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(1,4,7,10,13,16-Hexaoxa­cyclo­octa­decane-κ6O)­potassium penta­iodide, [K(C12H24O6)]I5, obtained by slow evaporation of an ethanol solution of KI, 18-crown-6 and I2, contains [K(18-crown-6)]+ cations (Ci symmetry) and I5 anions (C2 symmetry), which are arranged in alternating layers parallel to (001). In contrast to the well known tendency of I5 ions to form chains and nets, the I5 units in the title compound are isolated.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S010827010301953X/jz1580sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S010827010301953X/jz1580Isup2.hkl
Contains datablock I

CCDC reference: 224504

Comment top

Polyiodide anions are synthesized by addition of elemental iodine to I ions and can be incorporated into crystalline solids in the presence of suitable cations. They show considerable diversity in I—I bond lengths, covering the whole region between a strongly covalent bond and the sum of the van der Waals radii of two I atoms. However, the bond lengths are never uniform. As a consequence, the structural diversity of polyiodide ions is remarkably great (Svensson & Kloo, 2003). To date, no systematic procedure for the synthesis and crystallization of iodine-rich polyiodides is known, and this remains an ultimate goal of our work. We wish to take account of the structures and composition of polyiodide matrices by variation of the shape, charge and size of the corresponding cations. In previous work, we showed that bulky low-charged cations of the general formula [M(crown-ether)]x+ (where M is an element of group 1 or 2, crown-ether is benzo-18-crown-6, benzo-15-crown-5 or dibenzo-18-crown-6, and x = 1 or 2) positively influence the stability of polyiodides in the solid state (Tebbe & Dombrowski, 1999; Pantenburg & Tebbe, 2001, 2002; Pantenburg et al., 2002).

In the series of polyiodides with the cation potassium(18-crown-6), [K(18-crown-6)]Ix, only the triiodide (x = 3) has been structurally characterized (Sievert et al., 1996); it represents the first member of the series with x = 2n + 1. In this paper, the second representative, (I), [K(18-crown-6)]I5 (n = 2), is presented. Investigations on the selective synthesis of [K(18-crown-6)]I7 (n = 3) and [K(18-crown-6)]I9 (n = 4) are in progress. \sch

The asymmetric unit in the molecular structure of (I) shows features characteristic of compounds containing the [K(18-crown-6)]+ moiety (Fig. 1). The macrocyclic ligand crystallizes in the usual manner, showing an all-gauche conformation with almost D3 d symmetry (Pedersen & Frensdorff, 1972). The K+ ion (4a, Ci symmetry, 1/2,0,0) is located in the centre of the 18-crown-6 ligand and coordinated by six O atoms. The K—O distances vary between 2.777 (2) and 2.812 (2) Å (Table 1). The position of the K+ centre deviates by 0.550 (1) Å from the O6 mean plane (PARST95; Nardelli, 1995). Distances and angles within the crown ether moiety are in good agreement with published data [mean values from the Cambridge Structural Database (Version?): CH2—O 1.43 (3) and CH2—CH2 1.51 (2) Å, and O—CH2—CH2 108.9 (13) and CH2—O—CH2 111.4 (10)° (Allen, 2002)].

The pentaiodide ion, as often observed, forms a V-shaped unit (Tebbe, 1997; Pantenburg & Tebbe, 2001), with the central I1 atom located on the special site 4 e (C2 symmetry, 1/2,y,1/4). This atom is linked to an iodine molecule [I2—I3 2.792 (1) Å] via a bond length of 3.116 (1) Å. The angle within the triiodide moiety thus formed (I1—I2—I3) is 178.67 (1)°. The angle at the central atom, I2—I1—I2iii 102.83 (1)°, is significantly widened from the usually observed values of close to 90° [symmetry code: (iii) ?].

An investigation of possible secondary contacts reveals only I2···I3iv 3.909 (1) Å [symmetry code: (iv) 1/2 − x, y − 1/2, 1/2 − z], and thus shows that the iodine substructure of (I) consists of essentially isolated pentaiodide units. This result is remarkable, because isolated I5 units are rare structural elements. In contrast with the frequently found chains and networks, few examples of this structural motif have been mentioned in the literature (Pantenburg & Tebbe, 2001).

In the crystal structure of (I), the ions form planes parallel to (110) (Fig. 2). No significant contacts are observed between the anions and cations of neighbouring planes, as indicated by I3···H1B 3.263 (2) and I1···K1 3.686 (1) Å.

Experimental top

The title compound was prepared by thoroughly mixing KI (0.083 g, 0.5 mmol), 18-crown-6 (0.132 g, 0.5 mmol) and I2 (0.380 g, 1.5 mmol) in ethanol (40 ml). Red plate-like crystals of (I) were obtained after a few days by slow evaporation of the solvent under ambient conditions.

