Role of Organic Fluoride Salts in Stabilizing Niobium Oxo-Clusters Catalyzing Epoxidation.
TL;DR: In this paper, easily available organic salts can stabilize/modify niobium (Nb) oxo-clusters and showed the highest catalytic activity, which can be attributed to the following reasons on the basis of characterization.
Abstract: We present here that easily available organic salts can stabilize/modify niobium (Nb) oxo-clusters. The as-synthesized Nb oxo-clusters have been characterized by various methods. These Nb oxo-clusters were catalytically active for the epoxidation of allylic alcohols and olefins with H2O2 as an oxidant. Notably, Nb-OC@TBAF-0.5 appeared as highly dispersed nanosized particles and showed the highest catalytic activity, which can be attributed to the following reasons on the basis of characterization. First, the strong coordination of fluorine ions with Nb sites and the steric protection with bulky organic cations led to high stabilization and dispersion of the oxo-clusters in the course of the reaction. Second, a hydrogen-bond interaction between the coordinated fluorine atom and the -OH group of allylic alcohol favored the epoxidation reaction. Third, the electron density of Nb sites decreased due to the strong electron-withdrawing ability of F- adjacent to Nb sites, thus promoting the electrophilic oxygen transfer to the C═C bond.
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TL;DR: In this paper , the tartaric acid-coordinated peroxoniobate salts can be employed as highly efficient catalysts in the oxidative coupling of aniline to azoxybenzene under green and very mild conditions.
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TL;DR: The introduction of oxygen vacancies improved 1-hexene epoxidation performance over WO3−x/SBA-15 catalysts, which was attributed to the enhanced Lewis acidity of the active centers and the reduced energy barrier of the rate-determining step as mentioned in this paper .
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TL;DR: In this article , the superior performance of WO3-SBA-15 for epoxidation was attributed that the abundant isolated WO4 benefited the coordination and activation of H2O2, and strong electron-withdrawing by the support facilitated weakening the bond strength of the O O bond in WOOH.
Abstract: The superior performance of WO3–SBA-15 for epoxidation was attributed that the abundant isolated WO4 benefited the coordination and activation of H2O2, and strong electron-withdrawing by the support facilitated weakening the bond strength of the O–O bond in W–OOH.
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TL;DR: In this article, the epoxidation of propylene with hydrogen peroxide in the liquid phase, in the presence of titanium silicalite catalyst (TS-1), is described.
681 citations
TL;DR: In this article, the epoxidation of lower olefins, catalysed by titanium silicalite (TS-1) under mild conditions, is reported. But the reaction may be performed at near room temperature, in dilute alcoholic or aqueous solutions of hydrogen peroxide.
671 citations
TL;DR: A part of the adducts can still function as effective Lewis acid sites, catalyzing the allylation of benzaldehyde with tetraallyl tin and the conversion of glucose into 5-(hydroxymethyl)furfural in water.
Abstract: Niobic acid, Nb(2)O(5)·nH(2)O, has been studied as a heterogeneous Lewis acid catalyst. NbO(4) tetrahedra, Lewis acid sites, on Nb(2)O(5)·nH(2)O surface immediately form NbO(4)-H(2)O adducts in the presence of water. However, a part of the adducts can still function as effective Lewis acid sites, catalyzing the allylation of benzaldehyde with tetraallyl tin and the conversion of glucose into 5-(hydroxymethyl)furfural in water.
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TL;DR: The progress achieved during the past decade has been spectacular and herein the authors critically review the most important papers to provide the reader with an almost complete perspective of the field.
Abstract: In the thematic review dedicated to polyoxometalate (POM) chemistry published in Chemical Reviews in 1998, no contribution was devoted to theory This is not surprising because computational modelling of molecular metal-oxide clusters was in its infancy at that time Nowadays, the situation has completely changed and modern computational methods have been successfully applied to study the structure, electronic properties, spectroscopy and reactivity of POM clusters Indeed, the progress achieved during the past decade has been spectacular and herein we critically review the most important papers to provide the reader with an almost complete perspective of the field
346 citations