The reaction of the copper(I) β-diketiminate copper complex {(Cu(BDI Mes )) 2 (μ-C 6 H 6 )} (BDI Mes = N,N′-bis(2,4,6trimethylphenyl)pentane-2,4-diiminate) with the low-valent group 13 metal β-diketiminates M(BDI Dip ) (M = Al or Ga; BDI Dip = N,N′-bis(2,6-diisopropylphenyl)pentane-2,4-diiminate) in toluene afforded the complexes {(BDI Mes )CuAl(BDI Dip )} and {(BDI Mes )-CuGa(BDI Dip )}. These feature unsupported copper−aluminum or copper−gallium bonds with short metal−metal distances, Cu−Al = 2.3010(6) Å and Cu−Ga = 2.2916(5) Å. Density functional theory (DFT) calculations showed that approximately half of the calculated association enthalpies can be attributed to London dispersion forces.