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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - OrFuNCo (Organic Functionalisation of N2 Using Metal-Main Group and Metal-Metal Cooperativity)

Teaser

Summary

\"Conversion of dinitrogen, N2, into N-containing compounds is a challenge for chemists due to the inertness of this molecule. Paradoxically, our atmosphere is an inexhaustible reservoir of dinitrogen that supplies the biosphere with the essential nitrogen element through a biological process called \"\"nitrogen fixation\"\", in which dinitrogen is converted into ammonia (NH3). This process is still poorly understood and due to the sensitivity of the microorganisms that express the enzymes responsible of nitrogen fixation, there is no chance mankind could implement bio-reactors for anthropogenic nitrogen fixation. Instead, the well-known industrial Haber-Bosch process allows reduction of dinitrogen into ammonia at hundreds of million tons scale, but it is an energy-demanding and fossil fuel-intensive process, which goes with the indirect production of large amounts of greenhouse gas waste. Besides, the primary use of NH3 is the manufacture of millions of tons of N fertilizers, which abusive agricultural use has negatively impacted our environment. Reconsidering the use of dinitrogen in the perspective of climate change and energy transition is a challenge modern chemistry has to take up.
The nitrogenase, the enzyme that allows conversion of dinitrogen to ammonia in some microorganisms, contains several metal atoms at the site where the transformation of dinitrogen occurs. The latter is proposed to bind an iron atom before being transformed into bioavailable ammonia, that is subsequently transformed into numerous small molecules that are essential to life. The mild conditions under which this process occurs has fueled us to take inspiration from it to develop methods that allow the transformation of dinitrogen in a sustainable way. More precisely, we wish to use one or two metal atoms to bind dinitrogen and let it reacts with carbon-based reagents, allowing us to bypass ammonia synthesis and afford, directly from atmospheric dinitrogen, a value-added, nitrogen containing compound.\"

Work performed

Since the beginning of the project, we have been working on making molecules with two central atoms, and shown their ability to activate the dinitrogen molecule in order to make it react under very mild conditions. We have focused, as of 2019, on molybdenum or tungsten/boron, molybdenum/lithium and tungsten/gold combinations and demonstrated such combinations are indeed able to activate the dinitrogen molecule. We have attached importance to ease of production of these molecules, as well as their complete description in terms of spectroscopic methods, in particular by nuclear magnetic resonance and x-ray diffraction. We are currently exploring their reactivity, and we have shown that the molybdenum or tungsten/boron systems were good candidate for the building of nitrogen-boron bonds between dinitrogen and a boron reagent, paving the way for the production of nitrogen-boron compounds.

Final results

The project will allow deeper understanding on cooperative activation of dinitrogen, i. e. how two elements can join forces within a single molecule to perform unprecedented transformations of dinitrogen. We are ultimately aiming at the production of nitrogen compounds that are of relevance for fine chemistry directly from the simple yet diffcult-to-tranform dinitrogen molecule, in a sustainable way.