Crystal structure of bis(dimethylammonium) hexaaquacobalt(II) bis(sulfate) dihydrate

Abstract

The title salt, (C2H8N)2[Co(H2O)6)](SO4)2·2H2O, is isotypic with (C2H8N)2[Ni(H2O)6)](SO4)2·2H2O. The Co—O bond lengths in the [Co(H2O)6]2+complex cation show very similar distances as in the related Tutton salt (NH4)2[Co(H2O)6)](SO4)2[average 2.093 (17) Å], but are significantly longer than in the isotypic NiIIcompound (Δd≃ 0.04 Å). The cobalt cation reaches an overall bond-valence sum of 1.97 valence units. The S—O distances are nearly equal, ranging from 1.454 (4) to 1.470 (3) Å [mean 1.465 (12) Å]; however, the O—S—O angles vary clearly from 108.1 (2) to 110.2 (2)° [average bond angle 109.5 (9)°]. The non-coordinating water molecules and dimethylammonium cations connect the sulfate tetrahedra and the [Co(H2O)6]2+octahedronviaO—H...O and N—H...O hydrogen bonds of weak up to medium strength into a three-dimensional framework whereby the complex metal cations and sulfate anions are arranged in sheets parallel to (001).