Conférence LCC
Pr Albert Poater
Universitat de Girona
Hydrogenation vs Generation of H 2 : on the way to green chemistry
Vendredi 22 février 2019 à 11h00 Auditorium Fernand Gallais
Campus CNRS 205
205, route de Narbonne, Toulouse
Contact LCC: Dr Eric Manoury , eric.manoury@lcc-toulouse.fr
Retrouvez le programme complet des séminaires sur le site web du LCC : http://www.lcc-toulouse.fr/
Hydrogenation vs Generation of H
2: on the way to green chemistry
Albert Poater
Institut de Química Computacional i Catàlisi and Departament de Química, Universitat de Girona, c/ Mª Aurèlia Capmany 69, 17003 Girona, Catalonia, Spain albert.poater@udg.edu
ABSTRACT
First, cyclopentadienone iron dicarbonyl complexes were applied in the alkylation of ketones with various aliphatic and aromatic ketones and alcohols via the borrowing hydrogen strategy in mild reaction conditions. DFT calculations and experimental works highlight the role of the transition metal Lewis pairs and the base. These iron complexes demonstrated a broad applicability in mild conditions and extended the scope of substrates. Then a general iron-catalyzed chemo- and diastereoselective reduction of unsaturated ketones into the corresponding saturated ketones in mild reaction conditions.
On the other hand, the hydrogenation of nitrous oxide by pincer ruthenium complexes supposes a promising way to functionalize a hazardous gas and reduce the greenhouse effect, generating dinitrogen and water. The particular PCsp2P ligand (see Figure 1a), which is not a simple spectator, but it directly assists in the formation of a characterized epoxide complex, affording the N2 release if N2O is used as a reactant.[1,2] Next the hydrogenation is undertaken with H2 as a reactant, generating water as a main product. All these statements are discussed mechanistically, by means of DFT calculations. The stoichiometric nature of the reaction described here is rationalized by the competition between N2O and H2 to react with the PCP iridium pincer complex.
a) b)
Figure 1. (a) PCsp2P ligand–pincer Ir based catalyst. (b) Hydrogenation of N2O by the PNP- pincer Ru based catalyst (P = P(iPr)2).
The whole reaction mechanism for a PNP pincer based catalyst has also been undertaken, see Figure 1b.[3,4] The possibility of a water autocatalysis at the initial stages of the reaction was determined, while it would be hindered as time progresses and water is formed as a product of the hydrogenation of N2O.
Furthermore, acceptorless dehydrogenative coupling of alcohols and amines using a manganese based catalyst is able to produce aldimines,[5,6] which have a wide reactivity, without underestimating the generation of a clean fuel, since as a result of this coupling, molecular hydrogen is also obtained. DFT calculations provide insight into the catalytic pathway, coupled with a non- catalyzed organic transformation to reach the desired aldimine; based on the aldehyde generated in the catalytic cycle.
[1] L. E. Doyle, W. E. Piers, J. Borau-Garcia, J. Am. Chem. Soc. 2015, 137, 2187.
[2] L. E. Doyle, W. E. Piers, J. Borau-Garcia, M. J. Sgro, D. M. Spasyuk, Chem. Sci. 2016, 7, 921.
[3] R. Zeng, M. Feller, Y. Ben-David, D. Milstein, J. Am. Chem. Soc. 2017, 139, 5720.
[4] J. A. Luque-Urrutia, A. Poater, Inorg. Chem. 2017, 56, 14383.
[5] S. Chakraborty, U. Gellrich, Y. Diskin-Posner, G. Leitus, L. Avram, D. Milstein, Angew. Chem. Int. Ed. 2017, 56, 4229.
[6] A. Mukherjee, A. Nerush, G. Leitus, L. J. W. Shimon, Y. B. David, N. A. E. Jalapa, D. Milstein, J. Am. Chem. Soc. 2016, 138, 4298.
