Dichlorogallane (HGaCl2)(2) is readily prepared from gallium trichloride and triethylsilane in quantitative yield. Its crystal structure has been determined by single crystal X-ray diffraction. In the chlorine-bridged dimers of crystallographically imposed C-2h symmetry, the terminal hydrogen atoms are in trans positions. In the reaction with 2 equiv of triethylphosphine, the mononuclear complex (Et3P)GaHCl2 is formed. Thermal decomposition of (HGaCl2)(2) affords hydrogen gas and quantitative yields of "GaCl2" as mixed-valent Ga[GaCl4]. Treatment of this product with triethylphosphine gives the symmetrical, Ga-Ga-bonded gallium(II) complex [GaCl2(PEt3)](2) with an ethane-type structure and with the phosphine ligands in a single-trans conformation. The corresponding [GaBr2(Pet(3))](2) complex is prepared from Ga[GaBr4] and has an analogous structure. (Et3P)GaCl3 has been synthesized and structurally characterized as a reference compound.