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

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

doi:10.1107/S1600536811052482

Volume 68
Part 1
Pages i5-i6
January 2012

Received 4 November 2011
Accepted 6 December 2011
Online 10 December 2011

Key indicators
Single-crystal X-ray study
T = 173 K
Mean (Fe-O) = 0.003 Å
R = 0.040
wR = 0.085
Data-to-parameter ratio = 12.2
Details

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

Biao Liu,^a Xin Zhang,^a Lei Wen,^a Wei Sun ^a and Ya-Xi Huang ^a ^*

^aDepartment of Materials Science and Engineering, College of Materials, Xiamen University, Xiamen 361005, Fujian Province, People's Republic of China
Correspondence e-mail: yaxihuang@xmu.edu.cn

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-HO and N-HO 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).

Related literature

For background to this compound, see: Moore & Shen (1983); Lii et al. (1998); Alfonso et al. (2010); Mi et al. (2010). For background to the bond-valence method, see: Brown & Altermatt (1985). For related structures, see: Chippindale et al. (2003) for (NH₄)₂[Mn₃(P₂O₇)₂(H₂O)₂]; Lightfoot et al. (1990) for K₂Co₃(P₂O₇)₂·2H₂O; Liu et al. (2004) for Na(NH₄)[Ni₃(P₂O₇)₂(H₂O)₂]; Wei et al. (2010) for (NH₄)₂[Ni₃(P₂O₇)₂(H₂O)₂].

Experimental

Crystal data

(NH₄)₂[Fe₃(P₂O₇)₂(H₂O)₂]
M_r = 587.55
Monoclinic, P 2₁ /c
a = 9.4131 (17) Å
b = 8.1940 (15) Å
c = 9.3987 (17) Å
= 99.651 (3)°
V = 714.7 (2) Å³
Z = 2
Mo K radiation
= 3.55 mm^-1
T = 173 K
0.08 × 0.06 × 0.06 mm

Data collection

Bruker Smart APEXI diffractometer equipped with CCD area-detector
Absorption correction: numerical (SMART; Bruker, 2001) T_min = 0.775, T_max = 0.808
4127 measured reflections
1652 independent reflections
1417 reflections with I > 2(I)
R_int = 0.035

Refinement

R[F² > 2(F²)] = 0.040
wR(F²) = 0.085
S = 1.05
1652 reflections
135 parameters
All H-atom parameters refined
_max = 0.55 e Å^-3
_min = -0.55 e Å^-3

Table 1
Selected geometric parameters (Å, °)

Fe1-O1ⁱ	2.055 (3)
Fe1-O4ⁱⁱ	2.092 (3)
Fe1-O6ⁱⁱⁱ	2.108 (3)
Fe1-O8	2.134 (3)
Fe1-O6ⁱ	2.185 (3)
Fe1-O5	2.261 (3)
Fe2-O5	2.127 (3)
Fe2-O4	2.135 (3)
Fe2-O3^iv	2.201 (3)
P1-O3	1.514 (3)
P1-O6	1.517 (3)
P1-O4	1.523 (3)
P1-O2	1.620 (3)
P2-O7	1.510 (3)
P2-O1	1.516 (3)
P2-O5	1.518 (3)
P2-O2	1.631 (3)

P1-O2-P2	128.83 (18)
Symmetry codes: (i) $[x, -y+{\script{3\over 2}}, z+{\script{1\over 2}}]$ ; (ii) -x+2, -y+1, -z+1; (iii) $[-x+2, y+{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (iv) $[x, -y+{\script{1\over 2}}, z+{\script{1\over 2}}]$ .

Table 2
Hydrogen-bond geometry (Å, °)

D-HA	D-H	HA	DA	D-HA
O8-H1O3^v	0.89 (6)	1.87 (6)	2.734 (4)	162 (5)
O8-H2O7^vi	0.82 (6)	2.00 (6)	2.785 (4)	159 (5)
N1-H3O1^vii	0.91 (7)	1.86 (7)	2.717 (5)	156 (6)
N1-H4O8^viii	0.89 (6)	2.56 (7)	3.310 (6)	142 (5)
N1-H5O7^ix	0.96 (7)	1.99 (7)	2.859 (5)	150 (5)
N1-H6O7	0.88 (7)	1.91 (7)	2.791 (5)	174 (6)
Symmetry codes: (v) x, y+1, z; (vi) $[-x+1, y+{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (vii) $[-x+1, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (viii) x, y-1, z; (ix) -x+1, -y+1, -z+1.

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2005) and ATOMS (Dowty, 2004); software used to prepare material for publication: SHELXL97 and WinGX (Farrugia, 1999).

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: FI2119 ).

Acknowledgements

This work was supported by the National Natural Science Foundation of China (No. 40972035), the Natural Science Foundation of Fujian Province of China (No. 2010 J01308) and the Scientific and Technical Project of Fujian Province of China (No. 2009 J1009).

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