The First Stable Argon Compound

When Neil Bartlett formed a compound between xenon and PtFg in 1962, he broke a psychological barrier. A number of other xenon compounds were synthesized in short order as was KrF2 and probably a radon compound. The next lightest member of the series, argon, resisted attempts to make a stable compound for almost four more decades. There are still no argon compounds isolable at ambient conditions. 

Leonid Khriachtchev, Markku Rasanen (1949- ), and their colleagues at the University of Helsinki synthesized argon fluorohydride (HArF) in 2000. They formed a solid matrix of HF in argon at 7.5 K (-447°F or -266°C). Photolysis of the matrix in the vacuum ultraviolet (127-160 nm) dissociates HF into H and F atoms. These form a new species demonstrated by IR spectroscopy and computation to be HArF The calculations indicated resonance of the type  

The HArF molecule decomposes upon heating at 27 K (-411°F or -246°C). It appears that small amounts of oxygen-containing impurities in the matrix initiate decomposition. It is possible that without these impurities HArF could survive at higher temperatures. A substance that decomposes at -411°F (-246°C) does not fit conventional notions of stability. It is also predicted, using high-levels molecular orbital calculations, to be 5.87 eV (135 kcal/mol) less stable than Ar and HF. But HArF still requires an activation energy in excess of 0.35 eV (8.1 kcal/mol) to decompose. It is thus a real molecule with vibrations of its H-Ar and Ar-F bonds. 

Molecular nitrogen (N2, or dinitrogen) is the most abundant component of the atmosphere. Its extremely strong N=Nbond is very resistant to chemical reaction. In nature, only certain anaerobic bacteria and leguminous 

In 1995, Christopher C. Cummins (1966- ) and his student Catalina E. Laplaza at MIT discovered that a molybdenum(III) compound of formula Mo(NRAr)3 (R is an alkyl group and Ar an aromatic group, not argon) could decompose the extremely stable N2 molecule under relatively mild conditions. The s) tem converts N2 to two nitrido (N ) ligands which can, in turn, be converted to ammonia (NH3) and other useful nitrogen compounds. 

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