Christian-Albrechts-Universität zu Kiel, Institut für Anorganische Chemie, Max-Eyth-Str. 2, 24118 Kiel, Germany.
Dalton Trans. 2013 Aug 14;42(30):10746-58. doi: 10.1039/c3dt51085a. Epub 2013 Jun 21.
Reaction of Fe(NCS)2 and Co(NCS)2 with 2-methylpyrazine in different molar ratios and solvents at room temperature leads to the formation of five new coordination compounds of composition M(NCS)2(2-methylpyrazine)2(H2O)2 (M = Fe (1-Fe) , Co (1-Co)), Co(NCS)2(2-methylpyrazine)2(CH3OH)2 (2-Co) and Co(NCS)2(2-methylpyrazine)4·2-methylpyrazine solvate (3-Co). In all of these compounds, discrete complexes are found in which the metal cations are octahedrally coordinated by two terminal N-bonded thiocyanato anions and four N- or O-donor co-ligands. On heating compounds 1-3 in a thermobalance new coordination polymers of composition M(NCS)2(2-methylpyrazine)2 (M = Co (4-Co) , Fe (4-Fe)) are obtained in the first step, which transform into M(NCS)2(2-methylpyrazine) (M = Co (5-Co) , Fe (5-Fe)) in the second. Because of the low chalcophilicity of these cations, compounds 4 and 5 are not accessible from solution. Further investigations prove that 4-Co and 4-Fe obtained by thermal decomposition are of low crystallinity, might be isotypic and might consist of metal cations, in which the anionic ligands are only terminal N-bonded. In contrast, 5-Co and 5-Fe are of good crystallinity but their structure cannot be solved from X-ray powder data. However, a compound of the same composition (5-Cd) based on the more chalcophilic cadmium can easily be crystallized from solution and characterized by single crystal X-ray diffraction. This compound is isotypic to 5-Co and 5-Fe and therefore their structures were determined by Rietveld refinements. In their crystal structures the metal atoms are linked by μ-1,3-bridging thiocyanato anions into a 2D network. Magnetic measurements reveal that compounds 1-4 show only Curie-Weiss paramagnetism and that for 5-Fe antiferromagnetic ordering is observed. In contrast, 5-Co shows metamagnetic behavior with a very large critical field. Finally, it was shown that 4-Co and 4-Fe are hygroscopic and transform within minutes into the hydrates 1-Co and 1-Fe.
室温下，用不同摩尔比的 2-甲基吡嗪和 Fe(NCS)2、Co(NCS)2 在不同溶剂中反应，生成了 5 种新的配位化合物，组成为 M(NCS)2(2-甲基吡嗪)2(H2O)2（M = Fe(1-Fe)、Co(1-Co)）、Co(NCS)2(2-甲基吡嗪)2(CH3OH)2(2-Co)和 Co(NCS)2(2-甲基吡嗪)4·2-甲基吡嗪溶剂化物（3-Co）。在所有这些化合物中，都发现了离散的配合物，其中金属阳离子被两个末端 N 键合的硫氰酸根阴离子和四个 N 或 O 供体配位基配位形成八面体。在热天平中加热化合物 1-3，首先得到组成 M(NCS)2(2-甲基吡嗪)2（M = Co(4-Co)、Fe(4-Fe)）的新型配位聚合物，然后在第二步中转化为 M(NCS)2(2-甲基吡嗪)（M = Co(5-Co)、Fe(5-Fe)）。由于这些阳离子的亲硫性较低，因此无法从溶液中获得化合物 4 和 5。进一步的研究证明，通过热分解得到的 4-Co 和 4-Fe 结晶度较低，可能是同构的，并且可能由金属阳离子组成，其中阴离子配体仅为末端 N 键合。相比之下，5-Co 和 5-Fe 结晶度良好，但无法通过 X 射线粉末数据解析其结构。然而，基于更亲硫的镉的同组成化合物（5-Cd）可以很容易地从溶液中结晶出来，并通过单晶 X 射线衍射进行表征。该化合物与 5-Co 和 5-Fe 同构，因此通过 Rietveld 精修确定了它们的结构。在它们的晶体结构中，金属原子通过μ-1,3-桥连硫氰酸根阴离子连接成二维网络。磁测量表明，化合物 1-4 仅表现出居里-外斯顺磁行为，而对于 5-Fe 则观察到反铁磁有序。相比之下，5-Co 表现出变磁行为，具有非常大的临界场。最后，结果表明 4-Co 和 4-Fe 具有吸湿性，并且在几分钟内转化为水合物 1-Co 和 1-Fe。
