inorganic compounds
Dicobalt copper bis[orthophosphate(V)] monohydrate, Co2.39Cu0.61(PO4)2·H2O
aLaboratoire de Chimie du Solide Appliquée, Faculté des Sciences, Université Mohammed V-Agdal, Avenue Ibn Battouta, BP 1014, Rabat, Morocco
*Correspondence e-mail: mohamedsaadi82@gmail.com
In an attempt to hydrothermally synthesize a phase with composition Co2Cu(PO4)2·H2O, we obtained the title compound, Co2.39Cu0.61(PO4)2·H2O instead. Chemical analysis confirmed the presence of copper in the crystal. The of the title compound can be described as a three- dimensional network constructed from the stacking of two types of layers extending parallel to (010). These layers are made up from more or less deformed polyhedra: CoO6 octahedra, (Cu/Co)O5 square pyramids and PO4 tetrahedra. The first layer is formed by pairs of edge-sharing (Cu/Co)O5 square pyramids linked via a common edge of each end of the (Cu/Co)2O8 dimer to PO4 tetrahedra. The second layer is undulating and is built up from edge-sharing CoO6 octahedra. The linkage between the two layers is accomplished by PO4 tetrahedra. The presence of water molecules in the CoO4(H2O)2 octahedron also contributes to the cohesion of the layers through O—H⋯O hydrogen bonding.
Related literature
For the properties of and background to metal phosphates, see: Clearfield (1988); Gao & Gao (2005); Viter & Nagornyi (2009); Harrison et al. (1995). For compounds with the same structure, see: Anderson et al. (1976); Liao et al. (1995); Sørensen et al. (2004); Moore & Araki (1975).
Experimental
Crystal data
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Refinement
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Data collection: APEX2 (Bruker, 2005); cell SAINT (Bruker, 2005); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and DIAMOND (Brandenburg, 2006); software used to prepare material for publication: WinGX (Farrugia, 1999).
Supporting information
https://doi.org/10.1107/S1600536810015382/wm2323sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810015382/wm2323Isup2.hkl
The crystals of the title compound were hydrothermally synthesized starting from a mixture of metallic copper (0.0381 g), basic cobalt(II) carbonate (0.0318 g), 85 %wt phosphoric acid (0.10 ml) and 10 ml distilled water. The hydrothermal synthesis was carried out in 23 ml Teflon-lined autoclave under autogeneous pressure at 468 K during 24 h. The product was filtered off, washed with deionized water and air dried. The reaction product consists of two types of crystals. The first one, dark violet crystals, corresponds to the title compound with the refined composition Co2.39Cu0.61(PO4)2.H2O. An elemental chemical analysis (EDS) confirms the presence of copper in the crystal. The second type of crystals is identified to be the known cobalt hydroxy phosphate Co2(OH)PO4 (Harrison et al., 1995).
All H atoms were initially located in a difference map and refined with a O—H distance restraint of 0.84 (1) Å. Later they were refined in the riding model approximation with Uiso(H) set to 1.5 Ueq(O). Refinements of the site ocupancy factors of the metal sites revealed the octahedrally coordinated sites solely occupied by Co, whereas the 5-coordinated site shows a mixed occupancy of Co:Cu = 0.387 (11):0.613 (11).
Metal-phosphates have received great attention owing to their applications such as catalysts (Viter & Nagornyi, 2009; Gao & Gao, 2005) and as ion-exchangers (Clearfield, 1988)). Mainly, the flexibility of the metal coordination and the possibility to generate anionic frameworks MIIPO4-, analogous to AlSiO4- in the well known aluminosilicate zeolites, offer a rich structural diversity of this family of compounds.
Our interest is particularly focused on the hydrothermally synthesized orthophosphates with formula MM'2(PO4)2.H2O (M and M'= bivalent cations). In this work, a new dicobalt copper bis[orthophosphate] monohydrate, Co2.39Cu0.61(PO4)2.H2O was synthesized and structurally characterized.
