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- Title
Ionic Liquid Stabilized Niobium Oxoclusters Catalyzing Oxidation of Sulfides with Exceptional Activity.
- Authors
Zhou, Qingqing; Ye, Man; Ma, Wenbao; Li, Difan; Ding, Bingjie; Chen, Manyu; Yao, Yefeng; Gong, Xueqing; Hou, Zhenshan
- Abstract
We present here a new class of niobium oxoclusters that are stabilized effectively by carboxylate ionic liquids. These functionalized ILs are designated as [TBA][LA], [TBA][PA], and [TBA][HPA] in this work, in which TBA represents tetrabutylammonium and LA, PA, and HPA refer to lactate, propionate, 3‐hydroxypropionate anions, respectively. The as‐synthesized Nb oxoclusters have been characterized by use of elemental analysis, NMR, IR, XRD, TGA, HRTEM. It was found that [TBA][LA]‐stabilized Nb oxoclusters (Nb−OC@[TBA][LA]) are uniformly dispersed with an average particle size of 2–3 nm and afforded exceptionally high catalytic activity for the selective oxidation of various thioethers. The turnover number with Nb−OC@[TBA][LA] catalyst was over 56 000 at catalyst loading as low as 0.0033 mol % (1 ppm). Meantime, the catalyst also showed the high activity for the epoxidation of olefins and allylic alcohols by using only 0.065 mol % of catalyst (50 ppm). The characterization of 93Nb NMR spectra revealed that the Nb oxoclusters underwent structural transformation in the presence of H2O2 but regenerated to their initial state at the end of the reaction. In particular, the highly dispersed Nb oxoclusters can absorb a large amount of polar organic solvents and thus were swollen greatly, which exhibited "pseudo" liquid phase behavior, and enabled the substrate molecules to be highly accessible to the catalytic center of Nb oxocluster units. Go oxo! A new class of niobium (Nb) oxocluster has been developed through coordination stabilization with carboxylate ionic liquids (ILs), which are uniformly dispersed with an average particle size of 2–3 nm. These oxoclusters afforded high catalytic activity for the selective oxidation of thioethers and olefins with ultra‐low catalyst loading. Characterization revealed that the Nb oxoclusters underwent structural transformation in the reaction but regenerated to their initial state at the end of reaction (see figure).
- Subjects
NIOBIUM compounds; IONIC liquids; OXIDATION of sulfides
- Publication
Chemistry - A European Journal, 2019, Vol 25, Issue 16, p4206
- ISSN
0947-6539
- Publication type
Article
- DOI
10.1002/chem.201806178