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The smallest 4f-metalla-aromatic molecule of cyclo-PrB2− with Pr–B multiple bonds†‡ † Dedicated to Professor Dr W. H. E. Schwarz on his 85th birthday.‡ Electronic supplementary information (ESI) available. See https://doi.org/10.1039/d2sc02852b

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. We report the smallest 4f-metalla-aromatic molecule of PrB2− exhibiting σ and π double aromaticity and multiple Pr–B bond characters.

SUBMITTER: Wang Z

PROVIDER: S-EPMC9430590 | biostudies-literature | 2022 Aug

REPOSITORIES: biostudies-literature

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