A three-dimensional view of the
of the title compound is given in Fig. 1. It shows that the metal cations are located in three crystallographically different sites, two octahedra entirely occupied by cobalt and one square-pyramid statistically filled with Co/Cu. of the occupancy of this metal site has led to the following composition, Co2.39Cu0.61(PO4)2.H2O. The cationic distributions indicate that Cu prefers the site with a lower whereas Co prefers of 6. This may be attributed to a gain in crystal field stabilisation energy for Co2+ in the octahedral sites and to the small difference between the sizes of the two cations Co2+ and Cu2+.The network is built up from three different types of polyhedra more or less distorted: CoO6 octahedra , (Cu/Co)O5 square-pyramids and PO4 tetrahedra. One octahedron (Co1), slightly distorted, has a coordination sphere composed of O atoms from PO4 groups, while that of the other (Co2) is made up of four O atoms from PO4 groups and by two water molecules (O9). This fact explains its more pronounced distortion, with Co—O bond lengths in the range 2.0407 (11)-2.3310 (13) Å.
All CoO6 octahedra are linked together by edge-sharing and sharing three corners of PO4 tetrahedra, in the way to built a layer parallel to (010) as shown in Fig. 2. Therefore, the presence of the water molecule involved in the formation of the CoO4(H2O)2 octahedron causes a corrugation in this layer through O—H···O hydrogen bonds. Furthermore, Fig. 3 shows that each pair of distorted square-pyramids share an edge and built up a dimer linked to two regular PO4 tetrahedra via a common edge. The sequence of (Cu/Co)O5 and PO4 polyhedra leads to the formation of another layer (Fig. 3). As a matter of fact, the network of this structure can be described by stacking these two types of layers as represented in Fig. 4.
Compounds isotypic with the title phase are relatively rare, however, there are four known compounds which adopt this structure, viz. Co3(PO4)2.H2O (Anderson et al., 1976), CuMn2(PO4)2.H2O (Liao et al., 1995), Co2.59Zn0.41(PO4)2.H2O (Sørensen et al., 2004) and Fe3(PO4)2.H2O (Moore & Araki, 1975).
For the properties of and background to metal phosphates, see: Clearfield (1988); Gao & Gao (2005); Viter & Nagornyi (2009); Harrison et al. (1995). For compounds with the same structure, see: Anderson et al. (1976); Liao et al. (1995); Sørensen et al. (2004); Moore & Araki (1975).
Data collection: APEX2 (Bruker, 2005); cell
SAINT (Bruker, 2005); data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia,1997) and DIAMOND (Brandenburg, 2006); software used to prepare material for publication: WinGX (Farrugia, 1999).Co2.39Cu0.61(PO4)2·H2O | F(000) = 745 |
