Crystal structure of K0.75[FeII 3.75FeIII 1.25(HPO3)6]- 0.5H2O, an open-framework iron phosphite with mixed-valent FeII/FeIII ions
Fecha
2016Autor
Serrano Larrea, Edurne
Mesa Rueda, José Luis
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Acta Crystallographica E72 : 63-65 (2016) // doi:10.1107/S2056989015024007
Resumen
Single crystals of the title compound, potassium hexaphosphitopentaferrate(
II,III) hemihydrate, K0.75[FeII
3.75FeIII
1.25(HPO3)6] 0.5H2O, were grown
under mild hydrothermal conditions. The crystal structure is isotypic with
Li1.43[FeII
4.43FeIII
0.57(HPO3)6] 1.5H2O and (NH4)2[FeII
5(HPO3)6] and exhibits a
[FeII
3.75FeIII
1.25(HPO3)6]0.75
open framework with disordered K+ (occupancy
3/4) as counter-cations. The anionic framework is based on (001) sheets of two
[FeO6] octahedra (one with point group symmetry 3.. and one with point group
symmetry .2.) linked along [001] through [HPO3]2
oxoanions. Each sheet is
constructed from 12-membered rings of edge-sharing [FeO6] octahedra, giving
rise to channels with a radius of ca 3.1 A ˚ where the K+ cations and likewise
disordered water molecules (occupancy 1/4) are located. O O contacts
between the water molecule and framework O atoms of 2.864 (5) A ˚ indicate
hydrogen-bonding interactions of medium strength. The infrared spectrum of
the compound shows vibrational bands typical for phosphite and water groups.
The Mössbauer spectrum is in accordance with the presence of FeII and FeIII
ions.