[γ-1,2-H2SiV2W10O40] immobilized on surface-modified SiO2 as a heterogeneous catalyst for liquid-phase oxidation with H2O2
[γ-1,2-H2SiV2W10O40] immobilized on surface-modified SiO2 as a heterogeneous catalyst for liquid-phase oxidation with H2O2
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DOI：
10.1002/chem.200501414
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发表时间：
2006-05-15
影响因子：
4.3
通讯作者：
Mizuno, Noritaka
中科院分区：
文献类型：
--
作者：
Kasai, Jun;Nakagawa, Yoshinao;Mizuno, Noritaka
通过将 N-辛基二氢咪唑鎓阳离子片段共价锚定到 SiO2（表示为 1-SiO2）上，合成了有机-无机杂化载体。这种改性载体通过固态 C-13、Si-29 和 P-31 NMR 光谱、IR 光谱和元素分析进行了表征。结果表明，SiO2表面保留了二氢咪唑骨架的结构。改性载体可以作为良好的阴离子交换剂，使催化活性多金属氧酸盐阴离子[γ-1,2-H2SiV2W10O40](4-)(I)通过化学计量阴离子交换（表示为I/1-SiO2）固定在载体上。经 IR 和 V-51 NMR 光谱证实，阴离子 I 的结构在阴离子交换后得以保留。以过氧化氢（相对于底物仅一当量）作为唯一氧化剂，用 I/1-SiO2 研究了烯烃和硫化物氧化的催化性能。这种负载型催化剂表现出高立体专一性、非对映选择性、区域选择性，以及过氧化氢氧化各种烯烃和硫化物的高效率，而不会损失相应均相I类似物（即1的四正丁基铵盐，TBA-I）的固有催化性质，尽管速率下降到TBA-I的一半左右。除去固体催化剂可以立即停止氧化，并且除去催化剂后的滤液中几乎找不到钒和钨物质。这些结果排除了浸入反应溶液中的钒和钨物质对所观察到的催化作用的任何贡献，这意味着所观察到的催化本质上是真正非均相的。此外，该催化剂可重复用于环氧化和磺氧化，而不会损失任何催化性能。
An organic-inorganic hybrid support has been synthesized by covalently anchoring an N-octyldihydroimidazolium cation fragment onto SiO2 (denoted as 1-SiO2). This modified support was characterized by solid-state C-13, Si-29, and P-31 NMR spectroscopy, IR spectroscopy, and elemental analysis. The results showed that the structure of the dihydroimidazolium skeleton is preserved on the surface Of SiO2. The modified support can act as a good anion exchanger, which allows the catalytically active polyoxometalate anion [gamma-1,2-H2SiV2W10O40](4-) (I) to be immobilized onto the support by a stoichiometric anion exchange (denoted as I/1-SiO2). The structure of anion I is preserved after the anion exchange, as confirmed by IR and V-51 NMR spectroscopy. The catalytic performance for the oxidation of olefins and sulfides, with hydrogen peroxide (only one equivalent with respect to substrate) as the sole oxidant, was investigated with I/1-SiO2. This supported catalyst shows a high stereospecificity, diastereoselectivity, regioselectivity, and a high efficiency of hydrogen peroxide utilization for the oxidation of various olefins and sulfides without any loss of the intrinsic catalytic nature of the corresponding homogeneous analogue of I (i.e., the tetra-n-butylammonium salt of 1, TBA-I), although the rates decreased to about half that with TBA-I. The oxidation can be stopped immediately by removal of the solid catalyst, and vanadium and tungsten species can hardly be found in the filtrate after removal of the catalyst. These results rule out any contribution to the observed catalysis from vanadium and tungsten species that leach into the reaction solution, which means that the observed catalysis is truly heterogeneous in nature. In addition, the catalyst is reusable for both epoxidation and sulfoxidation without any loss of catalytic performance.