Nikol Alexander Tobias, Rabell Brenda, Jørgensen Mike Steffen Bernhard, Larsen René Wugt, Nielsen Martin
Department for Chemistry, Technical University of Denmark (DTU), Kongens Lyngby, 2800, Denmark.
Sci Rep. 2024 Oct 31;14(1):26209. doi: 10.1038/s41598-024-76782-3.
Formic acid is one of the most promising candidates for the long-term storage of hydrogen in liquid form. Herein, we present a new collection of ruthenium pincer complexes of the general formula [RuHCl(POP)(PPh)] using commercially available or easy-to-synthesize tridentate xantphos-type POP pincer ligands. We applied these complexes in the dehydrogenation of formic acid to CO and H using the ionic liquid BMIM OAc (1-butyl-3-methylimidazolium acetate) as solvent under mild, reflux-free conditions. The best performing catalyst with respect to maximum turnover frequency, the literature-known complex [RuHCl(xantphos)(PPh)] Ru-1, produced a maximum turnover frequency of 4525 h with 74% conversion after 10 min at 90 °C and complete conversion (> 98%) occurring within 3 h. On the other hand, the best overall performing catalyst, the novel complex [RuHCl(iPr-dbfphos)(PPh)] Ru-2, facilitated full conversion within 1 h leading to an overall turnover frequency of 1009 h. Moreover, catalytic activity was observed at temperatures as low as 60 °C. Only CO and H are observed in the gas phase, with no CO detected. High-resolution mass spectrometry suggests the presence of N-heterocyclic carbene complexes in the reaction mixture.
甲酸是最有前景的以液态形式长期储存氢的候选物之一。在此，我们使用市售或易于合成的三齿呫吨膦型POP钳形配体，展示了通式为[RuHCl(POP)(PPh)]的钌钳形配合物的新集合。我们在温和、无回流条件下，以离子液体BMIM OAc（1-丁基-3-甲基咪唑鎓乙酸盐）为溶剂，将这些配合物应用于甲酸脱氢生成CO和H的反应中。就最大周转频率而言，性能最佳的催化剂是文献中已知的配合物[RuHCl(xantphos)(PPh)] Ru-1，在90°C下10分钟后，其最大周转频率为4525 h，转化率为74%，3小时内完全转化（>98%）。另一方面，总体性能最佳的催化剂是新型配合物[RuHCl(iPr-dbfphos)(PPh)] Ru-2，它在1小时内实现了完全转化，总周转频率为1009 h。此外，在低至60°C的温度下也观察到了催化活性。气相中仅观察到CO和H，未检测到CO。高分辨率质谱表明反应混合物中存在N-杂环卡宾配合物。
