title: Novel heptavalent actinide compounds: tetrasodium dihydroxidotetraoxidoneptunate(VII) hydroxide dihydrate and its plutonium analogue.
abstract: The title compounds, Na(4)[NpO(4)(OH)(2)]OH.2H(2)O and Na(4)[PuO(4)(OH)(2)]OH.2H(2)O, are isostructural and isomorphous, and contain complex [AnO(4)(OH)(2)](3-) anions (Ac is an actinide) in the form of distorted tetragonal bipyramids, Na(+) cations, crystallization water molecules and outer-sphere OH groups. The complex [AnO(4)(OH)(2)](3-) anions occupy general positions and the coordinated OH groups deviate significantly from a centrosymmetric relative orientation. The [AnO(4)(OH)(2)](3-) anions exhibit anisotropic actinide contraction; the shortening of the An-O(hydroxide) bonds on going from Np to Pu is greater than that of the AnO(4) groups.
authors: A. N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, 31 Leninsky Prospekt, 119991 Moscow, Russian Federation. mickgrig@mail.ru
authors: Mikhail S
authors: MS
authors: Grigoriev
authors: Nikolai N
authors: NN
authors: Krot