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.

Electron Transfer−Oxygen Transfer Oxygenation of Sulfides Catalyzed by the H5PV2Mo10O40 Polyoxometalate

Abstract: The oxygenation of sulfides to the corresponding sulfoxides catalyzed by H5PV2Mo10O40 and other acidic vanadomolybdates has been shown to proceed by a low-temperature electron transfer−oxygen transfer (ET−OT) mechanism. First, a sulfide reacts with H5PV2Mo10O40 to yield a cation radical−reduced polyoxometalate ion pair, R2+•,H5PVIVVVMo10O40, that was identified by UV−vis spectroscopy (absorptions at 650 and 887 nm for PhSMe+• and H5PVIVVVMo10O40) and EPR spectroscopy (quintet at g = 2.0079, A = 1.34 G for the thianthrene cation radical and the typical eight-line spectrum for VIV). Next, a precipitate is formed that shows by IR the incipient formation of the sulfoxide and by EPR a VO2+ moiety supported on the polyoxometalate. Dissolution of this precipitate releases the sulfoxide product. ET−OT oxidation of diethylsulfide yielded crystals containing [V(O)(OSEt2)x(solv)5−x]2+ cations and polyoxometalate anions. Under aerobic conditions, catalytic cycles can be realized with formation of mostly sulfoxide (90...

Surfactant-Encapsulated Polyoxometalates as Immobilized Supramolecular Catalysts for Highly Efficient and Selective Oxidation Reactions

Abstract: A type of interesting immobilized supramolecular catalysts based on surfactant-encapsulated polyoxometalates has been developed for oxidation reactions. Through a sol-gel process with tetraethyl orthosilicate, hydroxyl-terminated surfactant-encapsulated polyoxometalate complexes have been covalently and uniformly bound to a silica matrix with unchanged complex structure. The formed hybrid catalysts possess a defined hydrophobic nano-environment surrounding the inorganic clusters, which is conducive to compatibility between the polyoxometalate catalytic centres and organic substrates. The supramolecular synergy between substrate adsorption, reaction, and product desorption during the oxidation process has been found to have an obvious influence on the reaction kinetics, with the activity of the catalyst being greatly improved. The supramolecular catalysts performed effectively in the selective oxidation of several different kinds of organic compounds, such as alkenes, alcohols, and sulfides, and the main products were the corresponding epoxides, ketones, sulfoxides, and sulfones. More significantly, the catalyst could be easily recovered by simple filtration, and the catalytic activity was well retained for at least five cycles. Finally, the present strategy has proved to be a general route for the fabrication of supramolecular hybrid catalysts containing common polyoxometalates suitable for various purposes.

Nanoscale polyoxometalate‐based inorganic/organic hybrids

Abstract: The latest advances in the area of polyoxometalate (POM)-based inorganic/organic hybrid materials prepared by self-assembly, covalent modification, and supramolecular interactions are presented. This Review is composed of five sections and documents the effect of organic cations on the formation of novel POMs, surfactant encapsulated POM-based hybrids, polymeric POM/organic hybrid materials, POMs-containing ionic crystals, and covalently functionalized POMs. In addition to their role in the charge-balancing, of anionic POMs, the crucial role of organic cations in the formation and functionalization of POM-based hybrid materials is discussed.

Phenanthroline decorated by a crown ether as a module for metallorganic-polyoxometalate hybrid catalysts: the Wacker type oxidation of alkenes with nitrous oxide as terminal oxidant.

Abstract: A 1,10-phenanthroline ligand decorated at the 5,6-position by a 15-crown-5 ether moiety was prepared. Ligation of Pd(II) at the nitrogen atom positions followed by complexation at the crown ether group of a redox active H(5)PV(2)Mo(10)O(40) polyoxometalate yielded a hybrid metallorganic-polyoxometalate complex, Pd(II)(15-crown-5-phen)Cl(2)-H(5)PV(2)Mo(10)O(40). This complex was characterized by IR, UV-vis, ESI-MS, and NMR spectroscopy and elemental analysis that all confirmed the hybrid nature of the complex. Pd(II)(15-crown-5-phen)Cl(2)-H(5)PV(2)Mo(10)O(40) was used as a catalyst for the Wacker type oxidation of 1-alkenes to yield the corresponding methylketones in essentially quantitative yields using nitrous oxide as the terminal oxidant.