Synthesis, Crystal Structure and Stability of a New Isomer of Bis­(ethyl­ene­thio­urea)di­thio­cyanatocobalt(ii)

The title compound, bis­(imidazolidine-2-thione-κS)di­thio­cyanato­cobalt(II), [Co(NCS)2(C3H6N2S)2], was prepared by the reaction of cobalt thio­cyanate with ethyl­ene­thio­urea in ethanol solution. The asymmetric unit (space group P21/c) consists of one cobalt cation, as well as two crystallographically independent thio­cyanate anions and two ethyl­ene­thio­urea ligands, all of them located in general positions. The metal cations are tetra­hedrally coordinated by two N-bonding anionic ligands and two ethyl­ene­thio­urea 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 tetra­hedral coordination with N-bonding thio­cyanate 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#). Polyhedron154, 436–442]. In contrast to the title compound, in the triclinic isomer the cobalt cations are octa­hedrally coordinated and linked into chains by μ-1,3-bridging thio­cyanate 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.