Nanocluster catalyst

Scheme 4 Hydrogenation of anisole by polyoxoanion-stabilized Rh(0) nanocluster catalyst...

A similar result is obtained with 30 equivalents of H2O added but a long reaction time is required namely 215 h. Nevertheless, in all cases a black precipitate of bulk Rh(0) is visible at the end of the reaction justifying the destabilization of nanoclusters due to the interaction of H or H2O with the basic P2Wi5Nb3062 polyoxoanion. Finally, the partial hydrogenation of anisole to yield 1-methoxycyclohexane (up to 8%) with a soluble nanocluster catalyst has been reported by Finke and coworkers (see Sect. 3). 

Copper-catalyzed Suzuki cross-coupling reactions using mixed nanocluster catalysts have been studied recently. Copper-based catalysts were shown to be effective as reagents that can present an inexpensive and environmentally friendly alternative to noble metal catalysts. In the hydrogenation of cinnamic acid to corresponding alcohol, the selectivity can be varied by doping Sn with Rh colloid catalysts. A selectivity of 86% was achieved using a colloidal Rh/Sn (Rh/Sn = 1.5 1) catalyst on... 

Toshima, N. and Hirakawa, K., Polymer protected bimetallic nanocluster catalysts having core/shell structure for accelerated electron transfer in visible-light-induced hydrogen generation, Polymer J., 31, 1127, 1999. 

Atomic-Scale Imaging of Supported Metal Nanocluster Catalysts in the Working State... 

With the ability to obtain information about the concentrations of various types of metal surface sites in complex metal nanocluster catalysts, HRTEM provides new opportunities to include nanoparticle structure and dynamics into fundamental descriptions of the catalyst properties. This chapter is a survey of recent HRTEM investigations that illustrate the possibilities for characterization of catalysts in the functioning state. This chapter is not intended to be a comprehensive review of the applications of TEM to characterize catalysts in reactive atmospheres such reviews are available elsewhere (e.g., 1,8,9 )). Rather, the aim here is to demonstrate the future potential of the technique used in combination with surface science techniques, density functional theory (DFT), other characterization techniques, and catalyst testing. 

II] ATOMIC-SCALE IMAGING OF SUPPORTED METAL NANOCLUSTER CATALYSTS 79... 

High-resolution transmission electron microscopy (HRTEM) has matured markedly in the preceding decade and has emerged as a powerful technique for investigation of nanostructured metal catalysts at the atomic level, even under working conditions. The ability to image the dynamic structure and morphology of supported metal nanocluster catalysts in such detail makes HRTEM an essential complement to the arsenal of spectroscopic techniques used for characterization of... 

Figure 5.5 Catalytic cycle for the oxidation of benzylalcohol using a Pd° nanocluster catalyst.

Thathagar, M.B., Beckers, J. and Rothenberg, G. (2002) Copper-catalyzed Suzuki cross-coupling using mixed nanocluster catalysts. J. Am. Chem. Soc., 124, 11858. 

Hansen PL, Helveg S, Datye A. Atomic-scale imaging of supported metal nanocluster catalysts in the working state. J Catal. 2006 50 77. 

Chauhan BPS, Rathore J S. (May 16-20, 2006) Synthesis of Isolable Nanocluster Catalysts and Their Applications in Macromolecular Hydrosilylation Catalysis. 39th Silicon Symposium, Frankenmuth, MI USA, Abs. No. 300... 

Figure 6.62. Silicon nanowire growth from a gold nanocluster catalyst. Shown is (a) the phase diagram for the Au/Si system, showing the eutectic temperature/composition (b) SEM image and (c) high-resolution TEM image of the nanowires grown at a temperature of 450° C. The dark tip of the nanowire is from the gold nanocluster. Reproduced with permission from Hu, J. Odom, T. W. Lieber, C. M. Acc. Chem. Res. 1999, 32, 435. Copyright 1999 American Chemical Society.

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