NEPTUNIUM(V) MALONATES

Neptunium(V) malonates of formula (NpO2)2CH2(CO2)2.xH2O with x = 1, 3, and 4, MNpO2CH2(CO2)2, where M = NH4 or Cs, and NaNpO2CH2(CO2)2.2H2O are synthesized. The x-ray powder diffraction patterns, derivatograms, and electronic and IR spectra of the compounds are recorded. The spec troscopic measurements suggest that the NpO2+ ions are five-coordinate in the simple malonates and form a network of cation-cation bonds. In the tri- and tetrahydrates, they occupy two crystallographically equi valent positions. In the double Np(V) malonates with outer-sphere Na+, NH4+, and Cs+, the central ion evidently has a hexagonal bipyramidal oxygen environment. The composition, structure, and properties of the monotypic neptunyl oxalates and malonates are distinctly different.