Na₃Co₂(AsO₄)(As₂O₇): a new sodium cobalt arsenate.

In the title compound, tris-odium dicobalt arsenate diarsenate, Na₃Co₂AsO₄As₂O₇, the two Co atoms, one of the two As and three of the seven O atoms lie on special positions, with site symmetries 2 and m for the Co, m for the As, and 2 and twice m for the O atoms. The two Na atoms are disordered over two general and special positions [occupancies 0.72 (3):0.28 (3) and 0.940 (6):0.060 (6), respectively]. The main structural feature is the association of the CoO₆ octa-hedra in the ab plane, forming Co₄O₂₀ units, which are corner- and edge-connected via AsO₄ and As₂O₇ arsenate groups, giving rise to a complex polyhedral connectivity with small tunnels, such as those running along the b- and c-axis directions, in which the Na⁺ ions reside. The structural model is validated by both bond-valence-sum and charge-distribution methods, and the distortion of the coordination polyhedra is analyzed by means of the effective coordination number.

Related literature

For related structures, see: Ruiz-Valero et al. (1996 ▶); Ben Smail & Jouini (2005 ▶); Guesmi & Driss (2002a ▶,b ▶). For bond-valence analysis, see: Brown (2002 ▶); Adams (2003 ▶). For the charge distribution method, see: Nespolo et al. (2001 ▶); Nespolo (2001 ▶); Guesmi et al. (2006 ▶).

Experimental

Crystal data

Na3Co2(AsO4)(As2O7)

M = 587.59

Monoclinic,

a = 10.484 (3) Å

b = 16.309 (2) Å

c = 6.531 (1) Å

β = 120.40 (2)°

V = 963.2 (3) Å3

Z = 4

Mo Kα radiation

μ = 13.87 mm−1

T = 293 K

0.20 × 0.10 × 0.10 mm

Data collection

Enraf–Nonius CAD-4 diffractometer

Absorption correction: ψ scan (North et al., 1968 ▶) T min = 0.168, T max = 0.338

1765 measured reflections

1183 independent reflections

998 reflections with I > 2σ(I)

R int = 0.041

2 standard reflections every 120 min intensity decay: 1%

Refinement

R[F 2 > 2σ(F 2)] = 0.027

wR(F 2) = 0.067

S = 1.01

1183 reflections

103 parameters

Δρmax = 0.72 e Å−3

Δρmin = −0.80 e Å−3

Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1995 ▶); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995 ▶); 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: WinGX (Farrugia, 1999 ▶) and publCIF (Westrip, 2010) ▶.

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536812027791/jj2142sup1.cif

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812027791/jj2142Isup2.hkl

Supplementary material file. DOI: 10.1107/S1600536812027791/jj2142Isup3.cml

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

Na3Co2(AsO4)(As2O7)	F(000) = 1096
Mr = 587.59	Dx = 4.052 Mg m−3
Monoclinic, C2/m	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2y	Cell parameters from 25 reflections
a = 10.484 (3) Å	θ = 11.7–14.5°
b = 16.309 (2) Å	µ = 13.87 mm−1
c = 6.531 (1) Å	T = 293 K
β = 120.40 (2)°	Parallelepiped, pink
V = 963.2 (3) Å3	0.20 × 0.10 × 0.10 mm
Z = 4

Enraf–Nonius CAD-4 diffractometer	998 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.041
Graphite monochromator	θmax = 28.0°, θmin = 2.5°
ω/2θ scans	h = −13→13
Absorption correction: ψ scan (North et al., 1968)	k = −1→21
Tmin = 0.168, Tmax = 0.338	l = −8→3
1765 measured reflections	2 standard reflections every 120 min
1183 independent reflections	intensity decay: 1%

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)] = 0.027	w = 1/[σ2(Fo2) + (0.0261P)2] where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.067	(Δ/σ)max = 0.005
S = 1.01	Δρmax = 0.72 e Å−3
1183 reflections	Δρmin = −0.80 e Å−3
103 parameters	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
0 restraints	Extinction coefficient: 0.00124 (17)

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.

