A series of bis(σ-B–H) complexes of copper(I) have been prepared by displacement of arene solvent from a β-diketiminate copper(I) complex by four-coordinate boranes, H₃B–L (L = NMe₃, lutidine). In the presence of the same copper arene complex, the secondary amine–borane H₃B–NMe₂H undergoes dehydrogenation. We provide evidence for formation of a heterogengous catalyst from decomposition of the solution species.