Synthesis, Crystal Structures and Properties of Ni(NCS)2‐3‐Cyanopyridine Coordination Compounds including a Ferromagnetic Layered Compound

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AbstractReactions of Ni(NCS)2 and 3‐cyanopyridine in different solvents lead to the formation of Ni(NCS)2(3‐cyanopyridine)4 (1) already reported in the literature, Ni(NCS)2(3‐cyanopyridine)2(H2O)2 (2), Ni(NCS)2(3‐cyanopyridine)2(CH3OH)2 (3), Ni(NCS)2(3‐cyanopyridine)2(CH3CN)2 (4) and Ni(NCS)2(3‐cyanopyridine)2 (5). The crystal structures of 1–4 consist of discrete octahedral complexes, in which the thiocyanate anions, as well as the 3‐cyanopyridine coligands, are only terminally N‐bonded. In compound 5 the Ni cations are octahedrally coordinated and linked by pairs of thiocyanate anions into dinuclear units that are further connected into layers by single μ‐1,3‐bridging anionic ligands. TG‐DTA measurements of the discrete complex 1 reveal that in the first step half of the coligands are emitted leading to the formation of compound 5. In contrast, compounds 2 and 3 transform into a new crystalline phase of the same composition (6) upon heating that should also contain μ‐1,3‐bridging anionic ligands, but the outcome of this reaction strongly depends on the reaction conditions. The acetonitrile complex 4 is unstable at room temperature and decomposes into a mixture of different phases including the aqua complex 2. Magnetic measurements of compound 5 prove a ferromagnetic transition at Tc=6.0 K. This result is compared to those obtained for other thiocyanate compounds exhibiting a similar layer topology.