Manganese(II) sulfate tetrahydrate (ilesite)

The title compound, Mn(SO₄)·4H₂O, contains centrosymmetric bis(μ-sulfato-O:O′)­bis­[tetra­aqua­manganese(II)] di­mers, with two cis-located bridging sulfate anions and two coordination octahedra around manganese(II) forming eight-membered rings. The manganese cations are surrounded by six O atoms of four water mol­ecules and two sulfate groups, forming a slightly distorted octahedron. The [Mn(H₂O)₄(SO₄)]₂ rings are linked by hydrogen bonds of weak to medium strength.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](S-O) = 0.002 Å
• R factor = 0.027
• wR factor = 0.073
• Data-to-parameter ratio = 16.3

checkCIF results

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S1. Comment

The tetrahydrates of the sulfates of the divalent cations, Mg, Mn and Fe, were synthesized and morphologically described by the middle of the 19t h century (for a summary, see Groth, 1908). The first X-ray single-crystal structure determination of the Mg and Fe compound was achieved by Baur (1962), followed by a detailed neutron diffraction structure analysis of a single-crystal of the Mg compound (Baur, 1964). About 30 years later, the structure of the Co member was determined (Kellersohn, 1992) and recently the structure of Zn(SO₄)·4H₂O was published (Blake et al., 2001; annotated by Baur, 2002). All the tetrahydrates mentioned above are isostructural. In this paper we present the structure of MnSO₄·4H₂O, (I), whose isostructurality was predicted by Baur (2002). The manganese compound exists also in nature with the mineralogical name ilesite, which belongs to the starkeyite group (Strunz & Nickel, 2001). The authors already mentioned emphasize that tetrahydrates are unstable in air, but can easily stored for months in inert liquids such as paraffin oil without decomposition. We observed that after the decomposition has started on the crystal surface, the dehydration cannot be stopped without taking steps against such as controlled humidity or passivation.

The crystallization of MnSO₄·4H₂O from an aqueous solution of sulfuric acid, manganese sulfate monohydrate and ethylenediamine in the molar ratio 1:1:1 was not expected (in our search of double sulfates of ethylenediammonium and divalent cations). The heating up to 340 K of the solution attending the neutralization reaction of sulfuric acid and ethylenediamine underlies the synthesis of the title compound. The crystal consists of dimers containing two [Mn(H₂O)₄(SO₄)] units related by a centre of symmetry and forming an eight-membered ring (Fig. 1). The manganese cations are surrounded by six oxygen atoms of four water molecules and two sulfate groups in the form of an almost ideal octahedron. The obvious deviation from ideal geometry is expressed in the enlargement of the Mn—O5 distance accompanied by a decrease in the Mn—O6 distance. In the dimer, the manganese cations are separated by a distance of 4.5464 (7) Å. The tetrahedral configuration of the sulfate atoms is almost ideal, although two oxygen atoms (O3, O4) do not take part in the dimer formation. The bis(µ-sulfato-O:O')bis[tetraaquamanganese(II)] rings are interconnected via hydrogen bonds of medium strength in the range of 2.740 (2) to 2.857 (3) Å (with the exception of the intramolecular O6—H62···O2) forming a three-dimensional body-centred framework (Fig.2). An analogous hydrogen bonding system was found in the Mg, Fe and Co sulfate tetrahydrates (for schematic presentation see Baur, 1964), whereas the hydrogen-bonding data reported for the Zn compound are not convincing, because the hydrogen-bond length was constrained in the refinement calculation. The existence of the O6—H62···O2 hydrogen bond was discussed in detail in early works. Baur (1962, 1964) negates the formation because of unfavourable geometric parameters in combination with a large thermal vibration amplitude of H62. We agree with Kellersohn (1992) in including H62 in the hydrogen-bonding scheme, because of bond-valence considerations and the calculations he presents. Moreover it is not possible to decide whether one or both bifurcating hydrogen-bonds to two symmetrically equivalent O2 atoms exist. The first one reinforces the ring construction as a intra-dimer bond, the second one interconnects two different dimers. Owing to the abundance of examples, we are inclined to extend the geometric criteria for the existence of a hydrogen bond, but in the end this has to be confirmed in combination with vibrational spectroscopic studies.

