Bis- and Tris(dimethylgallyl)benzenes: Synthesis, Solid-State Structures, and Redistribution Reactions

Abstract

Benzene derivatives containing dimethylgallyl substituents in 1,3- (compounds 5 and 6), 1,4- (compound 9), and 1,3,5-position (compound 12) were prepared by reaction of the corresponding chloromercuriobenzenes with an excess of trimethylgallium at higher temperatures. These compounds decompose in solution at room temperature and in the solid state upon mild heating with elimination of trimethylgallium to give oligomeric condensation products of unknown detailed composition. These condensation products can be transformed back into the starting compounds by treatment with an excess of trimethylgallium at higher temperatures. Highly air-sensitive crystals of 5, 6, 9, and 12 suitable for an X-ray analysis are obtained from trimethylgallium as solvent. The X-ray crystallographic studies revealed the presence of higher coordinate gallium atoms, which lead to the formation of strand- or sheet-like polymers. A trigonal-bipyramidal coordination sphere is observed for the gallium atoms in 9. A distorted tetrahedral coordination is found for the gallium atoms in 5, 6, and 12. The latter compounds possess asymmetric aryl-dimethylgallyl bridging units.