research communications
1.655Co1.64Fe1.36(PO4)3
of a silver-, cobalt- and iron-based phosphate with an alluaudite-like structure: AgaLaboratoire de Chimie du Solide Appliquée, Faculty of Sciences, Mohammed V University in Rabat, Avenue Ibn Battouta, BP 1014, Rabat, Morocco, and bDépartement de Chimie, Faculté des Sciences, Université des Sciences et Techniques de Masuku, BP 943, Franceville, Gabon
*Correspondence e-mail: adam_bouraima@yahoo.fr
The new silver-, cobalt- and iron-based phosphate, silver cobalt iron tris(orthophosphate), Ag1.655Co1.64Fe1.36(PO4)3, was synthesized by solid-state reactions. Its structure is isotypic to that of Na2Co2Fe(PO4)3, and belongs to the alluaudite family, with a partial cationic disorder, the AgI atoms being located on an inversion centre and twofold rotation axis sites (Wyckoff positions 4a and 4e), with partial occupancies of 0.885 (2) and 0.7688 (19), respectively. One of the two P atoms in the completely fills one 4e site while the Co and Fe atoms fill another 4e site, with partial occupancies of 0.86 (5) and 0.14 (5), respectively. The remaining Co2+ and Fe3+ cations are distributed on a general position, 8f, in a 0.39 (4):0.61 (4) ratio. All O atoms and the other P atoms are in general positions. The structure is built up from zigzag chains of edge-sharing [MO6] (M = Fe/Co) octahedra stacked parallel to [101]. These chains are linked together through PO4 tetrahedra, forming polyhedral sheets perpendicular to [010]. The resulting framework displays two types of channels running along [001], in which the AgI atoms (coordination number eight) are located.
Keywords: crystal structure; Ag1.655Co1.64Fe1.36(PO4)3; transition metal phosphate; solid-state reaction synthesis; alluaudite-like structure.
CCDC reference: 1551181
1. Chemical context
Compounds belonging to the large alluaudite structural family (Moore, 1971; Moore & Ito, 1979; Hatert et al., 2000, 2004) have been of continuing interest owing to their open-framework architecture, with hexagonal-shaped channels, and their physical properties. This fact is amply justified by their practical applications, for example as corrosion inhibitors, passivators of metal surfaces, and catalysts (Korzenski et al., 1999). In addition, interest in alluaudite phosphates with monovalent cations has continued to grow in the electrochemical field, where they have applications as positive electrodes in lithium and sodium batteries (Trad et al., 2010). Accordingly, our attention is mostly focused on the elaboration and structural characterization of new alluaudite-type phosphates within the A2O–MO–P2O5 systems (A = monovalent cation M = divalent cation). For instance, most recently, the hydrothermal investigation of the Na2O–MO–P2O5 pseudo-ternary system has allowed the isolation of the sodium- and magnesium-based alluaudite phosphate NaMg3(PO4)(HPO4)2 (Ould Saleck et al., 2015). On the other hand, within the Na2O–CoO–Fe2O3–P2O5 and Na2O–ZnO–Fe2O3–P2O5 pseudo-quaternary systems, solid-state synthesis has allowed Na2Co2Fe(PO4)3 (Bouraima et al., 2015) and Na1.67Zn1.67Fe1.33(PO4)3 (Khmiyas et al., 2015) to be obtained. With the same objective, a new silver-, cobalt- and iron-based alluaudite-type phosphate, namely Ag1.655Co1.64Fe1.36(PO4)3, has been synthesized by means of solid-state reactions and characterized by single crystal X-ray diffraction.
2. Structural commentary
In the new isolated compound, either cobalt or iron atoms are distributed in the two octahedral sites while the phosphorus atoms are tetrahedrally coordinated, as shown in Fig. 1. The structure is built up from two edge-sharing [(Co1/Fe1)O6] octahedra, leading to the formation of [(Co1/Fe1)2O10] dimers. Those dimers are connected by a common edge to [(Fe2/Co2)O6] octahedra, forming an infinite chain (Fig. 2). The junction between these chains is ensured by sharing vertices with the PO4 tetrahedra so as to form an open layer perpendicular to [010] (Fig. 3). The three-dimensional framework resulting from the stacking of the sheets along the b-axis direction delimits channels parallel to [001] in which the Ag+ cations are accommodated, as shown in Fig. 4.
