Polyoxometalate

About: Polyoxometalate is a research topic. Over the lifetime, 3493 publications have been published within this topic receiving 94123 citations. The topic is also known as: POM.

Rational Design of a Polyoxometalate Intercalated Layered Double Hydroxide: Highly Efficient Catalytic Epoxidation of Allylic Alcohols under Mild and Solvent‐Free Conditions

Abstract: Intercalation catalysts, owing to their modular and accessible gallery and unique interlamellar chemical environment, have shown wide application in various catalytic reactions. However, the poor mass transfer between the active components of the intercalated catalysts and organic substrates is one of the challenges that limit their further application. Herein, we have developed a novel heterogeneous catalyst by intercalating the polyoxometalate (POM) of Na9LaW10O36⋅32 H2O (LaW10) into layered double hydroxides (LDHs), which have been covalently modified with ionic liquids (ILs). The intercalation catalyst demonstrates high activity and selectivity for the epoxidation of various allylic alcohols in the presence of H2O2. For example, trans-2-hexen-1-ol undergoes up to 96 % conversion and 99 % epoxide selectivity at 25 °C in 2.5 h. To the best of our knowledge, the Mg3Al−ILs−C8−LaW10 composite material constitutes one of the most efficient heterogeneous catalysts for the epoxidation of allylic alcohols (including the hydrophobic allylic alcohols with long alkyl chains) reported so far.

Organoantimony-containing polyoxometalate: [{PhSbOH}3(A-alpha-PW9O34)2]9-.

Abstract: The dimeric, sandwich-type tungstophosphate [{PhSbOH}(3)(A-alpha-PW(9)O(34))(2)](9-) (1) has idealized D(3h) symmetry and represents the first organoantimony-containing polyoxometalate. Polyanion 1 was synthesized in an aqueous, acidic medium via three different routes and was fully characterized in the solid state by X-ray diffraction, IR, and thermogravimetric analysis and in solution by multinuclear NMR ((1)H, (13)C, (31)P, and (183)W).

Alkyltin Keggin Clusters Templated by Sodium

Abstract: Dodecameric (Sn12 ) and hexameric topologies dominate monoalkyltin-oxo cluster chemistry. Their condensation, triggered by radiation exposure, recently produced unprecedented patterning performance in EUV lithography. A new cluster topology was crystallized from industrial n-BuSnOOH, and additional characterization techniques indicate other clusters are present. Single-crystal X-ray analysis reveals a β-Keggin cluster, which is known but less common than other Keggin isomers in polyoxometalate and polyoxocation chemistry. The structure is formulated [NaO4 (BuSn)12 (OH)3 (O)9 (OCH3 )12 (Sn(H2 O)2 )] (β-NaSn13 ). SAXS, NMR, and ESI MS differentiate β-NaSn13 , Sn12 , and other clusters present in crude "n-BuSnOOH" and highlight the role of Na as a template for alkyltin Keggin clusters. Unlike other alkyltin clusters that are cationic, β-NaSn13 is neutral. Consequently, it stands as a unique model system, absent of counterions, to study the transformation of clusters to films and nanopatterns.

Epoxidation of alkenes catalyzed by heteropolyoxometalate as pillars in layered double hydroxides

Abstract: The epoxidation of alkenes with hydrogen peroxide or molecular oxygen, in the presence of aldehyde catalyzed by heteropolyoxometalate (HPOM) salts and layered double hydroxides (LDHs) containing HPOM anions as pillars, has been investigated. In the case of oxidation with hydrogen peroxide, a lacunary Keggin-ion, SiW 11 O 39 8− , was more active than SiW 12 O 40 4− . For this reaction system using hydrogen peroxide, intercalated SiW 11 O 39 8− showed higher stability in structure and activity than free K 8 SiW 11 O 39 . For the oxidation using molecular oxygen and aldehyde, SiW 12 O 40 4− showed higher activity than SiW 11 O 39 8− . It was confirmed that SiW 12 O 40 4− was intercalated between the brucite-type layers of the LDHs without change in structure. Ni-containing LDHs without any interstitial polyoxometalate showed high activity for the oxidation of cyclohexene with the combination of O 2 and aldehyde.