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

Abstract

Reactions 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.