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The crystal structure of cobalt vanadophosphate dihydrate {systematic name: poly[diaqua-[mu]-oxido-[mu]-phosphato-hemi­cobalt(II)vanadium(II)]}, Co0.50VOPO4·2H2O, shows a three-dimensional framework assembled from VO5 square pyramids, PO4 tetra­hedra and Co[O2(H2O)4] octa­hedra. The CoII ions have local 4/m symmetry, with the equatorial water mol­ecules in the mirror plane, while the V and apical O atom of the vanadyl group are located on the fourfold rotation axis and the P atoms reside on \overline{4} sites. The PO4 tetra­hedra connect the VO5 polyhedra to form a planar P-V-O layer. The [Co(H2O)4]2+ cations link adjacent P-V-O layers via vanadyl O atoms to generate an unprecedented three-dimensional open framework. Powder diffraction measurements reveal that the framework collapses on removal of the water mol­ecules.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S010827010902397X/sq3194sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S010827010902397X/sq3194Isup2.hkl
Contains datablock I

Comment top

Over the past few decades, the synthesis of solid-state inorganic materials with new topological structures built up of oxygen polyhedra has received much attention because of the functional applications of these materials in ion-exchange, adsorption, catalysis and radioactive waste remediation. As the tetrahedral building elements of polyhedral frameworks, not only Si and Ge, but also P have been chosen to synthesize inorganic materials (Li et al., 1998; Xu et al., 2004; Xu et al., 2006). In the past few years, an important advance in layered materials has been the study of vanadophosphates (Soghomonian et al., 1993; Huang et al., 2001; Cui et al., 2004). Our research concentrates on connecting V—P—O layers by transition metals to make new three-dimensional inorganic materials. As part of this work, we designed and synthesized the title compound, which features a three-dimensional framework constructed from V—P—O layers and [Co(H2O)4]2+ cations.

The asymmetric unit of Co0.50VOPO4.2H2O contains nine crystallographically independent non-H atoms (Fig. 1). The octahedrally coordinated Co1 atom is located on the origin with 4/m symmetry. The four coordinated water molecules (O1W) are located in the equatorial (mirror) plane. Atom V1 is coordinated by five O atoms in a typical square pyramid. Both the V atom and the apical O atom are on the fourfold rotation axis. The basal O atoms, which are shared with the P atoms, make O—V—O angles of 85.56 (2) and 147.67 (8)° [or 85.632 (14) and 147.96 (5)°?]. The short apical V—O distance (Table 1) indicates a vanadyl-type interaction (VO). The V atom carries a formal oxidation state of +4, which is confirmed by bond-valence sum calculations (Brown & Altermatt, 1985), S = (R/R0)-N = 4.0024. Atom P1 of the tetrahedral phosphate group is located on a special position of 4 symmetry. Each V atom makes four V—O—P linkages, and the polyhedra thus connect to produce a very flat VOPO4 layer (Fig. 2), which is similar to that found in the previously reported compounds (NH4)VOPO4.1.5H2O (Do et al., 2000a), Na0.5VOPO4.2H2O and K0.5VOPO4.1.5H2O (Wang et al., 1991), and (C4H12N2)[VO(VO2)PO4]2 (Do et al., 2000b). In contrast to these phases, the interlayer ammonium or alkali metal cations are replaced by [Co(H2O)4]2+ cations that coordinate to the vanadyl O atoms and thus link adjacent layers to generate a three-dimensional framework (Fig. 3). To the best of our knowledge, this is the first example in which a transition metal (Co2+) connects flat V—O—P layers. The layers, which are 7.44 (2) Å apart, contain channels running along the b direction. These secondary building units are constructed from four VO5 square pyramids, two PO4 tetrahedra and two CoO6 octahedra (Fig. 4). In the reported three-dimensional vanadophosphates with larger 10-polyhedron ring channels (Zhang et al., 1995; Chen et al., 2006), templating organic amines are located in the channels.

Thermal analysis of Co0.50VOPO4.2H2O in an N2 atmosphere shows a one-step mass loss of 15.85% between 573 and 623 K, with no further loss up to 1073 K. The total weight loss is in excellent agreement with the calculated weight loss for desorption of coordinated water. Powder X-ray diffraction indicates that the inorganic framework collapses completely after the removal of water.