Refinement top

The H atoms were placed in idealized positions and constrained to ride on their parent atom, with C—H distances of 0.970 Å and Uiso(H) = 0.038 Å2.

Computing details top

Data collection: X-AREA (Stoe & Cie, 2001); cell refinement: X-AREA; data reduction: X-AREA; program(s) used to solve structure: SIR92 (Altomare et al., 1993); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg, 2001); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. The structure of (I), showing the atom-numbering scheme and 50% probability displacement ellipsoids. Symmetry-related atoms are drawn as empty ellipsoids. Dashed lines denote K—O contacts. H atoms have been omitted for clarity.
[Figure 2] Fig. 2. A projection of the structure of (I) along the ac plane. H atoms have been omitted for clarity.
(1,4,7,10,13,16-Hexaoxacyclooctadecane)potassium pentaiodide top
Crystal data top
[K(C12H24O6)]I5F(000) = 1712
Mr = 937.91Dx = 2.475 Mg m3
Monoclinic, C2/cMelting point: unknown K
Hall symbol: -C 2ycMo Kα radiation, λ = 0.71073 Å
a = 19.9194 (17) ÅCell parameters from 19494 reflections
b = 8.6554 (7) Åθ = 1.1–29.8°
c = 14.6049 (14) ŵ = 6.36 mm1
β = 91.208 (7)°T = 170 K
V = 2517.5 (4) Å3Plate, red
Z = 40.31 × 0.22 × 0.05 mm
Data collection top
Stoe IPDS II image-plate
diffractometer
3513 independent reflections
Radiation source: fine-focus sealed tube2779 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.056
Detector resolution: not measured pixels mm-1θmax = 29.6°, θmin = 2.1°
ω and ϕ scansh = 2725
Absorption correction: numerical
The absorption correction (X-RED; Stoe & Cie, 2001) was performed after optimizing the crystal shape using X-SHAPE (Stoe & Cie, 1999).
k = 1112
Tmin = 0.193, Tmax = 0.691l = 2020
26538 measured reflections
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.024H-atom parameters constrained
wR(F2) = 0.057 w = 1/[σ2(Fo2) + (0.0303P)2 + 1.232P]
where P = (Fo2 + 2Fc2)/3
S = 1.02(Δ/σ)max = 0.001
3513 reflectionsΔρmax = 0.90 e Å3
113 parametersΔρmin = 1.03 e Å3
0 restraintsExtinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.00503 (10)
Crystal data top
[K(C12H24O6)]I5V = 2517.5 (4) Å3
Mr = 937.91Z = 4
Monoclinic, C2/cMo Kα radiation
a = 19.9194 (17) ŵ = 6.36 mm1
b = 8.6554 (7) ÅT = 170 K
c = 14.6049 (14) Å0.31 × 0.22 × 0.05 mm
β = 91.208 (7)°
Data collection top
Stoe IPDS II image-plate
diffractometer
3513 independent reflections
Absorption correction: numerical
The absorption correction (X-RED; Stoe & Cie, 2001) was performed after optimizing the crystal shape using X-SHAPE (Stoe & Cie, 1999).
2779 reflections with I > 2σ(I)
Tmin = 0.193, Tmax = 0.691Rint = 0.056
26538 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0240 restraints
wR(F2) = 0.057H-atom parameters constrained
S = 1.02Δρmax = 0.90 e Å3
3513 reflectionsΔρmin = 1.03 e Å3
113 parameters
Special details top

Experimental. A suitable single-crystal was carefully selected under a polarizing microscope and mounted in a glass capillary. The scattering intensities were collected on an imaging plate diffractometer (IPDS II, Stoe & Cie) equipped with a fine focus sealed tube X-ray source (Mo Kα, λ = 0.71073 Å) operating at 50 kV and 40 mA. Intensity data for [K(C12H24O6)]I5 were collected at 170 K by ω-scans in 203 frames (0 < ω < 180°; ϕ = O°, 0 < ω < 180°; ϕ = 90°, 0 < ω < 46°; ϕ = 135°, Δω = 2°, exposure time of 2 min) in the 2 Θ range 2.2 to 59.5°. Structure solution and refinement were carried out using the programs SIR92 (Altomare et al., 1993) and SHELXL97 (Sheldrick, 1997). The H atom positions for [K(C12H24O6)]I5 were fixed geometrically (C - H = 0.970 Å). A numerical absorption correction (X-RED (Stoe & Cie, 2001) was applied after optimization of the crystal shape (X-SHAPE (Stoe & Cie, 1999)). The last cycles of refinement included atomic positions for all atoms, anisotropic parameters for all non-hydrogen atoms and isotropic thermal parameters for all hydrogen atoms. The final difference maps were free of any chemically significant features. The refinement was based on F2 for ALL reflections.

