Reversible Electron Transfer in the Formation of Radical Anionic and Dianionic 1,4-Diborabutatrienes
Lizhao Zhu, Chenyu Du, Yin Yang, Chunming Cui
Abstract
One- and two-electron reductions of diborylacetylene 1 with potassium graphite (KC 8 ) yielded radical anionic and dianionic 1,4-diborabutatrienes 1 •– K + (thf) 2 and 1 2– (K + ) 2, respectively. X-ray diffraction, electron paramagnetic resonance, and computational studies indicated the π electron delocalization over the B–C–C–B cumulene skeleton. 1 2– (K + ) 2 possesses a relatively small HOMO–LUMO gap and exhibits a significantly red-shifted UV–vis absorption at λ max = 578 nm, compared to the all-carbon tetraarylbutatrienes. 1 2– (K + ) 2 could undergo a formal 1,4-addition with the C sp –H bond of phenylacetylene to produce 2, while the reaction with an organic azide led to the cleavage of B═C bonds with the formation of anionic iminoborane 3 . This work showcases a potential method for the facile construction of boracumulenes.