Related literature top

For related literature, see: Chen et al. (2006); Cui et al. (2004); Do, Bontchev & Jacobson (2000a,b); Huang et al. (2001); Li et al. (1998); Soghomonian et al. (1993); Wang et al. (1991); Xu et al. (2004, 2006); Zhang et al. (1995).

Experimental top

The title crystal was synthesized by a hydrothermal reaction using NH4VO3 (0.2339 g), Co(OAc)2.2H2O (0.2490 g) and water (10 ml) in a molar ratio 2:1:555. The mixture was adjusted to pH 3 with H3PO4 (50%), placed in a 25 ml Teflon-lined autoclave and heated at 443 K for 7 d. After the sample was cooled to room temperature, washed with distilled water, filtered and dried in air, block-shaped green crystals of the title compound were obtained. The reduction of vanadium from +5 to +4 may be due to reaction with acetic acid, which may act as a reducing agent at low pH.

Refinement top

The unique H atom of the water molecule was located in a difference map and included in the refinement with the H—O bond length restrained to 0.82 (2) Å and with the Uiso(H) value fixed to 1.5Ueq(O1W).

Computing details top

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: SHELXTL (Version 5.10; Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Version 5.10; Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. The molecular structure of the title compound, with displacement ellipsoids at the 50% probability level. [Symmetry codes: (i) -x, -y, -z; (ii) -y, x, z; (iii) y, -x, -z; (iv) -x, -y, z; (v) y, -x, z; (vi) -x + 1, -y, z; (vii) y + 1/2, -x + 1/2, -z - 1/2; (viii) -y - 1/2, x - 1/2, -z - 1/2.]
[Figure 2] Fig. 2. The structure of a single V—P—O layer.
[Figure 3] Fig. 3. Stacking of the layers and linkage by [Co(H2O)4]2+ groups. Note the open spaces between the tetraaquacobalt groups.
[Figure 4] Fig. 4. The channels along the b axis, shown as secondary building units consisting of two CoO6 octahedra (dark gray), two PO4 tetrahedra (light gray) and four VO5 square pyramids (black).
poly[diaqua-µ-oxido-µ-phosphato-hemiocobalt(II)vanadium(II)] top
Crystal data top
Co0.50VOPO4·2H2ODx = 2.879 Mg m3
Mr = 227.41Mo Kα radiation, λ = 0.71073 Å
Tetragonal, I4/mCell parameters from 58 reflections
Hall symbol: -I 4θ = 2.4–24.6°
a = 6.2570 (5) ŵ = 3.69 mm1
c = 13.400 (2) ÅT = 293 K
V = 524.62 (10) Å3Block, green
Z = 40.13 × 0.12 × 0.12 mm
F(000) = 446
Data collection top
Bruker APEXII CCD
diffractometer
275 independent reflections
Radiation source: fine-focus sealed tube274 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.027
ω scansθmax = 25.8°, θmin = 3.0°
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003)
h = 67
Tmin = 0.645, Tmax = 0.666k = 77
1403 measured reflectionsl = 1616
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.017H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.040 w = 1/[σ2(Fo2) + (0.P)2 + 1.2075P]
where P = (Fo2 + 2Fc2)/3
S = 1.20(Δ/σ)max = 0.021
275 reflectionsΔρmax = 0.27 e Å3
30 parametersΔρmin = 0.53 e Å3
1 restraintExtinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.0571 (12)
Crystal data top
Co0.50VOPO4·2H2OZ = 4
Mr = 227.41Mo Kα radiation
Tetragonal, I4/mµ = 3.69 mm1
a = 6.2570 (5) ÅT = 293 K
c = 13.400 (2) Å0.13 × 0.12 × 0.12 mm
V = 524.62 (10) Å3
Data collection top
Bruker APEXII CCD
diffractometer
