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Suzuki coupling catalyzed by palladium shells H ollow palladium spheres fabricated in the laboratory have been successfully used as a recyclable heterogeneous catalyst for Suzuki coupling reactions [J. Am. Chem. Soc., 124, 7642 (2002)]. Taeghwan Hyeon, an associate professor of chemical engineering at Seoul National University, in South Korea, and coworkers prepared spherical shells that are 300 nm across and consist of 10-nm palladium particles. The large surface area of these shells makes them highly active catalysts in Suzuki cross-coupling reactions such as the one shown here. In previous studies, other groups reported that palladium nanoparticles used in these reactions agglomerated after one cycle, resulting in a loss of catalytic activity. "To our surprise," Hyeon and coworkers write, "[our Pd spheres] maintained their catalytic activities even after seven recycles. In addition, simple filtering can retrieve the catalyst from the reaction pot." Hyeon says this heterogeneous catalyst is nearly as active as the most popular homogeneous palladium catalyst used for Suzuki coupling. Furthermore, he believes the new catalyst could also be applied to other important carbon-carbon coupling reactions |
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