Xe as a Ligand

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Science  11 Feb 2005:
Vol. 307, Issue 5711, pp. 817
DOI: 10.1126/science.307.5711.817c

For more than 20 years, liquid xenon (Xe) has been used as a solvent for studying highly reactive transition metal compounds that attack solvents usually thought of as inert, such as alkanes and fluoro- carbons. Nevertheless, infrared spectroscopy showed that in some cases, the Xe reacted transiently with the metal centers, binding with an enthalpy comparable to that of a hydrogen bond. Ball et al. have characterized a rhenium (Re)-Xe linkage directly by low-temperature nuclear magnetic resonance (NMR) spectroscopy. They prepared a Xe solution of (iPrCp)Re(CO)2PF3 (where iPrCp is isopropylcyclopentadienyl) and induced CO loss by ultraviolet irradiation through an optical fiber inserted into the sample probe. The appearance of a 129Xe NMR signal, shifted more than 700 parts per million upfield from the free solvent, confirmed that a Xe atom was coordinated to the unsaturated Re center, and further evidence came from nuclear spin coupling of the bound Xe to the PF3 ligand, observed via 31P and 19F NMR spectra. The compound persists for hours in liquid Xe at −110°C. — JSY

Proc. Natl. Acad. Sci. U.S.A. 102, 1853 (2005).

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