The synthetic cobalt vanadium selenite, Co₂V₂Se₂O₁₁

The crystal structure of dicobalt(II) divanadium(V) disel­enium(IV) undeca­oxide, Co₂V₂Se₂O₁₁, exhibits a three-dimensional framework, the building units being distorted CoO₆ octa­hedra and VO₅ square pyramids arranged so as to form alternate chains along [010]. The framework has channels along [100] and [010] in which the two Ψ-SeO₃E (site symmetries m; E being the 4s² lone electron pair of Se^IV) tetra­hedra reside and connect to the other building blocks. The structure contains corner- and edge-sharing CoO₆ octa­hedra, corner- and edge-sharing VO₅ square pyramids and edge-sharing Ψ-SeO₃E tetra­hedra. Co₂V₂Se₂O₁₁ is the first oxide containing all the cations Co^II, V^V and Se^IV.

Related literature

For general background, including bond-valence-sum calculations, see: Brown & Altermatt (1985). For related structures, see: Allen et al. (2004); Becker et al. (2007a,b); Jiang et al. (2008); Millet et al. (1999); Pitzschenke & Jansen (2007); Sauerbrei et al. (1974).

Experimental

Crystal data

• Co₂V₂Se₂O₁₁

• M_r = 553.66

• Monoclinic, P 2₁ /m

• a = 4.7913 (2) Å

• b = 8.8680 (4) Å

• c = 10.6156 (5) Å

• β = 101.115 (5)°

• V = 442.59 (3) ų

• Z = 2

• Mo Kα radiation

• μ = 14.01 mm⁻¹

• T = 292 K

• 0.05 × 0.03 × 0.02 mm

Data collection

• Oxford Diffraction Xcalibur Sapphire3 diffractometer

• Absorption correction: analytical [CrysAlis RED (Oxford Diffraction, 2007), based on expressions derived by Clark & Reid (1995)] T_min = 0.659, T_max = 0.756

• 4219 measured reflections

• 1534 independent reflections

• 1023 reflections with I > 2σ(I)

• R_int = 0.051

Refinement

• R[F² > 2σ(F²)] = 0.032

• wR(F²) = 0.048

• S = 0.76

• 1534 reflections

• 85 parameters

• Δρ_max = 1.28 e Å⁻³

• Δρ_min = −0.98 e Å⁻³

Data collection: CrysAlis CCD (Oxford Diffraction, 2007); cell refinement: CrysAlis RED (Oxford Diffraction, 2007); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2001); software used to prepare material for publication: enCIFer (Allen et al., 2004).

Supporting information

S1. Comment

The synthesis and crystal structure determination of the new compound Co₂V₂Se₂O₁₁ is a result of an ongoing investigation of the structural chemistry of selenium and tellurium oxides and oxohalides. Transition metal oxides and oxohalides containing p-block cations, such as Se^IV and Te^IV, with stereochemically active lone pairs frequently show a low-dimensional arrangement of the metal ions. The Se^IV lone pairs act as 'chemical scissors' and help to reduce the dimensionality of the atomic arrangements in the crystal structure (Becker et al., 2007a,b). The aim of the present study was to test the synthesis concept in a system containing two transition metals taking different coordination polyhedra: CoO-V₂O₅—SeO₂. The present compound is, to the best of our knowledge, the first oxide to contain all the cations Co^II, V^V and Se^IV. A few selenites containing vanadium plus another transition metal have previously been described; Cd₆V₂Se₅O₂₁ (Jiang et al., 2008), α-CuVSe₂O₇ and β-CuVSe₂O₇ (Millet et al., 1999), AgVSeO₅ and ZnVSe₂O₇ (Pitzschenke & Jansen, 2007). The stereochemically active lone electron pairs open up the crystal structures by creating non-bonding volumes and occupy space similar to that taken by an oxygen anion in the crystal structure. α-CuVSe₂O₇ is a layered compound with only weak van der Waals interactions in between the layers while the others are three-dimensional framework structures where the lone pairs on Se^IV are located in voids in the crystal structure.

