Pentakis(carbamide)dioxoneptunium(V) nitrate [NpO2 {OC(NH2)2}5](NO3):: Synthesis, crystal structure, and some properties

X-ray diffraction and spectroscopic data for a new Np(V) compound, namely, [NpO2{OC(NH2)(2)}(5)](NO3) (I) are presented. Crystals are monoclinic, space group P2(1), a = 11.142(2) Angstrom, b = 7.6379(9) Angstrom, c = 11.143(2) Angstrom, beta = 108.9(1), Z = 2, V = 897.1(2) Angstrom(3). The neptunium atom has a typical pentagonal-bipyramidal environment with five oxygen atoms of the carbamide molecules in the equatorial plane. The nitrate ion is in the outer sphere. Carbamide is a strong molecular ligand with respect to Np(V) and hence, cation-cation bonds of the Np O-2(+) ions are not realized in structure I. The wave length of the f-f transition in the electronic absorption spectra of crystalline complex I and Np(V) in a saturated carbamide solution is virtually the same and is equal to 991 nm.