Composé à charpente bidimensionnelle K₃Fe₃(AsO₄)₄

Tripotassium triiron(III) tetraarsenate, K₃Fe₃(AsO₄)₄, has been synthesized at high temperature by solid-state reaction. The structure is built up from corner- and edge-sharing between FeO₆ octahedra and AsO₄ tetrahedra. The structure can be described as infinite anionic layers parallel to the (010) plane. Alkali metal cations are located in the interlayer space. The relationship between the title compound and K₃Fe₃(PO₄)₄·H₂O structures is discussed. The title compound is isostructural with K₃Cr₃(AsO₄)₄.

Key indicators

• Single-crystal X-ray study
• T = 298 K
• Mean [sigma](e-O) = 0.005 Å
• Disorder in main residue
• R factor = 0.040
• wR factor = 0.102
• Data-to-parameter ratio = 10.1

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT041_ALERT_1_C Calc. and Rep. SumFormula Strings    Differ ....          ?
PLAT042_ALERT_1_C Calc. and Rep. MoietyFormula Strings Differ ....          ?
PLAT045_ALERT_1_C Calculated and Reported Z Differ by ............       0.25 Ratio
PLAT066_ALERT_1_C Predicted and Reported Transmissions Identical .          ?
PLAT220_ALERT_2_C Large Non-Solvent    O     Ueq(max)/Ueq(min) ...       3.10 Ratio
PLAT301_ALERT_3_C Main Residue  Disorder .........................       1.00 Perc.
PLAT302_ALERT_4_C Anion/Solvent Disorder .........................      20.00 Perc.

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

   4 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
   1 ALERT type 4 Improvement, methodology, query or suggestion

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Computing details

Data collection: CAD-4 EXPRESS (Duisenberg, 1992; Macíček & Yordanov, 1992; Enraf–Nonius, 1994); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg, 1998); software used to prepare material for publication: SHELXL97 and WinGX (Farrugia, 1999).

tripotassium triiron(III) tetraarsenate

Crystal data

K3Fe3(AsO4)4	F(000) = 1580
Mr = 840.53	Dx = 3.594 Mg m^−3
Orthorhombic, Cmca	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2bc 2	Cell parameters from 25 reflections
a = 10.898 (2) Å	θ = 11.5–14.2°
b = 21.521 (5) Å	µ = 12.11 mm^−1
c = 6.623 (2) Å	T = 298 K
V = 1553.3 (7) Å^3	Parallelepiped, green
Z = 4	0.18 × 0.08 × 0.02 mm

Data collection

Enraf–Nonius CAD-4 diffractometer	714 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.026
Graphite monochromator	θmax = 27.0°, θmin = 3.6°
ω/2θ scans	h = −2→13
Absorption correction: psi scan (North et al., 1968)	k = 0→27
Tmin = 0.325, Tmax = 0.785	l = 0→8
1074 measured reflections	2 standard reflections every 120 min
893 independent reflections	intensity decay: 1%

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.040	w = 1/[σ^2(Fo^2) + (0.0275P)^2 + 68.5196P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.102	(Δ/σ)max < 0.001
S = 1.08	Δρmax = 1.62 e Å^−3
893 reflections	Δρmin = −1.65 e Å^−3
88 parameters	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
2 restraints	Extinction coefficient: 0.00122 (8)

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	Occ. (<1)
As1	0.0000	0.15191 (5)	0.07045 (18)	0.0132 (3)
As2	0.2500	−0.04411 (5)	0.2500	0.0086 (3)
Fe1	0.0000	0.0000	0.0000	0.0177 (5)
Fe2	0.2500	0.08971 (7)	0.2500	0.0141 (4)
O1	0.0000	0.0870 (3)	−0.0712 (12)	0.0142 (16)
O2	0.1377 (5)	0.0110 (2)	0.2059 (7)	0.0100 (11)
O3	0.2142 (5)	−0.0882 (2)	0.4490 (8)	0.0127 (11)
O4	0.1235 (5)	0.1506 (2)	0.2261 (9)	0.0174 (12)
O5	0.0000	0.2139 (4)	−0.0758 (15)	0.031 (2)
K1	0.0000	0.1642 (3)	−0.4271 (8)	0.0422 (15)	0.614 (9)
K2	0.2269 (15)	0.2700 (6)	0.122 (2)	0.0422 (15)	0.193 (4)
K3	−0.087 (3)	0.1860 (15)	−0.420 (5)	0.052 (4)	0.087 (5)
K4	0.2500	0.2715 (10)	0.2500	0.052 (4)	0.199 (10)
K5	0.2500	0.2500	0.0000	0.052 (4)	0.091 (8)
K6	0.0000	−0.047 (5)	0.478 (19)	0.052 (4)	0.036 (9)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
As1	0.0096 (5)	0.0118 (5)	0.0182 (6)	0.000	0.000	0.0034 (5)
As2	0.0106 (5)	0.0097 (5)	0.0056 (5)	0.000	−0.0005 (4)	0.000
Fe1	0.0156 (12)	0.0207 (12)	0.0168 (12)	0.000	0.000	0.0000 (10)
Fe2	0.0131 (8)	0.0160 (8)	0.0131 (8)	0.000	−0.0008 (7)	0.000
O1	0.013 (4)	0.014 (4)	0.015 (4)	0.000	0.000	0.003 (3)
O2	0.009 (2)	0.009 (2)	0.012 (3)	0.002 (2)	−0.002 (2)	−0.001 (2)
O3	0.015 (3)	0.014 (2)	0.009 (2)	−0.006 (2)	−0.002 (2)	0.004 (2)
O4	0.012 (3)	0.019 (3)	0.022 (3)	0.001 (2)	−0.003 (2)	−0.005 (2)
O5	0.038 (6)	0.020 (5)	0.036 (6)	0.000	0.000	0.018 (4)
K1	0.060 (4)	0.041 (3)	0.025 (2)	0.000	0.000	−0.002 (2)
K2	0.060 (4)	0.041 (3)	0.025 (2)	0.000	0.000	−0.002 (2)
K3	0.050 (9)	0.045 (9)	0.062 (12)	−0.017 (12)	0.011 (9)	0.005 (12)
K4	0.050 (9)	0.045 (9)	0.062 (12)	−0.017 (12)	0.011 (9)	0.005 (12)
K5	0.050 (9)	0.045 (9)	0.062 (12)	−0.017 (12)	0.011 (9)	0.005 (12)
K6	0.050 (9)	0.045 (9)	0.062 (12)	−0.017 (12)	0.011 (9)	0.005 (12)

