Crystal structure of bis(N,N′-dimethylthiourea-κS)bis(thiocyanato-κN)cobalt(II)

During systematic investigations on the synthesis of coordination polymers with Co(NCS)2 involving different thiourea derivatives as coligands, crystals of the title compound Co(NCS)2(N,N′-dimethylthiourea)2, or [Co(C3H8N2S)2(NCS)2], were obtained. These crystals were non-merohedric twins and therefore, a twin refinement using data in HKLF-5 format was performed. In the crystal structure of this compound, the CoII cations are coordinated by two N-terminally bonded thiocyanate anions as well as two S-bonding N,N′-dimethylthiourea molecules, forming two crystallographically independent discrete complexes each with a strongly distorted tetrahedral geometry. An intricate network of intermolecular N—H...S and C—H...S hydrogen bonds can be found between the complexes. The thermogravimetric curve of the title compound shows two discrete steps in which all coligand molecules have been emitted, which is also accompanied by partial decomposition of the cobalt thiocyanate. If the measurement is stopped after the first mass loss, only broad reflections of CoS can be found in the XRPD pattern of the residue, which proves that this compound decomposes completely upon heating. However, at lower temperatures an endothermic signal can be found in the DTA and DSC curve, which corresponds to melting, as proven by thermomicroscopy.