4-Ammonio-2,2,6,6-tetramethylpiperidinium chromate dihydrate

The title compound, 4-ammonio-2,2,6,6-tetramethylpiperidinium chromate dihy drate, (C9H22N2)[CrO4]. 2H(2)O, crystallizes in the monoclinic system with one organic cation and one chromate anion in the asymmetric unit, together with three independent sites for water molecules, two of which have their O atoms located on twofold axes. The structure is composed of layers built u p from CrO42- tetrahedra and water molecules alternating with C9H22N22+ cat ions and additional water molecules. Two types of hydrogen bonds, O-H . . . O and N-H . . .O, ensure the cohesion and stability of the structure.