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...
Saved in:
| Main Authors: | , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Elsevier
2024-12-01
|
| Series: | Results in Chemistry |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S2211715624005666 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Summary: | 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. |
|---|---|
| ISSN: | 2211-7156 |