Synthesis, Crystal Structures, and Properties of Ni(NCS)2‐4‐methoxypyridine Coordination Compounds

Abstract

Two polymorphs of Ni(NCS)2(4‐methoxypyridine)4 (1‐I, 1‐II) as well as compounds with the compositions Ni(NCS)2(4‐methoxypyridine)4(MeCN)1.33 (1‐MeCN), Ni(NCS)2(4‐methoxypyridine)2(MeCN)2 (2) and [Ni(NCS)2(4‐methoxypyridine)2]n (3) are reported. For 1‐II no single crystals were obtained, but this compound is isotypic to the Fe analog 1‐II‐Fe. The crystal structures of 1 and 2 show discrete octahedral NiII complexes, whereas in 3 the cations are connected by pairs of thiocyanate anions into chains. Solvent mediated conversion experiments reveal that 1‐I is thermodynamically stable at room temperature and differential scanning calorimetry shows no indication for a polymorphic transition. The thermal behavior of 1‐I, 1‐II, and 2 was investigated by simultaneous thermogravimetry and differential scanning calorimetry, which shows that they decompose in two discrete steps. In the first step compound 3 is formed as an intermediate, which decomposes on further heating into Ni(NCS)2. Time dependent XRPD investigations prove, that 2 transforms already at room temperature into 3. Upon heating 1‐MeCN transforms into 1‐I in the first TG step, which decomposes on further heating into 3. Investigation of the magnetic behavior of 3 shows dominating ferromagnetic exchange interactions along the chains with J = 5.9(1) K. Susceptibility measurements indicate antiferromagnetic ordering, which was confirmed by specific heat measurements, revealing that magnetic ordering occurs at 1.91(5) K.