Redetermination of the mixed-valence manganese arsenate flinkite, Mn^II₂Mn^III(OH)₄(AsO₄)

The crystal structure of the rare mixed-valence manganese(II,III) arsenate mineral flinkite [dimanganese(II) manganese(III) arsenate tetra­hydro­xide], Mn^II₂Mn^III(OH)₄(AsO₄) has been redetermined from single-crystal X-ray data. The previously unknown positions of both H atoms could be identified. Flinkite contains one unique Mn^IIIO₂(OH)₄ polyhedron with a Jahn-Teller-distorted [4+2]-coordination of Mn^III, one Mn^IIO₃(OH)₃ octahedron, and one fairly regular AsO₄ tetrahedron. Atoms on special sites are Mn1 (site symmetry ), As, O4 and O5 (all with site symmetry .m.). The structure is based upon pyrochroite [Mn(OH)₂]-type sheets of edge-sharing Mn(O,OH)₆ octahedra parallel to (100). Some Mn(O,OH)₆ octahedra are omitted to allow AsO₄ tetrahedra to connect the sheets via shared corners. Additional strong hydrogen bonds between the sheets provide further strengthening. Relations to the structures of antlerite, Cu₃(SO₄)(OH)₄, synthetic Cu₃(SeO₄)(OH)₄, synthetic Cu₃(CrO₄)(OH)₄, and szenicsite, Cu₃(MoO₄)(OH)₄, are pointed out.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](Mn-O) = 0.002 Å
• R factor = 0.018
• wR factor = 0.055
• Data-to-parameter ratio = 14.3

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level B:



PLAT_420  Alert B D-H Without Acceptor       OH1    -   H1                ?


 0 Alert Level A = Potentially serious problem

 1 Alert Level B = Potential problem

 0 Alert Level C = Please check

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Computing details

Data collection: COLLECT (Nonius, 2001); cell refinement: HKL SCALEPACK (Otwinowski & Minor, 1997); data reduction: HKL DENZO (Otwinowski & Minor, 1997) and SCALEPACK; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ATOMS (Shape Software, 1999) and ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: SHELXL97.

dimanganese(II) manganese(III) arsenate tetrahydroxide ?

Crystal data

Mn3(OH)4(AsO4)	Dx = 3.743 Mg m^−3
Mr = 371.77	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pnma	Cell parameters from 1212 reflections
a = 9.483 (2) Å	θ = 2.5–29.9°
b = 13.030 (3) Å	µ = 10.64 mm^−1
c = 5.339 (1) Å	T = 293 K
V = 659.7 (2) Å^3	Fragment, red–brown
Z = 4	0.10 × 0.06 × 0.05 mm
F(000) = 704

Data collection

Nonius KappaCCD diffractometer	1002 independent reflections
Radiation source: fine-focus sealed tube	969 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.011
ψ and ω scans	θmax = 30.0°, θmin = 3.1°
Absorption correction: multi-scan (HKL SCALEPACK; Otwinowski & Minor, 1997)	h = −13→13
Tmin = 0.416, Tmax = 0.618	k = −18→18
1785 measured reflections	l = −7→7

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.018	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.055	w = 1/[σ^2(Fo^2) + (0.03P)^2 + 1.5P] where P = (Fo^2 + 2Fc^2)/3
S = 1.00	(Δ/σ)max < 0.001
1002 reflections	Δρmax = 0.81 e Å^−3
70 parameters	Δρmin = −0.52 e Å^−3
2 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0084 (6)

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
Mn1	0.0000	0.0000	0.0000	0.00784 (12)
Mn2	0.02051 (3)	0.13025 (3)	0.48313 (6)	0.01049 (11)
As	0.15431 (3)	0.7500	0.02622 (5)	0.00615 (11)
OH1	0.14134 (14)	0.08274 (11)	0.1580 (3)	0.0106 (3)
O2	−0.09358 (16)	0.14410 (11)	0.8279 (3)	0.0115 (3)
OH3	−0.09925 (15)	0.00406 (10)	0.3108 (3)	0.0092 (3)
O4	0.1032 (2)	0.7500	0.7226 (4)	0.0121 (4)
O5	0.1677 (2)	0.2500	0.5548 (4)	0.0106 (4)
H1	0.160 (4)	0.128 (2)	0.045 (5)	0.030*
H3	−0.185 (2)	0.021 (2)	0.302 (6)	0.030*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Mn1	0.0076 (2)	0.0095 (2)	0.0065 (2)	−0.00051 (14)	0.00026 (13)	−0.00132 (13)
Mn2	0.01290 (18)	0.00879 (18)	0.00977 (17)	−0.00048 (11)	0.00050 (10)	−0.00059 (10)
As	0.00659 (16)	0.00550 (16)	0.00636 (15)	0.000	0.00033 (8)	0.000
OH1	0.0099 (6)	0.0111 (6)	0.0108 (6)	−0.0015 (5)	0.0003 (5)	−0.0009 (5)
O2	0.0151 (7)	0.0091 (6)	0.0104 (6)	0.0035 (5)	0.0025 (5)	−0.0013 (5)
OH3	0.0077 (6)	0.0109 (6)	0.0089 (6)	0.0014 (5)	0.0009 (5)	−0.0006 (5)
O4	0.0170 (10)	0.0110 (9)	0.0084 (8)	0.000	−0.0027 (8)	0.000
O5	0.0062 (9)	0.0090 (9)	0.0166 (10)	0.000	0.0009 (7)	0.000

