M. S. Grigor'ev

Crystal Structure of the Mixed-Valence Neptunium Compound Na6[(NpVO2)2(NpVIO2)(MoO4)5] · 13H2O

The crystal structure of the mixed-valence Np(V) and Np(VI) compound Na6[(NpVO2)2(NpVIO2)(MoO4)5] · 13H2O was determined. The structure is built of the anionic layers [(NpVO2)2(NpVIO2)(MoO4)5]6n-n with the Na+ cations and crystal water molecules between them. The Np(V) and Np(VI) atoms in the anionic layers are ordered. The motif of the anionic layer is close to that found in Mg2[(UO2)3(SeO4)5] · 16H2O. The isostructural mixed-valence Np(V) and U(VI) compound was also synthesized.

Behavior of Anhydrous Uranyl Acetate at Heating in CH3CN. Crystal Structures of New Uranyl Acetates

Finely crystalline anhydrous uranyl acetate UO2(OOCCH3)2 (I) was prepared by recrystallization from acetonitrile at 140-145°C. Its X-ray diffraction pattern was indexed in the monoclinic system: a = 7.4311(5), b = 12.6622(9), c = 4.1985(2) Å, β = 92.01(1)°, V = 394.8(2) Å3, Z = 2, ρcalc = 3.265 g cm-3; probable space group C2, Cm, or C2/m. Presumably, in structure I, the coordination polyhedra of U atoms (hexagonal bipyramids), sharing common equatorial edges, are linked to form infinite chains via bridging oxygen atoms of acetate ions. Under the same conditions, the presence of water in acetonitrile results in formation of crystalline [UO2(OOCCH3)2·HOOCCH3] (II) and (NH4)2[(UO2)5(μ3-O)2(OOCCH3)8] (III), whose composition and structure were determined by single crystal X-ray analysis. In the structure of II, one acetate ion is bidentate chelate and the other, bidentate bridging; the coordination number (CN) of the U atom is 7. In the structure of III, there are three crystallographically independent U atoms with CN 7 and 8. The coordination polyhedra of the U atoms, sharing common edges and vertices, are linked via bridging O2- ions and oxygen atoms of acetate ions.

Double Np(V) Malonates with Co(NH3)63+ in the Outer Sphere

Light yellow crystalline products of the general formula Co(NH3)6(NpO2L)2A·xH2O, where A = Cl, NO3, or ClO4, are precipitated with Co(NH3)63+ ions from weakly acidic chloride, nitrate, and perchlorate solutions of Np(V), containing up to 0.3 M CH2(COO)22- (L2-). When only malonate ions are present in the solution, Np(V) precipitates in the form of Co(NH3)6(NpO2L)2HL·H2O. These compounds are virtually insoluble in water and have similar X-ray patterns. Unlike oxalate and phthalate solutions, complex neptunyl(V) ion NpO2L23- is not precipitated with Co(NH3)63+ ions from malonate media of the above composition.

Synthesis and Study of Complexes of Some Trivalent Lanthanides and Americium with N,N-Dimethylacetamide and PW12O403–Anions

The synthesis of crystalline complexes of trivalent lanthanides and americium with N,N-dimethylacetamide (DMAA) and PW12O403–anions was described. Their IR and electronic absorption spectra were studied. The structure of the neodymium complex [Nd(DMAA)6PW12O40] was determined using X-ray diffraction analysis. The thermal behavior of the lanthanide complexes was studied. In the 300–400°C temperature interval, even in air, intramolecular partial reduction of the anion occurs to form products which can be characterized as tungsten bronzes.

Model of the (PuO2)2SiO4·2H2O Crystal Structure, Based on Powder X-ray Diffraction Data

Plutonyl orthosilicate dihydrate (PuO2)2SiO4·2H2O was prepared by a hydrothermal procedure at 180°C. Its powder diffraction pattern (Guinier camera, CuKα1 radiation) was indexed in the tetragonal crystal system: a 6.912(3), c 18.563(3) Å, space group I41/amd. The structure of (PuO2)2SiO4·2H2O is similar to the known structures of (UO2)2SiO4·2H2O and (UO2)2GeO4·2H2O, but differs in the mutual orientation of the chains of coordination polyhedra of actinide atoms (pentagonal bipyramids) sharing common equatorial edges.

Crystal structure of hexakis(N,N-dimethylacetamide)ytterbium(III) dodecawolframophosphate [Yb(DMAA)6]PW12O40

An X-ray diffraction study of the [Yb(DMAA)6]PW12O40 complex (DMAA is N,N-dimethylacetamide) is performed. The structure contains isolated cationic complexes [Yb(DMAA)6]3+ and heteropolyanions PW12O403−. The cationic complexes and the heteropolyanions occupy centrosymmetric positions. The coordination polyhedron of the Yb atom is a slightly distorted octahedron. Unlike the Nd complex of the same composition, which was studied earlier, O atoms of the heteropolyanion are not included in the Yb coordination. All the O atoms of the heteropolyanion are disordered. Analysis of the disordering reveals that the heteropolyanion has a Keggin structure (α isomer), and its disordering results from the centrosymmetric position.

Neptunium(IV) Complex with Carbamide [Np(Urea)8]SiW12O40 · 2Urea · H2O: Synthesis, Crystal Structure, and Properties

The synthesis and crystal structure of [Np(Urea)8]SiW12O40 · 2Urea · H2O complex are reported. Crystallographic parameters: space groups C2/c, a = 18.972(5) Å, b = 18.891(5) Å, c = 16.654(4) Å, β = 100.847(6)°, Z = 4, V = 5862(3) Å3, ρ(calcd) = 4.226 g/cm3. Thermal properties of this compound are studied; absorption spectra in the IR and visible regions are measured.