Synthesis and crystal structures of [Al(H2O)6](SO4)NO3·2H2O and [Al(H2O)6](SO4)Cl·H2O

Two novel aluminium double salts, [Al(H2O)6](SO4)NO3·2H2O, hexa­qua­alumin­ium sulfate nitrate dihydrate, (1), and [Al(H2O)6](SO4)Cl·H2O, hexaqua­aluminium sulfate chloride hydrate, (2), were obtained in the form of single crystals. Their crystal structures are each based on an octa­hedral [Al(H2O)6]3+ unit and both structures have in common one charge-balancing SO42− anion. The final positive charge from the aluminium(III) cation is balanced by an NO3− or a Cl− anion for (1) and (2), respectively. Compound (1) further contains two unligated water mol­ecules while compound (2) only contains one unligated water mol­ecule. In the crystal structures, all components are spatially separated and inter­actions are mediated via medium–strong hydrogen bonding, compared to many other reported aluminium sulfates where corner-sharing of the building units is common. The two compounds represent rare cases where one aluminium(III) cation is charge-balanced by two different anions.