Co₃(PO₄)₂·4H₂O

Abstract

Single crystals of Co₃(PO₄)₂·4H₂O, tricobalt(II) bis­[ortho­phosphate(V)] tetra­hydrate, were obtained under hydro­thermal conditions. The title compound is isotypic with its zinc analogue Zn₃(PO₄)₂·4H₂O (mineral name hopeite) and contains two independent Co²⁺ cations. One Co²⁺ cation exhibits a slightly distorted tetra­hedral coordination, while the second, located on a mirror plane, has a distorted octa­hedral coordination environment. The tetra­hedrally coordinated Co²⁺ is bonded to four O atoms of four PO₄ ³⁻ anions, whereas the six-coordinate Co²⁺ is cis-bonded to two phosphate groups and to four O atoms of four water mol­ecules (two of which are located on mirror planes), forming a framework structure. In addition, hydrogen bonds of the type O—H⋯O are present throughout the crystal structure.

Related literature

Besides crystals of the title compound, crystals of Co₃(PO₄)₂·H₂O (Lee et al., 2008 ▶) have also been obtained under hydro­thermal conditions. For reviews, synthesis, structures and applications of open framework structures with different cations and/or structure directing mol­ecules, see: Kuzicki et al. (2001 ▶); Chen et al. (2006 ▶); Jiang & Gao (2007 ▶); Cheetham et al. (1999 ▶); Forster et al. (2003 ▶); Jiang et al. (2001 ▶); Cooper et al. (2004 ▶); Choudhury et al. (2000 ▶). The structure of the isotypic mineral hopeite was first described by Liebau (1965 ▶).

Experimental

Crystal data

• Co₃(PO₄)₃·4H₂O

• M _r = 438.79

• Orthorhombic,

• a = 10.604 (3) Å

• b = 18.288 (5) Å

• c = 5.0070 (13) Å

• V = 971.0 (5) ų

• Z = 4

• Mo Kα radiation

• μ = 5.46 mm⁻¹

• T = 150 (2) K

• 0.52 × 0.39 × 0.38 mm

Data collection

• Siemens SMART 1000 CCD diffractometer

• Absorption correction: multi-scan (SADABS; Sheldrick, 1999 ▶) T _min = 0.068, T _max = 0.125

• 8780 measured reflections

• 1228 independent reflections

• 1166 reflections with I > 2σ(I)

• R _int = 0.026

Refinement

• R[F ² > 2σ(F ²)] = 0.035

• wR(F ²) = 0.102

• S = 1.16

• 1228 reflections

• 101 parameters

• 10 restraints

• H atoms treated by a mixture of independent and constrained refinement

• Δρ_max = 0.55 e Å⁻³

• Δρ_min = −1.38 e Å⁻³

Data collection: SMART (Siemens, 1995 ▶); cell refinement: SAINT (Siemens, 1995 ▶); data reduction: SAINT and XPREP (Siemens, 1995 ▶); program(s) used to solve structure: SIR97 (Altomare et al., 1999 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 (Farrugia, 1997 ▶), WebLab ViewerPro (Molecular Simulations, 2000 ▶) and POV-RAY (Cason, 2002 ▶); software used to prepare material for publication: enCIFer (Allen et al., 2004 ▶).

Supplementary Material

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Selected bond lengths (Å).

Co1—O7i	1.901 (3)
Co1—O1	1.918 (3)
Co1—O2ii	1.983 (3)
Co1—O2iii	1.986 (3)
Co2—O4	2.106 (4)
Co2—O5	2.118 (4)
Co2—O6	2.138 (3)
P1—O7	1.519 (3)
P1—O3	1.521 (3)
P1—O1	1.537 (3)
P1—O2	1.570 (3)

Symmetry codes: (i) ; (ii) ; (iii) .

Table 2. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O4—H5⋯O3iv	0.894 (10)	2.25 (8)	2.764 (4)	116 (7)
O4—H5⋯O7v	0.894 (10)	2.49 (8)	3.209 (3)	138 (9)
O4—H6⋯O3vi	0.894 (10)	2.02 (7)	2.764 (4)	140 (10)
O5—H4⋯O3vii	0.892 (10)	2.25 (2)	3.133 (5)	170 (8)
O5—H4⋯O3viii	0.892 (10)	2.66 (8)	3.133 (5)	115 (6)
O6—H1⋯O1vii	0.90 (4)	1.94 (3)	2.690 (4)	140 (4)
O6—H2⋯O7	0.90 (3)	2.35 (3)	3.008 (5)	130 (3)

