Cleaved Ether Reveals Trace Palladium

Palladium reagents are prized for their powerful ability to catalyze covalent bond formation. But that usefulness has a downside: Residual palladium is notoriously difficult to remove from final products and from chemical reactors. Furthermore, expensive spectrometers are usually needed to detect trace amounts of the metal. To help work around this problem, University of Pittsburgh chemists have now developed a sensitive fluorescent sensor for detecting palladium at levels as low as 0.3 ppb (J. Am. Chem. Soc., DOI: 10.1021/ja073910q). The fluorescein-based sensor shown, developed by Kazunori Koide, Fengling Song, and Amanda L. Garner, capitalizes on palladium's ability to catalytically cleave the C–O bond of allylic ethers. In the presence of Pd(0) or Pd(II), the allylic group in the sensor molecule is cleaved. The resulting alkoxide fragment fluoresces, indicating the presence of palladium. The researchers think the user-friendly sensor will be helpful for monitoring the presence of palladium in pharmaceuticals and in chemical reactors as well as for detecting palladium in mining operations.