Issue 34, 2022

The smallest 4f-metalla-aromatic molecule of cyclo-PrB2 with Pr–B multiple bonds

Abstract

The concept of metalla-aromaticity proposed by Thorn–Hoffmann (Nouv. J. Chim. 1979, 3, 39) has been expanded to organometallic molecules of transition metals that have more than one independent electron-delocalized system. Lanthanides, with highly contracted 4f atomic orbitals, are rarely found in multiply aromatic systems. Here we report the discovery of a doubly aromatic triatomic lanthanide-boron molecule PrB2 based on a joint photoelectron spectroscopy and quantum chemical investigation. Global minimum structural searches reveal that PrB2 has a C2v triangular structure with a paramagnetic triplet 3B2 electronic ground state, which can be viewed as featuring a trivalent Pr(III,f2) and B24−. Chemical bonding analyses show that this cyclo-PrB2 species is the smallest 4f-metalla-aromatic system exhibiting σ and π double aromaticity and multiple Pr–B bonding characters. It also sheds light on the formation of the rare B24− tetraanion by the high-lying 5d orbitals of the 4f-elements, completing the isoelectronic B24−, C22−, N2, and O22+ series.

Graphical abstract: The smallest 4f-metalla-aromatic molecule of cyclo-PrB2− with Pr–B multiple bonds

Supplementary files

Article information

Article type
Edge Article
Submitted
21 may 2022
Accepted
18 iyl 2022
First published
08 avq 2022
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2022,13, 10082-10094

The smallest 4f-metalla-aromatic molecule of cyclo-PrB2 with Pr–B multiple bonds

Z. Wang, T. Chen, W. Chen, W. Li, J. Zhao, X. Jiang, J. Li, L. Wang and H. Hu, Chem. Sci., 2022, 13, 10082 DOI: 10.1039/D2SC02852B

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