New Cobalt and Nickel Sulfates Templated with N,N'-Dimethyletethylenediammonium Cation: Synthesis, Crystal Structures, and Topological Features

Abstract

Crystals of new double sulfates (dmedaH₂)[Co(H₂O)₆](SO₄)₂ (1) and (dmedaH₂)[Ni(H₂O)₄(SO₄)₂] (2), as well as (dmedaH₂)₂(SO₄)₂⋅3H₂O (3), where dmeda is N,N'-dimethyl-ethylenediamine, were obtained by isothermal evaporation. The compounds crystallize in the triclinic symmetry, space group P\(\bar {1}\), while compound 3 is characterized by the orthorhombic symmetry with the space group P2₁2₁2₁. The crystal structure of 1 contains isolated octahedral cations [Co(H₂O)₆]²⁺ and \({\text{SO}}_{4}^{{2 - }}\) tetrahedra, while the crystal structure of 2 contains complex anions trans-[Ni(H₂O)₄(SO₄)₂]^2–. Structures of 1 and 2 are compared with the structures of double cobalt and nickel sulfates with ethylenediammonium, where the opposite case is observed. The formation of both aqua- and aquasulfate complexes is quite typical for cations of transition metals of the 3d series. While for double sulfates of transition metals with inorganic cations the hydration number depends to a greater extent on the synthesis temperature and the ionic radius of the monovalent metal, for double sulfates with organic cations the picture is more complex. The crystal structure of compound 3 can also be considered as pseudolayered, with the cationic layer formed only by the organic component, while the anionic layer also includes water molecules. The anionic layer contains cavities, the volume of which allows us to assume that, under certain conditions, they can be occupied by water molecules, which would correspond to the composition (dmedaH₂)(SO₄)⋅2H₂O. Topological analysis of the obtained compounds showed that metal complexes with ethylenediammonium demonstrate a relatively high structural complexity of H-bonds with a lower complexity of structural units, as compared to N,N'-dimethylethylenediammonium.