Geometric parameters (Å, º)

As1—O5	1.649 (8)	K1—O3^iii	2.854 (6)
As1—O1	1.683 (8)	K1—O3^iv	2.854 (6)
As1—O4	1.696 (6)	K2—O4	2.891 (14)
As1—O4^i	1.696 (6)	K2—O5^x	3.012 (16)
As2—O3^ii	1.670 (5)	K3—O4^vii	2.50 (4)
As2—O3	1.670 (5)	K3—O3^iii	2.53 (3)
As2—O2^ii	1.729 (5)	K3—O5	2.54 (4)
As2—O2	1.729 (5)	K3—O5^ix	2.57 (3)
Fe1—O1^iii	1.931 (7)	K4—O4	2.950 (19)
Fe1—O1	1.931 (7)	K4—O4^ii	2.950 (19)
Fe1—O2^iii	2.041 (5)	K4—O5^x	2.975 (4)
Fe1—O2	2.041 (5)	K4—O5^xi	2.975 (4)
Fe1—O2^iv	2.041 (5)	K5—O5^x	2.877 (3)
Fe1—O2^i	2.041 (5)	K5—O5	2.877 (3)
Fe2—O4^ii	1.908 (6)	K5—O4^x	2.953 (6)
Fe2—O4	1.908 (6)	K5—O4	2.953 (6)
Fe2—O3^v	2.032 (5)	K6—O3	2.50 (4)
Fe2—O3^vi	2.032 (5)	K6—O3^i	2.50 (4)
Fe2—O2	2.110 (5)	K6—O2^i	2.66 (10)
Fe2—O2^ii	2.110 (5)	K6—O2	2.66 (10)
K1—O5	2.561 (12)	K6—O2^vi	2.69 (11)
K1—O4^vii	2.678 (8)	K6—O2^xii	2.69 (11)
K1—O4^viii	2.678 (8)	K6—O1^iii	2.83 (13)
K1—O5^ix	2.802 (11)
O5—As1—O1	110.2 (4)	O2—Fe1—O2^iv	85.4 (3)
O5—As1—O4	111.8 (3)	O1^iii—Fe1—O2^i	87.1 (2)
O1—As1—O4	108.9 (2)	O1—Fe1—O2^i	92.9 (2)
O5—As1—O4^i	111.8 (3)	O2^iii—Fe1—O2^i	85.4 (3)
O1—As1—O4^i	108.9 (2)	O2—Fe1—O2^i	94.6 (3)
O4—As1—O4^i	105.1 (4)	O2^iv—Fe1—O2^i	180.0 (4)
O3^ii—As2—O3	110.8 (4)	O4^ii—Fe2—O4	93.3 (3)
O3^ii—As2—O2^ii	110.9 (2)	O4^ii—Fe2—O3^v	87.3 (2)
O3—As2—O2^ii	114.9 (2)	O4—Fe2—O3^v	94.0 (2)
O3^ii—As2—O2	114.9 (2)	O4^ii—Fe2—O3^vi	94.0 (2)
O3—As2—O2	110.9 (2)	O4—Fe2—O3^vi	87.3 (2)
O2^ii—As2—O2	93.4 (3)	O3^v—Fe2—O3^vi	178.1 (3)
O1^iii—Fe1—O1	180.0 (5)	O4^ii—Fe2—O2	169.0 (2)
O1^iii—Fe1—O2^iii	92.9 (2)	O4—Fe2—O2	96.9 (2)
O1—Fe1—O2^iii	87.1 (2)	O3^v—Fe2—O2	87.9 (2)
O1^iii—Fe1—O2	87.1 (2)	O3^vi—Fe2—O2	90.6 (2)
O1—Fe1—O2	92.9 (2)	O4^ii—Fe2—O2^ii	96.9 (2)
O2^iii—Fe1—O2	180.0 (4)	O4—Fe2—O2^ii	169.0 (2)
O1^iii—Fe1—O2^iv	92.9 (2)	O3^v—Fe2—O2^ii	90.6 (2)
O1—Fe1—O2^iv	87.1 (2)	O3^vi—Fe2—O2^ii	87.9 (2)
O2^iii—Fe1—O2^iv	94.6 (3)	O2—Fe2—O2^ii	73.2 (3)

Symmetry codes: (i) −x, y, z; (ii) −x+1/2, y, −z+1/2; (iii) −x, −y, −z; (iv) x, −y, −z; (v) −x+1/2, −y, z−1/2; (vi) x, −y, −z+1; (vii) −x, y, z−1; (viii) x, y, z−1; (ix) −x, −y+1/2, z−1/2; (x) −x+1/2, −y+1/2, −z; (xi) −x, −y+1/2, z+1/2; (xii) −x, −y, −z+1.