Synthesis, crystal structure and thermal properties of bis(acetonitrile-κN)bis(3-bromopyridine-κN)bis(thiocyanato-κN)cobalt(II)

Single crystals of the title compound, [Co(NCS)2(C5H4BrN)2(C2H3N)2], were obtained by the reaction of Co(NCS)2 with 3-bromopyridine in acetonitrile. The CoII cations lie on crystallographic inversion centers and are coordinated by two N-bonded thiocyanate anions, two 3-bromopyridine and two acetonitrile ligands thereby forming slightly distorted CoN6 octahedra. In the crystal, these complexes are linked by C-H⋯S and C-H⋯N hydrogen bonds into a three-dimensional network. In the direction of the crystallographic b-Axis, the complexes are arranged into columns with neighboring 3-bromopyridine ligands stacked onto each other, indicating π-π interactions. The CN stretching vibration of the thiocyanate anions is observed at 2066 cm-1, in agreement with the presence of only N-bonded anionic ligands. TG-DTA measurements reveal that in the first mass loss the acetonitrile ligands are removed and that in the second step, half of a 3-bromopyridine ligand is lost, leading to the formation of a polymeric compound with the composition [(Co(NCS)2)2(C5H4BrN)3] n already reported in the literature.