Dehydrocoupling reactions between the boranes HBpin and 9‐borabicyclo3.3.1nonane and a range of amines and anilines ensue under very mild reaction conditions in the presence of a simple β‐diketiminato magnesium n‐butyl precatalyst. The facility of the reactions is suggested to be a function of the Lewis acidity of the borane substrate, and is dictated by resultant pre‐equilibria between, and the relative stability of, magnesium hydride and borohydride intermediates during the course of the catalysis. BoNd‐forming catalysis: Dehydrocoupling reactions between the boranes HBpin and 9‐borabicyclo3.3.1nonane, and a range of amines and anilines ensue under very mild reaction conditions in the presence of a simple β‐diketiminato magnesium n‐butyl precatalyst. The reaction is facilitated by the Lewis acidity of the borane substrate, and is dictated by resultant pre‐equilibria between magnesium hydride and borohydride.