Siyuan Liu, Marc-André Légaré, Jens Seufert, Dominic Prieschl, Anna Rempel, Lukas Englert, Theresa Dellermann, Valerie Paprocki, Andreas Stoy, Holger Braunschweig

• 2,2′-Bipyridyl is shown to spontaneously abstract a borylene fragment (R–B:) from various hypovalent boron compounds. This process is a redox reaction in which the bipyridine is reduced and becomes a dianionic substituent bound to boron through its two nitrogen atoms. Various transition metal–borylene complexes and diboranes, as a well as a diborene, take part in this reaction. In the latter case, our results show an intriguing example of the homolytic cleavage of a B═B double bond.