Aromatic Tetralithiodigalloles with a Ga–Ga Bond: Synthesis and Structural Characterization

Aromatic 1,1,2,2-tetralithiodigalloles 5 with a Ga–Ga bond were realized. Reaction of 1,4-dilithio-1,3-butadienes 6 with 0.5 equiv of GaCl3 afforded lithium spirogallane ate complexes 7 in excellent isolated yields. Reduction of the above ate complexes 7 with an excess amount of lithium generated the 1,1,2,2-tetralithiodigalloles 5 in moderate isolated yields. The structures of compounds 5 and 7 were both determined by single-crystal X-ray structural analysis. The 1,1,2,2-tetralithiodigalloles 5 contained two aromatic dilithiogalloles connected by a Ga–Ga bond. The aromaticity of 5 was confirmed by both experimental measurements (X-ray structural analysis, NMR spectroscopy) and theoretical analysis (ISE, NICS).