title: Crystal structure of bis-(di-methyl-ammonium) hexa-aqua-cobalt(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 Ni(II) compound (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 mol-ecules and di-methyl-ammonium cations connect the sulfate tetrahedra and the [Co(H2O)6](2+) octa-hedron via O-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).
authors.affiliation: Institut für Kristallographie, Universität zu Köln, Greinstr. 6, D-50939 Köln, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Held
keywords: crystal structure; di­meth­ylammonium salt; hexa­aqua­cobalt(II) salt; hydrogen bonding; sulfate