Symmetry codes: (iv) ; (v) ; (vi) ; (vii) ; (viii) .

supplementary crystallographic information

Comment

The synthesis and investigation of open-framework transition-metal phosphates has been a growing area of research over recent times. This is not only because of the rich structural chemistry involved, but is also due to many potential applications such as for catalysis, as alternatives for zeolites in separation and storage applications and, in particular, as potential gas storage materials (Kuzicki et al., 2001; Chen et al., 2006; Jiang & Gao, 2007; Cheetham et al., 1999). For example, microporous nickel phosphates incorporating 24-membered rings such as VSB-5 (Versailles/Santa Barbara-5) have been demonstrated to exhibit hydrogen uptake at low temperatures (Forster et al., 2003). Over the past couple of decades, a considerable number of metal phosphates/phosphites with open molecular architectures have also been synthesized incorporating organic units (see, for example: Jiang et al., 2001) and ionic liquids (Cooper et al., 2004) as structure-directing agents, often under hydrothermal or solvothermal conditions. One of the best known families of this type consists of zinc phosphate structures; individual materials of this type can exist as one dimensional (chain and ladder), two dimensional (layer) and three dimensional framework arrangements (Choudhury et al., 2000).

We are currently investigating the synthesis of a variety of similar functional materials through templation effects under hydrothermal conditions. The title compound, Co₃(PO₄)₂.4H₂O, (I), and the related compound Co₃(PO₄)₂.H₂O (Lee et al., 2008) were synthesized and structurally characterized as a part of these studies.

The structure of (I) is isotypic with the mineral hopeite, Zn₃(PO₄)₂.4H₂O (Liebau, 1965) and contains two different Co²⁺ centres bridged by orthophosphate anions (Fig. 1). The coordination environment of Co1 is slightly distorted tetrahedral while that of Co2 is close to octahedral (Table 1). Co1 is bonded to the O atoms of four different phosphate ligands, while Co2 is bonded to the O atoms of two orthophosphate ligands in a cis-arrangement. The other coordination sites are occupied by O atoms of the water ligands. A mirror plane passes through Co2 and two of the water molecules (O4 and O5). This coordination geometry leads to the formation of a three-dimensional framework (Fig. 2). A number of hydrogen bonding interactions O—H···O are present and stabilize the structure (Table 2).

Experimental

H₃PO₄ (85%_wt, 2.3 g, 20 mmol) was added to an aqueous solution (20 ml) of Co(NO₃)₂.6H₂O (2.6 g, 9 mmol) with stirring for 30 min and the ionic liquid, 1-butyl-3-methylimidazolium bromide (2.7 g, 9 mmol), was added dropwise under continuous stirring. The mixture was transferred to a teflon-coated autoclave, heated at 453 K for 3 d and then allowed to cool slowly. A mixture of plate-like and prismatic purple crystals had formed and was filtered off. The crystals were washed with water, dried under vacuum and were manually separated under a microscope. The yields were approximately 0.4 g of the plate-like crystals of the compound Co₃(PO₄)₂.H₂O (Lee et al., 2008) and and 0.2 g of the prismatic crystals of compound (I).

Refinement

Water H atoms were located in difference Fourier maps and were refined with U_iso(H) values fixed at 1.5U_eq of the parent O atoms. O—H bond length restraints of 0.89 (1) Å were also employed. The highest peak and the deepest hole in the final Fourier map are located 0.49 Å from Co1 and 0.33 Å from P2, respectively.

Figures

Fig. 1.

The asymmetric unit of compound (I), drawn with displacement parameters at the 50% probability level. H atoms are given as spheres of arbitrary radius.

Fig. 2.

A schematic representation of a section of the three-dimensional network in a projection along [001]. Hydrogen atoms are omitted for clarity.

Crystal data

Co3(PO4)3·4H2O	F(000) = 860
Mr = 438.79	Dx = 3.002 Mg m−3
Orthorhombic, Pnma	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2n	Cell parameters from 5943 reflections
a = 10.604 (3) Å	θ = 2.9–28.3°
b = 18.288 (5) Å	µ = 5.46 mm−1
c = 5.0070 (13) Å	T = 150 K
V = 971.0 (5) Å3	Prism, purple
Z = 4	0.52 × 0.39 × 0.38 mm

Data collection

Siemens SMART 1000 CCD diffractometer	1228 independent reflections
Radiation source: sealed tube	1166 reflections with I > 2σ(I)
graphite	Rint = 0.026
ω scans	θmax = 28.3°, θmin = 2.2°
Absorption correction: multi-scan (SADABS; Sheldrick, 1999)	h = −13→13
Tmin = 0.068, Tmax = 0.125	k = −24→24
8780 measured reflections	l = −6→6

