Introduction of Nitrogen into uranium and thorium halides: Reactions with liquid ammonia, amides, imides, nitrides, and azides

• Applicant: Professor Dr. Florian Kraus
• Subject Area: Inorganic Molecular Chemistry - Synthesis and Characterisation ; Solid State and Surface Chemistry, Material Synthesis
• Term: from 2010 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 189244078

The chemistry of uranium and thorium is well known - in sections dealing for nuclear purposes such as isolation of the elements, isotope separation, or workup of nuclear fuels. Besides these nuclear topics the knowledge is scarce.With our project we would like to stay away from such nuclear purposes and focus on the basic chemistry of uranium and thorium. The chemical reactions of uranium and thorium halides, with a special emphasis on those of the fluorides, are to be explored further. Our main interest is the synthesis of fluorine and nitrogen containing compounds like fluoride ammines, but also mixed-anionic compounds like fluoride amides, imides, and the respective nitrides. Nitrogen is to be introduced using ammonia, hydrazine, amides, imides, nitrides, and azides using solid state techniques as well as solution techniques in liquid ammonia solution. To the best of our knowledge such compounds are - except for a few examples - unknown. However, as they should be structurally related to oxides, the compounds should feature interesting and similar usable magnetic, optic, and electronic properties. In recent years mixed-anionic compounds have become more important, as for example superconducting fluoride oxides have been discovered.Nitrides are industrially used as hard materials, high temperature resistant substances, but also as light emitters in LEDs. Usually nitrides are synthesized at high temperatures and/or pressures. In our project we would like to develop a low temperature route to nitrides based on successive ammonolysis of halides in liquid ammonia.Our preliminary work during the first proposal was very successful: Besides a couple of novel compounds, the engagement with uranium, thorium, and fluorine chemistry allowed us to spot and settle an almost 200 year old dispute: Only with the knowledge gained in the first proposal we could unambiguosly proof the existence of elemental fluorine in nature.

• DFG Programme: Research Grants