Dicobalt copper bis­[orthophosphate(V)] monohydrate, Co_2.39Cu_0.61(PO₄)₂·H₂O

In an attempt to hydro­thermally synthesize a phase with composition Co₂Cu(PO₄)₂·H₂O, we obtained the title compound, Co_2.39Cu_0.61(PO₄)₂·H₂O instead. Chemical analysis confirmed the presence of copper in the crystal. The crystal structure 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.

Key indicators

• Single-crystal X-ray study
• T = 296 K
• Mean [sigma](Co-O) = 0.001 Å
• Disorder in main residue
• R factor = 0.022
• wR factor = 0.051
• Data-to-parameter ratio = 27.4

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT232_ALERT_2_C Hirshfeld Test Diff (M-X)  Co2    --  O9      ..       7.78 su
PLAT041_ALERT_1_C Calc. and Reported SumFormula    Strings  Differ          ?
PLAT042_ALERT_1_C Calc. and Reported MoietyFormula Strings  Differ          ?
PLAT045_ALERT_1_C Calculated and Reported Z Differ by ............       0.25 Ratio
PLAT077_ALERT_4_C Unitcell contains non-integer number of atoms ..          ?
PLAT912_ALERT_4_C Missing # of FCF Reflections Above STh/L=  0.600         16

Alert level G
PLAT301_ALERT_3_G Note: Main Residue  Disorder ...................       5.00 Perc.
PLAT128_ALERT_4_G Non-standard setting of Space-group P21/c   ....      P21/n
PLAT793_ALERT_4_G The Model has Chirality at P2      (Verify) ....          R

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   6 ALERT level C = Check and explain
   3 ALERT level G = General alerts; check

   3 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   1 ALERT type 2 Indicator that the structure model may be wrong or deficient
   1 ALERT type 3 Indicator that the structure quality may be low
   4 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

---

S1. Comment

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 M^IIPO₄^-, 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, Co_2.39Cu_0.61(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, Co_2.39Cu_0.61(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), Co_2.59Zn_0.41(PO₄)₂.H₂O (Sørensen et al., 2004) and Fe₃(PO₄)₂.H₂O (Moore & Araki, 1975).

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).

S2. Experimental

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 Co_2.39Cu_0.61(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).

S3. Refinement

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 U_iso(H) set to 1.5 U_eq(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).

Computing details

Data collection: APEX2 (Bruker, 2005); cell refinement: 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).

Figures

	Fig. 1. A three-dimensional view of the crystal structure of the Co2.39Cu0.61(PO4)2.H2O compound drawn with displacement parameters at the 60% probability level. H atoms are given as small spheres of arbitrary radius. For symmetry operators, see geometric parameters Table.
	Fig. 2. The undulated layer built up from edge sharing CoO6 octahedra and water molecules.
	Fig. 3. A copper phosphate layer formed by (Cu/Co)2P2O12 linked to PO4 tetrahedra.
	Fig. 4. Stacking of the two types of layers projected approximately along [101].

Dicobalt copper bis[orthophosphate(V)] monohydrate

Crystal data

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) Å^3	0.24 × 0.12 × 0.06 mm
Z = 4

Data collection

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

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.022	H-atom parameters constrained
wR(F^2) = 0.051	w = 1/[σ^2(Fo^2) + (0.0196P)^2 + 0.5902P] where P = (Fo^2 + 2Fc^2)/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+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0034 (3)

Special details

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	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*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
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)

Geometric parameters (Å, º)