Co₂V₂Se₂O₁₁ crystallizes in the centrosymmetric monoclinic space group P2₁/m. The Co^II ions are in a slightly distorted octahedral environment. The CoO₆ octahedra are connected via O2ⁱⁱⁱ···O2^v and O1···O3ⁱⁱⁱ edge sharing [symmetry code: (iii) x + 1,y,z; (v) -x + 1,y + 1/2,-z + 1] to form zigzag chains having the formula [CoO₄]_n along [100]. The Co···O bonds are in the range 2.074 (3) Å to 2.123 (3) Å which is comparable to what is found in e.g. Co₂V₂O₇ (Sauerbrei et al., 1974). There are two Co—Co distances within a chain; 3.160 (1) Å and 3.179 (2) Å. The V^V atoms are surrounded by five O atoms forming a very distorted square pyramid comprising two V1=O vanadyl double bonds of 1.627 (3) Å and 1.635 (3) Å and two long V1–O bonds 2.038 (3) Å and 2.087 (3) Å (Fig. 1). As a consequence, the V atom is located above the square plane. Bond valence sum analysis (Brown & Altermatt, 1985) confirms the coordination, with the calculated valence (V^V, the bond valence parameter R_o = 1.803) equal to 5.15. The VO₅ square pyramids are connected via O5···O5ⁱⁱ edge sharing and O7 corner sharing [symmetry code: (ii) -x + 1,-y + 1,z - 2] to form chains having the formula [V₂O₇]_n along [010]. The V···V distances in a chain are 3.328 (1) Å and 3.443 (2) Å. The chains of CoO₆ and VO₅ bridge by corner sharing at O4 and O6. The Se^IV ions have both one sided SeO₃ coordination owing to the presence of the 4s² stereochemically active lone pair, E, and they do not polymerize. The crystal structure can be described as being a three-dimensional framework structure made up of [CoO₄]_n– and [V₂O₇]_n chains (Fig. 2 and 3). The SeO₃ groups connect to the metal-oxide framework by corner sharing (Fig. 3). The stereochemically active Se^IV lone pairs are located in voids in the structure. Those voids are present as tunnels along (100) and (010) respectively.

Bond valence sum analysis (Brown & Altermatt, 1985) confirms the coordination for all the ions and give 2.04 for Co1, 5.15 for V1, 4.01 for Se1, 3.84 for Se2, 2.07 for O1, 2.02 for O2, 2.11 for O3, 1.92 for O4 and 2.36 for O5.

Related literature

For general background, including bond-valence-sum calculations, see: Brown & Altermatt (1985). For related structures, see: Allen et al. (2004); Becker et al. (2007a,b); Jiang et al. (2008); Millet et al. (1999); Pitzschenke & Jansen (2007); Sauerbrei et al. (1974).

S2. Experimental

Single crystals of Co₂V₂Se₂O₁₁ are non-hygroscopic and were synthesized via chemical vapour transport reactions in sealed evacuated silica tubes. The starting materials were 0.150 g (2 mmol) CoO (ABCR GmbH 97.999%), 0.182 g (1 mmol) V₂O₅ (ABCR GmbH 99.9%), and 0.222 g (2 mmol) SeO₂, (Alfa Aesar 99.4%) mixed in a stoichiometric 2:1:2 molar ratio and placed in a 5 cm long silica tube which was first dried for 1 h at 100°C and subsequently evacuated and sealed. The silica tube was treated in a muffle furnace at 500°C for 100 h followed by slow cooling at a rate of 10°C/h to room temperature. The synthesis products were a mixture of red single crystals of Co₂V₂Se₂O₁₁ and a brown-red powder of undetermined composition.

S3. Refinement

The structure was solved using SHELXS97 (Sheldrick, 2008), and refined by full-matrix least-squares using SHELXL97 (Sheldrick, 2008).

Computing details

Data collection: CrysAlis CCD (Oxford Diffraction, 2007); cell refinement: CrysAlis RED (Oxford Diffraction, 2007); data reduction: CrysAlis RED (Oxford Diffraction, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2001); software used to prepare material for publication: enCIFer (Allen et al. 2004).

Figures

	Fig. 1. A displacement ellipsoid diagram showing the coordination around the cations. Atomic displacement parameters are given at the 50% probability level [Symmetry codes: (i) x,-y + 1/2,z; (ii) -x + 1,-y - 1,z - 2; (iii) x + 1,y,z; (iv) x + 1,-y + 1/2,z; (v) -x + 1,y + 1/2,-z + 1].
	Fig. 2. A view of the structure of Co2V2Se2O11 along (100).
	Fig. 3. A view of the structure of Co2V2Se2O11 along (010).

dicobalt(II) divanadium(V) diselenium(IV) undecaoxide

Crystal data

Co2V2Se2O11	F(000) = 512
Mr = 553.66	Dx = 4.155 Mg m^−3
Monoclinic, P21/m	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yb	Cell parameters from 1387 reflections
a = 4.7913 (2) Å	θ = 3.9–32.2°
b = 8.8680 (4) Å	µ = 14.01 mm^−1
c = 10.6156 (5) Å	T = 292 K
β = 101.115 (5)°	Block, red
V = 442.59 (3) Å^3	0.05 × 0.03 × 0.02 mm
Z = 2

Data collection

Oxford Diffraction Xcalibur Sapphire3 diffractometer	1534 independent reflections
Radiation source: fine-focus sealed tube	1023 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.051
Detector resolution: 16.5 pixels mm^-1	θmax = 32.3°, θmin = 3.9°
ω scans	h = −7→7
Absorption correction: analytical [CrysAlis RED (Oxford Diffraction, 2007), based on expressions derived by Clark & Reid (1995)]	k = −11→12
Tmin = 0.659, Tmax = 0.756	l = −15→13
4219 measured reflections

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	Primary atom site location: structure-invariant direct methods
R[F^2 > 2σ(F^2)] = 0.032	Secondary atom site location: difference Fourier map
wR(F^2) = 0.048	w = 1/[σ^2(Fo^2) + (0.0114P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 0.76	(Δ/σ)max = 0.001
1534 reflections	Δρmax = 1.28 e Å^−3
85 parameters	Δρmin = −0.98 e Å^−3

