A Simple High-Yield Synthesis of Gallium(I) Tetrachlorogallate(III) and the Reaction of Digallium Tetrachloride Tetrahydrofuran Solvate with 1,2-Diols

Gallium(I) tetrachlorogallate(III) Ga[GaCU] was prepared in quantitative yield by thermal de­ composition of dichlorogallane [HGaChk, which is readily available from EtsSiH and [GaCl3]2. The reaction of catechol with solutions of this gallium(I) tetrachlorogallate(III) in tetrahydro­ furan leads to the evolution of hydrogen gas and affords a dinuclear gallium(III) complex with penta-coordinate metal atoms chelated and bridged by mono-deprotonated catechol ligands. In the crystalline phase tetrahydrofuran molecules are hydrogen-bonded to the hydroxy groups: [Ga(l,2 -0 CöH4 0 H)Cl2(C4H8 0 )]2. The reaction with pinacol also gives hydrogen and the anal­ ogous product [Ga(0 CMe2CMe2 0 H)Cl2(C4Hg0 )]2. The structures of the two compounds have been determined by X-ray diffraction. A mechanism of the new reaction has been proposed which involves oxidative addition of the diol to the solvate (THF)Cl2Ga-GaCl2(THF) present in the tetrahydrofuran solution to give a gallium hydride intermediate.