Mr = 387.57 | Dx = 3.942 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2yn | Cell parameters from 13678 reflections |
a = 8.086 (2) Å | θ = 2.9–38.0° |
b = 9.826 (3) Å | µ = 8.49 mm−1 |
c = 9.042 (3) Å | T = 296 K |
β = 114.621 (1)° | Block, dark violet |
V = 653.1 (3) Å3 | 0.24 × 0.12 × 0.06 mm |
Z = 4 |
Bruker X8 APEX diffractometer | 3531 independent reflections |
Radiation source: fine-focus sealed tube | 3278 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.023 |
φ and ω scans | θmax = 38.0°, θmin = 2.9° |
Absorption correction: multi-scan (SADABS; Bruker, 2005) | h = −11→14 |
Tmin = 0.306, Tmax = 0.601 | k = −16→16 |
13678 measured reflections | l = −15→15 |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.022 | H-atom parameters constrained |
wR(F2) = 0.051 | w = 1/[σ2(Fo2) + (0.0196P)2 + 0.5902P] where P = (Fo2 + 2Fc2)/3 |
S = 1.10 | (Δ/σ)max = 0.001 |
3531 reflections | Δρmax = 1.01 e Å−3 |
129 parameters | Δρmin = −0.79 e Å−3 |
0 restraints | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0034 (3) |
Co2.39Cu0.61(PO4)2·H2O | V = 653.1 (3) Å3 |
Mr = 387.57 | Z = 4 |
Monoclinic, P21/n | Mo Kα radiation |
a = 8.086 (2) Å | µ = 8.49 mm−1 |
b = 9.826 (3) Å | T = 296 K |
c = 9.042 (3) Å | 0.24 × 0.12 × 0.06 mm |
β = 114.621 (1)° |
Bruker X8 APEX diffractometer | 3531 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2005) | 3278 reflections with I > 2σ(I) |
Tmin = 0.306, Tmax = 0.601 | Rint = 0.023 |
13678 measured reflections |
R[F2 > 2σ(F2)] = 0.022 | 0 restraints |
wR(F2) = 0.051 | H-atom parameters constrained |
S = 1.10 | Δρmax = 1.01 e Å−3 |
3531 reflections | Δρmin = −0.79 e Å−3 |
129 parameters |
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. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
Cu3 | 0.14535 (2) | 0.125674 (19) | −0.43994 (2) | 0.00920 (5) | 0.613 (11) |
Co3 | 0.14535 (2) | 0.125674 (19) | −0.43994 (2) | 0.00920 (5) | 0.387 (11) |
Co1 | 0.51531 (2) | 0.129584 (19) | 0.27594 (2) | 0.00646 (4) | |
Co2 | 0.11526 (2) | 0.133641 (19) | 0.03006 (2) | 0.00808 (4) | |
P1 | 0.38414 (4) | 0.16385 (4) | −0.13938 (4) | 0.00589 (6) | |
P2 | 0.20915 (4) | −0.08141 (3) | −0.67010 (4) | 0.00519 (6) | |
O1 | 0.57091 (13) | 0.22680 (11) | −0.09698 (12) | 0.01030 (17) | |
O2 | 0.36035 (14) | 0.13059 (11) | 0.01540 (12) | 0.00958 (16) | |
O3 | 0.35326 (13) | 0.03970 (11) | −0.25406 (12) | 0.00944 (16) | |
O4 | 0.22753 (13) | 0.25872 (11) | −0.25036 (12) | 0.00952 (16) | |
O5 | 0.08457 (14) | −0.02059 (11) | −0.59509 (12) | 0.01044 (17) | |
O6 | 0.08992 (13) | −0.18315 (10) | −0.80105 (11) | 0.00813 (15) | |
O7 | 0.37173 (13) | −0.15475 (11) | −0.53900 (12) | 0.00950 (16) | |
