Lanthanide Complexes for the Transformation of CO into Value-Added Multicarbon Products – MultiCO
Low-valent lanthanide complexes for the transformation of small molecules (N₂, CO, CO₂)
This ANR project is based on the activation and transformation of small, inert and widely available small molecules (N₂, CO, CO₂) with the objective to selectively obtain molecules with higher added value. From simple building blocks, it is thus possible to obtain highly functionalised molecule.
Nature has the ability to selectively and efficiently transform simple, inert building blocks into highly functionalised molecules. The amino acid family is a representative example, featuring a multicarbon (C2+) backbone and various functional groups. Although the activation of small molecules such as carbon monoxide (CO), carbon dioxide (CO₂) and dinitrogen (N₂) has recently attracted a large attention, very few systems allow these building blocks to be transformed into highly functionalised molecules. In particular, their functionalisation of CO and CO₂ into high value-added C2+ molecules is very poorly documented. In general, the transformation of small elementary building blocks into functionalised molecules with greater structural complexity and higher added value is a major challenge in order to minimise our dependence on the use of pre-functionalised reagents, often derived from the petroleum chemistry.
Divalent lanthanide complexes are highly reducing species that enable the activation of particularly inert molecules such as N₂, CO and CO₂.
The specific properties of the lanthanide elements, in particular their highly electropositive nature, lead to reactivity that differs from that observed with transition metals. In particuler, some divalent lanthanide complexes are able to reduce N₂ to the diazenido ligand (N₂)²⁻ and CO to the ethyndiolate ligand (OCCO)²⁻. The complexes obtained remain highly reactive and can be functionalised by other small inert molecules (such as CO₂) to produce products with greater structural complexity and added value.
The activation of dinitrogen (N₂) and dihydrogen (H₂) was made possible by a highly reactive divalent lutetium complex. This is the first example of direct H₂ cleavage by a divalent lanthanide complex, and this unique reactivity has been confirmed by theoretical calculations (DFT). Furthermore, the diazenido complex obtained following the reduction of dinitrogen exhibits unique reactivity and can be hydrogenated under very mild conditions to form an amido-type Lu(III)-NH₂ complex. This work shows that hydrogenation and direct N₂ cleavage reactions are not only catalysed by transition metals but can also be easily achieved in the presence of rare earth molecular complexes.
HAL weblink: hal.science/hal-05213394/
Nature achieves the selective transformation of simple and inert chemical building blocks into highly functionalised molecules. The amino acid family is one representative example which features a multicarbon backbone and different functional groups. Although the activation of small molecules such as carbon monoxide (CO) and carbon dioxide (CO2) has attracted a lot of recent attention, systems allowing the transformation of these C1 building blocks into multicarbon (C2+) products are scarce, with very little precedence for their functionalisation into value-added C2+ molecules of high general interest.
In this JCJC project, I describe an innovative strategy using divalent lanthanide complexes for the activation and reductive coupling of CO into reactive oxocarbon products. Upon treatment with CO2, very reactive intermediates are formed that allow C–H activation on typically inert hydrocarbon substrates, as well as other functionalisation patterns through the formation of new C–C or C–N bonds. Supported by preliminary results, the goal of this project is to create functionalised molecules of high structural complexity through a unique activation and functionalisation procedure of CO and CO2.
Following the functionalisation reactions, I will develop strategies for the recycling of the active divalent lanthanide complexes under mild conditions. For this purpose, electrochemical procedures will be of high interest as they constitute resource-economical alternatives to the use of external reducing agents. The ultimate goal is to achieve electrocatalytic procedures for these transformations. Successful results will open new avenues in the field of small molecule activation, as value-added functionalised C2+ products will be directly formed from simple abundant and polluting gaseous molecules, therefore minimising our dependency on pre-functionalised petroleum-derived reagents.
Project coordination
Thomas SIMLER (Laboratoire de Chimie Moléculaire)
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.
Partnership
LCM Laboratoire de Chimie Moléculaire
Help of the ANR 218,914 euros
Beginning and duration of the scientific project:
October 2023
- 48 Months
