Strukturbestimmung von Ga[GaCl₄] und α-Ga[GaBr₄] nach Kristallisation aus Halogenbenzolen / Structure Determination of Ga[GaCl₄] and α-Ga[GaBr₄] Crystallized from Halobenzene Solvents

Abstract

Single crystals of Ga[GaCl 4 ] and α-Ga[GaBr 4 ] have been obtained by crystallization from chlorobenzene and bromobenzene, respectively. The crystal structures of the two compounds, determined previously only on the basis of photographic data, were refined to a more satisfactory level of accuracy. The results confirm the presence of tetrahedral GaX 4 - anions as thecounterions to dodecahedrally coordinated Ga + cations. The gallium-halogen distances in these dodecahedral arrays fall into four classes, thus resulting in a significant asymmetry of the Ga(I) center. This deviation from ideal S 4 symmetry is also apparent in the 69 Ga NMR spectra of the crystalline powder samples. Approximate calculation of the data leads to asymmetry parameters (η) of 0.44 and 0.27 for the chloride and bromide, respectively. Crystal data Ga[GaCl 4 ]: Pnna (#52), a = 7.200(1), b = 9.625(1), c = 9.498(1) Å; Z = 4. For α-Ga[GaBr 4 ]: Pnna, a = 7.528(1), b = 9.972(1), c = 10.010(1) Å, Z = 4.