CBe2H5−: Unprecedented 2σ/2π Double Aromaticity and Dynamic Structural Fluxionality in a Planar Tetracoordinate Carbon Cluster

• Published in: Chemistry : a European journal Vol. 30; no. 15
• Main Authors: Jin, Bo, Yan, Miao, Feng, Lin‐Yan, Miao, Chang‐Qing, Wang, Ying‐Jin
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 12.03.2024
• Subjects: Aromaticity; Beryllium; Carbon; Clusters; Covalent bonds; Dynamic Fluxionality; Electronic structure; Global Minimum; Hydrogen atoms; Ligands; Molecular motors; Molecular Rotor; Planar Tetracoordinate Carbon; Structural analysis
• DOI: 10.1002/chem.202304134
• ISSN: 0947-6539

A 14‐electron ternary anionic CBe2H5− cluster containing a planar tetracoordinate carbon (ptC) atom is designed herein. Remarkably, it can be stabilized by only two beryllium atoms with both π‐acceptor/σ‐donor properties and two hydrogen atoms, which means that the conversion from planar methane (transition state) to ptC species (global minimum) requires the substitution of only two hydrogen atoms. Moreover, two ligand H atoms exhibit alternate rotation, giving rise to interesting dynamic fluxionality in this cluster. The electronic structure analysis reveals the flexible bonding positions of ligand H atoms due to C−H localized bonds, highlighting the rotational fluxionality in the cluster, and two CBe2 3c–2e delocalized bonds endow its rare 2σ/2π double aromaticity. Unprecedentedly, the fluxional process exhibits a conversion in the type of bonding (σ bond↔π bond), which is an uncommon fluxional mechanism. The cluster can be seen as an attempt to apply planar hypercoordinate carbon species to molecular motors. The 14‐electron ternary anionic CBe2H5− cluster with a planar tetracoordinate carbon center is reported. Unprecedentedly, two ligand hydrogen atoms attached to the carbon rotate alternately, leading to it exhibiting interesting dynamic fluxionality that can be regarded as a molecular rotor.