Preparations,structures and thermal decomposition of some bis(pentafluorobenzoato)dioxouranium(VI) complexes

Reaction Of UO₂(O₂CCH₃)₂ with pentafluorobenzoic acid yields UO₂(O₂CC₆F₅)₂, which has been converted into the solvated complexes UO₂(O₂CC₆F₅)₂L₂·S [L₂ = 2,2′-bipyridyl (bpy), S = 0.33 (PhH) or 0.07 (t-BuOH); L = Ph₃PO, S = t-BuOH; L = Ph₃AsO, S = 0.40 (t-BuOH)] and the solvent free UO₂(O₂CC₆F₅)₂L₂ [L₂ = bpy; L = Ph₃PO]. The crystal structure of UO₂(O₂CC₆F₅)₂bpy (orthorhombic, space group P2₁2₁2₁; a = 18.45(2), b = 18.94(2), c = 7.069(8) Å, Z = 4] reveals distorted hexagonal bipyramidal stereochemistry with a trans UO₂ group, chelating pentafluorobenzoate ligands, and chelating 2,2′-bipyridyl, which is significantly displaced from the hexagonal plane. The structure of UO₂(O₂CC₆F₅)₂(OPPh₃)₂·t-BuOH [rhombohedral, space group R3; a = 21.51(3) Å, α = 117.28(5)°, Z = 3] shows trans UO₂, pseudo trans Ph₃PO ligands, and one unidentate and one disordered chelating pentafluorobenzoate ligand, whilst t-BuOH could not be located because it is highly disordered. Relationships between ν (CO₂) frequencies and the carboxylate coordination are discussed, and UO₂(O₂CC₆F₅)₂(OAsPh₃)₂.0.40 (t-BuOH) is considered to have stereochemistry similar to that of the phosphine oxide complex. The complexes undergo decarboxylation in dimethyl sulphoxide yielding pentafluorobenzene and carbonatodioxouranium(VI) species not UO₂(C₆F₅)₂ derivatives.     

Highly efficient epoxidation of unsaturated steroids using magnesium bis(monoperoxyphthalate) hexahydrate

Fast generation of epoxides from the corresponding homoallylic and allylic steroidal olefins was developed by using magnesium bis(monoperoxyphthalate) hexahydrate (MMPP) as oxidant suspended in acetonitrile (CH₃CN) at reflux temperature. The protocol involves the use of a safe readily available oxidant along with an easy work-up, which renders the process very efficient. Selective 4,5- and 5,6-epoxidations of steroids are reported. Among them, highly stereoselective epoxidation of Δ⁵-B-nor-cholestanes was achieved. Moreover, the method is chemoselective for the 5,6-position and can be applied to the epoxidation of ring-A enones.     

Synthesis and X-ray structural study of bis(2-sodiumsulfonylethyl) sulfoxide hexahydrate

The structure of bis(2-sodiumsulfonylethyl) sulfoxide hexahydrate (1), which was synthesized by the reaction of divinyl sulfoxide with sodium metabisulfite in an aqueous ethanol medium, has been determined by X-ray structural analysis. Both Na⁺ cations are coordinated by six O atoms of crystallization water molecules and SO₃ groups; the coordination sphere is a distorted octahedron. The crystals are stabilized by an extensive network of hydrogen bonds through the water molecules of crystallization.