O8 | 0.27312 (13) | 0.03376 (10) | −0.74946 (12) | 0.00871 (16) | |
O9 | −0.10961 (14) | 0.08498 (12) | 0.07202 (12) | 0.01199 (18) | |
H9A | −0.2021 | 0.1199 | −0.0001 | 0.018* | |
H9B | −0.1031 | 0.0899 | 0.1749 | 0.018* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Cu3 | 0.01172 (8) | 0.00784 (8) | 0.00548 (7) | 0.00309 (5) | 0.00105 (6) | −0.00054 (5) |
Co3 | 0.01172 (8) | 0.00784 (8) | 0.00548 (7) | 0.00309 (5) | 0.00105 (6) | −0.00054 (5) |
Co1 | 0.00605 (7) | 0.00578 (8) | 0.00694 (7) | 0.00026 (5) | 0.00208 (5) | −0.00043 (5) |
Co2 | 0.00620 (7) | 0.00832 (8) | 0.00848 (7) | −0.00025 (5) | 0.00182 (6) | 0.00165 (6) |
P1 | 0.00590 (11) | 0.00584 (13) | 0.00529 (12) | 0.00016 (10) | 0.00170 (9) | −0.00011 (10) |
P2 | 0.00508 (11) | 0.00526 (13) | 0.00475 (11) | −0.00017 (9) | 0.00156 (9) | 0.00037 (9) |
O1 | 0.0077 (4) | 0.0124 (5) | 0.0107 (4) | −0.0029 (3) | 0.0037 (3) | −0.0035 (3) |
O2 | 0.0093 (4) | 0.0125 (4) | 0.0068 (4) | −0.0004 (3) | 0.0033 (3) | 0.0012 (3) |
O3 | 0.0091 (4) | 0.0081 (4) | 0.0081 (4) | 0.0015 (3) | 0.0006 (3) | −0.0024 (3) |
O4 | 0.0093 (4) | 0.0095 (4) | 0.0086 (4) | 0.0038 (3) | 0.0026 (3) | 0.0017 (3) |
O5 | 0.0102 (4) | 0.0120 (4) | 0.0115 (4) | −0.0003 (3) | 0.0069 (3) | −0.0029 (3) |
O6 | 0.0088 (4) | 0.0067 (4) | 0.0067 (3) | −0.0016 (3) | 0.0011 (3) | −0.0004 (3) |
O7 | 0.0087 (4) | 0.0090 (4) | 0.0076 (4) | 0.0012 (3) | 0.0002 (3) | 0.0017 (3) |
O8 | 0.0082 (3) | 0.0081 (4) | 0.0092 (4) | −0.0017 (3) | 0.0029 (3) | 0.0024 (3) |
O9 | 0.0104 (4) | 0.0165 (5) | 0.0094 (4) | 0.0019 (3) | 0.0045 (3) | 0.0015 (3) |
Cu3—O5 | 1.9236 (11) | P1—O4 | 1.5558 (11) |
Cu3—O1i | 1.9411 (11) | P2—O7 | 1.5343 (11) |
Cu3—O3 | 2.0026 (11) | P2—O8 | 1.5402 (11) |
Cu3—O4 | 2.0347 (12) | P2—O6 | 1.5427 (11) |
Cu3—O5ii | 2.2614 (11) | P2—O5 | 1.5496 (10) |
Co1—O3iii | 2.0274 (11) | O1—Co3vi | 1.9411 (11) |
Co1—O6iv | 2.0791 (11) | O1—Cu3vi | 1.9411 (11) |
Co1—O8v | 2.0976 (11) | O3—Co1iii | 2.0274 (11) |
Co1—O4vi | 2.1321 (11) | O4—Co1i | 2.1320 (11) |
Co1—O2 | 2.1588 (12) | O5—Co3ii | 2.2613 (11) |
Co1—O7iii | 2.1779 (12) | O5—Cu3ii | 2.2613 (11) |
Co2—O2 | 2.0407 (11) | O6—Co1viii | 2.0790 (11) |
Co2—O9 | 2.0625 (11) | O6—Co2ii | 2.1010 (11) |
Co2—O7iv | 2.0818 (13) | O7—Co2viii | 2.0818 (12) |
Co2—O6ii | 2.1010 (11) | O7—Co1iii | 2.1779 (12) |
Co2—O8v | 2.1088 (11) | O8—Co1ix | 2.0976 (10) |
Co2—O9vii | 2.3310 (13) | O8—Co2ix | 2.1087 (11) |
P1—O2 | 1.5254 (11) | O9—Co2vii | 2.3310 (13) |
P1—O1 | 1.5257 (11) | O9—H9A | 0.8342 |
P1—O3 | 1.5525 (11) | O9—H9B | 0.9111 |
O5—Cu3—O1i | 96.74 (5) | O9—Co2—O7iv | 104.98 (4) |
O5—Cu3—O3 | 99.61 (5) | O2—Co2—O6ii | 109.20 (4) |
O1i—Cu3—O3 | 145.59 (4) | O9—Co2—O6ii | 80.81 (4) |
