Conversion of N2 into oxadiazoles promoted by a multinuclear samarium complex

The nitrogenous compounds play a substantial role in life. Transformation of N₂ into high-value nitrogen-containing organic compounds, not through NH₃, is of great significance but poses a long-standing challenge. Compared with d-block metals, the derivatization chemistry of rare-earth metal dinitrogen complexes remains elusive. Here we report the single-electron reductions of tetrametallic samarium dinitrogen complex 1 [L₄Sm₄N₂(THF)₂] (L = [(CH₂)₅C(C₄H₃N)₂]^2-) in THF with dipyrrolide dianion as the ligand, to obtain ionic complexes 2 and 3, [L₄Sm₄N₂]M(THF)₆ (M = K, Na), respectively. Different from 2, 3 could dissolve in Et₂O to give complex 4 [L₄Sm₄N₂Na(Et₂O)], featuring a side-on coordination of Na to dinitrogen molecule. When upon extended reaction time, a more nucleophilic complex 5 [L₄Sm₃N₂Na₃] is achieved. Moreover, further reaction of 5 with many aroyl chlorides to successfully afford corresponding oxadiazole organic compounds from N₂, facilitated by rare-earth metal [(N₂)^4-] unit.