High-resolution crystal structure of the double nitrate hydrate [La(NO 3 ) 6 ] 2 [Ni(H 2 O) 6 ] 3 ·6H 2 O.

This study introduces bis-[hexa-kis-(nitrato-κ 2 O , O ')lanthanum(III)] tris-[hexa-aqua-nickel(II)] hexa-hydrate, [La(NO 3 ) 6 ] 2 [Ni(H 2 O) 6 ] 3 ·6H 2 O, with a structure refined in the hexa-gonal space group R . The salt com-prises [La(NO 3 ) 6 ] 3- icosa-hedra and [Ni(H 2 O) 6 ] 2+ octa-hedra, thus forming an intricate network of inter-penetrating honeycomb lattices arranged in layers. This arrangement is stabilized through strong hydrogen bonds. Two successive layers are connected via the second [Ni(H 2 O) 6 ] 2+ octa-hedra, forming sheets which are stacked perpendicular to the c axis and held in the crystal by van der Waals forces. The synthesis of [La(NO 3 ) 6 ] 2 [Ni(H 2 O) 6 ] 3 ·6H 2 O involves dissolving lanthanum(III) and nickel(II) oxides in nitric acid, followed by slow evaporation, yielding green hexa-gonal plate-like crystals.