New cadmium thio- and selenocyanato coordination compounds: structural snapshots on the reaction pathway to more condensed anionic networks.
New cadmium thio- and selenocyanato coordination compounds: structural snapshots on the reaction pathway to more condensed anionic networks.
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DOI：
10.1039/c1dt11377a
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发表时间：
2012-01
影响因子：
4
通讯作者：
I. Jess;J. Boeckmann;C. Näther
中科院分区：
文献类型：
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作者：
I. Jess;J. Boeckmann;C. Näther
本文以硫代镉和硒氰酸酯为基料，以嘧啶为配体制备了几种新的配位化合物，并对它们的结构、热性质和光谱性质进行了研究。硫氰酸镉（II）与嘧啶反应生成四种化合物，从结构上看，这四种化合物是密切相关的。在最富嘧啶的1:2化合物[Cd(NCS)(2)（嘧啶）(2)](n) (1A)（1:2 =金属盐与共配体嘧啶的比例）中，Cd阳离子由嘧啶配体连接成层，另外由两个末端n键阴离子配位。在2:3化合物{[Cd(NCS)(2)](2)（嘧啶）(3)}(n) （1B）中，Cd阳离子由μ-1,3桥接硫氰酸盐阴离子连接成链，而这些阴离子仅由一半的嘧啶配体连接成层，而其他共配体仅是末端配位的。进一步降低嘧啶含量，形成1:1 2D化合物[Cd(NCS)(2)（嘧啶）](n) (1CI)，其中末端n键的硫氰酸酯阴离子起桥接作用。令人惊讶的是，结晶实验导致形成额外的嘧啶缺乏中间体组成{[Cd(NCS)(2)](3)（嘧啶）(2)}(n) (1D)，其中一些μ-1,3配位阴离子转化为μ-1,1,3桥接硫氰酸盐阴离子。因此，这四种结构可以作为中间产物的快照，以形成更浓缩的硫氰酸酯配位网络。相比之下，硒氰酸镉只得到两种不同的化合物。1: 2化合物[Cd(NCSe)(2)（嘧啶）(2)](n) （2A）与1A不是同型的，表现出完全不同的配位拓扑结构，而缺乏嘧啶的1:1化合物（2B）表现出μ-1,3配位硒氰酸酯阴离子更凝聚的网络。在加热条件下，1:2化合物1A通过一种新的多态修饰（1CII）作为亚稳态中间体分解成Cd(NCS)(2)，而1:2硒氰酸酯化合物2A在加热条件下转化为1:1化合物2B，在这种条件下无法获得物纯。如果使用更快的加热速率，有迹象表明会形成一种3:2的化合物，这种化合物在x射线下是无定形的。并与以吡啶、吡啶、吡嗪为配体的相关硫代和硒氰酸酯配位聚合物进行了比较。此外，还详细讨论了它们对类似顺磁性化合物的结构和热反应性的影响。根据化合物1D的结构数据，确定了两种中间体的未知结构，这两种中间体是最近报道的Mn和Fe硫氰酸嘧啶配位聚合物在热分解反应中形成的。
In this contribution several new coordination compounds on the basis of cadmium(II) thio- and selenocyanate with pyrimidine as co-ligand were prepared and investigated for their structural, thermal and spectroscopic properties. The reaction of cadmium(II) thiocyanate with pyrimidine leads to the formation of four compounds, which from a structural point of view are closely related. In the most pyrimidine-rich 1 : 2 compound [Cd(NCS)(2)(pyrimidine)(2)](n) (1A) (1 : 2 = ratio between metal salt and the co-ligand pyrimidine) the Cd cations are linked by the pyrimidine ligands into layers and are additionally coordinated by two terminal N-bonded anions. In the 2 : 3 compound {[Cd(NCS)(2)](2)(pyrimidine)(3)}(n) (1B) the Cd cations are linked into chains by μ-1,3 bridging thiocyanato anions, which are connected into layers by only half of the pyrimidine ligands, whereas the other co-ligands are only terminal coordinated. Further reduction of the pyrimidine content leads to the formation of the 1 : 1 2D compound [Cd(NCS)(2)(pyrimidine)](n) (1CI) in which the terminal N-bonded thiocyanato anions become bridging. Surprisingly, crystallization experiments lead to the formation of an additional pyrimidine-deficient intermediate of composition {[Cd(NCS)(2)](3)(pyrimidine)(2)}(n) (1D), in which some of the μ-1,3 coordinated anions transform into μ-1,1,3 bridging thiocyanato anions. Consequently the four structures can be used as snapshots of intermediates on the way to a more condensed thiocyanato coordination network. In contrast, with cadmium selenocyanate only two different compounds were obtained. The 1 : 2 compound [Cd(NCSe)(2)(pyrimidine)(2)](n) (2A) is not isotypic to 1A and shows a completely different coordination topology whereas the pyrimidine-deficient 1 : 1 compound (2B) shows a more condensed network with μ-1,3 coordinating selenocyanato anions. On heating, the 1 : 2 compound 1A decomposes into Cd(NCS)(2)via a new polymorphic modification (1CII) as intermediate which is metastable, whereas the 1 : 2 selenocyanato compound 2A transforms into the 1 : 1 compound 2B on heating which cannot be obtained phase pure under these conditions. If faster heating rates are used, there are indications for the formation of a 3 : 2 compound, which is amorphous to X-rays. The results are compared with those obtained for related thio- and selenocyanato coordination polymers with pyridine, pyridazine and pyrazine as co-ligand. Moreover, their impact on the structures and thermal reactivity of analogous paramagnetic compounds is discussed in detail. Based on the structural data of compound 1D the unknown structures of two intermediates were determined, which are formed in the thermal decomposition reaction of the Mn and Fe thiocyanato pyrimidine coordination polymers, reported recently.