Progress of Azametallacyclopentadienes in the New Century

Ze-Jie Lv, Wei Liu, and Wen-Xiong Zhang*

Chem. Eur. J. 2023, 29, e202204079. ( Invited Concept )

https://doi.org/10.1002/chem.202204079

      As the key intermediates in metal promoted/catalyzed C‒C bond coupling reactions of nitriles and alkynes, azametallacyclopentadienes, M(N=CR¹‒CR²=CR³), are an important class of azametallacycles. Although the first authentic azametallacyclopentadienes were documented in 1986, their chemistry towards solid-state structures, intrinsic reactivity and synthetic application was rarely investigated for a long time. At the beginning of this century, seminal works about the applications of azametallacyclopentadienes in the synthesis of heterocycles, including multi-substituted pyridines, isoquinolines, furans and pyrroles were reported. Subsequently, a series of new complexes with this motif, namely the group 4, aluminum, actinide and rare-earth azametallacyclopentadienes were isolated and structurally characterized. Among them, the rare-earth metallacyclopentadiene expresses high reactivity towards unsaturated molecules, such as nitriles, isocyanides and Mo(CO)₆ to provide novel fused metallacycles. In this concept, we summarized the advances towards the preparation, reactivity and synthetic application of azametallacyclopentadienes in past twenty years.