Non-aqueous neptunium and plutonium redox behaviour in THF - access to a rare Np(III) synthetic precursor

Solvent exchange of NpCl4(DME)(2) with THF proceeds simply to yield NpCl4(THF)(3), whereas PuCl4(DME)(2) is unstable in THF, partially decomposing to the mixed valent [(PuCl2)-Cl-III(THF)(5)][(PuCl5)-Cl-IV(THF)] salt. Reduction of NpCl4(THF)(3) with CsC8 ultimately afforded NpCl3(py)(4), the only example of a structurally characterized solvated Np(III) halide. The method demonstrates a route to a well-defined Np(III) starting material without the need to employ scarcely available Np metal.