Geometric parameters (Å, º)

Mn1—OH3^i	1.9085 (14)	As—O2^iv	1.6858 (14)
Mn1—OH3	1.9085 (14)	As—O2^vi	1.6858 (14)
Mn1—OH1^i	1.9158 (14)	As—O4^ii	1.692 (2)
Mn1—OH1	1.9158 (14)	As—O5^vii	1.695 (2)
Mn1—O2^ii	2.2709 (15)	OH1—H1	0.857 (18)
Mn1—O2^iii	2.2709 (15)	O2—As^iv	1.6858 (14)
Mn1—Mn2	3.0938 (6)	O2—Mn1^viii	2.2709 (15)
Mn1—Mn2^i	3.0938 (6)	OH3—Mn2^iii	2.1977 (15)
Mn2—O5	2.1280 (14)	OH3—H3	0.844 (18)
Mn2—O2	2.1430 (15)	O4—As^viii	1.692 (2)
Mn2—OH1	2.1702 (15)	O4—Mn2^vi	2.2399 (15)
Mn2—OH3^iii	2.1977 (15)	O4—Mn2^iv	2.2399 (15)
Mn2—OH3	2.1999 (15)	O5—As^ix	1.695 (2)
Mn2—O4^iv	2.2399 (15)	O5—Mn2^v	2.1280 (14)
Mn2—Mn2^v	3.1208 (10)
OH3^i—Mn1—OH3	180.00 (11)	OH1—Mn2—O4^iv	94.76 (7)
OH3^i—Mn1—OH1^i	86.94 (6)	OH3^iii—Mn2—O4^iv	167.98 (6)
OH3—Mn1—OH1^i	93.06 (6)	OH3—Mn2—O4^iv	92.59 (6)
OH3^i—Mn1—OH1	93.06 (6)	O2^iv—As—O2^vi	109.88 (10)
OH3—Mn1—OH1	86.94 (6)	O2^iv—As—O4^ii	110.16 (6)
OH1^i—Mn1—OH1	180.00 (12)	O2^vi—As—O4^ii	110.16 (6)
OH3^i—Mn1—O2^ii	82.18 (6)	O2^iv—As—O5^vii	107.38 (7)
OH3—Mn1—O2^ii	97.82 (6)	O2^vi—As—O5^vii	107.38 (7)
OH1^i—Mn1—O2^ii	90.79 (6)	O4^ii—As—O5^vii	111.82 (11)
OH1—Mn1—O2^ii	89.21 (6)	Mn1—OH1—H1	103 (2)
OH3^i—Mn1—O2^iii	97.82 (6)	Mn2—OH1—H1	118 (2)
OH3—Mn1—O2^iii	82.18 (6)	As^iv—O2—Mn2	129.66 (8)
OH1^i—Mn1—O2^iii	89.21 (6)	As^iv—O2—Mn1^viii	128.57 (8)
OH1—Mn1—O2^iii	90.79 (6)	Mn2—O2—Mn1^viii	94.62 (5)
O2^ii—Mn1—O2^iii	180.00 (4)	Mn1—OH3—Mn2^iii	104.22 (6)
O5—Mn2—O2	96.59 (7)	Mn1—OH3—Mn2	97.45 (6)
O5—Mn2—OH1	90.39 (7)	Mn2^iii—OH3—Mn2	102.15 (6)
O2—Mn2—OH1	167.90 (6)	Mn1—OH3—H3	116 (2)
O5—Mn2—OH3^iii	105.73 (6)	Mn2^iii—OH3—H3	124 (2)
O2—Mn2—OH3^iii	78.97 (5)	Mn2—OH3—H3	109 (2)
OH1—Mn2—OH3^iii	89.65 (6)	As^viii—O4—Mn2^vi	128.31 (6)
O5—Mn2—OH3	164.11 (7)	As^viii—O4—Mn2^iv	128.31 (6)
O2—Mn2—OH3	99.30 (5)	Mn2^vi—O4—Mn2^iv	88.31 (8)
OH1—Mn2—OH3	74.03 (5)	As^ix—O5—Mn2	129.56 (6)
OH3^iii—Mn2—OH3	77.85 (6)	As^ix—O5—Mn2^v	129.56 (6)
O5—Mn2—O4^iv	85.46 (6)	Mn2—O5—Mn2^v	94.32 (8)
O2—Mn2—O4^iv	95.63 (7)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
OH3—H3···OH1^x	0.84 (2)	1.85 (2)	2.670 (2)	165 (3)

Symmetry code: (x) x−1/2, y, −z+1/2.