inorganic compounds
Dilithium hexahydroxidostannate(IV) dihydrate, a second monoclinic modification with a layer structure
aInstitut für Chemie neuer Materialien, Strukturchemie, Universität Osnabrück, Barbarastrasse 7, D-49069 Osnabrück, Germany
*Correspondence e-mail: hreuter@uos.de
The title compound, Li2[Sn(OH)6]·2H2O, is dimorphic. As for the previously described α-modification, the title β-modification crystallizes in the monoclinic system and contains the same primary building units, viz [Sn(OH)6]2− octahedra and [Li(μ2-OH)3(H2O)] tetrahedra. In contrast to the Sn—O bond lengths that are very similar in both modifications, the Li—O bond lengths differ significantly, in particular those involving the water molecule. In the new β-modification, the primary building units are linked into layers parallel to (010). The [Sn(OH)6]2− octahedra (-1 symmetry) form hexagonal nets and the [Li(μ2-OH)3(H2O)] tetrahedra are situated in between, with their apices in an alternating fashion up and down. O—H⋯O hydrogen bonds between OH groups and water molecules exist within the layers as well as between them.
Related literature
For background to the structures of M2[Sn(OH)6] with M = Na, K, see: Jacobs & Stahl (2000). For literature on Li2[Sn(OH)6]·nH2O, see: Reuter & Bargon (1997) for n = 2; Yang et al. (2001) for n = 0. For M[Sn(OH)6] compounds (M = divalent metal), see: Strunz & Nickel (2001); Basciano et al. (1998).
Experimental
Crystal data
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Refinement
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Data collection: APEX2 (Bruker, 2009); cell SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2006) and Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).
Supporting information
https://doi.org/10.1107/S1600536813008416/wm2733sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536813008416/wm2733Isup2.hkl
In a typical experiment, equimolar amounts of freshly prepared K2[Sn(OH)6] and LiNO3 were dissolved as far as possible in 15 ml H2O2 (15%wt). Undissolved reagents were removed by centrifugation before the solvent was allowed to evaporate slowly. Compact, colorless single crystals of the title compound were formed during some weeks.
Hydrogen atoms were clearly identified in difference Fourier syntheses. Their positions were refined with respect to a common O—H distance of 0.96 Å and for the water molecule an H—O—H angle of 104.9° before they were fixed and allowed to ride on the corresponding oxygen atoms. One common isotropic displacement factor was refined for all H-atoms.
Compounds of the hexahydroxidostannate(IV) anion, [Sn(OH)6]2-, are well defined in chemistry as well as in mineralogy. In combination with bivalent cations, the anion is found in some rare tin minerals of natural and anthropogenic (Basciano et al., 1998) origin like schoenfliesite, Mg[Sn(OH)]6, the prototype and name giver for a large group of isostructural compounds of composition M[Sn(OH)6] with M = Mg, Fe, Mn, Zn and Ca (Strunz & Nickel, 2001). Corresponding compounds of univalent cations are of general formula M2[Sn(OH)]6 or exist as hydrates, M2[Sn(OH)6].nH2O. The anhydrous compounds of sodium and potassium are long known and commercially available products (preparing salt, M = Na) used in dye industry. Their structures have been determined recently (Jacobs & Stahl, 2000). Only from lithium, the structures of the anhydrous compound (Yang et al., 2001) as well as that of the dihydrate (Reuter & Bargon, 1997) are known. The last one crystallizes in the monoclinic β) of the dihydrate. This polymorph likewise crystallizes in the same and consists of the same building units as the known modification (in the following called α), but these primary units are linked two-dimensionally.
