The cornerstone of the Ferracycles project is the development of well-defined iron metalacycles and their use as catalysts in hydroelementation or borrowing-hydrogen reactions. Metalacycles are well established with many transition metals, but in comparison, extremely scarce with iron. Nevertheless, cyclometalated complexes have been demonstrated to exhibit unique properties in catalysis. The key feature is the presence of both the metal-carbon bond supported by the chelation of the second donor atom in order to stabilize the complex, modulate the reactivity at the metal center and, potentially, give a bifunctional catalyst at the same time. The general approach is summarized below:
(i) Synthesis of ferracycles. We plan to develop new routes, in particular through the use of the iron (II) precursors, and meanwhile to reinvestigate in details the reactivity of iron (0) carbonyl precursors.
(ii) Catalysis. The new iron complexes will be tested in reduction catalysis, hydrogenation, hydrogen transfer and hydrosilylation and then in hydrogen borrowing reactions.
The synthesis of ferracycles with simple, inexpensive and commercial iron pentacarbonyl has accomplished with good yield in the case of tridentate ligands PCP bearing to phosphorus atoms. These complexes have applied as efficient catalysts for the dehydrogenative borylation of styrene with pinacolborane (Dalton Tans. 2016).
In parallel, starting from iron (0) polyphosphines precurors, used as starting material for the synthesis of ferracycles, the dehydrogenative borylation of styrene has been significantly improved. An article will be sumitted very soon.
Using a similar strategy, with manganese complexes, highly promissing results have been obtained in hydrogenation (Catal. Commun. 2017) and hydrogen borrowing reactions (methylation of amines with methanol, J. Catal. 2017).
Therefore, we have focused our work on manganese chemistry, notablly by developping transfer hydrogenation catalyst (Org. Lett. 2017 and Catal. Commun. 2018). The first generation catalyst has been improved (Adv. Synth. Catal. 2018, Organometallics 2018), leading the the first reductive amination using hydrogen as reductant (Chem. Commun. 2018).
For the second part of the project, the development of catalysts based on cyclometalated complexes obtained from iron (0) precursors will be continued.
In parallel, the development of efficient manganese catalysts for hydrogenation, hydrogen transfer and hydrogen borrowing reactions is highly promissing.
1. S. Jiang, S. Quintero-Duque, T. Roisnel, V. Dorcet, M. Grellier, S. Sabo-Etienne, C. Darcel, J.-B. Sortais, Dalton Trans. 2016, 45, 11101-11108.
2. A. Bruneau-Voisine, D. Wang, T. Roisnel, C. Darcel, J.-B. Sortais, Catal. Commun. 2017, 92, 1-4.
3. A. Bruneau-Voisine, D. Wang, V. Dorcet, T. Roisnel, C. Darcel, J.-B. Sortais, J. Catal. 2017, 347, 57-62
4. A. Bruneau-Voisine, D. Wang, V. Dorcet, T. Roisnel, C. Darcel, J.-B. Sortais, Org. Lett. 2017, 19, 3656-3659.
5. D. Wang, A. Bruneau-Voisine, J.-B. Sortais, Catal. Commun. 2018, 105, 31-36.
6. D. Wei, A. Bruneau-Voisine, T. Chauvin, V. Dorcet, T. Roisnel, D. A. Valyaev, N. Lugan, J. B. Sortais, Adv. Synth. Catal. 2018, 360, 676-681.
7. H. Li, D. Wei, A. Bruneau-Voisine, M. Ducamp, M. Henrion, T. Roisnel, V. Dorcet, C. Darcel, J.-F. Carpentier, J.-F. Soulé, J.-B. Sortais, Organometallics 2018. Doi : 10.1021/acs.organomet.8b00020
8. D. Wei, A. Bruneau-Voisine, D. A. Valyaev, N. Lugan, J.-B. Sortais, Chem. Commun. 2018. Doi : 10.1039/C8CC01787E
The decrease in non-renewable natural resources has become a global concern for the future, and it is usually the main issue associated with fossil fuel feedstock. However, precious transition metals, such as palladium, rhodium, platinum or ruthenium which are extensively used for catalytic processes in the chemical industry are also limited, and their cost has already increased tremendously over the last decade. New directions for homogeneous catalysis should not only address energy issues by developing highly reactive catalysts, but should also favour the use of earth-abundant materials as catalysts. Iron, in terms of its abundance and low cost is especially an attractive surrogate to precious transition metals. During the last decade, the use of iron as an efficient catalyst has dramatically increased, and important breakthroughs have recently been achieved in the field of reduction. Nevertheless, new efficient and selective catalytic systems are still needed.
On the other hand, despite the prominent role of iron in many biological C-H activations and despites the fact that the cyclometalation of ligands by transition metals is one of the oldest area of organometallic chemistry, studies on cyclometalation using iron have remained remarkably scarce.
The cornerstone of the “Ferracycles” project will be the development of well-defined iron metalacycles and their use as catalysts in reduction and in borrowing-hydrogen reactions. The key feature is the presence of both the metal-carbon bond supported by the chelation of the second donor atom in order to stabilize the complex and, potentially, give a bifunctional catalyst at the same time. The main objectives of the project are i) to develop new methodologies to get access to cyclometalated iron complexes based either on iron (II) precursors or on iron (0) ones; ii) to use these complexes as catalysts for reduction reactions such as hydrogenation, hydrogen transfer or hydrosilylation and for hydrogen borrowing reactions.
Monsieur Jean-Baptiste SORTAIS (CNRS/Laboratoire de Chimie de coordination)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
UR1 CNRS/Laboratoire de Chimie de coordination
UR1 Université de Rennes 1, UMR 6226, Institut des Sciences Chimiques de Rennes
Help of the ANR 197,599 euros
Beginning and duration of the scientific project: September 2015 - 42 Months