A series of chromium complexes bearing a carbene‐ and phosphine‐based PCP‐type pincer ligand has been newly prepared, and some of them are found to work as effective catalysts to reduce dinitrogen into ammonia and hydrazine under atmospheric pressure. This reaction can be expressed as nitrogen molecules (raindrops) being converted into ammonia and hydrazine on the chromium complex (umbrella). More information can be found in the Research Article by K. Yoshizawa, Y. Nishibayashi et al. (DOI: 10.1002/chem.202200557).

A series of chromium–halide, –nitride, and –dinitrogen com-plexes bearing a carbene- and phosphine-based PCP-type pin-cer ligand is newly prepared and some of them are found to work as effective catalysts to reduce dinitrogen under atmos-pheric pressure, whereby up to 8.40 equiv of ammonia and 2.46 equiv of hydrazine (13.32 equiv of fixed N atom) are produced based on the chromium atom. To the best of our knowledge, this is the first successful example of chromium-catalyzed conversion of dinitrogen to ammonia and hydrazine under mild reaction conditions.

Herein, we established an iridium- and molybdenum-catalysed process for the synthesis of ammonia from dinitrogen that takes place under ambient reaction conditions and under visible light irradiation. In this reaction system, cationic iridium complexes bearing 2-(2-pyridyl)phenyl and 2,2’-bipyridine-type ligands and molybdenum triiodide complexes bearing N-heterocyclic carbene-based PCP-type pincer ligands acted as cooperative catalysts to activate 9,10-dihydroacridine and dinitrogen, respectively. Interestingly, under visible light irradiation, 9,10-dihydroacridine acted as a one-electron and one-proton source. The findings of this study provide a novel approach to catalytic nitrogen fixation that is driven by visible light energy. The reaction of dinitrogen with 9,10-dihydroacridine was not thermodynamically favoured, and it only took place under visible light irradiation. Therefore, the described reaction system is one that affords visible light energy–driven ammonia formation from dinitrogen. The findings reported herein can contribute to the development of novel next-generation nitrogen fixation systems powered by renewable energy.