P21/n with [Sn(OH)6]2- octahedra and [Li(µ2-OH)3(H2O)] tetrahedra linked in a three-dimensional way. By changing the crystallization conditions, we were able to isolate a new modification (in the following calledThe α-modification [d(Sn—O) = 2.053 (1) - 2.075 (1), mean value 2.060 (13) Å; O—Sn—O = 87.21 (4)° - 92.79 (4)°]. The lithium ion is tetrahedrally coordinated by three hydroxyl groups of three different hexahydroxidostannate(IV) anions and by one water molecule to form a [Li(µ2-OH)3(H2O)] unit. The Li—OHhydroxyl bond lengths are in the range from 1.948 (3) Å to 1.965 (3) Å, mean value 1.958 (9) Å, whereas the bond to the water molecule is somewhat longer [2.030 (3) Å]. Although similar in constitution with the of Li in the α-modification, the Li—O bond lengths in the β-modification differ significantly. In the α-modification the Li—OHhydroxyl bond lengths cover a larger range [1.932 (2) Å - 1.987 (2) Å] whereas the Li—H2O bond is considerably shorter [1.946 (3) Å].
of the title compound (Fig. 1) consists of half a formula unit with the tin atom at a crystallographic centre of symmetry [Wyckoff letter 2b], and with all other atoms in general positions. Within the centrosymmetric hexahydroxidostannate(IV) anion, [Sn(OH)6]2-, the Sn—O bond lengths range from 2.0567 (11) to 2.0699 (11) Å [mean value: 2.064 (7) Å] and the O—Sn—O bond angles from 86.92 (4)° to 93.08 (4)° and are comparable with the corresponding values in theIn contrast to the previous modification, where [Sn(OH)6]-octahedra and [Li(OH)3(H2O)]-tetrahedra are linked three-dimensionally, they form in the new modification a two-dimensional layer structure (Fig. 2) parallel to (010). Within the almost planar layers, the [Sn(OH)6]-octahedra build up a hexagonal net with the tetrahedra in between, very similar to the situation of octahedral and tetrahedral voids in a close-packed layer. In summary, each octahedron is surrounded by six tetrahedra, with their apices in an alternating fashion up and down (Fig. 3).
In addition to the strong covalent and electrostatic interactions between cations, anions and water molecules, hydrogen bonds (Fig. 4) are important and fall into two categories: hydrogen bonds within the layers and those between the layers. The first ones are dominated by the water molecules that are coplanar with the layer plane and act as donors of two hydrogen bonds to two OH-groups of two different neighboring octahedra as well as acceptors of a hydrogen bond of an hydroxyl group of a third octahedron. The water molecules are also involved in the interlayer hydrogen bonds as acceptors resulting in an overall trigonal-bipyramidal coordination mode at the oxygen atom of the water molecule.
For background to the structures of M2[Sn(OH)6] with M = Na, K, see: Jacobs & Stahl (2000). For literature on Li2[Sn(OH)6].nH2O, see: Reuter & Bargon (1997) for n = 2; Yang et al. (2001) for n = 0. For M[Sn(OH)6] compounds (M = divalent metal), see: Strunz & Nickel (2001); Basciano et al. (1998).
