Crystal structure of tris[4-(dimethylamino)pyridinium] tris(oxalato-κ2O,O′)chromate(III) tetrahydrate

In the title hybrid salt, (C7H11N2)3[Cr(C2O4)3]·4H2O, the central CrIII ion of the complex anion (point group symmetry 2) is coordinated by six O atoms from three chelating oxalate(2−) ligands in a slightly distorted octahedral coordination sphere. The Cr—O bond lengths vary from 1.9577 (11) to 1.9804 (11) Å, while the chelate O—Cr—O angles range from 82.11 (6) to 93.41 (5)°. The 4-(dimethylamino)pyridinium cations (one situated in a general position and one on a twofold rotation axis) are protonated at the pyridine N atoms. In the crystal, N—H...O and O—H...O hydrogen bonds link the cations and anions into a three-dimensional network. π–π interactions between the pyridine rings of adjacent cations provide additional stabilization of the crystal packing, with the closest centroid-to-centroid distances being 3.541 (1) and 3.575 (1) Å