Crystal structure of Ni3[(UO2)2F7]2 � 18H2O

Density functional calculations on actinide compounds: Survey of recent progress and application to [UO2X4]2? (X=F, Cl, OH) and AnF6 (An=U, Np, Pu)

“…As could be expected from the other examples, the longest bond lengths are predicted by ECP-BLYP; the calculated U-F bond length is shortest for QR-BLYP, and the uranyl bond length is shortest for ECP-B3LYP. Experimental 227,233,234 are shown in Table IV. All theoretical methods underestimate the value of this frequency.…”

Insight into the Uranyl Oxyfluoride Topologies through the Synthesis, Crystal Structure, and Evidence of a New Oxyfluoride Layer in [(UO2)4F13][Sr3(H2O)8](NO3)·H2O

“…The chains present in these compounds are mainly built from UO 2 F 5 entities that share edges to form chains. Up to now this building block has only been observed in organic templated structures. ,, When the chains are obtained with an inorganic cation and/or ammonium, the UO 2 F 5 entities are linked by sharing alternatively corners and edges, seemingly U 2 O 4 F 8 dimers linked by corners. − With a lower fluorine-to-oxygen ratio (F/O = 0.2), the structures are most likely to be constituted of chains of corner-sharing UO 5 F 2 polyhedra, linked by the fluorine atoms. This type of chain is the most common found in systems where oxoanions such as sulfates, selenates or phosphates are present in the coordination of uranium and where the countercation is inorganic or ammonium. − As obtained in this study and in a previous organically templated compound, chains are built from a tetrameric structural unit in which four UO 2 F 5 polyhedra are connected by corner sharing, which are further connected by edge-sharing .…”

“…The other zero-dimensional structures can display dimers that present degrees of fluorination varying from F/O = 2 to F/O = 0.2. The fully fluorinated dimer U 2 O 4 F 8 has been mostly found in inorganic combinations with Ni, Cs, or Rb cations, and only with piperazine in organically templated structures. − , The unusual U 2 O 4 F 7 (H 2 O) dimer with a single water molecule substituted for a fluorine is only found with the templating effect of 4,4′-bipyridine in [(UO 2 ) 2 F 8 (H 2 O) 2 Zn 2 ]­(4,4′-bpy) 2 . This surprising dimer is the result of the organic template’s linking to the uranyl oxyfluoride and to Zn polyhedra .…”

“…Most were described after the Manhattan project by Zachariasen, − and few have been investigated since. − Organically templated uranium oxyfluorides have been reported with a wide variety of structures. − A large number of these oxyfluorides adopt either mono or bidimensional structures, while only a few exhibit a three-dimensional (3D) framework. Inorganic uranium oxyfluorides were found only with few monovalent cations, such as K, Rb, and Cs or network-forming metals such as Ni, − and form crystal structures with a lower variety of dimensionalities than hybrid uranium oxyfluorides. While most of these compounds were discovered nearly half a century ago, our recent successful work on inorganic oxyfluorides has helped in developing an understanding of inorganic actinide fluorides and has shed light on fluorination processes, while also giving insight into the use of UF 6 in the nuclear fuel industry. , We report in this paper an example of uranyl oxyfluoride with the divalent cation Sr 2+ , displaying an unprecedented structural arrangement for inorganic uranyl oxyfluorides.…”

Hydrothermal Preparation of Nickel(II)/Uranium(IV) Fluorides with One-, Two-, and Three-Dimensional Topologies

“…The majority of well-characterized representatives of transition metal/uranium fluorides are found to contain transition metals in the +2 oxidation state, especially Ni(II), and U(VI) in the form of uranyl, UO 2 2+ , cations. Members of this group include [Ni(H 2 O) 6 ] 2 [(UO 2 ) 2 F 8 ]·2H 2 O, [Ni(H 2 O) 6 ] 3 [(UO 2 ) 4 F 14 ], and [NH 4 ] 2 [Ni(H 2 O) 6 ][(UO 2 ) 2 F 8 ] . Limited crystallographic information has also been reported for the mixed-metal U(IV) fluorides [M(H 2 O) 6 ][U 2 F 10 ]·2H 2 O (M = Co, Ni, Cu) .…”