Pyridyl-triazole ligands enable in situ generation of a highly active dihydride iridium(III) complex for formic acid dehydrogenation
The reaction of [Cp*IrCl2]2 with 1-pyridyl-1,2,3-triazoles La-Ld in the presence of sodium triflate yielded the complexes [Cp*Ir(k2-NN)(Cl)][OTf] (1a?1d) in which the k2-NN ligand coordinates to iridium through the pyridyl nitrogen and the N2 nitrogen of the triazole ring, leaving the more basic N3...
| Authors: | , , , , , , , |
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| Format: | article |
| Publication Date: | 2024 |
| Country: | España |
| Institution: | Universidad de Alcalá (UAH) |
| Repository: | e_Buah Biblioteca Digital Universidad de Alcalá |
| Language: | English |
| OAI Identifier: | oai:ebuah.uah.es:10017/62809 |
| Online Access: | http://hdl.handle.net/10017/62809 https://dx.doi.org/10.1039/D4QI01818D |
| Access Level: | Open access |
| Keyword: | Química Chemistry |
| Summary: | The reaction of [Cp*IrCl2]2 with 1-pyridyl-1,2,3-triazoles La-Ld in the presence of sodium triflate yielded the complexes [Cp*Ir(k2-NN)(Cl)][OTf] (1a?1d) in which the k2-NN ligand coordinates to iridium through the pyridyl nitrogen and the N2 nitrogen of the triazole ring, leaving the more basic N3 atom free. These complexes effectively catalyze the dehydrogenation of formic acid in the presence or absence of an external solvent, achieving turnover frequencies (TOFmax) of up to 10703 h-1 and producing a 1:1 mixture of hydrogen and carbon dioxide with no detectable carbon monoxide. The catalysts can be reused after a single reaction cycle, as they retain their activity. This retention of activity has allowed to reach a cumulative turnover number (TON) of 26876 after six reloading cycles of formic acid with catalyst 1d in the presence of sodium formate as a base. Kinetic and 1H NMR spectroscopy studies indicate that the active catalyst of the reaction is complex [Cp*Ir(CO)H2] (2), which was formed under the reaction conditions from precursors 1a-1d. Consequently, complexes 1a-1d act as stable precatalyst, avoiding the difficulties associated with handling the unstable complex 2. The reaction mechanism is likely to involve mono- and dihydride species. The decarboxylation of the coordinated formate is the rate-determining step at high formic acid concentrations, according to the kinetic profiles and kinetic isotope effect (KIE) values obtained |
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