	x	y	z	Uiso*/Ueq	Occ. (<1)
Co1	0.5000	0.32196 (5)	1.0000	0.0091 (2)
Co2	0.29864 (9)	0.5000	0.08408 (15)	0.0090 (2)
As1	0.38970 (6)	0.5000	0.67693 (11)	0.00692 (16)
As2	0.11973 (5)	0.33430 (3)	0.76867 (8)	0.00892 (14)
O1	0.5206 (4)	0.2480 (2)	0.7535 (6)	0.0219 (8)
O2	0.2686 (3)	0.3079 (2)	0.7525 (6)	0.0173 (7)
O3	0.2608 (5)	0.5000	0.7550 (8)	0.0097 (9)
O4	0.1460 (3)	0.40124 (19)	0.9821 (6)	0.0136 (6)
O5	0.0000	0.3884 (3)	0.5000	0.0133 (9)
O6	0.5077 (3)	0.41858 (19)	0.7766 (6)	0.0126 (6)
O7	0.2869 (5)	0.5000	0.3808 (8)	0.0193 (11)
Na1A	0.1740 (18)	0.1692 (4)	0.5940 (15)	0.032 (2)	0.72 (3)
Na1B	0.225 (3)	0.1686 (13)	0.617 (4)	0.032 (2)	0.28 (3)
Na2A	0.0488 (3)	0.5000	0.2908 (8)	0.0353 (11)	0.940 (6)
Na2B	−0.021 (6)	0.5000	−0.054 (13)	0.0353 (11)	0.060 (6)

	U11	U22	U33	U12	U13	U23
Co1	0.0097 (4)	0.0075 (4)	0.0088 (4)	0.000	0.0037 (3)	0.000
Co2	0.0094 (4)	0.0105 (4)	0.0067 (4)	0.000	0.0038 (3)	0.000
As1	0.0077 (3)	0.0073 (3)	0.0047 (3)	0.000	0.0023 (2)	0.000
As2	0.0091 (2)	0.0071 (2)	0.0073 (2)	−0.00090 (15)	0.00172 (18)	0.00007 (17)
O1	0.0297 (19)	0.0157 (17)	0.015 (2)	0.0132 (15)	0.0073 (16)	−0.0024 (15)
O2	0.0091 (14)	0.0211 (18)	0.0157 (18)	0.0020 (13)	0.0018 (14)	−0.0030 (14)
O3	0.0093 (19)	0.015 (2)	0.008 (2)	0.000	0.0072 (18)	0.000
O4	0.0163 (14)	0.0152 (15)	0.0089 (15)	−0.0044 (13)	0.0061 (13)	−0.0053 (14)
O5	0.0128 (19)	0.011 (2)	0.008 (2)	0.000	−0.0008 (18)	0.000
O6	0.0114 (13)	0.0098 (14)	0.0158 (16)	0.0014 (12)	0.0064 (13)	0.0017 (13)
O7	0.014 (2)	0.040 (3)	0.004 (2)	0.000	0.005 (2)	0.000
Na1A	0.047 (6)	0.0192 (12)	0.021 (2)	0.012 (3)	0.011 (4)	−0.0034 (12)
Na1B	0.047 (6)	0.0192 (12)	0.021 (2)	0.012 (3)	0.011 (4)	−0.0034 (12)
Na2A	0.0179 (15)	0.0196 (17)	0.059 (3)	0.000	0.0126 (18)	0.000
Na2B	0.0179 (15)	0.0196 (17)	0.059 (3)	0.000	0.0126 (18)	0.000