3. Comparison with a related structure
It is worth mentioning that the distribution of metallic cations observed in the case of the silver–cobalt–iron-based phosphate is not encountered in the sodium homologue. Hence, in the title silver-based phosphate, the octahedral M1 site (Wyckoff position 8f) is occupied to 60% by Fe1 and to 40% by Co1. The octahedrally surrounded M2 site (Wyckoff position 4e) is essentially occupied by Fe2 atoms (43%) along with a small amount of Co2 (7%). However, in the Na2Co2Fe(PO4)3 phosphate, the M1 and M2 sites are entirely occupied by Fe and Co atoms, respectively. For the mixed sites, the occupancy rate was refined without any constraint. The results of the refinements are in good agreement with the electrical neutrality of the compound and calculations of the bond-valence sums of the atoms in the structure (Brown & Altermatt, 1985). Accordingly, in the silver-based phosphate, the cations at the M1 site form double octahedra [(Fe1/Co1)2O10] alternating with [(Fe2/Co2)O6] octahedra, while in the sodium homologue phosphate, the obtained [Co2O10] double octahedra alternate with [FeO6] octahedra (Fig. 4). Moreover, both the Ag1 and Ag2 atoms are located in channels, surrounded by eight oxygen atoms with Ag1—O bond lengths between 2.3320 (13) Å and 2.9176 (13) Å, whereas Ag2—O bond lengths are in the range 2.4733 (13)–2.9035 (12) Å. The structure of the title phosphate is isotypic to that of Na2Co2Fe(PO4)3 (Bouraima et al., 2015) and Na1.67Zn1.67Fe1.33(PO4)3 (Khmiyas et al., 2015).
4. Synthesis and crystallization
The title compound was isolated from solid-state reactions in air by mixing nitrates of silver, cobalt and iron with phosphoric acid. The various precursors are taken in the molar ratio Ag:Co:Fe:P = 2:2:1:3. The mixture was stirred at room temperature overnight. After different heat treatments in a platinum crucible at up to 873 K, the reaction mixture was heated to the melting temperature of 1221 K. The molten product was then cooled to room temperature at a rate of 5 K h−1. Brown homogeneous crystals corresponding to the title compound of a suitable size for X-ray diffraction were obtained.
5. Refinement
Crystal data, data collection and structure . The maximum and minimum residual electron densities in the final Fourier map are 0.68 and 0.55 Å from Ag1 and Ag2, respectively.
details are summarized in Table 1Supporting information
CCDC reference: 1551181
https://doi.org/10.1107/S205698901700740X/hp2074sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S205698901700740X/hp2074Isup2.hkl
Data collection: APEX2 (Bruker, 2009); cell
SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXT2014 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015b); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012) and DIAMOND (Brandenburg, 2006); software used to prepare material for publication: publCIF (Westrip, 2010).Ag1.655Co1.64Fe1.36(PO4)3 | F(000) = 1194 |
Mr = 2544.10 | Dx = 4.822 Mg m−3 |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71073 Å |
a = 11.8680 (3) Å | Cell parameters from 2137 reflections |
b = 12.5514 (3) Å | θ = 3.3–36.3° |
c = 6.4386 (2) Å | µ = 9.51 mm−1 |
β = 114.012 (1)° | T = 296 K |
V = 876.09 (4) Å3 | Block, brown |
Z = 1 | 0.31 × 0.26 × 0.22 mm |
Bruker X8 APEX diffractometer | 2137 independent reflections |
Radiation source: fine-focus sealed tube | 2079 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.030 |
φ and ω scans | θmax = 36.3°, θmin = 3.3° |
Absorption correction: multi-scan (SADABS; Krause et al., 2015) | h = −19→19 |
Tmin = 0.066, Tmax = 0.124 | k = −20→20 |
13097 measured reflections | l = −10→10 |
Refinement on F2 | 0 restraints |
Least-squares matrix: full | w = 1/[σ2(Fo2) + (0.0121P)2 + 3.2851P] where P = (Fo2 + 2Fc2)/3 |
R[F2 > 2σ(F2)] = 0.020 | (Δ/σ)max = 0.001 |
wR(F2) = 0.047 | Δρmax = 1.47 e Å−3 |
S = 1.19 | Δρmin = −0.92 e Å−3 |
2137 reflections | Extinction correction: SHELXL2014 (Sheldrick, 2015b), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
99 parameters | Extinction coefficient: 0.00102 (10) |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
Ag1 | 0.5000 | 0.5000 | 0.5000 | 0.01952 (7) | 0.885 (2) |
Ag2 | 1.0000 | 0.48916 (3) | 0.7500 | 0.02408 (10) | 0.7688 (19) |
Fe1 | 0.78227 (2) | 0.34311 (2) | 0.37115 (3) | 0.00565 (6) | 0.61 (4) |
Co1 | 0.78227 (2) | 0.34311 (2) | 0.37115 (3) | 0.00565 (6) | 0.39 (4) |
Fe2 | 1.0000 | 0.76503 (2) | 0.7500 | 0.00714 (8) | 0.14 (5) |
Co2 | 1.0000 | 0.76503 (2) | 0.7500 | 0.00714 (8) | 0.86 (5) |
P1 | 0.76272 (3) | 0.61138 (3) | 0.37428 (6) | 0.00502 (8) | |
P2 | 0.5000 | 0.28909 (4) | 0.2500 | 0.00535 (10) | |
O1 | 0.77807 (11) | 0.67841 (10) | 0.18620 (19) | 0.00908 (19) | |
O2 | 0.81856 (12) | 0.49999 (9) | 0.3820 (2) | 0.0112 (2) | |
O3 | 0.62598 (11) | 0.60711 (11) | 0.3280 (2) | 0.0135 (2) | |
O4 | 0.83676 (12) | 0.66524 (9) | 0.60788 (19) | 0.00917 (19) | |
O5 | 0.45841 (10) | 0.21873 (10) | 0.03381 (18) | 0.00821 (19) | |
O6 | 0.60284 (12) | 0.36401 (10) | 0.2530 (2) | 0.0122 (2) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Ag1 | 0.02917 (14) | 0.00879 (9) | 0.01123 (10) | −0.00389 (7) | −0.00138 (8) | −0.00128 (6) |
Ag2 | 0.01069 (12) | 0.02795 (16) | 0.02519 (15) | 0.000 | −0.00133 (10) | 0.000 |
Fe1 | 0.00485 (9) | 0.00657 (9) | 0.00575 (9) | 0.00037 (6) | 0.00240 (6) | 0.00058 (6) |
Co1 | 0.00485 (9) | 0.00657 (9) | 0.00575 (9) | 0.00037 (6) | 0.00240 (6) | 0.00058 (6) |