Data collection: APEX2 (Bruker, 2009); cell
SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2006) and Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).Li2[Sn(OH)6]·2H2O | F(000) = 260 |
Mr = 270.65 | Dx = 2.661 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ybc | Cell parameters from 9252 reflections |
a = 6.1028 (2) Å | θ = 3.8–33.2° |
b = 10.4708 (3) Å | µ = 3.78 mm−1 |
c = 6.0003 (2) Å | T = 100 K |
β = 118.249 (1)° | Block, colourless |
V = 337.76 (2) Å3 | 0.15 × 0.14 × 0.11 mm |
Z = 2 |
Bruker APEXII CCD diffractometer | 986 independent reflections |
Radiation source: fine-focus sealed tube | 964 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.024 |
phi and ω scans | θmax = 30.0°, θmin = 3.8° |
Absorption correction: multi-scan (SADABS; Bruker, 2009) | h = −8→8 |
Tmin = 0.601, Tmax = 0.681 | k = −14→14 |
11484 measured reflections | l = −8→8 |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.013 | H-atom parameters constrained |
wR(F2) = 0.032 | w = 1/[σ2(Fo2) + (0.0111P)2 + 0.5571P] where P = (Fo2 + 2Fc2)/3 |
S = 1.09 | (Δ/σ)max < 0.001 |
986 reflections | Δρmax = 0.36 e Å−3 |
54 parameters | Δρmin = −0.39 e Å−3 |
0 restraints | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0094 (10) |
Li2[Sn(OH)6]·2H2O | V = 337.76 (2) Å3 |
Mr = 270.65 | Z = 2 |
Monoclinic, P21/c | Mo Kα radiation |
a = 6.1028 (2) Å | µ = 3.78 mm−1 |
b = 10.4708 (3) Å | T = 100 K |
c = 6.0003 (2) Å | 0.15 × 0.14 × 0.11 mm |
β = 118.249 (1)° |
Bruker APEXII CCD diffractometer | 986 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2009) | 964 reflections with I > 2σ(I) |
Tmin = 0.601, Tmax = 0.681 | Rint = 0.024 |
11484 measured reflections |
R[F2 > 2σ(F2)] = 0.013 | 0 restraints |
wR(F2) = 0.032 | H-atom parameters constrained |
S = 1.09 | Δρmax = 0.36 e Å−3 |
986 reflections | Δρmin = −0.39 e Å−3 |
54 parameters |
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. A suitable single-crystal was selected under a polarization microscope and mounted on a 50 µm MicroMesh MiTeGen MicromountTM using FROMBLIN Y perfluoropolyether (LVAC 16/6, Aldrich). 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 | ||
Sn1 | 0.5000 | 0.5000 | 0.5000 | 0.00669 (7) | |
O1 | 0.5924 (2) | 0.61350 (11) | 0.2773 (2) | 0.0092 (2) | |
H1 | 0.4344 | 0.6208 | 0.1278 | 0.045 (4)* | |
O2 | 0.2930 (2) | 0.38228 (11) | 0.1944 (2) | 0.0092 (2) | |
H2 | 0.3438 | 0.2947 | 0.2061 | 0.045 (4)* | |
O3 | 0.1780 (2) | 0.60408 (11) | 0.3926 (2) | 0.0088 (2) | |
H3 | 0.1965 | 0.6930 | 0.3659 | 0.045 (4)* | |
Li1 | 0.8284 (5) | 0.5657 (3) | 0.1561 (6) | 0.0123 (5) | |
O4 | 0.8497 (2) | 0.37229 (11) | 0.1795 (2) | 0.0101 (2) | |
H41 | 0.8643 | 0.3771 | 0.3458 | 0.045 (4)* | |
H42 | 1.0175 | 0.3651 | 0.2071 | 0.045 (4)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Sn1 | 0.00660 (8) | 0.00674 (9) | 0.00670 (9) | 0.00001 (4) | 0.00314 (6) | 0.00009 (5) |
O1 | 0.0091 (5) | 0.0103 (5) | 0.0081 (5) | −0.0009 (4) | 0.0039 (4) | 0.0007 (4) |
