Synthesis, crystal structure and properties of bis-(iso-seleno-cyanato-κN)tetra-kis-(pyridine-κN)nickel(II).

Abstract

The reaction of nickel chloride hexa-hydrate with potassium seleno-cyanate and pyridine in water leads to the formation of crystals of the title complex, [Ni(NCSe)2(C5H5N)4], which were characterized by single-crystal X-ray diffraction. Its crystal structure consists of discrete complexes, located on centers of inversion, in which the Ni cations are sixfold coordinated by two terminal N-bonded seleno-cyanate anions and four pyridine ligands within a slightly distorted octa-hedral coordination. In the crystal, the complexes are connected by weak C-H⋯Se inter-actions. PXRD investigations revealed that a pure crystalline phase has formed. In the IR and Raman spectra, the C-N stretching vibrations are observed at 2083 and 2079 cm-1, respectively, in agreement with the presence of only terminally bonded anionic ligands. Upon heating, one well-resolved mass loss is observed, in which two of the four pyridine ligands are removed, leading to a compound with the composition Ni(NCSe)2(C5H5N)2. In this compound, the C-N stretching vibration is shifted to 2108 cm-1 (Raman) and 2115 cm-1 (IR), indicating the presence of μ-1,3-bridging anionic ligands. In its PXRD pattern, very broad reflections are observed, indicating for poor crystallinity and/or very small particle size. This crystalline phase is not isotypic to its Co and Fe analogs.