Intercalation of KCl into layered neptunyl and plutonyl iodates

Abstract

The hydrothermal reaction of Np(IV) or Pu(IV) with KIO 4 and CsCl at 180°C for 1 day results in the formation of NpO 2(IO 3) 2·0.5KCl·3.25H 2O ( 1) or PuO 2(IO 3) 2·0.5KCl·2.5H 2O ( 2). The neutral layers in compounds 1 and 2 are isostructural with NpO 2(IO 3) 2·H 2O and PuO 2(IO 3) 2·H 2O, respectively. The Np and Pu centers are found in distorted pentagonal bipyramidal [ AnO 7] environments that are formed from the ligation of NpO 2 2+ or PuO 2 2+ cations by iodate anions. There are two crystallographically unique pyramidal iodate anions in 1 and 2. One of these anions utilizes all three oxygen atoms to simultaneously bridge three neptunyl or plutonyl units. The second anion only bridges two actinyl units and has a terminal oxo atom. The bridging of the actinyl cations by iodate anions creates neutral ∞ 2[ AnO 2(IO 3) 3] ( An=Np, Pu) sheets that are separated by K + cations, Cl − anions, and water molecules. Crystallographic data (203 K, Mo Kα, λ=0.71073): 1, monoclinic, space group C2/ c, a=21.537(5) Å, b=11.670(3) Å, c=7.315(2) Å, β=93.033(4)°, Z=4, R( F)=5.43% for 136 parameters with 1309 reflections with I>2 σ( I); 2, monoclinic, space group C2/ c, a=21.570(4) Å, b=11.656(2) Å, c=7.348(2) Å, β=94.00(3), Z=4, R( F)=4.92% for 148 parameters with 1317 reflections with I>2 σ( I).