Synthesis, crystal structure and thermal properties of catena-poly[[bis(4-methylpyridine)nickel(II)]-di-μ-thiocyanato], which shows an alternating all-trans and cis–cis–trans-coordination of the NiS2Np 2Nt 2 octahedra (p = 4-methylpyridine, t = thiocyanate)

Abstract

The title compound, [Ni(NCS)2(C6H7N)2] n , was prepared by the reaction of Ni(NCS)2 with 4-methylpyridine in water. Its asymmetric unit consists of two crystallographically independent NiII cations, of which one is located on a twofold rotational axis whereas the second occupies a center of inversion, two independent thiocyanate anions and two independent 4-methylpyridine coligands in general positions. Each NiII cation is octahedrally coordinated by two 4-methylpyridine coligands as well as two N- and two S-bonded thiocyanate anions. One of the cations shows an all-trans, the other a cis–cis–trans configuration. The metal centers are linked by pairs of μ-1,3-bridging thiocyanate anions into [101] chains. X-ray powder diffraction shows that a pure crystalline phase has been obtained and thermogravimetry coupled to differential thermoanalysis reveals that the title compound loses half of the 4-methylpyridine coligands and transforms into Ni(NCS)2(C6H7N). Nearly pure samples of this compound can be obtained by thermal annealing and a Rietveld refinement demonstrated that it is isotypic to its recently reported Cd analog [Neumann et al., (2020). CrystEngComm. 22, 184–194] In its crystal structure, the metal cations are linked by one μ-1,3(N,S)- and one μ-1,3,3(N,S,S)-bridging thiocyanate anion into single chains that condense via the μ-1,3,3(N,S,S)-bridging anionic ligands into double chains.