| Summary: | The title compound, [Al(H2O)6](CH3SO3)3 (common name: aluminium methanesulfonate hexahydrate), was crystallized from an aqueous solution prepared by the precipitation reaction of aluminium sulfate and barium methanesulfonate. Its crystal structure is the first of the boron group methanesulfonates to be determined. The characteristic building block is a centrosymmetric unit containing two hexaaquaaluminium cations that are connected to each other by two O atoms of the –SO3 groups in an O—H...O...H—O sequence. Further O—H...O hydrogen bonding links these blocks in orthogonal directions – along [010] forming a double chain array, along [10-1] forming a layered arrangement of parallel chains and along [101] forming a three-dimensional network. As indicated by the O...O distances of 2.600 (3)–2.715 (3) Å, the hydrogen bonds are from medium–strong to strong. A further structural feature is the arrangement of two and four methyl groups, respectively, establishing `hydrophobic islands' of different size, all positioned in a layer-like region perpendicular to [101]. The only other building block within this region is one of the –SO3 groups giving a local connection between the hydrophilic structural regions on both sides of the `hydrophobic' one. Thermal analysis indicates that a stepwise dehydration process starts at about 413 K and proceeds via the respective penta- and dihydrate until the compound completely decomposes at about 688 K.
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