UF6 and UF4 in Liquid Ammonia: [UF7(NH3)]3− and [UF4(NH3)4]

✍ Scribed by Florian Kraus; Sebastian A. Baer

• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 323 KB
• Volume: 15
• Category: Article
• ISSN: 0947-6539
• DOI: 10.1002/chem.200901044

✦ Synopsis

Abstract

From the reaction of uranium hexafluoride UF~6~ with dry liquid ammonia, the [UF~7~(NH~3~)]^3−^ anion and the [UF~4~(NH~3~)~4~] molecule were isolated and identified for the first time. They are found in signal‐green crystals of trisammonium monoammine heptafluorouranate(IV) ammonia (1:1; [NH~4~]~3~[UF~7~(NH~3~)]⋅NH~3~) and emerald‐green crystals of tetraammine tetrafluorouranium(IV) ammonia (1:1; [UF~4~(NH~3~)~4~]⋅NH~3~). [NH~4~]~3~[UF~7~(NH~3~)]⋅NH~3~ features discrete [UF~7~(NH~3~)]^3−^ anions with a coordination geometry similar to a bicapped trigonal prism, hitherto unknown for U^IV^ compounds. The emerald‐green [UF~4~(NH~3~)~4~]⋅NH~3~ contains discrete tetraammine tetrafluorouranium(IV) [UF~4~(NH~3~)~4~] molecules. [UF~4~(NH~3~)~4~]⋅NH~3~ is not stable at room temperature and forms pastel‐green [UF~4~(NH~3~)~4~] as a powder that is surprisingly stable up to 147 °C. The compounds are the first structurally characterized ammonia complexes of uranium fluorides.