2023-07-24 04:00:09
Scientists explain why despite their similarities, carbon monoxide (CO) and nitrogen dioxide (N2) exhibit very different reactivities when bound to certain metals. Key information because these molecules are at the heart of the most important processes for the production of ammonia and hydrocarbons, involving catalysts metallic.
Essential in industrial chemistry, the diazote (N2) and the carbon monoxide (CO) are at the heart of the most important processes in this field: dinitrogen is used in the Haber-Bosch process to synthesize ammonia (NH3) at height hundreds of millions of tons per year, while carbon monoxide carbone allows the production of hundreds of thousands of barrels of hydrocarbons per jour.
Although these two diatomic molecules are similar in terms of their electronic structure, they differ radically in their reactivity. Dinitrogen is commonly considered as inertthe basic constituent of our atmosphere that we breathe every day without metabolizing it (unlike the dioxygen O2). Carbon monoxide is a more reactive gas, toxic to living organisms, which is used in a wide catalog of reactions of Organic chemistry.
By involving a metal (in this study, the Manganese, Mn) it is possible to combine CO with phenyllithium, an electron-rich reagent. Since CO and N2 molecules are known to bind in the same way to a atom metal to form a coordination complex, chemists first suggested that the reactivity of dinitrogen was analogous to that of CO, namely their reaction with phenyllithium to form a carbon-carbon or nitrogen-carbon bond, respectively.
By combining experience and theoretical calculations, scientists from the Laboratory of Coordination Chemistry (CNRS) and the Laboratory of Physics and Chemistry of Nano-Objects (CNRS/INSA Toulouse/University of Toulouse) show that dinitrogen bound to manganese does not exhibit the same reactivity as carbon monoxide bound to the same metal. There diffraction single-crystal X-rays revealed the molecular structure of compounds resulting from the reaction of the dinitrogen complex with phenyllithium, ruling out the formation of a nitrogen-carbon bond as had been proposed.
These results, published in the journal Angewandte Chemie, shed new light on the avenues to be explored to operate the catalytic transformation of dinitrogen into a compound with high added value.
Reference
Quentin Le Dé, Amal Bouammali, Christian Bijani, Laure Vendier, Iker del Rosal, Dmitry A. Valyaev, Chiara Dinoi & Antoine Simonneau.
An Experimental and Computational Investigation Rules Out Direct Nucleophilic Addition on the N2 Ligand in Manganese Dinitrogen Complex [Cp(CO)2Mn(N2)]
Applied Chemistry International Edition 2023
1690171929
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