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
Se1	0.38839 (12)	0.2500	0.45047 (6)	0.00668 (13)
Se2	0.14374 (12)	0.2500	0.89926 (5)	0.00653 (13)
Co1	0.95757 (12)	0.42816 (6)	0.63219 (5)	0.00751 (13)
V1	0.53298 (15)	0.56239 (8)	0.85002 (6)	0.00660 (15)
O1	0.6860 (8)	0.2500	0.5658 (4)	0.0105 (9)
O6	0.7568 (6)	0.4597 (3)	0.7887 (3)	0.0118 (6)
O5	0.3738 (6)	0.4001 (3)	0.9523 (3)	0.0107 (6)
O2	0.2107 (6)	0.0989 (3)	0.4958 (3)	0.0093 (6)
O3	0.1701 (8)	0.2500	0.7454 (4)	0.0088 (9)
O4	0.2448 (6)	0.5786 (3)	0.7407 (3)	0.0132 (7)
O7	0.6843 (8)	0.7500	0.8501 (4)	0.0077 (9)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Se1	0.0068 (3)	0.0069 (3)	0.0064 (3)	0.000	0.0014 (2)	0.000
Se2	0.0080 (3)	0.0051 (3)	0.0063 (3)	0.000	0.0008 (2)	0.000
Co1	0.0080 (3)	0.0063 (3)	0.0082 (3)	0.0001 (2)	0.0016 (2)	0.0001 (2)
V1	0.0078 (3)	0.0063 (3)	0.0058 (3)	−0.0003 (3)	0.0017 (3)	0.0000 (3)
O1	0.008 (2)	0.005 (2)	0.017 (2)	0.000	−0.0012 (18)	0.000
O6	0.0140 (16)	0.0077 (15)	0.0148 (16)	0.0010 (12)	0.0059 (13)	−0.0014 (12)
O5	0.0153 (16)	0.0113 (15)	0.0045 (14)	−0.0088 (12)	−0.0003 (12)	−0.0024 (11)
O2	0.0106 (15)	0.0103 (16)	0.0071 (15)	−0.0021 (12)	0.0021 (12)	−0.0024 (11)
O3	0.012 (2)	0.006 (2)	0.007 (2)	0.000	−0.0022 (17)	0.000
O4	0.0139 (16)	0.0101 (16)	0.0132 (16)	−0.0020 (12)	−0.0031 (13)	0.0025 (12)
O7	0.009 (2)	0.005 (2)	0.010 (2)	0.000	0.0024 (17)	0.000

Geometric parameters (Å, º)

Se1—O1	1.691 (4)	Co1—O6	2.093 (3)
Se1—O2	1.706 (3)	Co1—O4^iv	2.095 (3)
Se1—O2^i	1.706 (3)	Co1—O3^iv	2.122 (3)
Se2—O3	1.663 (4)	V1—O4	1.630 (3)
Se2—O5	1.750 (3)	V1—O6	1.635 (3)
Se2—O5^i	1.750 (3)	V1—O7	1.8147 (17)
Co1—O2^ii	2.074 (3)	V1—O5	2.038 (3)
Co1—O1	2.081 (3)	V1—O5^v	2.086 (3)
Co1—O2^iii	2.090 (3)
O1—Se1—O2	101.12 (13)	O2^ii—Co1—O3^iv	91.59 (13)
O1—Se1—O2^i	101.12 (13)	O1—Co1—O3^iv	80.04 (12)
O2—Se1—O2^i	103.52 (19)	O2^iii—Co1—O3^iv	172.01 (14)
O3—Se2—O5	98.85 (13)	O6—Co1—O3^iv	83.90 (13)
O3—Se2—O5^i	98.85 (13)	O4^iv—Co1—O3^iv	88.29 (11)
O5—Se2—O5^i	98.97 (19)	O4—V1—O6	107.24 (15)
O2^ii—Co1—O1	95.00 (14)	O4—V1—O7	101.71 (16)
O2^ii—Co1—O2^iii	80.44 (12)	O6—V1—O7	102.62 (15)
O1—Co1—O2^iii	101.07 (12)	O4—V1—O5	95.11 (13)
O2^ii—Co1—O6	171.78 (11)	O6—V1—O5	99.22 (13)
O1—Co1—O6	90.99 (14)	O7—V1—O5	146.92 (14)
O2^iii—Co1—O6	103.94 (11)	O4—V1—O5^v	133.61 (14)
O2^ii—Co1—O4^iv	92.69 (12)	O6—V1—O5^v	117.38 (13)
O1—Co1—O4^iv	166.17 (13)	O7—V1—O5^v	81.09 (14)
O2^iii—Co1—O4^iv	91.51 (11)	O5—V1—O5^v	66.81 (12)
O6—Co1—O4^iv	80.34 (11)

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

 

Footnotes

‡Permanent address: Department of Chemistry, University of Engineering and Technology, Lahore 54890, Pakistan.