O5—Cu3—O4 | 171.47 (4) | O7iv—Co2—O6ii | 79.25 (4) |
O1i—Cu3—O4 | 91.68 (5) | O2—Co2—O8v | 80.38 (4) |
O3—Cu3—O4 | 72.46 (4) | O9—Co2—O8v | 87.19 (4) |
O5—Cu3—O5ii | 77.63 (4) | O7iv—Co2—O8v | 115.29 (4) |
O1i—Cu3—O5ii | 114.90 (4) | O6ii—Co2—O8v | 163.32 (4) |
O3—Cu3—O5ii | 98.14 (5) | O2—Co2—O9vii | 79.64 (4) |
O4—Cu3—O5ii | 100.04 (4) | O9—Co2—O9vii | 89.19 (4) |
O3iii—Co1—O6iv | 172.66 (4) | O7iv—Co2—O9vii | 158.15 (4) |
O3iii—Co1—O8v | 97.15 (5) | O6ii—Co2—O9vii | 86.90 (4) |
O6iv—Co1—O8v | 90.19 (4) | O8v—Co2—O9vii | 81.36 (4) |
O3iii—Co1—O4vi | 86.13 (5) | O2—P1—O1 | 110.26 (6) |
O6iv—Co1—O4vi | 86.65 (4) | O2—P1—O3 | 113.44 (6) |
O8v—Co1—O4vi | 167.68 (4) | O1—P1—O3 | 110.69 (6) |
O3iii—Co1—O2 | 89.25 (4) | O2—P1—O4 | 109.89 (6) |
O6iv—Co1—O2 | 92.14 (4) | O1—P1—O4 | 111.95 (6) |
O8v—Co1—O2 | 77.97 (4) | O3—P1—O4 | 100.30 (6) |
O4vi—Co1—O2 | 90.24 (4) | O7—P2—O8 | 111.04 (6) |
O3iii—Co1—O7iii | 101.61 (4) | O7—P2—O6 | 110.42 (6) |
O6iv—Co1—O7iii | 77.57 (4) | O8—P2—O6 | 110.02 (6) |
O8v—Co1—O7iii | 96.78 (4) | O7—P2—O5 | 110.30 (6) |
O4vi—Co1—O7iii | 94.16 (4) | O8—P2—O5 | 109.04 (6) |
O2—Co1—O7iii | 168.52 (4) | O6—P2—O5 | 105.87 (6) |
O2—Co2—O9 | 164.36 (4) | H9A—O9—H9B | 115.3 |
O2—Co2—O7iv | 89.00 (4) |
Symmetry codes: (i) x−1/2, −y+1/2, z−1/2; (ii) −x, −y, −z−1; (iii) −x+1, −y, −z; (iv) −x+1/2, y+1/2, −z−1/2; (v) x, y, z+1; (vi) x+1/2, −y+1/2, z+1/2; (vii) −x, −y, −z; (viii) −x+1/2, y−1/2, −z−1/2; (ix) x, y, z−1. |
D—H···A | D—H | H···A | D···A | D—H···A |
O9—H9A···O1 | 0.83 | 1.97 | 2.768 (2) | 159 |
O9—H9B···O5v | 0.92 | 2.27 | 2.942 (2) | 130 |
O9—H9B···O4x | 0.92 | 2.30 | 2.905 (2) | 123 |
Symmetry codes: (v) x, y, z+1; (x) x−1/2, −y+1/2, z+1/2. |
Experimental details
Crystal data | |
Chemical formula | Co2.39Cu0.61(PO4)2·H2O |
Mr | 387.57 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 296 |
a, b, c (Å) | 8.086 (2), 9.826 (3), 9.042 (3) |
β (°) | 114.621 (1) |
V (Å3) | 653.1 (3) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 8.49 |
Crystal size (mm) | 0.24 × 0.12 × 0.06 |
Data collection | |
Diffractometer | Bruker X8 APEX diffractometer |
Absorption correction | Multi-scan (SADABS; Bruker, 2005) |
Tmin, Tmax | 0.306, 0.601 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 13678, 3531, 3278 |
Rint | 0.023 |
(sin θ/λ)max (Å−1) | 0.866 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.022, 0.051, 1.10 |
No. of reflections | 3531 |
No. of parameters | 129 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 1.01, −0.79 |
Computer programs: APEX2 (Bruker, 2005), SAINT (Bruker, 2005), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia,1997) and DIAMOND (Brandenburg, 2006), WinGX (Farrugia, 1999).
