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Acta Cryst. (2012). E68, i5-i6  [ doi:10.1107/S1600536811052482 ]

An ammonium iron(II) pyrophosphate, (NH4)2[Fe3(P2O7)2(H2O)2], with a layered structure

B. Liu, X. Zhang, L. Wen, W. Sun and Y.-X. Huang

Abstract: Diammonium diaquabis(phosphato)triferrate(II), (NH4)2[Fe3(P2O7)2(H2O)2], was synthesized under solvothermal conditions at 463 K. The crystal structure, isotypic to its Mn and Ni analogues, is built from iron pyrophosphate layers parallel to (100), which are linked by ammonium ions sitting in the interlayer space via O-H...O and N-H...O hydrogen bonds. There are two crystallographic Fe sites in the crystal structure, one at a special position (2a, -1), the other at a general position (4e, 1). The former Fe atom on the inversion centre is coordinated by six O atoms, forming an FeO6 octahedron, while the latter is coordinated by five phosphate O atoms and one water molecule, forming an FeO5(H2O) octahedron. Each FeO6 octahedron shares trans edges with two FeO5(H2O) octahedra, forming a linear trimeric unit. These trimers share the lateral edges of FeO5(H2O) with other trimers, forming a zigzag chain running along [010]. The zigzag chains are further linked by P2O7 groups into a layered structure parallel to (100).

Online 10 December 2011

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