Co1—O1	2.108 (3)	Na1A—O6viii	2.621 (11)
Co1—O1i	2.108 (3)	Na1A—O2viii	2.646 (11)
Co1—O2	2.141 (3)	Na1A—O1vii	2.682 (13)
Co1—O2i	2.141 (3)	Na1A—O4ix	2.694 (10)
Co1—O6	2.177 (3)	Na1A—O7viii	2.782 (7)
Co1—O6i	2.177 (3)	Na1A—O6vii	2.936 (13)
Co2—O3ii	1.978 (4)	Na1B—O2	2.39 (2)
Co2—O7	2.003 (5)	Na1B—O2viii	2.47 (2)
Co2—O4ii	2.126 (3)	Na1B—O4ix	2.53 (2)
Co2—O4iii	2.126 (3)	Na1B—O7viii	2.75 (2)
Co2—O6iv	2.201 (3)	Na1B—O1viii	2.83 (2)
Co2—O6v	2.201 (3)	Na1B—O6viii	2.87 (2)
As1—O3	1.669 (4)	Na2A—O7	2.257 (5)
As1—O7	1.671 (5)	Na2A—O5	2.480 (4)
As1—O6vi	1.704 (3)	Na2A—O5x	2.480 (4)
As1—O6	1.704 (3)	Na2A—O4xi	2.501 (4)
As2—O1vii	1.670 (3)	Na2A—O4x	2.501 (4)
As2—O2	1.673 (3)	Na2B—O4xi	2.27 (6)
As2—O4	1.680 (3)	Na2B—O4x	2.27 (6)
As2—O5	1.790 (2)	Na2B—O4ii	2.30 (5)
Na1A—O2	2.475 (9)	Na2B—O4iii	2.30 (5)
Na1A—O1viii	2.540 (12)	Na2B—O7xii	2.51 (5)
O1—Co1—O1i	110.2 (2)	O3ii—Co2—O6iv	94.87 (13)
O1—Co1—O2	82.94 (14)	O7—Co2—O6iv	95.48 (14)
O1i—Co1—O2	90.01 (14)	O4ii—Co2—O6iv	93.63 (12)
O1—Co1—O2i	90.01 (14)	O4iii—Co2—O6iv	167.77 (12)
O1i—Co1—O2i	82.94 (14)	O3ii—Co2—O6v	94.87 (13)
O2—Co1—O2i	167.7 (2)	O7—Co2—O6v	95.48 (14)
O1—Co1—O6	81.33 (13)	O4ii—Co2—O6v	167.77 (12)
O1i—Co1—O6	168.19 (14)	O4iii—Co2—O6v	93.63 (12)
O2—Co1—O6	89.07 (13)	O6iv—Co2—O6v	74.22 (16)
O2i—Co1—O6	99.88 (13)	O3—As1—O7	101.9 (2)
O1—Co1—O6i	168.19 (14)	O3—As1—O6vi	115.27 (14)
O1i—Co1—O6i	81.33 (13)	O7—As1—O6vi	111.14 (15)
O2—Co1—O6i	99.88 (13)	O3—As1—O6	115.27 (14)
O2i—Co1—O6i	89.07 (13)	O7—As1—O6	111.14 (14)
O6—Co1—O6i	87.23 (18)	O6vi—As1—O6	102.4 (2)
O3ii—Co2—O7	167.01 (18)	O1vii—As2—O2	111.18 (19)
O3ii—Co2—O4ii	87.38 (12)	O1vii—As2—O4	114.04 (17)
O7—Co2—O4ii	84.15 (12)	O2—As2—O4	116.98 (16)
O3ii—Co2—O4iii	87.38 (12)	O1vii—As2—O5	103.39 (16)
O7—Co2—O4iii	84.15 (12)	O2—As2—O5	106.19 (13)
O4ii—Co2—O4iii	98.49 (17)	O4—As2—O5	103.43 (16)

Cation	q(i).sof(i)	V(i)	Q(i)	CN(i)	ECoN(i)	dmoy(i)	dmed(i)
Co1	2.00	1.87	2.01	6	5.97	2.14	2.14
Co2	2.00	2.05	2.03	6	5.62	2.11	2.08
As1	5.00	4.99	5.13	4	3.99	1.69	1.69
As2	5.00	4.93	4.94	4	3.89	1.70	1.69
Na1A	0.72	0.65	0.72	8	7.33	2.67	2.63
Na1B	0.28	0.25	0.27	8	5.72	2.74	2.58
Na2A	0.94	1.02	0.92	7	5.52	2.58	2.45
Na2B	0.06	0.07	0.06	6	4.78	2.45	2.31

Table 1

Bond-valence-sum and charge distribution analysis

Cation	q(i)·sof(i)	V(i)	Q(i)	CN(i)	ECoN(i)	d moy(i)	d med(i)
Co1	2.00	1.87	2.01	6	5.97	2.14	2.14
Co2	2.00	2.05	2.03	6	5.62	2.11	2.08
As1	5.00	4.99	5.13	4	3.99	1.69	1.69
As2	5.00	4.93	4.94	4	3.89	1.70	1.69
Na1A	0.72	0.65	0.72	8	7.33	2.67	2.63
Na1B	0.28	0.25	0.27	8	5.72	2.74	2.58
Na2A	0.94	1.02	0.92	7	5.52	2.58	2.45
Na2B	0.06	0.07	0.06	6	4.78	2.45	2.31

q(i) = formal oxidation number; sof(i) = site occupation factor; d moy(i) = arithmetic average distance (Å); d med(i) = weighted average distance (Å); sodium CNS for d(Na—O)max = 3.10 Å; σcat = dispersion factor on cationic charges measuring the deviation of the computed charges (Q) with respect to the formal oxidation numbers; σcat = [Σ(q −Q )2/N−1]1/2 = 0.055.