D—H···A | D—H | H···A | D···A | D—H···A |
O9—H9A···O1 | 0.83 | 1.97 | 2.768 (2) | 158.52 |
O9—H9B···O5i | 0.92 | 2.27 | 2.942 (2) | 129.85 |
O9—H9B···O4ii | 0.92 | 2.30 | 2.905 (2) | 123.02 |
Symmetry codes: (i) x, y, z+1; (ii) x−1/2, −y+1/2, z+1/2. |
Acknowledgements
The authors thank the Unit of Support for Technical and Scientific Research (UATRS, CNRST) for the X-ray measurements.
References
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Metal-phosphates have received great attention owing to their applications such as catalysts (Viter & Nagornyi, 2009; Gao & Gao, 2005) and as ion-exchangers (Clearfield, 1988)). Mainly, the flexibility of the metal coordination and the possibility to generate anionic frameworks MIIPO4-, analogous to AlSiO4- in the well known aluminosilicate zeolites, offer a rich structural diversity of this family of compounds.
Our interest is particularly focused on the hydrothermally synthesized orthophosphates with formula MM'2(PO4)2.H2O (M and M'= bivalent cations). In this work, a new dicobalt copper bis[orthophosphate] monohydrate, Co2.39Cu0.61(PO4)2.H2O was synthesized and structurally characterized.
A three-dimensional view of the crystal structure of the title compound is given in Fig. 1. It shows that the metal cations are located in three crystallographically different sites, two octahedra entirely occupied by cobalt and one square-pyramid statistically filled with Co/Cu. Refinement of the occupancy of this metal site has led to the following composition, Co2.39Cu0.61(PO4)2.H2O. The cationic distributions indicate that Cu prefers the site with a lower coordination number, whereas Co prefers coordination number of 6. This may be attributed to a gain in crystal field stabilisation energy for Co2+ in the octahedral sites and to the small difference between the sizes of the two cations Co2+ and Cu2+.
The network is built up from three different types of polyhedra more or less distorted: CoO6 octahedra , (Cu/Co)O5 square-pyramids and PO4 tetrahedra. One octahedron (Co1), slightly distorted, has a coordination sphere composed of O atoms from PO4 groups, while that of the other (Co2) is made up of four O atoms from PO4 groups and by two water molecules (O9). This fact explains its more pronounced distortion, with Co—O bond lengths in the range 2.0407 (11)-2.3310 (13) Å.
All CoO6 octahedra are linked together by edge-sharing and sharing three corners of PO4 tetrahedra, in the way to built a layer parallel to (010) as shown in Fig. 2. Therefore, the presence of the water molecule involved in the formation of the CoO4(H2O)2 octahedron causes a corrugation in this layer through O—H···O hydrogen bonds. Furthermore, Fig. 3 shows that each pair of distorted square-pyramids share an edge and built up a dimer linked to two regular PO4 tetrahedra via a common edge. The sequence of (Cu/Co)O5 and PO4 polyhedra leads to the formation of another layer (Fig. 3). As a matter of fact, the network of this structure can be described by stacking these two types of layers as represented in Fig. 4.
Compounds isotypic with the title phase are relatively rare, however, there are four known compounds which adopt this structure, viz. Co3(PO4)2.H2O (Anderson et al., 1976), CuMn2(PO4)2.H2O (Liao et al., 1995), Co2.59Zn0.41(PO4)2.H2O (Sørensen et al., 2004) and Fe3(PO4)2.H2O (Moore & Araki, 1975).