Chemists prepare novel xenon-gold compound

The noble gas xenon can be coaxed with difficulty into forming compounds with fluorine, oxygen, nitrogen, carbon, xenon itself, and most recently chlorine. Now, scientists in Germany have made a novel compound in which xenon atoms are directly bonded to gold atoms.

According to a report in the October 6 issue of Science from chemists Stefan Seidel and Konrad Seppelt of the Free University of Berlin, the discovery of the xenon-gold compound was serendipitous. They had originally set out to prepare the elusive gold(I) fluoride (AuF) by reducing AuF₃ with a weakly coordinating agent, arsenic trifluoride (AsF₃) in a solution of HF/SbF₅. This reaction resulted in a novel derivative of AuF. To obtain AuF itself, the researchers decided to replace AsF₃ in their reaction with xenon, another mild reducing agent and coordinating agent. To their surprise, the reduction reaction stopped at the Au²⁺ state and produced an unexpected cation, AuXe₄²⁺. The investigators found they could grow dark red crystals of this cation in the reaction solution at 78°C. The cation decomposed when the xenon was removed from the reaction mixture by vacuum, but the cation was stable at room temperature if the xenon pressure was maintained at about 1000 kPa.

The Berlin researchers raise the question in their paper whether the new gold-xenon complex is unique or the first in a series of new complexes. This is difficult to answer, they conclude. But they are buoyed by the discovery of a novel Au²⁺ salt -- Au(SbF₆)₂ –in the course of their research because it is one of the few such compounds known.

For more information, contact Konrad Seppelt, Free University of Berlin, at seppelt@chemie.fu-berlin.de.

By Gordon Graff
Managing Editor, Laboratory Network.com
ggraff@vertical.net"