % for acetophenone with a turnover number (TON) of 790 after 2 h at 82 °C. Comparatively, when a base (2 mol% KOH) was used, the conversion dropped to 17–25 %. Extending the reaction time to 3 h under base-free conditions increased the conversion to 90 %, with a TON of 900. The catalysts were also tested on a range of substrates: acetophenone derivatives with electron-donating substituents showed conversions up to 89 %, while electron-withdrawing groups resulted in lower conversions (67 %). Additionally, sterically hindered substrates like benzophenone yielded 72 % conversion. Visible light exposure significantly reduced catalytic activity, resulting in up to a 26 % decrease in conversion due to the formation of an inactive bis(salicylaldimine) ruthenium species. Mechanistic studies revealed that the reaction proceeds via an oxidative addition pathway, with the formation of a ruthenium-hydride intermediate confirmed by NMR and FT-IR spectroscopy. |
| format | Article |
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| institution | Kabale University |
| issn | 2211-7156 |
| language | English |
| publishDate | 2024-12-01 |
| publisher | Elsevier |
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| series | Results in Chemistry |
| spelling | doaj-art-6fa6f82ca8d24fd3917dc218da3bbc3b2024-12-11T05:56:15ZengElsevierResults in Chemistry2211-71562024-12-0112101870Base-free transfer hydrogenation of carbonyl substrates catalysed by neutral ruthenium(salicylaldimine) complexes: Inhibitory effect of visible lightN. Visagie0M.C. Joseph1E.D. Maggott2S.F. Mapolie3Department of Chemistry and Polymer Science, Stellenbosch University, Private Bag 1, Matieland, 7601 Stellenbosch, South AfricaCorresponding authors.; Department of Chemistry and Polymer Science, Stellenbosch University, Private Bag 1, Matieland, 7601 Stellenbosch, South AfricaDepartment of Chemistry and Polymer Science, Stellenbosch University, Private Bag 1, Matieland, 7601 Stellenbosch, South AfricaCorresponding authors.; Department of Chemistry and Polymer Science, Stellenbosch University, Private Bag 1, Matieland, 7601 Stellenbosch, South AfricaIn this study, a series of neutral ruthenium salicylaldimine complexes were synthesized and evaluated as catalysts for the base-free transfer hydrogenation of carbonyl compounds, including acetophenone. Under base-free conditions, the complexes demonstrated high catalytic activity, achieving conversions of up to 79 % for acetophenone with a turnover number (TON) of 790 after 2 h at 82 °C. Comparatively, when a base (2 mol% KOH) was used, the conversion dropped to 17–25 %. Extending the reaction time to 3 h under base-free conditions increased the conversion to 90 %, with a TON of 900. The catalysts were also tested on a range of substrates: acetophenone derivatives with electron-donating substituents showed conversions up to 89 %, while electron-withdrawing groups resulted in lower conversions (67 %). Additionally, sterically hindered substrates like benzophenone yielded 72 % conversion. Visible light exposure significantly reduced catalytic activity, resulting in up to a 26 % decrease in conversion due to the formation of an inactive bis(salicylaldimine) ruthenium species. Mechanistic studies revealed that the reaction proceeds via an oxidative addition pathway, with the formation of a ruthenium-hydride intermediate confirmed by NMR and FT-IR spectroscopy.http://www.sciencedirect.com/science/article/pii/S2211715624005666SalicylaldimineRuthenium cymene complexesBase-free transfer hydrogenationMechanistic investigation |
| spellingShingle | N. Visagie M.C. Joseph E.D. Maggott S.F. Mapolie Base-free transfer hydrogenation of carbonyl substrates catalysed by neutral ruthenium(salicylaldimine) complexes: Inhibitory effect of visible light Results in Chemistry Salicylaldimine Ruthenium cymene complexes Base-free transfer hydrogenation Mechanistic investigation |
| title | Base-free transfer hydrogenation of carbonyl substrates catalysed by neutral ruthenium(salicylaldimine) complexes: Inhibitory effect of visible light |
| title_full | Base-free transfer hydrogenation of carbonyl substrates catalysed by neutral ruthenium(salicylaldimine) complexes: Inhibitory effect of visible light |
| title_fullStr | Base-free transfer hydrogenation of carbonyl substrates catalysed by neutral ruthenium(salicylaldimine) complexes: Inhibitory effect of visible light |
| title_full_unstemmed | Base-free transfer hydrogenation of carbonyl substrates catalysed by neutral ruthenium(salicylaldimine) complexes: Inhibitory effect of visible light |
| title_short | Base-free transfer hydrogenation of carbonyl substrates catalysed by neutral ruthenium(salicylaldimine) complexes: Inhibitory effect of visible light |
| title_sort | base free transfer hydrogenation of carbonyl substrates catalysed by neutral ruthenium salicylaldimine complexes inhibitory effect of visible light |
| topic | Salicylaldimine Ruthenium cymene complexes Base-free transfer hydrogenation Mechanistic investigation |
| url | http://www.sciencedirect.com/science/article/pii/S2211715624005666 |
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