Palladium nanopartides

The successful deposition of silver and palladium nanopartides proves the applicability of the PECD concept in ionic liquids. We expect that the cathodic deposition of other elements can be run in the same way under comparable conditions from... 

Figure 10.8 gives an overview of some hydrogen sorption measurements for nanoparticles of different sizes and shapes. Two striking observations are that there are important differences between nanoparticulate palladium and bulk palladium, and that the scatter in the data for the palladium nanopartides is very large. All nanoparticulate samples have a few characteristics in common compared to the bulk ... 

One paper by the same group reports on the sonochemical insertion of palladium nanopartides loaded within mesoporous silica [111]. The formation of Pd nanopartides (5-6 nm in diameter) was restricted by the coalescence of the so-nochemically reduced Pd atoms inside the confined volumes of the porous solid. 

At the opposite of the molecular chemistry described until now, nanoparticles are reminiscent of heterogeneous catalysts. However, these colloid-derived materials have been shown to catalyze efficiently in water coupling reactions which have been previously described in pure homogeneous systems. For instance, poly(N-vi-nyl-2-pyrrolidine)-stabilized palladium nanopartides promote the Suzuki crosscoupling in aqueous media with high yields (see also Section 6.6) [87]. 

Propylene carbonate-stabilized palladium nanopartides were also shown to be active catalysts for the Heck reaction [116, 117]. The formation of olefins from aldehydes and ketones via McMurry-type coupHng reactions was reported using Bu4NBr-stabihzedTi colloids (3nm) [22]. TheTHF-protectedTi,3-nanocluster (Fig. 

I 10 The Role of Palladium Nanopartides as Catalysts for Carbon-Carbon Coupling Reactions... 

Heck reactions catalyzed by 10, performed with phenyl bromide and n-butyl acrylate in NMP at 140 °C with 0.01 mol% of catalyst and K2CO3 as base. Whereas dramatically retarded conversion rates were observed with the phosphine-based pincer complex 21 in the presence of l-methyl-l,4-cydohexadiene [42], only a marginal effect was noticed under identical reaction conditions with catalyst 10 (as well as with 3). These results exclude the possibihty that the catalyticaUy active species derived from 10 (or 3) and from 21 are of the same type, and in turn imply that different reaction mechanisms can indeed be operative with different pincer complexes in Heck reactions (and most probably also in other cross-coupling reactions). Therefore, its reasonable to anticipate that palladium pincer Heck catalysts can operate via homogeneous (Pd /Pd ) mechanisms and serve as sources of palladium nanopartides, depending on the reaction conditions applied. 

SCHEME 12.3 Hydrogenation of olefins in SCCO2 catalyzed by palladium nanopartides in a water-in-C02 microemulsion. (Adapted from Ref. [52] with permission of American Chemical... 

Cacchi, S., Cotet, C.L, Fabrizi, G., Forte, G., Goggiamani, A., Martinez, S., Molins, E., Moreno-Manas, M., Petrucd, F., Roig, A. and VaDribera, A. (2007) Fffident hydroxycarbonylation of aryl iodides using recoverable and reusable carbon aerogels doped with palladium nanopartides as catalyst Tetrahedron, 63, 2519-2523. 

Grigg, R., Zhang, L Collard, S. and Keep, A. (2003) Isoindolinones via a room temperature palladium nanopartide-catalysed 3-component cydative carbonylation-amination cascade. Tetrahedron Letters, 44, 6979-6982. 

Stable palladium nanopartides were also prepared using thermosensitive VE star polymers. The obtained partides were shown to work as a catalyst for the Heck coupling of iodobenzene and ethyl acrylate. A feature of this system is nonnecessity of expensive and toxic phosphine ligands. In mechanistic point of view, this zero-valent Pd-mediated reaction would shed new light on how Heck coupling reactions proceed. 

In situ preparation of amorphous carbon-activated palladium nanopartides. Journal of Physical Chemistry B, 101, 6834-8. 

Size control of palladium nanopartides and their crystal structures. Chemistry of Materials, 10, 594. 

Effect of catalysis on the stability of metallic nanopartides Suzuki reaction catalyzed by PVP-palladium nanopartides. Journal of the American Chemical Society, 125, 8340. 

Meier, M.A.R., FilaU, M., Gohy, J.-F. and Schubert, U.S. (2006) Star-shaped block copolymer stabilized palladium nanopartides for elEdent catalytic Heck cross-coupling reactions. Journal of Materials Chemistry, 16, 3001. 

Piao, Y., Jang, Y., Shokouhimehr, M.D., Lee, I.S. and Hyeon, T. (2007) Fadle aqueous-phase synthesis of uniform palladium nanopartides of various shapes and sizes. Small, 3, 255. 

Li, Y., Hong, X.M., Collard, D.M. and El-Sayed, M.A. (2000) Suzuki aoss-coupling reactions catalyzed by palladium nanopartides in aqueous solution. 

Zelakievricz, B.S., lica, G.C., Deacon, M.L. and Tong, Y. (2004) C NM R and infrared evidence of a dioctyl-disulfide structure on octanethiol-protected palladium nanopartide surfaces. Journal of the American Chemical Society, 126,10053. 

Alkanethiolate-protected palladium nanopartides. Chemistry of Materials, 12, 540. 

Scott, R.W.J., Ye, H., Henriquez, R.R. and Crooks, R.M. (2003) Synthesis, characterization, and stabflity of dendrimer-encapsulated palladium nanopartides. Chemistry of Materials, 15,... 

Ganesan, M., Ereemantle, R.G. and Obare, S.O. (2007) Monodisperse thioether-stabilized palladium nanopartides synthesis, characterization, and reactivity. 

Son, S.U., Jang, Y., Yoon, K.Y., Kang, E. and Hyeon, T. (2004) Eadle synthesis of various phosphine-stabilized monodisperse palladium nanopartides through the understanding of coordination chemistry of the nanopartides. Nano Letters, 4,1147. 

H. (2005) Synthesis of small palladium nanopartides stabilized by bisphosphine BINAP bearing an alkyl chain and their palladium nanopartide-catalyzed carbon-carbon coupling... 

G. J., linn, L. and Rafeah, S. (2007) DNA-templated preparation of palladium nanopartides and their application. Sensors and Actuators B Chemical, 126, 684. 

H., Zhang, L, Zhu, Y Rafailovich, M. and Sokolov, J. (2006) Charaderization of palladium nanopartides by musing x-ray reflectivity, EXAFS and electron microscopy. Langmiur, 22, 807. 

Diaz-Ayala, R., Raptis, R. and Cabrera, C.R. (2005) Formation of palladium nanopartides and other structures from molecular precursors a microscopy and spectroscopy study. Reviews on Advanced Materials Science, 10, 375. 

Shape-selective synthesis of palladium nanopartides stabilized... 

Tabuani, D., Monticelli, O., Chincarini, A., Bianchini, C., Vizza, F., Moneti, S. and Russo, S. (2003) Palladium nanopartides supported on hyperbranched aramids synthesis, characterization, and some applications in the hydrogenation of unsaturated substrates. Macromolecules, 36,4294. 

Horinoudii, S., Yamanoi, Y., Yonezawa, T., Mouri, T. and Nishihara, H. (2006) Hydrogen storage properties of isocyanide-stabilized palladium nanopartides. Langmuir, 22,1880. 

Palladium nanopartides passivated by metal-carbon covalent linkages. Journal of Materials Chemistry, 18, 755. 

Effect of palladium nanopartides on the thermal degradation kinetics of alpha crystalline syndiotactic polystyrene. Journal of Industrial and Engineering Chemistry, 12(6), 862-7. 

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