Synthesis and structure of the rubidium uranium selenophosphate Rb ₄U₂P₅Se₁₇

Black crystals of the rubidium uranium selenophosphate Rb₄U ₂P₅Se₁₇ have been prepared by the solid-state reaction of uranium, P₂Se₅, and Rb₂Se ₃ at 1023 K. The compound crystallizes with four formula units in the triclinic space group P1 with cell constants at 100 K of a =10.0824(2), b = 10.6905(2), c = 15.7845(3) Å, α = 84.678(1), β = 76.125(1), γ = 85.874(1)°. Its complex three-dimensional structure displays four different types of ligands that bridge uranium atoms. Three are P ₂Se₆^4- anions in different bonding modes and the fourth is an asymmetric Se₂^2- dianion. The compound may be written Rb₄U₂(P₂Se₆) _2.5(Se₂) and is charge-balanced as a U⁴⁺ compound.