Synthesis, structure, and absorption spectra of complex neptunium(V) chromate with the guanidinium cation, [C(NH2)3]3[NpO2(CrO4)2] · (H2O)

A new complex of Np(V) with the chromate ion and an organic outer-sphere guanidinium cation is isolated from an aqueous solution. Its composition and structure are determined by X-ray diffraction analysis. The structure of [C(NH2)3]3[NpO2(CrO4)2](H2O) (I) is based on anionic chains [CpO2(CrO4)2][n3nt- between which guanidinium cations and crystallization water molecules are localized. Coordination polyhedra of the Np atoms (pentagonal bipyramids) in the anionic chains are joined in pairs through common equatorial edges. Singularities of the electronic and IR absorption spectra of compound I are discussed.