Nonplanar Aromaticity of Dinuclear Rare-Earth Metallacycles

Dajiang Huang^#, Wei Liu^#, Yu Zheng, Rui Feng, Zhengqi Chai, Junnian Wei, and Wen-Xiong Zhang*

 J. Am. Chem. Soc. 2024, 146, 15609–15618. ( ^#Authors contributed equally)

https://doi.org/10.1021/jacs.4c04683

      While the concept of metalla-aromaticity has well been extended to transition organometallic compounds in diverse geometries, aromatic rare-earth organometallic complexes are rare due to the special (n-1)d⁰ configuration and high-lying (n-1)d orbitals of rare-earth centers. In particular, the nonplanar cases of rare-earth complexes have not been reported so far. Here, we disclose the nonplanar aromaticity of dinuclear scandium and samarium metallacycles characterized by various aromaticity indices (NICS, ICSS, AICD, and ISE). Bonding analyses (KS-MO, AdNDP, MCBI, and PIO) reveals that three delocalized π orbitals, predominantly contributed by the 2-butene tetraanion (BTA) ligand, result in the formation of six-electron conjugated systems. Guided by these findings, we predicted the lutetium and gadolinium analogs of dinuclear rare-earth metallacycles should be aromatic, which have been verified by the successful synthesis of real molecules. This work extends the concept of nonplanar aromaticity to the field of rare-earth metallacycles and illuminates the path for designing and synthesizing various rare-earth metalla-aromatics.