Comparison of the crystal structures of the low- and high-temperature forms of bis-[4-(di-methyl-amino)-pyridine]-dithio-cyanato-cobalt(II)

Crystal structures of two Co(NCS)2 urotropine coordination compounds with different Co coordinations

In the crystal structure of the title compounds, discrete complexes with different Co coordinations are observed, which are linked by inter­molecular hydrogen bonding into three-dimensional networks.

The reaction of Co(NCS)₂ with urotropine in ethanol leads to the formation of two different compounds, namely, bis­(ethanol-κO)bis­(hexa­methyl­ene­tetra­mine-κN)bis­(thio­cyanato-κN)cobalt(II)–di­aqua-κ²O-bis­(hexa­methyl­ene­tetra­mine-κN)bis­(thio­cyanato-κN)cobalt(II)–ethanol–hexa­methyl­ene­tetra­mine (1.2/0.8/1.6/4), [Co(NCS)₂(C₆H₁₂N₄)₂(C₂H₆O)₂]_1.2·[Co(NCS)₂(C₆H₁₂N₄)₂(H₂O)₂]_0.8·1.6C₂H₆O·4C₆H₁₂N₄, 1, and tris­(ethanol-κO)(hexa­methyl­ene­tetra­mine-κN)bis(thio­cyanato-κN)cobalt(II), [Co(NCS)₂(C₆H₁₂N₄)(C₂H₆O)₃], 2. In the crystal structure of compound 1, two crystallographically independent discrete complexes are observed that are located on centres of inversion. In one of them, the Co cation is octa­hedrally coordinated to two terminal N-bonded thio­cyanate anions, two urotropine ligands and two ethanol mol­ecules, whereas in the second complex 80% of the coordinating ethanol is exchanged by water. Formally, compound 1 is a mixture of two different complexes, i.e. di­aqua­dithio­cyanato­bis­(urotropine)cobalt(II) and di­ethano­ldi­thio­cyanato­bis­(uro­trop­ine)cobalt(II), that contain additional ethanol and urotropine solvate mol­ecules leading to an overall composition of [Co(NCS)₂(urotropine)₂(ethanol)_1.2(H₂O)_0.8·0.8ethanol·4urotropine. Both discrete complexes are linked by inter­molecular O—H⋯O and O—H⋯N hydrogen bonding and additional urotropine solvate mol­ecules into chains, which are further connected into layers. These layers combine into a three-dimensional network by pairs of centrosymmetric inter­molecular C—H⋯S hydrogen bonds. In the crystal structure of compound 2, di­thio­cyanato­(urotropine)tri­ethano­lcobalt(II), the cobalt cation is octa­hedrally coordinated to two terminal N-bonded thio­cyanate anions, one urotropine ligand and three ethanol mol­ecules into discrete complexes, which are located in general positions. These complexes are linked by inter­molecular O—H⋯N hydrogen bonding into layers, which are further connected into a three-dimensional network by inter­molecular C—H⋯S hydrogen bonding.

Synthesis, crystal structure and thermal properties of bis-(1,3-di-cyclo-hexyl-thio-urea-κS)bis(iso-thiocyanato-κN)cobalt(II)

Crystals of the title compound, [Co(NCS)2(C13H24N2S)2], were obtained by the reaction of Co(NCS)2 with 1,3-di-cyclo-hexyl-thio-urea in ethanol. Its crystal structure consists of discrete complexes that are located on twofold rotation axes, in which the CoII cations are tetra-hedrally coordinated by two terminal N-bonded thio-cyanate anions and two 1,3-di-cyclo-hexyl-thio-urea ligands. These complexes are linked via inter-molecular N-H⋯S and C-H⋯S hydrogen bonding into chains, which elongate in the b-axis direction. These chains are closely packed in a pseudo-hexa-gonal manner. The CN stretching vibration of the thio-cyanate anions located at 2038 cm-1 is in agreement with only terminal bonded anionic ligands linked to metal cations in a tetra-hedral coordination. TG-DTA measurements prove the decomposition of the compound at about 227°C. DSC measurements reveal a small endothermic signal before decomposition at about 174°C, which might correspond to melting.