Donor-acceptor (DA) complexes MX ₃·LL·M′X ₃ (M, M′ = Al, Ga; X = Cl, Br; LL = 4,4′-bipyridyl) have been theoretically investigated at the B3LYP/pVDZ level of theory. Addition of the first molecule of MX ₃ to 4,4′-bipyridyl has a similar exothermicity compared to complexes with the monodentate donor pyridine. Addition of the second molecule of MX ₃ is significantly (by about 15 kJ mol ^-1) less exothermic. Nevertheless all 2:1 complexes (including heteroacceptor) are predicted to be stable in the vapor phase up to 660, 760, 830 and 920 K for GaBr ₃, GaCl ₃, AlBr ₃, and AlCl ₃, respectively. Four homoacceptor MX ₃·4,4′bpy·MX ₃ complexes have been synthesized for the first time, and their existence in the vapor phase has been proven by mass spectrometry. The theoretically predicted order of the complex stability AlCl ₃ > AlBr ₃ > GaCl ₃ > GaBr ₃ correlates well with the experimental observations of M ₂X ₅bpy ⁺ ion abundances in the mass spectra. The results obtained show for the first time that the synthesis of the gas-phase stable heteroacceptor complexes is feasible, which opens the prospect for their future use as single-source precursors to the stoichiometry-controlled synthesis of 13-15 alloys.