Alkoxides of Trivacant Lacunary Polyoxometalates
Alkoxides of Trivacant Lacunary Polyoxometalates
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DOI：
10.1002/chem.201702883
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发表时间：
2017-10-12
影响因子：
4.3
通讯作者：
Mizuno, Noritaka
中科院分区：
文献类型：
--
作者：
Minato, Takuo;Suzuki, Kosuke;Mizuno, Noritaka
缺位多氧杂环丁烷酸盐（POM）是一种刚性多齿无机配体，可用于构建多核金属氧簇合物和无机-有机杂化材料。然而，使用多配位的缺位多金属氧酸盐常常在高活性空位处发生不希望的缩合反应。本文首次报道了将烷氧基保护基引入有机介质中空位多金属氧化合物的空位中。通过将可溶于有机溶剂的三空位Keggin型多金属氧酸盐与甲醇反应，成功地将六个甲氧基引入到空位中，生成醇盐TBA（4）[A-alpha-XW9O28（OCH3）（6）]（I-x-OMe; X = Si，Ge）.这些甲氧基基团可以保护活性空位，并抑制不期望的二聚反应成相应的α-Dawson型POM。由于引入的单齿甲氧基容易被水解解离，I-Si-OMe可以用作合成金属取代的POM的前体。此外，以季戊四醇为多齿烷氧基配体，成功地合成了单体醇盐TBA（4）[A-alpha-SiW_9O_（28）{（OCH_2）（2）C（CH_2OH）（2）}（3）]（I-Si-PE）。特别地，这些多齿烷氧基显示出高的耐水解性。此外，通过I-Si-PE与三空位Keggin型多金属氧酸盐反应，成功地合成了具有相同或不同杂原子（Si和Ge）的二聚体无机-有机-无机杂化结构TBA（n）H（8-n）[（A-alpha-SiW_9O_（28））{（OCH_2）（2）C（CH_2O）（2）}（3）-（A-alpha-XW_9O_（28）]（IISiX-PE; X = Si，Ge）。
Lacunary polyoxometalates (POMs) are useful rigid multidentate inorganic ligands to construct multinuclear metal oxo clusters and inorganic-organic hybrid materials. However, the use of multivacant lacunary POMs often suffers from their undesired condensation reactions at the highly reactive vacant sites. Herein, the introduction of alkoxy protecting groups into the vacant sites of lacunary POMs in organic media is reported for the first time. By reacting organic solvent-soluble trivacant lacunary Keggin-type POMs with methanol, six methoxy groups were successfully introduced into the vacant sites, resulting in the formation of the alkoxides TBA(4)[A-alpha-XW9O28(OCH3)(6)] (I-x-OMe; X = Si, Ge). These methoxy groups could protect the reactive vacant sites and suppress the undesired dimerization reaction into the corresponding alpha-Dawson-type POMs. Since the introduced monodentate methoxy groups could easily be dissociated by hydrolysis, I-Si-OMe could be utilized as the precursor for the synthesis of metal-substituted POMs. In addition, by using pentaerythritol as the multidentate alkoxy ligand, the monomeric alkoxide TBA(4)[A-alpha-SiW9O28{(OCH2)(2)C(CH2OH)(2)}(3)] (I-Si-PE) was successfully synthesized. In particular, these multidentate alkoxy groups showed high resistance against hydrolysis. Moreover, by reacting I-Si-PE with trivacant lacunary Keggin-type POMs, the dimeric inorganic-organic-inorganic hybrid structures TBA(n)H(8-n)[(A-alpha-SiW9O28){(OCH2)(2)C(CH2O)(2)}(3)-(A-alpha-XW9O28)] (IISiX-PE; X = Si, Ge) with the same or different heteroatoms (Si and Ge) were successfully synthesized.