High-resolution crystal structure of the double nitrate hydrate [La(NO3)6]2[Ni(H2O)6]3·6H2O

Abstract

This study introduces bis[hexakis(nitrato-κ2 O,O′)lanthanum(III)] tris[hexaaquanickel(II)] hexahydrate, [La(NO3)6]2[Ni(H2O)6]3·6H2O, with a structure refined in the hexagonal space group R\overline{3}. The salt comprises [La(NO3)6]3− icosahedra and [Ni(H2O)6]2+ octahedra, thus forming an intricate network of interpenetrating honeycomb lattices arranged in layers. This arrangement is stabilized through strong hydrogen bonds. Two successive layers are connected via the second [Ni(H2O)6]2+ octahedra, forming sheets which are stacked perpendicular to the c axis and held in the crystal by van der Waals forces. The synthesis of [La(NO3)6]2[Ni(H2O)6]3·6H2O involves dissolving lanthanum(III) and nickel(II) oxides in nitric acid, followed by slow evaporation, yielding green hexagonal plate-like crystals.