Chemistry

Magnetic Catalysts

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Science  02 Sep 2005:
Vol. 309, Issue 5740, pp. 1461
DOI: 10.1126/science.309.5740.1461a

In the chemical synthesis of drugs, the route via homogeneous catalysis by metal complexes is plagued by the challenge of separating residual toxic metal from the product. Binding the catalyst to a heterogeneous support can simplify this purification step, but at the expense of reducing the mixing efficiency between catalyst and reagent.

Hu et al.have found a compromise by fusing a ruthenium catalyst to magnetite (Fe3O4) nanoparticles. The tiny particles mix efficiently with molecular reagents and would ordinarily be hard to remove by filtration, but by holding a small magnet to the flask, the authors can retain the catalyst and decant the product. The Ru complex, a variant of Noyori's binaphthyl-based asymmetric hydrogenation catalyst, was attached to 8-nm-diameter particles through a phosphonate group. A range of aromatic ketones were reduced quantitatively to alcohols at room temperature and 0.1 mol % catalyst loading, with enantiomeric excesses ranging from 77 to 98%, and the catalyst could be recycled 10 times without loss of activity. — JSY

J. Am. Chem. Soc. 10.1021/ja053881o (2005).

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