Synthesis, crystal structure and stability of a new isomer of bis-(ethyl-ene-thio-urea)di-thio-cyanatocobalt(II).

The title compound, bis-(imidazolidine-2-thione-κS)di-thio-cyanato-cobalt(II), [Co(NCS)2(C3H6N2S)2], was prepared by the reaction of cobalt thio-cyanate with ethyl-ene-thio-urea in ethanol solution. The asymmetric unit (space group P21/c) consists of one cobalt cation, as well as two crystallographically independent thio-cyanate anions and two ethyl-ene-thio-urea ligands, all of them located in general positions. The metal cations are tetra-hedrally coordinated by two N-bonding anionic ligands and two ethyl-ene-thio-urea ligands into discrete complexes. These complexes are linked by N-H⋯S hydrogen bonds into layers. The IR spectrum is in agreement with the presence of a tetra-hedral coordination with N-bonding thio-cyanate anions and measurements using X-ray powder diffraction indicate that a pure crystalline phase has been obtained. The title compound represents a new isomer of Co(NCS)2(C3H6N2S)2, which was already reported in the literature in space group P1 [Mautner et al., (2018 ▸). Polyhedron 154, 436-442]. In contrast to the title compound, in the triclinic isomer the cobalt cations are octa-hedrally coordinated and linked into chains by μ-1,3-bridging thio-cyanate anions. Solvent-mediated conversion experiments starting from a mixture of both isomers show that the title complex is the thermodynamically stable form at room temperature.