Selective C−C Coupling of Two Nitriles Affording Rare-Earth Diazametallacyclopentadienes: Synthesis, Cooperative Reactivity and Mechanistic Studies

Miaomiao Zhu^#, Zhengqi Chai^#, Tianyu Li, Junnian Wei, Ze-Jie Lv*, and Wen-Xiong Zhang*

Inorg. Chem. Front. 2023, 4569–4577.

https://doi.org/10.1039/D3QI00946G.

While the reductive coupling of two nitriles mediated by transition metals has been widely studied in the past ten years, the analogous process promoted by rare-earth metals remains elusive. Herein, we report the selective C−C coupling of two nitriles by rare-earth metal reduced naphthalene complexes to assemble the first authentic rare-earth diazametallacyclopentadienes. Mechanistic studies reveal the reaction proceeds through the Insertion-Release-Insertion sequence, which is different from the known oxidative cyclometallation process for transition metals. This provides an alternative mechanism for metal-mediated reductive coupling of two nitriles. Furthermore, reactivity investigation indicates that diazascandacyclopentadiene exhibits distinct 1,4-hydrogenation and insertion reactions toward H₂, isothiocyanate, isocyanide, and W(CO)₆ to give diversified rare-earth metallacycles. These results indicate that rare-earth diazametallacyclopentadienes present unique chemistry, which is different from that of group 4 diazametallacyclopentadienes.