Cucurbit[6]uril‐Stabilized Palladium Nanoparticles as a Highly Active Catalyst for Chemoselective Hydrogenation of Various Reducible Groups in Aqueous Media. Issue 31 (3rd November 2017)

• Record Type: Journal Article
• Authors: Nandi, Sekhar; Patel, Parth; Jakhar, Ajay; Khan, Noorul H.; Biradar, Ankush V.; Kureshy, Rukhsana I.; Bajaj, Hari C.
• Is Part Of: ChemistrySelect. Volume 2:Issue 31(2017)
• Page Start: 9911
• Page End: 9919
• Publication Date: 2017-11-03
• Subjects: Chemoselective hydrogenation -- cucurbit[6]uril -- heterogeneous catalyst -- nitroarenes hydrogenation -- palladium.; Chemistry -- Periodicals; 540.5
• DOI: 10.1002/slct.201702196
• Languages: English
• ISSNs: 2365-6549

Abstract

Abstract: Herein, we report the synthesis, characterization, and application of uniformly dispersed palladium nanoparticles supported on cucurbit[6]uril. The 2.56 wt% Pd was loaded on cucurbit[6]uril by impregnation method. Cucurbit[6]uril is a macrocyclic compound in which six glycoluril units are joined with twelve methylene bridges which not only act as support but also helped in stabilizing Pd nanoparticles. The synthesized catalyst was thoroughly characterized by various physicochemical methods. The high resolution transmission electron microscopic analysis revealed the uniform distribution of Pd nanoparticles with average size of ∼3 nm over the cucurbit[6]uril surface. Furthermore, the synthesized catalyst was used for the chemoselective hydrogenation of various reducible (epoxide, olefin, carbonyls, nitrile, azo, imines and nitroarenes) groups with excellent conversion, selectivity (> 99%) and high turnover frequency (up to 2, 05, 882 h −1 ) in aqueous and in some cases with water‐THF mixture. Also, the catalyst was successfully recycled several times (>10 times) without losing any significant conversion and selectivity. Moreover, the leaching results were confirmed by analyzing reaction mixture by inductively coupled plasma atomic emission spectroscopy. Furthermore, the kinetic studies reveal the reaction rate depends on substrate concentration. The reaction mechanism was investigated by studying the reaction through drift FTIR studies. Abstract : Synopsis ‐ Cucurbit[6]uril (CB[6]) was used as an excellent nitrogen‐rich support for stabilization of the Pd nanoparticle that can hydrogenate the various reducible groups with molecular hydrogen as a hydrogen source and in aqueous condition with very high TOF value (Up to 2, 05, 841 h‐1). This catalytic system is working very well for the selective hydrogenation of nitroarenes at milder reaction condition with very high yield and TOF.