So far there are only very few uranium cyanides. Three novel uranium cyanides have been obtained from reactions of uranium halides with cyanides in liquid ammonia as a solvent.

Abstract

Reactions of uranium tri- and tetrahalides, UBr₃, UI_3, UCl₄, and UI₄, with different cyanides MCN (M=K, Ag) in liquid anhydrous ammonia led to three novel uranium(IV) cyanide compounds. The reaction of UCl₄ in the presence of KCN resulted in the compound [U(CN)(NH₃)₈]Cl₃ ⋅ 3NH₃, while UBr₃ and UI₃ were oxidized in the presence of AgCN to form the compounds (μ-CN){(H₃N)₅U(μ-NH₂)₃U(NH₃)₅}]Br₄ ⋅ 2NH₃, and (μ-CN){(H₃N)₅U(μ-NH₂)₃U(NH₃)₅}]I₄ ⋅ 2NH₃. The reaction of UI₄ with KCN in aNH₃ also yielded the compound (μ-CN){(H₃N)₅U(μ-NH₂)₃U(NH₃)₅}]I₄ ⋅ 2NH₃. The compounds (μ-CN){(H₃N)₅U(μ-NH₂)₃U(NH₃)₅}]X ₄ ⋅ 2NH₃ (X=Br, I) crystallize in different space groups, Pmn2₁ (no. 31) and Imm2 (no. 44), respectively. In both cases, the (μ-CN){(H₃N)₅U(μ-NH₂)₃U(NH₃)₅}]⁴⁺ cation forms infinite strands. We conducted quantum-chemical calculations and Intrinsic Bond Orbital analyses on the observed [U(CN)(NH₃)₈]³⁺ cation and the [(μ-CN)₂{(H₃N)₅U(μ-NH₂)₃U(NH₃)₅}]³⁺ model cation to gain insight into the bonding situation.