Fe2 | 0.00620 (12) | 0.00833 (13) | 0.00796 (13) | 0.000 | 0.00398 (10) | 0.000 |
Co2 | 0.00620 (12) | 0.00833 (13) | 0.00796 (13) | 0.000 | 0.00398 (10) | 0.000 |
P1 | 0.00488 (15) | 0.00490 (15) | 0.00521 (15) | 0.00006 (11) | 0.00198 (11) | 0.00022 (10) |
P2 | 0.00397 (19) | 0.0071 (2) | 0.00466 (19) | 0.000 | 0.00138 (16) | 0.000 |
O1 | 0.0101 (5) | 0.0112 (5) | 0.0062 (4) | −0.0001 (4) | 0.0036 (4) | 0.0020 (3) |
O2 | 0.0118 (5) | 0.0070 (4) | 0.0144 (5) | 0.0024 (4) | 0.0048 (4) | −0.0013 (4) |
O3 | 0.0067 (4) | 0.0125 (5) | 0.0221 (6) | 0.0007 (4) | 0.0066 (4) | 0.0031 (4) |
O4 | 0.0127 (5) | 0.0083 (4) | 0.0062 (4) | −0.0011 (4) | 0.0034 (4) | −0.0013 (3) |
O5 | 0.0064 (4) | 0.0124 (5) | 0.0053 (4) | −0.0011 (4) | 0.0018 (3) | −0.0017 (3) |
O6 | 0.0085 (5) | 0.0119 (5) | 0.0166 (5) | −0.0036 (4) | 0.0054 (4) | 0.0007 (4) |
Ag1—O6i | 2.3320 (13) | Fe1—O4viii | 2.0481 (12) |
Ag1—O6ii | 2.3320 (13) | Fe1—O1i | 2.0669 (11) |
Ag1—O3i | 2.4356 (14) | Fe1—O5vi | 2.0705 (12) |
Ag1—O3ii | 2.4356 (14) | Fe1—O1ix | 2.1695 (12) |
Ag1—O3iii | 2.5724 (13) | Fe2—O3x | 2.1099 (13) |
Ag1—O3 | 2.5725 (13) | Fe2—O3xi | 2.1099 (13) |
Ag1—O6iii | 2.9176 (13) | Fe2—O5xii | 2.1575 (11) |
Ag1—O6 | 2.9176 (13) | Fe2—O5xiii | 2.1575 (11) |
Ag2—O2iv | 2.4733 (13) | Fe2—O4iv | 2.1717 (12) |
Ag2—O2 | 2.4733 (13) | Fe2—O4 | 2.1717 (12) |
Ag2—O2i | 2.6204 (13) | P1—O3 | 1.5270 (13) |
Ag2—O2v | 2.6204 (13) | P1—O2 | 1.5393 (12) |
Ag2—O4 | 2.8341 (12) | P1—O1 | 1.5451 (12) |
Ag2—O4iv | 2.8341 (12) | P1—O4 | 1.5543 (12) |
Ag2—O5vi | 2.9035 (13) | P2—O6ii | 1.5346 (13) |
Ag2—O5vii | 2.9035 (12) | P2—O6 | 1.5346 (13) |
Fe1—O6 | 1.9656 (13) | P2—O5ii | 1.5498 (12) |
Fe1—O2 | 2.0108 (12) | P2—O5 | 1.5498 (12) |
O6i—Ag1—O6ii | 180.00 (4) | O2—Ag2—O1i | 64.62 (4) |
O6i—Ag1—O3i | 80.58 (4) | O2i—Ag2—O1i | 49.21 (3) |
O6ii—Ag1—O3i | 99.42 (4) | O2v—Ag2—O1i | 136.08 (3) |
O6i—Ag1—O3ii | 99.42 (4) | O4—Ag2—O1i | 92.94 (3) |
O6ii—Ag1—O3ii | 80.58 (4) | O4iv—Ag2—O1i | 162.54 (3) |
O3i—Ag1—O3ii | 180.0 | O5vi—Ag2—O1i | 52.36 (3) |
O6i—Ag1—O3iii | 108.21 (5) | O5vii—Ag2—O1i | 56.78 (3) |
O6ii—Ag1—O3iii | 71.79 (5) | O2iv—Ag2—O1v | 64.62 (4) |
O3i—Ag1—O3iii | 66.27 (5) | O2—Ag2—O1v | 119.96 (4) |
O3ii—Ag1—O3iii | 113.73 (5) | O2i—Ag2—O1v | 136.08 (3) |
O6i—Ag1—O3 | 71.79 (5) | O2v—Ag2—O1v | 49.21 (3) |
O6ii—Ag1—O3 | 108.21 (5) | O4—Ag2—O1v | 162.54 (3) |
O3i—Ag1—O3 | 113.73 (5) | O4iv—Ag2—O1v | 92.94 (3) |
O3ii—Ag1—O3 | 66.27 (5) | O5vi—Ag2—O1v | 56.78 (3) |
O3iii—Ag1—O3 | 180.0 | O5vii—Ag2—O1v | 52.36 (3) |
O6i—Ag1—O6iii | 53.64 (5) | O6—Fe1—O2 | 93.77 (5) |
O6ii—Ag1—O6iii | 126.36 (5) | O6—Fe1—O4viii | 110.10 (5) |
O3i—Ag1—O6iii | 95.49 (4) | O2—Fe1—O4viii | 86.76 (5) |
O3ii—Ag1—O6iii | 84.51 (4) | O6—Fe1—O1i | 86.70 (5) |