Computing details

Data collection: MACH3 (Nonius, 1993); cell refinement: MACH3; data reduction: MolEN (Fair, 1990); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ATOMS (Dowty, 2002) and ORTEPIII (Johnson, 1996); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. : ORTEP projection parallel to (100) of the title compound, with the atom-numbering scheme. Non-H atoms are shown as 50% probability ellipsoids. [Symmetry code: (i): −x, −y, −z.]
	Fig. 2. : Foreshortened (100) projection of the title compound, showing [SO4] tetrahedra (yellow), [Mn(H2O)4O2] octahedra (orange), oxygen (blue) and hydrogen (light grey) atoms. Hydrogen bonds (grey lines) interlink different dimers.

manganese(II) sulfate tetrahydrate

Crystal data

(Mn^2+)·(SO4^2^−)·4(H2O)	F(000) = 452
Mr = 223.06	Dx = 2.230 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 25 reflections
a = 5.9783 (6) Å	θ = 12.6–18.5°
b = 13.809 (1) Å	µ = 2.30 mm^−1
c = 8.0481 (7) Å	T = 293 K
β = 90.80 (1)°	Parallelepiped, pale red
V = 664.4 (1) Å^3	0.19 × 0.18 × 0.16 mm
Z = 4

Data collection

Nonius MACH3 diffractometer	1425 reflections with I > 2σ(I)
Radiation source: fine-focus sealed X-ray tube	Rint = 0.047
Graphite monochromator	θmax = 30.4°, θmin = 2.9°
ω/2θ scans	h = −8→8
Absorption correction: ψ scan MolEN (Nonius, 1990)	k = −19→19
Tmin = 0.644, Tmax = 0.692	l = −11→11
6258 measured reflections	3 standard reflections every 100 reflections
2026 independent reflections	intensity decay: 0.7%

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)] = 0.027	All H-atom parameters refined
wR(F^2) = 0.073	w = 1/[σ^2(Fo^2) + (0.0366P)^2 + 0.1046P] where P = (Fo^2 + 2Fc^2)/3
S = 1.05	(Δ/σ)max < 0.001
2026 reflections	Δρmax = 0.52 e Å^−3
124 parameters	Δρmin = −0.50 e Å^−3
0 restraints	Extinction correction: SHELXL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.041 (2)

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
Mn	0.06667 (5)	0.10261 (2)	0.21594 (4)	0.01747 (11)
S	0.20032 (8)	0.10849 (3)	0.82188 (6)	0.01560 (12)
O1	0.0109 (3)	0.05008 (11)	0.7552 (2)	0.0234 (3)
O2	0.2564 (3)	0.07572 (12)	0.99251 (18)	0.0239 (3)
O3	0.3984 (3)	0.09375 (12)	0.7163 (2)	0.0239 (3)
O4	0.1356 (3)	0.21082 (11)	0.82053 (19)	0.0237 (3)
O5	0.3669 (3)	0.07319 (14)	0.3593 (2)	0.0289 (4)
O6	0.7558 (3)	0.14361 (16)	0.0858 (2)	0.0304 (4)
O7	0.8842 (4)	0.12756 (16)	0.4446 (2)	0.0341 (4)
O8	0.1848 (3)	0.25134 (12)	0.2205 (2)	0.0274 (4)
H51	0.368 (6)	0.083 (3)	0.450 (5)	0.051 (11)*
H52	0.460 (6)	0.027 (3)	0.330 (4)	0.049 (10)*
H61	0.672 (7)	0.185 (3)	0.133 (5)	0.069 (13)*
H62	0.675 (7)	0.105 (3)	0.043 (5)	0.063 (13)*
H71	0.820 (5)	0.176 (2)	0.448 (4)	0.030 (8)*
H72	0.907 (7)	0.112 (3)	0.535 (5)	0.058 (12)*
H81	0.279 (7)	0.262 (3)	0.282 (4)	0.056 (11)*
H82	0.096 (6)	0.299 (3)	0.225 (4)	0.045 (10)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Mn	0.02056 (17)	0.01551 (16)	0.01631 (15)	−0.00034 (13)	−0.00026 (11)	−0.00003 (12)
S	0.0184 (2)	0.0134 (2)	0.0151 (2)	−0.00058 (18)	0.00095 (17)	−0.00009 (17)
O1	0.0264 (8)	0.0175 (7)	0.0260 (8)	−0.0053 (6)	−0.0048 (6)	0.0007 (6)
O2	0.0301 (9)	0.0256 (8)	0.0159 (7)	0.0044 (7)	−0.0008 (6)	0.0012 (6)
O3	0.0231 (8)	0.0254 (8)	0.0234 (7)	0.0008 (7)	0.0089 (6)	−0.0014 (6)
O4	0.0271 (8)	0.0139 (7)	0.0301 (8)	0.0008 (6)	−0.0006 (6)	−0.0002 (6)
O5	0.0268 (9)	0.0335 (9)	0.0262 (9)	0.0083 (8)	−0.0069 (7)	−0.0032 (7)
O6	0.0277 (9)	0.0355 (10)	0.0278 (9)	0.0028 (8)	−0.0048 (7)	−0.0026 (8)
O7	0.0467 (12)	0.0355 (10)	0.0201 (8)	0.0187 (9)	0.0065 (8)	0.0019 (7)
O8	0.0255 (9)	0.0188 (8)	0.0378 (10)	0.0006 (7)	−0.0046 (7)	−0.0036 (7)

