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, https://doi.org/10.1016/j.xcrp.2022.100831. (^#Authors contributed equally.)

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.