Dinitrogen is a challenging molecule to reduce to useful products under ambient conditions. The range of d-block metal complexes that can catalyze dinitrogen reduction to ammonia or tris(silyl)amines under ambient conditions has increased recently but lacks electropositive metal complexes, such as those of the f-block, which lack filled d-orbitals that would support classical binding modes of N₂. Here, metallacyclic phenolate structures with lanthanide or group 4 cations can bind dinitrogen and catalyze its conversion to bis(silyl)amines under ambient conditions. The formation of this unusual product is controlled by metallacycle sterics. The group 4 complexes featuring small cavities are most selective for bis(silyl)amine, while lanthanide complexes and the solvated uranium(IV) congener, with larger cavities, can also make a conventional tris(silyl)amine product. These results offer new catalytic applications for plentiful titanium and more earth-abundant members of the lanthanides that are also less toxic than many base metals used in catalysis.

二氮是一种在环境条件下还原成有用产品的具有挑战性的分子。最近，可以在环境条件下催化二氮还原为氨或三（甲硅烷基）胺的 d 区金属配合物的范围有所增加，但缺乏正电性金属配合物，例如 f 区的金属配合物，其缺乏填充的 d 轨道，支持 N ₂的经典结合模式。此处，具有镧系元素或第 4 族阳离子的金属环酚盐结构可以结合二氮并在环境条件下催化其转化为双（甲硅烷基）胺。这种不寻常产物的形成是由金属环空间位阻控制的。具有小空腔的第 4 族配合物对双（甲硅烷基）胺最具选择性，而具有较大空腔的镧系元素配合物和溶剂化铀（IV）同系物也可以制备传统的三（甲硅烷基）胺产品。这些结果为丰富的钛和地球上储量更丰富的镧系元素提供了新的催化应用，这些元素的毒性也低于催化中使用的许多贱金属。