Synthesis, crystal structure and properties of catena-poly[[bis­(4-methyl­pyridine-κN)cobalt(II)]-di-μ-thio­cyanato-κ2N:S;κ2S:N], which shows a rare coordination geometry

Abstract

In the crystal structure of the title compound, Co(NCS)₂(C₆H₇N)₂ (C₆H₇N = 4-methyl­pyridine), the Co^II cations are in an alternating octa­hedral all-trans and cis-cis-trans coordination and linked into corrugated chains by pairs of μ-1,3 bridging thio­cyanate anions.

Reaction of Co(NCS)₂ with 4-methyl­pyridine in water leads to the formation of single crystals of the title compound, [Co(NCS)₂(C₆H₇N)₂]_n. The asymmetric unit consists of two crystallographically independent thio­cyanate anions and two crystallographically independent 4-methyl­pyridine coligands in general positions, as well as of two different Co^II cations, of which one is located on a twofold rotational axis, whereas the second occupies a center of inversion. The methyl H atoms in both 4-methyl­pyridine ligands are disordered and were refined using a split model. Both Co^II cations are octa­hedrally coordinated by two N- and two S-bonded thio­cyanate anions and two 4-methyl­pyridine coligands and are linked by pairs of 1,3-bridging anionic ligands into chains. Within these chains the cations show an alternating all-trans and cis–cis–trans configuration, which leads to the formation of corrugated chains. Powder X-ray diffraction proves that a pure crystalline phase has been obtained and the values of the CN stretching vibrations of the anionic ligands observed in the IR and the Raman spectra are in agreement with the presence of bridging anionic ligands.