Palladium nanoparticles silica-supported

Leitner et al. have synthesized the PEG-modified silica stabilized and immobilized palladium nanoparticles for aerobic alcohol oxidation in combination with scC02 as reaction medium under mild conditions, which show high activity and excellent stability under continuous-flow operation [68], ScC02 could diffuse the substrates and products from the active nanoparticles in a gas-like manner. This allows rapid chemical transformation at the active center, ensures efficient removal of the products from the surface, and minimizes the mobility of solid-supported catalytically active species [69]. In this way, catalysts based on palladium nanoparticles together with PEG as stabilizing matrix could avoid aggregating and forming less active and selective Pd-black [20, 60, 70]. 

C imHPFe] Silica-supported Pd nanoparticles Et3N 80 °C. Phosphine-free arylation of acrylates with aryliodide PdCl2(NH3)2 as catalyst precursor palladium leaches from the support into the ionic liquid phase product extracted with tert-butyl methyl ether. [85]... 

Entrapment or intercalation of metal species in pores and cavities of solid supports has frequently been used for the immobilization of catalysts in inorganic materials such as zeolites, clays, charcoals, silicas, aluminas, and other solids. Though this review article focuses on the immobilization of palladium complexes on polymer supports via covalent and/or coordination bonds, recent novel approaches to polymer-supported palladium species (including palladium nanoparticles) via nonbonding immobilization, such as encapsulation and incarceration, are intriguing because of their high potential for utility. In this section, several representatives are introduced. 

Interestingly, Cai recently reported the use of fluorous silica gel (FSG)-supported palladium nanoparticles as an efficient and recyclable catalyst for the C2-arylation of indoles in conditions similar to the ones used by Sames (Scheme 6, 11CC806). The Pd-nanoparticles were prepared by... 

The deposition of metals has been observed in a number of catalytic processes in ionic liquids and this will be discussed in Section 6.3. This has encouraged the exploration of the possibility of the chemical deposition of metals from solutions in ionic liquids. For instance, lr(0) nanoparticles 2.3 0.4 run in diameter have been prepared by the reduction of [Ir(cod)Q]2 in [BMIMjfPFs] with H2 [24]. In a particularly elegant experiment, palladium nanoparticles were first formed by the thermal decomposition of paUadium(ii) acetate in the presence of triphenylphosphine (to give a regular particle size of 1 run) in [BMIM][Tf2N]. A silica aerogel support was then formed around the nanoparticles by adding (EtO)4Si and formic acid to the mixture [25],... 

Based on the above results, we have proposed a classical Chalk-Harrod-like mechanism for the Pd nanocluster catalyzed reaction (Scheme 3.10). " The first step involves the reduction of Pd(OAc)2 to zero-valent palladium nanoparticles followed by stabilization with a polysiloxane network. These particles followed the conventional pathway of oxidative-addition and reductive-elimination cycles to generate sUyl esters. After the transformation was over, these palladium colloids precipitated out of the solution as a black solid supported on a polysiloxane network. The presence of the soluble polysiloxane matrix, which was not fully condensed in the form of silica, allows particle redispersion— thus allowing particles to be reused as catalyst... 

Busca, G. and Finocchio, E. (2011). Surface science and industrial catalysis Redox states of alumina supported palladium nanoparticles. La Chimica e I Industria, 93, pp. 85-95. Montanari, T., Marie, O., Daturi, M., et al. (2005). Cobalt on and in zeolites and silica-alumina Spectroscopic characterization and reactivity, Catal. Today, 110, pp. 339-344. 

Barbara, P., Bianchini, C., Dal Santo, V., Meli, A., Moneti, S., Psaro, R., Scaffidi, A., Sordelli, L., and Vizza, F. (2006) Hydrogenation of arenes over silica-supported catalysts that combine a grafted rhodium complex and palladium nanoparticles evidence for substrate activation on Rhsi gle.site-Pdmelal moieties. /. Am, Chem. Soc 128 (21), 7065-7076. 

D. D. Das and A. Sayari, Apphcations of pore-expanded mesoporous silica. 6. Novel synthesis of monodispersed supported palladium nanoparticles and their catalytic activity for Suzuki reaction, J. Catal., 246, 60 5 (2007). 

Backvall s group has taken advantage of the catalyst immobilization in mesocellular silica foams (MCFs) to coimmobilize palladium nanoparticles and CALB in MCF, so that each cavity of the support will contain both the lipase and the nano-palladiinn, affording a single and recyclable hybrid catalyst of the DKR for primary amines [115]. The immobilization technique and the DKR of 91 were optimized, obtaining the chiral amide target in maximum yields and ee. 

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