A team of researchers at the U.S. Department of Energy’s Ames Laboratory has synthesized and accurately characterized cesium platinide hydride (4Cs2Pt*CsH), the first intermetallic double salt with platinum.
Crystals of cesium platinide hydride 4Cs2Pt*CsH. Image credit: Ames Laboratory, U.S. Department of Energy.
Cesium platinide hydride is a new member of a rare family of compounds in which a metal forms a truly negatively charged ion.
It has a salt-like character and forms a translucent cherry-red crystal, according to the authors, Prof. Anja-Verena Mudring and Dr. Volodymyr Smetana.
“It’s a compound that as a researcher you have trouble envisioning that it can even exist, but once you do have it and can analyze it, it’s nothing like what you expect,” Prof. Mudring explained.
“Instead of creating a gray, shiny alloy as typically observed for many hydrogen storage materials by reacting the metals cesium and platinum with hydrogen, these red crystals form. They are really quite beautiful.”
Cesium platinide hydride can exist only in an inert environment similar to conditions that exist in outer space.
The scientists said this compound was initially extracted from a cesium melt.
It is highly unstable, with the platinum returning to its elemental state if it is exposed to oxygen.
Single crystal studies combined with powder X-ray diffraction, solid-state nuclear magnetic resonance and deep theoretical investigations allowed the team to prove its existence.
Its unusual structure and properties, so different from typical intermetallic hydrides, are explained by the strong influence of relativistic effects on both cesium and platinum.
“It’s unique. It’s the first example we have of a salt with so strongly negatively charged metal ions,” Prof. Mudring said.
“Moreover, you mix an alloy with a salt and get another non-conducting salt.”
“This allows for some deep insight into the nature of chemical bonding — and as Goethe wrote, ultimately what holds the world and its compounds together in its inmost form,” she said.
The research is published in the Nov. 14 issue of the journal Angewandte Chemie.
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Volodymyr Smetana & Anja-Verena Mudring. 2016. Cesium Platinide Hydride 4Cs2Pt*CsH: An Intermetallic Double Salt Featuring Metal Anions. Angewandte Chemie 55 (47): 14838-14841; doi: 10.1002/anie.201606682