275 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003)
274 reflections with I > 2σ(I)
Tmin = 0.645, Tmax = 0.666Rint = 0.027
1403 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0171 restraint
wR(F2) = 0.040H atoms treated by a mixture of independent and constrained refinement
S = 1.20Δρmax = 0.27 e Å3
275 reflectionsΔρmin = 0.53 e Å3
30 parameters
Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 (Å2) top
xyzUiso*/Ueq
Co10.00000.00000.00000.01301 (11)
V10.00000.00000.27742 (3)0.00716 (9)
P10.50000.00000.25000.00769 (13)
O10.00000.00000.15812 (14)0.0146 (4)
O20.30301 (14)0.01887 (14)0.31812 (6)0.0108 (2)
O1W0.1814 (3)0.2717 (2)0.00000.0225 (3)
H10.176 (3)0.345 (3)0.0503 (10)0.034*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Co10.01560 (15)0.01560 (15)0.0078 (2)0.0000.0000.000
V10.00733 (11)0.00733 (11)0.00681 (18)0.0000.0000.000
P10.00690 (16)0.00690 (16)0.0093 (3)0.0000.0000.000
O10.0164 (5)0.0164 (5)0.0109 (8)0.0000.0000.000
O20.0075 (4)0.0138 (4)0.0112 (4)0.0003 (3)0.0001 (3)0.0012 (3)
O1W0.0334 (8)0.0225 (7)0.0118 (6)0.0063 (7)0.0000.000
Geometric parameters (Å, º) top
Co1—O1Wi2.0442 (15)V1—O2v1.9764 (9)
Co1—O1Wii2.0442 (15)V1—O21.9764 (9)
Co1—O1Wiii2.0442 (15)V1—O2ii1.9764 (9)
Co1—O1W2.0442 (15)P1—O21.5383 (9)
Co1—O1iii2.1189 (19)P1—O2vi1.5383 (9)
Co1—O12.1189 (19)P1—O2vii1.5383 (9)
V1—O11.5986 (19)P1—O2viii1.5383 (9)
V1—O2iv1.9764 (9)O1W—H10.815 (13)
O1Wi—Co1—O1Wii180.00 (9)O2iv—V1—O2v85.632 (14)
O1Wi—Co1—O1Wiii90.0O1—V1—O2106.02 (3)
O1Wii—Co1—O1Wiii90.0O2iv—V1—O285.632 (14)
O1Wi—Co1—O1W90.0O2v—V1—O2147.96 (5)
O1Wii—Co1—O1W90.0O1—V1—O2ii106.02 (3)
O1Wiii—Co1—O1W180.00 (8)O2iv—V1—O2ii147.96 (5)
O1Wi—Co1—O1iii90.0O2v—V1—O2ii85.632 (14)
O1Wii—Co1—O1iii90.0O2—V1—O2ii85.632 (14)
O1Wiii—Co1—O1iii90.0O2—P1—O2vi110.62 (3)
O1W—Co1—O1iii90.0O2—P1—O2vii110.62 (3)
O1Wi—Co1—O190.0O2vi—P1—O2vii107.20 (6)
O1Wii—Co1—O190.0O2—P1—O2viii107.20 (6)
O1Wiii—Co1—O190.0O2vi—P1—O2viii110.62 (3)
O1W—Co1—O190.0O2vii—P1—O2viii110.62 (3)
O1iii—Co1—O1180.0V1—O1—Co1180.0
O1—V1—O2iv106.02 (3)P1—O2—V1126.89 (5)
O1—V1—O2v106.02 (3)Co1—O1W—H1116.3 (13)
Symmetry codes: (i) y, x, z; (ii) y, x, z; (iii) x, y, z; (iv) y, x, z; (v) x, y, z; (vi) y+1/2, x+1/2, z1/2; (vii) y+1/2, x1/2, z1/2; (viii) x+1, y, z.

Experimental details

Crystal data
Chemical formulaCo0.50VOPO4·2H2O
Mr227.41
Crystal system, space groupTetragonal, I4/m
Temperature (K)293
a, c (Å)6.2570 (5), 13.400 (2)
V3)524.62 (10)
Z4
Radiation typeMo Kα
µ (mm1)3.69
Crystal size (mm)0.13 × 0.12 × 0.12
Data collection
DiffractometerBruker APEXII CCD
diffractometer
Absorption correctionMulti-scan
(SADABS; Sheldrick, 2003)
Tmin, Tmax0.645, 0.666
No. of measured, independent and
observed [I > 2σ(I)] reflections
1403, 275, 274
Rint0.027
(sin θ/λ)max1)0.613
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.017, 0.040, 1.20
No. of reflections275
No. of parameters30
No. of restraints1
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.27, 0.53

Computer programs: APEX2 (Bruker, 2005), SAINT (Bruker, 2005), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Version 5.10; Sheldrick, 2008).

Selected bond lengths (Å) top
Co1—O1W2.0442 (15)V1—O21.9764 (9)
Co1—O12.1189 (19)P1—O21.5383 (9)
V1—O11.5986 (19)O1W—H10.815 (13)
 

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