O2 | 0.0096 (5) | 0.0088 (5) | 0.0084 (5) | 0.0005 (4) | 0.0035 (4) | −0.0003 (4) |
O3 | 0.0085 (5) | 0.0075 (5) | 0.0107 (5) | 0.0006 (4) | 0.0047 (4) | 0.0006 (4) |
Li1 | 0.0136 (12) | 0.0121 (13) | 0.0117 (13) | −0.0001 (10) | 0.0063 (11) | −0.0006 (10) |
O4 | 0.0094 (5) | 0.0116 (5) | 0.0096 (5) | −0.0002 (4) | 0.0048 (4) | −0.0004 (4) |
Sn1—O1i | 2.0567 (11) | O2—H2 | 0.9600 |
Sn1—O1 | 2.0567 (11) | O3—Li1iii | 1.965 (3) |
Sn1—O3i | 2.0654 (11) | O3—H3 | 0.9600 |
Sn1—O3 | 2.0654 (11) | Li1—O2ii | 1.948 (3) |
Sn1—O2i | 2.0699 (11) | Li1—O3iv | 1.965 (3) |
Sn1—O2 | 2.0699 (11) | Li1—O4 | 2.030 (3) |
O1—Li1 | 1.961 (3) | O4—H41 | 0.9600 |
O1—H1 | 0.9600 | O4—H42 | 0.9600 |
O2—Li1ii | 1.948 (3) | ||
O1i—Sn1—O1 | 180.0 | Sn1—O1—H1 | 101.0 |
O1i—Sn1—O3i | 90.31 (4) | Li1ii—O2—Sn1 | 123.42 (11) |
O1—Sn1—O3i | 89.69 (4) | Li1ii—O2—H2 | 106.9 |
O1i—Sn1—O3 | 89.69 (4) | Sn1—O2—H2 | 117.6 |
O1—Sn1—O3 | 90.31 (4) | Li1iii—O3—Sn1 | 131.67 (10) |
O3i—Sn1—O3 | 180.0 | Li1iii—O3—H3 | 104.5 |
O1i—Sn1—O2i | 90.49 (4) | Sn1—O3—H3 | 113.2 |
O1—Sn1—O2i | 89.51 (4) | O2ii—Li1—O1 | 110.99 (15) |
O3i—Sn1—O2i | 86.92 (4) | O2ii—Li1—O3iv | 116.79 (15) |
O3—Sn1—O2i | 93.08 (4) | O1—Li1—O3iv | 114.65 (15) |
O1i—Sn1—O2 | 89.51 (4) | O2ii—Li1—O4 | 109.44 (15) |
O1—Sn1—O2 | 90.49 (4) | O1—Li1—O4 | 105.27 (14) |
O3i—Sn1—O2 | 93.08 (4) | O3iv—Li1—O4 | 98.16 (13) |
O3—Sn1—O2 | 86.92 (4) | Li1—O4—H41 | 89.5 |
O2i—Sn1—O2 | 180.0 | Li1—O4—H42 | 96.8 |
Li1—O1—Sn1 | 124.68 (10) | H41—O4—H42 | 105.0 |
Li1—O1—H1 | 105.2 |
Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) −x+1, −y+1, −z; (iii) x−1, y, z; (iv) x+1, y, z. |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O4ii | 0.96 | 1.84 | 2.7955 (16) | 173 |
O2—H2···O1v | 0.96 | 1.93 | 2.8853 (16) | 173 |
O3—H3···O4vi | 0.96 | 1.90 | 2.8343 (16) | 164 |
O4—H41···O3i | 0.96 | 1.72 | 2.6634 (16) | 167 |
O4—H42···O2iv | 0.96 | 1.73 | 2.6662 (16) | 165 |
Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) −x+1, −y+1, −z; (iv) x+1, y, z; (v) −x+1, y−1/2, −z+1/2; (vi) −x+1, y+1/2, −z+1/2. |
Experimental details
Crystal data | |
Chemical formula | Li2[Sn(OH)6]·2H2O |
Mr | 270.65 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 100 |
a, b, c (Å) | 6.1028 (2), 10.4708 (3), 6.0003 (2) |
β (°) | 118.249 (1) |
V (Å3) | 337.76 (2) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 3.78 |
Crystal size (mm) | 0.15 × 0.14 × 0.11 |
Data collection | |
Diffractometer | Bruker APEXII CCD |
Absorption correction | Multi-scan (SADABS; Bruker, 2009) |
Tmin, Tmax | 0.601, 0.681 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 11484, 986, 964 |
Rint | 0.024 |
(sin θ/λ)max (Å−1) | 0.703 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.013, 0.032, 1.09 |
No. of reflections | 986 |
No. of parameters | 54 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.36, −0.39 |
Computer programs: APEX2 (Bruker, 2009), SAINT (Bruker, 2009), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), DIAMOND (Brandenburg, 2006) and Mercury (Macrae et al., 2008), SHELXTL (Sheldrick, 2008).