Cu3—O5	1.9236 (11)	P1—O4	1.5558 (11)
Cu3—O1^i	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—O5^ii	2.2614 (11)	P2—O5	1.5496 (10)
Co1—O3^iii	2.0274 (11)	O1—Co3^vi	1.9411 (11)
Co1—O6^iv	2.0791 (11)	O1—Cu3^vi	1.9411 (11)
Co1—O8^v	2.0976 (11)	O3—Co1^iii	2.0274 (11)
Co1—O4^vi	2.1321 (11)	O4—Co1^i	2.1320 (11)
Co1—O2	2.1588 (12)	O5—Co3^ii	2.2613 (11)
Co1—O7^iii	2.1779 (12)	O5—Cu3^ii	2.2613 (11)
Co2—O2	2.0407 (11)	O6—Co1^viii	2.0790 (11)
Co2—O9	2.0625 (11)	O6—Co2^ii	2.1010 (11)
Co2—O7^iv	2.0818 (13)	O7—Co2^viii	2.0818 (12)
Co2—O6^ii	2.1010 (11)	O7—Co1^iii	2.1779 (12)
Co2—O8^v	2.1088 (11)	O8—Co1^ix	2.0976 (10)
Co2—O9^vii	2.3310 (13)	O8—Co2^ix	2.1087 (11)
P1—O2	1.5254 (11)	O9—Co2^vii	2.3310 (13)
P1—O1	1.5257 (11)	O9—H9A	0.8342
P1—O3	1.5525 (11)	O9—H9B	0.9111
O5—Cu3—O1^i	96.74 (5)	O9—Co2—O7^iv	104.98 (4)
O5—Cu3—O3	99.61 (5)	O2—Co2—O6^ii	109.20 (4)
O1^i—Cu3—O3	145.59 (4)	O9—Co2—O6^ii	80.81 (4)
O5—Cu3—O4	171.47 (4)	O7^iv—Co2—O6^ii	79.25 (4)
O1^i—Cu3—O4	91.68 (5)	O2—Co2—O8^v	80.38 (4)
O3—Cu3—O4	72.46 (4)	O9—Co2—O8^v	87.19 (4)
O5—Cu3—O5^ii	77.63 (4)	O7^iv—Co2—O8^v	115.29 (4)
O1^i—Cu3—O5^ii	114.90 (4)	O6^ii—Co2—O8^v	163.32 (4)
O3—Cu3—O5^ii	98.14 (5)	O2—Co2—O9^vii	79.64 (4)
O4—Cu3—O5^ii	100.04 (4)	O9—Co2—O9^vii	89.19 (4)
O3^iii—Co1—O6^iv	172.66 (4)	O7^iv—Co2—O9^vii	158.15 (4)
O3^iii—Co1—O8^v	97.15 (5)	O6^ii—Co2—O9^vii	86.90 (4)
O6^iv—Co1—O8^v	90.19 (4)	O8^v—Co2—O9^vii	81.36 (4)
O3^iii—Co1—O4^vi	86.13 (5)	O2—P1—O1	110.26 (6)
O6^iv—Co1—O4^vi	86.65 (4)	O2—P1—O3	113.44 (6)
O8^v—Co1—O4^vi	167.68 (4)	O1—P1—O3	110.69 (6)
O3^iii—Co1—O2	89.25 (4)	O2—P1—O4	109.89 (6)
O6^iv—Co1—O2	92.14 (4)	O1—P1—O4	111.95 (6)
O8^v—Co1—O2	77.97 (4)	O3—P1—O4	100.30 (6)
O4^vi—Co1—O2	90.24 (4)	O7—P2—O8	111.04 (6)
O3^iii—Co1—O7^iii	101.61 (4)	O7—P2—O6	110.42 (6)
O6^iv—Co1—O7^iii	77.57 (4)	O8—P2—O6	110.02 (6)
O8^v—Co1—O7^iii	96.78 (4)	O7—P2—O5	110.30 (6)
O4^vi—Co1—O7^iii	94.16 (4)	O8—P2—O5	109.04 (6)
O2—Co1—O7^iii	168.52 (4)	O6—P2—O5	105.87 (6)
O2—Co2—O9	164.36 (4)	H9A—O9—H9B	115.3
O2—Co2—O7^iv	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.

Hydrogen-bond geometry (Å, º)

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···O5^v	0.92	2.27	2.942 (2)	130
O9—H9B···O4^x	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.