Refinement

Refinement on F2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.035	Hydrogen site location: difference Fourier map
wR(F2) = 0.102	H atoms treated by a mixture of independent and constrained refinement
S = 1.16	w = 1/[σ2(Fo2) + (0.059P)2 + 3.8213P] where P = (Fo2 + 2Fc2)/3
1228 reflections	(Δ/σ)max < 0.001
101 parameters	Δρmax = 0.55 e Å−3
10 restraints	Δρmin = −1.38 e Å−3

Special details

Experimental. The crystal was coated in Exxon Paratone N hydrocarbon oil and mounted on a thin mohair fibre attached to a copper pin. Upon mounting on the diffractometer, the crystal was quenched to 150(K) under a cold nitrogen gas stream supplied by an Oxford Cryosystems Cryostream and data were collected at this temperature.

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)
Co1	0.64313 (4)	0.00064 (2)	0.20676 (8)	0.00402 (17)
Co2	0.26113 (6)	0.2500	0.42866 (12)	0.00838 (19)
P1	0.39745 (9)	0.09462 (5)	0.27639 (18)	0.0123 (2)
O1	0.5259 (3)	0.07872 (14)	0.1463 (7)	0.0202 (6)
O2	0.3026 (2)	0.03968 (15)	0.1432 (5)	0.0148 (5)
O3	0.3601 (3)	0.17305 (16)	0.2139 (6)	0.0201 (7)
O4	0.3927 (4)	0.2500	0.7439 (7)	0.0155 (8)
O5	0.1149 (4)	0.2500	0.1406 (9)	0.0192 (8)
O6	0.1642 (3)	0.16927 (15)	0.6593 (6)	0.0197 (6)
O7	0.4000 (4)	0.08075 (16)	0.5755 (6)	0.0311 (8)
H1	0.098 (4)	0.161 (3)	0.553 (10)	0.047*
H2	0.2194 (15)	0.1390 (19)	0.739 (9)	0.047*
H3	0.132 (8)	0.280 (5)	0.005 (15)	0.047*	0.50
H4	0.044 (5)	0.231 (5)	0.204 (18)	0.047*	0.50
H5	0.403 (13)	0.296 (3)	0.80 (3)	0.047*	0.50
H6	0.366 (13)	0.210 (4)	0.83 (3)	0.047*	0.50

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
Co1	0.0038 (3)	0.0055 (3)	0.0027 (3)	0.00152 (13)	0.00023 (14)	0.00025 (13)
Co2	0.0081 (3)	0.0088 (3)	0.0082 (3)	0.000	0.0006 (2)	0.000
P1	0.0179 (5)	0.0077 (4)	0.0114 (4)	0.0004 (3)	−0.0004 (3)	0.0003 (3)
O1	0.0128 (13)	0.0123 (12)	0.0357 (16)	−0.0008 (10)	−0.0008 (12)	0.0038 (12)
O2	0.0135 (12)	0.0177 (12)	0.0134 (11)	−0.0024 (10)	0.0020 (10)	−0.0028 (10)
O3	0.0331 (17)	0.0099 (13)	0.0174 (14)	0.0061 (11)	0.0094 (11)	0.0022 (10)
O4	0.017 (2)	0.0169 (19)	0.0130 (16)	0.000	−0.0012 (15)	0.000
O5	0.0136 (18)	0.026 (2)	0.0183 (18)	0.000	−0.0003 (16)	0.000
O6	0.0175 (14)	0.0149 (13)	0.0267 (14)	−0.0024 (11)	0.0027 (12)	0.0026 (12)
O7	0.066 (2)	0.0131 (13)	0.0142 (13)	−0.0105 (14)	−0.0095 (15)	0.0020 (10)

Geometric parameters (Å, °)

