Synthesis and crystal structure of diiso-thio-cyanato-tetra-kis-(4-methyl-pyridine -oxide)cobalt(II) and diiso-thio-cyanato-tris-(4-methyl-pyridine -oxide)cobalt(II) showing two different metal coordination polyhedra.

The reaction of Co(NCS) with 4-methyl-pyridine -oxide (CHNO) leads to the formation of two compounds, namely, tetra-kis-(4-methyl-pyridine -oxide-κ)bis-(thio-cyanato-κ)cobalt(II), [Co(NCS)(CHNO)] (), and tris-(4-methyl-pyridine -oxide-κ)bis-(thio-cyanato-κ)cobalt(II), [Co(NCS)(CHNO)] (). The asymmetric unit of consists of one Co cation located on a centre of inversion, as well as one thio-cyanate anion and two 4-methyl-pyridine -oxide coligands in general positions. The Co cations are octa-hedrally coordinated by two terminal -bonding thio-cyanate anions in positions and four 4-methyl-pyridine -oxide ligands. In the extended structure, these complexes are linked by C-H⋯O and C-H⋯S inter-actions. In compound , two crystallographically independent complexes are present, which occupy general positions. In each of these complexes, the Co cations are coordinated in a trigonal-bipyramidal manner by two terminal -bonding thio-cyanate anions in axial positions and by three 4-methyl-pyridine -oxide ligands in equatorial positions. In the crystal, these complex mol-ecules are linked by C-H⋯S inter-actions. For compound , a nonmerohedral twin refinement was performed. Powder X-ray diffraction (PXRD) reveals that was nearly obtained as a pure phase, which is not possible for compound . Differential thermoanalysis and thermogravimetry data (DTA-TG) show that compound start to decompose at about 518 K.