Sn1—O1 | 2.0567 (11) | O2—Li1i | 1.948 (3) |
Sn1—O3 | 2.0654 (11) | O3—Li1ii | 1.965 (3) |
Sn1—O2 | 2.0699 (11) | Li1—O4 | 2.030 (3) |
O1—Li1 | 1.961 (3) |
Symmetry codes: (i) −x+1, −y+1, −z; (ii) x−1, y, z. |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O4i | 0.96 | 1.84 | 2.7955 (16) | 173.2 |
O2—H2···O1iii | 0.96 | 1.93 | 2.8853 (16) | 173.4 |
O3—H3···O4iv | 0.96 | 1.90 | 2.8343 (16) | 164.0 |
O4—H41···O3v | 0.96 | 1.72 | 2.6634 (16) | 167.2 |
O4—H42···O2vi | 0.96 | 1.73 | 2.6662 (16) | 164.8 |
Symmetry codes: (i) −x+1, −y+1, −z; (iii) −x+1, y−1/2, −z+1/2; (iv) −x+1, y+1/2, −z+1/2; (v) −x+1, −y+1, −z+1; (vi) x+1, y, z. |
References
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Compounds of the hexahydroxidostannate(IV) anion, [Sn(OH)6]2-, are well defined in chemistry as well as in mineralogy. In combination with bivalent cations, the anion is found in some rare tin minerals of natural and anthropogenic (Basciano et al., 1998) origin like schoenfliesite, Mg[Sn(OH)]6, the prototype and name giver for a large group of isostructural compounds of composition M[Sn(OH)6] with M = Mg, Fe, Mn, Zn and Ca (Strunz & Nickel, 2001). Corresponding compounds of univalent cations are of general formula M2[Sn(OH)]6 or exist as hydrates, M2[Sn(OH)6].nH2O. The anhydrous compounds of sodium and potassium are long known and commercially available products (preparing salt, M = Na) used in dye industry. Their structures have been determined recently (Jacobs & Stahl, 2000). Only from lithium, the structures of the anhydrous compound (Yang et al., 2001) as well as that of the dihydrate (Reuter & Bargon, 1997) are known. The last one crystallizes in the monoclinic space group P21/n with [Sn(OH)6]2- octahedra and [Li(µ2-OH)3(H2O)] tetrahedra linked in a three-dimensional way. By changing the crystallization conditions, we were able to isolate a new modification (in the following called β) of the dihydrate. This polymorph likewise crystallizes in the same space group and consists of the same building units as the known modification (in the following called α), but these primary units are linked two-dimensionally.
The asymmetric unit of the title compound (Fig. 1) consists of half a formula unit with the tin atom at a crystallographic centre of symmetry [Wyckoff letter 2b], and with all other atoms in general positions. Within the centrosymmetric hexahydroxidostannate(IV) anion, [Sn(OH)6]2-, the Sn—O bond lengths range from 2.0567 (11) to 2.0699 (11) Å [mean value: 2.064 (7) Å] and the O—Sn—O bond angles from 86.92 (4)° to 93.08 (4)° and are comparable with the corresponding values in the α-modification [d(Sn—O) = 2.053 (1) - 2.075 (1), mean value 2.060 (13) Å; O—Sn—O = 87.21 (4)° - 92.79 (4)°]. The lithium ion is tetrahedrally coordinated by three hydroxyl groups of three different hexahydroxidostannate(IV) anions and by one water molecule to form a [Li(µ2-OH)3(H2O)] unit. The Li—OHhydroxyl bond lengths are in the range from 1.948 (3) Å to 1.965 (3) Å, mean value 1.958 (9) Å, whereas the bond to the water molecule is somewhat longer [2.030 (3) Å]. Although similar in constitution with the coordination polyhedron of Li in the α-modification, the Li—O bond lengths in the β-modification differ significantly. In the α-modification the Li—OHhydroxyl bond lengths cover a larger range [1.932 (2) Å - 1.987 (2) Å] whereas the Li—H2O bond is considerably shorter [1.946 (3) Å].
In contrast to the previous modification, where [Sn(OH)6]-octahedra and [Li(OH)3(H2O)]-tetrahedra are linked three-dimensionally, they form in the new modification a two-dimensional layer structure (Fig. 2) parallel to (010). Within the almost planar layers, the [Sn(OH)6]-octahedra build up a hexagonal net with the tetrahedra in between, very similar to the situation of octahedral and tetrahedral voids in a close-packed layer. In summary, each octahedron is surrounded by six tetrahedra, with their apices in an alternating fashion up and down (Fig. 3).
In addition to the strong covalent and electrostatic interactions between cations, anions and water molecules, hydrogen bonds (Fig. 4) are important and fall into two categories: hydrogen bonds within the layers and those between the layers. The first ones are dominated by the water molecules that are coplanar with the layer plane and act as donors of two hydrogen bonds to two OH-groups of two different neighboring octahedra as well as acceptors of a hydrogen bond of an hydroxyl group of a third octahedron. The water molecules are also involved in the interlayer hydrogen bonds as acceptors resulting in an overall trigonal-bipyramidal coordination mode at the oxygen atom of the water molecule.