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Four Boron Atoms, Four Positive Charges, and Four Skeletal Electrons: A Fluorescent σ‐Aromatic Tetraborane(4)
Author(s) -
Widera Anna,
Wadepohl Hubert,
Himmel HansJörg
Publication year - 2019
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201814041
Subject(s) - chemistry , diborane , boron , trifluoromethanesulfonate , fluorescence , aromaticity , electrophilic aromatic substitution , photochemistry , crystallography , boranes , electron , electron affinity (data page) , molecule , medicinal chemistry , organic chemistry , catalysis , physics , quantum mechanics
Reaction of a ditriflatodiborane compound with the Lewis acids AlCl 3 or GaCl 3 leads to abstraction of the two triflate substituents and dimerization of the resulting dicationic diborane to give a σ‐aromatic tetracationic tetraborane with a planar, rhomboid B 4 core. The compound exhibits four skeletal σ‐electrons involved in two (3c,2e) bonds and represents the first stable fourfold base‐stabilized [B 4 H 4 ] 4+ analogue. The product is isolated from the reaction mixture in the form of bright orange crystals that display fluorescence. Further analysis shows that the new tetraborane(4) is stabilized in the solid state by the lattice energy. It exhibits an extremely high electron affinity and is only stable in solution after one‐electron reduction to the radical cation.