Uranyl Halides from Liquid Ammonia: [UO 2 (NH 3 ) 5 ]Cl 2 ·NH 3 and [UO 2 F 2 (NH 3 ) 3 ] 2 ·2NH 3 and Their Decomposition Products [UO 2 Cl 2 (NH 3 ) 3 ] and [UO 2 F 2 (NH 3 ) 3 ]

Uranyl chloride UO 2 Cl 2 and uranyl fluoride UO 2 F 2 react with dry liquid ammonia under the formation of traffic‐green crystals of pentaammine dioxido uranium(VI) dichloride ammonia (1/1) [UO 2 (NH 3 ) 5 ]Cl 2 · NH 3 ( 1 ) and sulfur‐yellow crystals of triammine difluorido dioxido uranium(VI) ammonia (2/2) [UO 2 F 2 (NH 3 ) 3 ] 2 · 2NH 3 ( 2 ), respectively. Low‐temperature X‐ray structure analyses on single crystals of the two compounds were conducted. Compound 1 crystallizes in the orthorhombic space group Cmcm with a = 12.7865(2), b = 10.5106(2), c = 8.7089(2) Å, V = 1170.45(4) Å 3 at 123 K with Z = 4. Compound 2 crystallizes in the orthorhombic space group Pnma with a = 20.8451(5), b = 9.1267(2), c = 8.3371(2) Å, V = 1586(6) Å 3 at 123 K with Z = 4. Further investigations on the room‐temperature decomposition products of compounds 1 and 2 by Raman and IR spectroscopy, TGA MS and X‐ray powder diffraction measurements and deuteration studies led to the identification of triammine dichlorido dioxido uranium(VI) UO 2 Cl 2 (NH 3 ) 3 ( 3 ) and triammine difluorido dioxido uranium(VI) UO 2 F 2 (NH 3 ) 3 ( 4 ) in the form of fern‐green and zinc‐yellow powders. Quantum chemical studies at the DFT‐PBE0/TZVP level of theory support the experimental observations andalso show that the O≡U≡O triple bonding in the [UO 2 F 2 (NH 3 ) 3 ] molecule of compound 2 is weaker in comparison to the one in the [UO 2 (NH 3 ) 5 ] 2+ dication of compound 1 .