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. The transformation of N2 into high-value nitrogen-containing organic compounds is of great significance and compared with d-block metals, the derivatization chemistry of rare-earth metal dinitrogen complexes remains elusive. Here, the authors report the formation of oxadiazoles promoted by multinuclear samarium [(N2)4-] species.