Co1—O7i	1.901 (3)	P1—O7	1.519 (3)
Co1—O1	1.918 (3)	P1—O3	1.521 (3)
Co1—O2ii	1.983 (3)	P1—O1	1.537 (3)
Co1—O2iii	1.986 (3)	P1—O2	1.570 (3)
Co2—O3iv	2.058 (3)	O4—H5	0.893 (10)
Co2—O3	2.058 (3)	O4—H6	0.893 (10)
Co2—O4	2.106 (4)	O5—H3	0.892 (10)
Co2—O5	2.118 (4)	O5—H4	0.891 (10)
Co2—O6	2.138 (3)	O6—H1	0.89 (4)
Co2—O6iv	2.138 (3)	O6—H2	0.90 (3)
O7i—Co1—O1	121.18 (15)	O7—P1—O3	111.40 (17)
O7i—Co1—O2ii	105.64 (13)	O7—P1—O1	111.8 (2)
O1—Co1—O2ii	110.16 (12)	O3—P1—O1	108.79 (16)
O7i—Co1—O2iii	106.57 (12)	O7—P1—O2	108.84 (17)
O1—Co1—O2iii	108.97 (13)	O3—P1—O2	110.43 (17)
O2ii—Co1—O2iii	102.75 (8)	O1—P1—O2	105.46 (16)
O3iv—Co2—O3	86.26 (16)	P1—O1—Co1	130.42 (18)
O3iv—Co2—O4	93.09 (12)	P1—O2—Co1v	128.01 (16)
O3—Co2—O4	93.09 (12)	P1—O2—Co1iii	115.24 (15)
O3iv—Co2—O5	91.00 (12)	Co1v—O2—Co1iii	116.58 (13)
O3—Co2—O5	91.00 (12)	P1—O3—Co2	132.08 (17)
O4—Co2—O5	174.38 (15)	Co2—O4—H5	108 (10)
O3iv—Co2—O6	178.01 (12)	Co2—O4—H6	98 (10)
O3—Co2—O6	93.16 (12)	H5—O4—H6	133 (3)
O4—Co2—O6	85.03 (11)	Co2—O5—H3	112 (6)
O5—Co2—O6	90.91 (12)	Co2—O5—H4	112 (6)
O3iv—Co2—O6iv	93.16 (12)	H3—O5—H4	134 (3)
O3—Co2—O6iv	178.01 (12)	Co2—O6—H1	100 (4)
O4—Co2—O6iv	85.03 (11)	Co2—O6—H2	110.7 (10)
O5—Co2—O6iv	90.91 (12)	H1—O6—H2	132 (2)
O6—Co2—O6iv	87.36 (16)	P1—O7—Co1i	133.79 (19)
O7—P1—O1—Co1	41.2 (3)	O1—P1—O2—Co1iii	−20.9 (2)
O3—P1—O1—Co1	164.7 (2)	O7—P1—O3—Co2	−22.9 (3)
O2—P1—O1—Co1	−76.9 (3)	O1—P1—O3—Co2	−146.5 (2)
O7i—Co1—O1—P1	8.8 (3)	O2—P1—O3—Co2	98.2 (3)
O2ii—Co1—O1—P1	−115.1 (2)	O3iv—Co2—O3—P1	153.57 (18)
O2iii—Co1—O1—P1	132.9 (2)	O4—Co2—O3—P1	60.7 (3)
O7—P1—O2—Co1v	34.1 (3)	O5—Co2—O3—P1	−115.5 (3)
O3—P1—O2—Co1v	−88.5 (2)	O6—Co2—O3—P1	−24.5 (3)
O1—P1—O2—Co1v	154.17 (19)	O3—P1—O7—Co1i	143.7 (3)
O7—P1—O2—Co1iii	−140.96 (19)	O1—P1—O7—Co1i	−94.4 (4)
O3—P1—O2—Co1iii	96.45 (18)	O2—P1—O7—Co1i	21.7 (4)

Symmetry codes: (i) −x+1, −y, −z+1; (ii) x+1/2, y, −z+1/2; (iii) −x+1, −y, −z; (iv) x, −y+1/2, z; (v) x−1/2, y, −z+1/2.

Hydrogen-bond geometry (Å, °)

D—H···A	D—H	H···A	D···A	D—H···A
O4—H5···O3vi	0.89 (1)	2.25 (8)	2.764 (4)	116 (7)
O4—H5···O7iv	0.89 (1)	2.49 (8)	3.209 (3)	138 (9)
O4—H6···O3vii	0.89 (1)	2.02 (7)	2.764 (4)	140 (10)
O5—H4···O3v	0.89 (1)	2.25 (2)	3.133 (5)	170 (8)
O5—H4···O3viii	0.89 (1)	2.66 (8)	3.133 (5)	115 (6)
O6—H1···O1v	0.90 (4)	1.94 (3)	2.690 (4)	140 (4)
O6—H2···O7	0.90 (3)	2.35 (3)	3.008 (5)	130 (3)

Symmetry codes: (vi) x, −y+1/2, z+1; (iv) x, −y+1/2, z; (vii) x, y, z+1; (v) x−1/2, y, −z+1/2; (viii) x−1/2, −y+1/2, −z+1/2.