O3iii—Ag1—O6iii | 68.02 (4) | O2—Fe1—O1i | 100.62 (5) |
O3—Ag1—O6iii | 111.98 (4) | O4viii—Fe1—O1i | 161.33 (5) |
O6i—Ag1—O6 | 126.36 (5) | O6—Fe1—O5vi | 163.25 (5) |
O6ii—Ag1—O6 | 53.64 (5) | O2—Fe1—O5vi | 101.04 (5) |
O3i—Ag1—O6 | 84.51 (4) | O4viii—Fe1—O5vi | 78.79 (5) |
O3ii—Ag1—O6 | 95.49 (4) | O1i—Fe1—O5vi | 82.95 (5) |
O3iii—Ag1—O6 | 111.98 (4) | O6—Fe1—O1ix | 80.26 (5) |
O3—Ag1—O6 | 68.02 (4) | O2—Fe1—O1ix | 171.95 (5) |
O6iii—Ag1—O6 | 180.0 | O4viii—Fe1—O1ix | 90.22 (4) |
O2iv—Ag2—O2 | 173.70 (6) | O1i—Fe1—O1ix | 84.52 (5) |
O2iv—Ag2—O2i | 101.33 (4) | O5vi—Fe1—O1ix | 85.66 (5) |
O2—Ag2—O2i | 78.34 (4) | O3x—Fe2—O3xi | 80.97 (7) |
O2iv—Ag2—O2v | 78.34 (4) | O3x—Fe2—O5xii | 91.27 (5) |
O2—Ag2—O2v | 101.33 (4) | O3xi—Fe2—O5xii | 112.81 (5) |
O2i—Ag2—O2v | 174.04 (5) | O3x—Fe2—O5xiii | 112.81 (5) |
O2iv—Ag2—O4 | 118.73 (4) | O3xi—Fe2—O5xiii | 91.27 (5) |
O2—Ag2—O4 | 55.50 (4) | O5xii—Fe2—O5xiii | 148.74 (7) |
O2i—Ag2—O4 | 61.33 (4) | O3x—Fe2—O4iv | 85.08 (5) |
O2v—Ag2—O4 | 113.50 (4) | O3xi—Fe2—O4iv | 164.39 (5) |
O2iv—Ag2—O4iv | 55.50 (4) | O5xii—Fe2—O4iv | 74.29 (4) |
O2—Ag2—O4iv | 118.73 (4) | O5xiii—Fe2—O4iv | 87.71 (4) |
O2i—Ag2—O4iv | 113.50 (4) | O3x—Fe2—O4 | 164.39 (5) |
O2v—Ag2—O4iv | 61.33 (4) | O3xi—Fe2—O4 | 85.08 (5) |
O4—Ag2—O4iv | 77.51 (5) | O5xii—Fe2—O4 | 87.71 (4) |
O2iv—Ag2—O5vi | 114.87 (4) | O5xiii—Fe2—O4 | 74.29 (4) |
O2—Ag2—O5vi | 71.23 (4) | O4iv—Fe2—O4 | 109.56 (7) |
O2i—Ag2—O5vi | 101.56 (4) | O3—P1—O2 | 112.57 (7) |
O2v—Ag2—O5vi | 83.86 (4) | O3—P1—O1 | 108.72 (7) |
O4—Ag2—O5vi | 125.84 (3) | O2—P1—O1 | 109.47 (7) |
O4iv—Ag2—O5vi | 144.70 (3) | O3—P1—O4 | 109.98 (7) |
O2iv—Ag2—O5vii | 71.23 (4) | O2—P1—O4 | 107.31 (7) |
O2—Ag2—O5vii | 114.87 (4) | O1—P1—O4 | 108.73 (7) |
O2i—Ag2—O5vii | 83.86 (4) | O6ii—P2—O6 | 104.43 (10) |
O2v—Ag2—O5vii | 101.56 (4) | O6ii—P2—O5ii | 108.75 (7) |
O4—Ag2—O5vii | 144.70 (3) | O6—P2—O5ii | 112.14 (7) |
O4iv—Ag2—O5vii | 125.84 (3) | O6ii—P2—O5 | 112.14 (7) |
O5vi—Ag2—O5vii | 52.03 (4) | O6—P2—O5 | 108.75 (7) |
O2iv—Ag2—O1i | 119.96 (4) | O5ii—P2—O5 | 110.52 (9) |
Symmetry codes: (i) x, −y+1, z+1/2; (ii) −x+1, y, −z+1/2; (iii) −x+1, −y+1, −z+1; (iv) −x+2, y, −z+3/2; (v) −x+2, −y+1, −z+1; (vi) x+1/2, −y+1/2, z+1/2; (vii) −x+3/2, −y+1/2, −z+1; (viii) x, −y+1, z−1/2; (ix) −x+3/2, y−1/2, −z+1/2; (x) x+1/2, −y+3/2, z+1/2; (xi) −x+3/2, −y+3/2, −z+1; (xii) −x+3/2, y+1/2, −z+1/2; (xiii) x+1/2, y+1/2, z+1. |
Acknowledgements
The authors thank the Unit of Support for Technical and Scientific Research (UATRS, CNRST) for the X-ray measurements.
Funding information
Funding for this research was provided by: Mohammed V University, Rabat, Morocco.
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