[UO2(NH3)5]Br2 ∙ NH3 : synthesis, crystal structure, and speciation in liquid ammonia solution by first-principles molecular dynamics simulations

Pentaammine dioxido uranium(VI) dibromide ammonia (1/1), [UO2(NH3)5]Br2·NH3, was synthesized in the form of yellow crystals by the reaction of uranyl bromide, UO2Br2, with dry liquid ammonia. The compound crystallizes orthorhombic in space group Cmcm and is isotypic to [UO2(NH3)5]Cl2·NH3 with a = 13.2499(2), b = 10.5536(1), c = 8.9126(1) Å, V = 1246.29(3) Å3 and Z = 4 at 123 K. The UO22+ cation is coordinated by five ammine ligands and the coordination polyhedron can be best described as pentagonal bipyramid. Car–Parrinello molecular dynamics simulations are reported for [UO2(NH3)5]2+ in the gas phase and in liquid NH3 solution (using the BLYP density functional). According to free-energy simulations, solvation by ammonia has only a small effect on the uranyl–NH3 bond strength.PostprintPeer reviewe

Crystal structure of Cs2[Th(NO3)6]

Dicaesium hexanitratothorate(IV), Cs2[Th(NO3)6], was synthesized in the form of colourless crystals by reaction of thorium nitrate and caesium nitrate in aqueous solution. The Th atom is located on an inversion centre and is coordinated by six chelating nitrate anions. The resulting ThO12 coordination polyhedron is best described as a slightly distorted icosahedron. The Cs atom also has a coordination number of 12, but its coordination polyhedron is considerably more distorted. The crystal packing can be derived from an hexagonal dense packing (hcp) of idealized spherical CsO12 and ThO12 units. The CsO12 units form a distorted hcp arrangement and half of the octahedral sites are occupied by the ThO12 units

Crystal structure of [UO2(NH3)5]NO3·NH3

Pentaammine dioxide uranium(V) nitrate ammonia (1/1), [UO2(NH3)5]NO3·NH3, was obtained in the form of yellow crystals from the reaction of caesium uranyl nitrate, Cs[UO2(NO3)3], and uranium tetrafluoride, UF4, in dry liquid ammonia. The [UO2]+ cation is coordinated by five ammine ligands. The resulting [UO2(NH3)5] coordination polyhedron is best described as a pentagonal bipyramid with the O atoms forming the apices. In the crystal, numerous N—H...N and N—H...O hydrogen bonds are present between the cation, anion and solvent molecules, leading to a three-dimensional network

The Unusual Coordination Sphere in the Octaammine Calcium(II) Ions of [Ca(NH3)8]Br2 and [Ca(NH3)8]I2 and the Thermal Decomposition of the Iodide to [Ca(NH3)6]I2

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