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 5 2022
Accepted
18 7 2022
First published
08 8 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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