Uranium Cyanides from Reactions in Liquid Ammonia Solution

Reactions of uranium tri‐ and tetrahalides, UBr 3 , UI 3, UCl 4 , and UI 4 , with different cyanides M CN ( M =K, Ag) in liquid anhydrous ammonia led to three novel uranium(IV) cyanide compounds. The reaction of UCl 4 in the presence of KCN resulted in the compound [U(CN)(NH 3 ) 8 ]Cl 3 ⋅ 3NH 3 , while UBr 3 and UI 3 were oxidized in the presence of AgCN to form the compounds (μ‐CN){(H 3 N) 5 U(μ‐NH 2 ) 3 U(NH 3 ) 5 }]Br 4 ⋅ 2NH 3 , and (μ‐CN){(H 3 N) 5 U(μ‐NH 2 ) 3 U(NH 3 ) 5 }]I 4 ⋅ 2NH 3 . The reaction of UI 4 with KCN in aNH 3 also yielded the compound (μ‐CN){(H 3 N) 5 U(μ‐NH 2 ) 3 U(NH 3 ) 5 }]I 4 ⋅ 2NH 3 . The compounds (μ‐CN){(H 3 N) 5 U(μ‐NH 2 ) 3 U(NH 3 ) 5 }] X 4 ⋅ 2NH 3 ( X =Br, I) crystallize in different space groups, Pmn 2 1 (no. 31) and Imm 2 (no. 44), respectively. In both cases, the (μ‐CN){(H 3 N) 5 U(μ‐NH 2 ) 3 U(NH 3 ) 5 }] 4+ cation forms infinite strands. We conducted quantum‐chemical calculations and Intrinsic Bond Orbital analyses on the observed [U(CN)(NH 3 ) 8 ] 3+ cation and the [(μ‐CN) 2 {(H 3 N) 5 U(μ‐NH 2 ) 3 U(NH 3 ) 5 }] 3+ model cation to gain insight into the bonding situation.