Geometric parameters (Å, º)

Mn—O5	2.1585 (18)	S—O1	1.4847 (16)
Mn—O2^i	2.1713 (16)	O5—H51	0.74 (4)
Mn—O1^ii	2.1721 (16)	O5—H52	0.88 (4)
Mn—O8	2.1721 (17)	O6—H61	0.85 (4)
Mn—O7^iii	2.1799 (19)	O6—H62	0.79 (4)
Mn—O6^iii	2.1949 (19)	O7—H71	0.77 (3)
S—O4	1.4650 (16)	O7—H72	0.77 (4)
S—O2	1.4799 (15)	O8—H81	0.76 (4)
S—O3	1.4811 (16)	O8—H82	0.85 (4)
O5—Mn—O1^ii	86.40 (7)	O8—Mn—O7^iii	90.17 (8)
O5—Mn—O2^i	88.30 (7)	O8—Mn—O6^iii	92.12 (8)
O5—Mn—O6^iii	174.75 (8)	O7^iii—Mn—O6^iii	86.08 (8)
O5—Mn—O7^iii	90.05 (8)	O4—S—O1	108.74 (10)
O5—Mn—O8	84.33 (7)	O4—S—O2	110.99 (9)
O2^i—Mn—O1^ii	92.15 (6)	O4—S—O3	109.97 (9)
O2^i—Mn—O8	90.12 (7)	O2—S—O3	108.52 (10)
O2^i—Mn—O7^iii	178.29 (7)	O2—S—O1	109.34 (10)
O2^i—Mn—O6^iii	95.60 (7)	O3—S—O1	109.26 (10)
O1^ii—Mn—O8	170.39 (7)	S—O1—Mn^ii	130.66 (10)
O1^ii—Mn—O7^iii	87.30 (7)	S—O2—Mn^iv	127.02 (10)
O1^ii—Mn—O6^iii	96.94 (7)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O5—H51···O3	0.74 (4)	2.16 (4)	2.891 (2)	172 (4)
O5—H52···O3^v	0.88 (4)	1.91 (4)	2.771 (3)	166 (3)
O6—H61···O4^vi	0.85 (4)	2.10 (4)	2.857 (3)	148 (4)
O6—H62···O2^v	0.79 (4)	2.55 (4)	3.094 (3)	127 (4)
O6—H62···O2^i	0.79 (4)	2.57 (4)	3.208 (3)	140 (4)
O7—H71···O4^vi	0.77 (3)	2.16 (3)	2.854 (3)	149 (3)
O7—H72···O1^vii	0.77 (4)	2.05 (4)	2.813 (2)	169 (4)
O8—H81···O4^vi	0.76 (4)	2.18 (4)	2.850 (3)	147 (4)
O8—H82···O3^viii	0.85 (4)	1.89 (4)	2.740 (2)	175 (3)

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