Borylenes help cleave dinitrogen into ammonium

The chemical reaction that splits dinitrogen and forms ammonia feeds the world by producing much of the global supply of fertilizer. But the process is energy intensive, requiring high pressure and temperatures in excess of 400 °C. Currently, the reaction is accomplished on an industrial scale with the help of iron catalysts. In earlier work, chemists led by Holger Braunschweig of Julius Maximilian University of Würzburg showed they could nab typically inert nitrogen with borylenes, reactive molecules with cores that feature reactive boron rather than a transition metal. Now, Braunschweig and coworkers show that they can cleave the borylene-bound N₂ into ammonium chloride in a one-pot reaction that takes place at room temperature (Nat. Chem. 2020, DOI: 10.1038/s41557-020-0520-6). A solid-phase reductant and acid reagents spur the transformation (shown), which is a complex sequence of multiple reductions and protonations. Braunschweig’s group was able to isolate and characterize the intermediates en route to ammonium. The chemists attribute the success of the reaction to electron-rich boron’s unwillingness to accept more electrons, which is a stark contrast to many transition-metal complexes. This, they note, forces the reduction steps to occur on N₂, ultimately leading to its breakup.