Synthesis, Structure, and Bonding of Spiro Rare-Earth Metallacyclopent-3-enes

via the Reduction of Metallacyclopentadienes

Yu Zheng^#, Chao Yu^#, Botao Wu, Junnian Wei, and Wen-Xiong Zhang*

Cell Rep. Phys. Sci. 2022,  (^#Authors contributed equally.)

https://doi.org/10.1016/j.xcrp.2022.100831.

Synthesis and characterization of metallacycles is an important research issue because they have acted as important building blocks and key intermediates in synthetic and catalytic chemistry. However, spiro rare-earth metallacyclopent-3-enes or metallacyclopentadienes are untouched species. Herein we report the construction of the spiro rare-earth metallacyclopent-3-enes 2 by ligand-based 4e^- reduction of spiro rare-earth metallacyclopentadienes 3 with excess lithium. Complexes 3 represent a class of spiro rare-earth metallacyclopentadienes and could be easily synthesized from the reaction of 1,4-dilithio-1,3-butadiene 1 with 0.5 equivalents of ScCl₃. X-ray characterization and theoretical analyses (MOs, NICS, AICD, ICSS, and ISE) are performed to visualize the structure and bond characteristics of 2. DFT calculations reveal that the Li cations play a vital role in stabilizing its geometric and electronic structures. Therefore, this work promotes the cooperative development of rare-earth organometallic chemistry and coordination chemistry.