Rb₂[U(NH₂)₆], a Rubidium Hexaamidouranate(IV) obtained from the Reaction of UI₃ with RbNH₂ in Anhydrous Ammonia

Abstract

The pyrophoric compound Rb2[U(NH2)6] was obtained as a grey to black powder from the reaction of more than three equivalents of RbNH2 with UI3 in anhydrous liquid ammonia. During the process, UIII is oxidized to UIV and ammonia is reduced under evolution of H2. Rb2[U(NH2)6] crystallizes in the cubic crystal system, space group Fm3m, with the lattice parameter a = 9.7870(12) Å, V = 937.4(2) Å3, Z = 4 at T = 293 K. It is isotypic to K2PtCl6. The compound contains the unprecedented hexaamidouranate(IV) anion [U(NH2)6]2–.

[U(NH3)10]4+ Cations in Azide, Bromide, and Iodide Ammoniates and a Hydrolysis Product with an unprecedented [U(H2O)9]4+ Cation

“…As NH 4 + cations are observed at room temperature, the uranium compounds must decompose under formation of an X‐ray amorphous amide, imide, nitride or a mixed‐anionic species to liberate the protons necessary for the formation of NH 4 Br. Similar processes have been observed previously for U and Th compounds in liquid ammonia [11,39,46] . The reaction of UBr 5 with RbPH 2 following below adds additional plausibility to this way of NH 4 + ion formation.…”

“…For example, UI 3 was oxidized to U(IV) in the presence of RbNH 2 in aNH 3 under evolution of H 2 gas and a blue solution of solvated electrons was observed. The very moisture sensitive compound Rb 2 [U(NH 2 ) 6 ] had previously been obtained in that way [39] …”

“…The very moisture sensitive compound Rb 2 [U-(NH 2 ) 6 ] had previously been obtained in that way. [39] Without the addition of AgClO 4 , UBr 3 is not oxidized in liquid ammonia, neither at À 40 nor at + 25 °C, and only the ammine complex compound [U(NH 3 ) 9 ]Br 3 is formed, [28,35] which will be reported in detail elsewhere. Therefore, Ag + cations act as an oxidant and that behavior has been used in the past for the syntheses of several compounds.…”

“…Similar processes have been observed previously for U and Th compounds in liquid ammonia. [11,39,46] The reaction of UBr 5 with RbPH 2 following below adds additional plausibility to this way of NH 4 + ion formation.…”

A Dinuclear Uranium Complex [{UO2F2(NH3)}2(μ‐F)2]2− from Reaction of TlF and UO2F2 in Liquid Anhydrous Ammonia and Fluoride Ion Affinities for Some Uranyl(VI) Species [UO2Fx]2−x and [UO2Fx(NH3)5−x]2−x

“…[44,56] The basis sets for U, H, N, O, and F have been published previously. [57,58] Full details on the Tl basis set are given in the Supporting Information. The crystal structure was fully optimized within the symmetry constrains of the space group.…”