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 (Å2) top
xyzUiso*/Ueq
I10.50000.05812 (3)0.25000.04024 (9)
I20.377703 (11)0.28267 (2)0.244026 (14)0.03381 (7)
I30.266350 (12)0.47845 (3)0.236736 (16)0.04209 (8)
K10.50000.00000.00000.0318 (2)
C10.31931 (15)0.0040 (4)0.0208 (2)0.0325 (6)
H1A0.27370.01390.00120.038 (3)*
H1B0.32370.03720.08240.038 (3)*
C20.33412 (15)0.1739 (4)0.0214 (2)0.0313 (6)
H2A0.30170.22760.05840.038 (3)*
H2B0.33090.21440.04040.038 (3)*
O30.39972 (10)0.1978 (2)0.05802 (15)0.0306 (4)
C40.41767 (16)0.3567 (4)0.0588 (3)0.0370 (7)
H4A0.42160.39410.00350.038 (3)*
H4B0.38330.41660.08870.038 (3)*
C50.48346 (17)0.3742 (4)0.1093 (2)0.0381 (7)
H5A0.48050.32900.16990.038 (3)*
H5B0.49420.48290.11630.038 (3)*
O60.53442 (11)0.2990 (2)0.05975 (15)0.0314 (4)
C70.59758 (16)0.3020 (3)0.1072 (2)0.0337 (6)
H7A0.60990.40780.12160.038 (3)*
H7B0.59470.24500.16410.038 (3)*
C80.64935 (16)0.2311 (4)0.0483 (2)0.0326 (6)
H8A0.69350.24380.07660.038 (3)*
H8B0.64920.28150.01100.038 (3)*
O90.63463 (10)0.0709 (2)0.03738 (15)0.0301 (4)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
I10.04330 (18)0.03350 (15)0.04405 (18)0.0000.00386 (14)0.000
I20.03964 (12)0.03384 (11)0.02802 (11)0.00951 (8)0.00258 (8)0.00356 (7)
I30.03898 (13)0.04675 (13)0.04054 (13)0.00051 (9)0.00109 (9)0.00483 (9)
K10.0220 (4)0.0315 (4)0.0417 (5)0.0019 (3)0.0009 (4)0.0116 (4)
C10.0221 (13)0.0389 (16)0.0366 (16)0.0015 (12)0.0015 (12)0.0028 (12)
C20.0252 (14)0.0359 (15)0.0328 (15)0.0061 (12)0.0010 (12)0.0018 (12)
O30.0251 (10)0.0284 (10)0.0382 (12)0.0041 (8)0.0030 (9)0.0035 (8)
C40.0336 (16)0.0286 (14)0.0489 (19)0.0078 (12)0.0046 (14)0.0048 (13)
C50.0385 (17)0.0334 (16)0.0424 (18)0.0024 (13)0.0042 (14)0.0129 (13)
O60.0285 (11)0.0331 (11)0.0325 (11)0.0016 (8)0.0022 (8)0.0092 (8)
C70.0355 (16)0.0307 (14)0.0345 (16)0.0034 (12)0.0073 (13)0.0058 (12)
C80.0282 (14)0.0319 (14)0.0377 (17)0.0060 (12)0.0041 (12)0.0001 (12)
O90.0244 (10)0.0302 (10)0.0359 (12)0.0025 (8)0.0035 (8)0.0027 (8)
Geometric parameters (Å, º) top
I1—I2i3.1162 (3)C2—O31.417 (4)
I1—I23.1162 (3)C2—H2A0.9700
I1—K1i3.6857 (4)C2—H2B0.9700
I2—I32.7915 (4)O3—C41.420 (4)
I2—I3ii3.9090 (4)C4—C51.498 (5)
I3—I2iii3.9090 (4)C4—H4A0.9700
I1—K13.6857 (3)C4—H4B0.9700
K1—O3iv2.777 (2)C5—O61.418 (4)
K1—O32.777 (2)C5—H5A0.9700
K1—O9iv2.794 (2)C5—H5B0.9700
K1—O92.794 (2)O6—C71.424 (4)
K1—O6iv2.812 (2)C7—C81.489 (5)
K1—O62.812 (2)C7—H7A0.9700
K1—I1iv3.6857 (3)C7—H7B0.9700
C1—O9iv1.421 (4)C8—O91.425 (3)
C1—C21.500 (4)C8—H8A0.9700
C1—H1A0.9700C8—H8B0.9700
C1—H1B0.9700O9—C1iv1.421 (4)
I2i—I1—I2102.83 (1)C2—C1—H1B109.9
I2i—I1—K195.539 (7)H1A—C1—H1B108.3
I2—I1—K194.227 (7)O3—C2—C1109.0 (2)
I2i—I1—K1i94.227 (7)O3—C2—H2A109.9
I2—I1—K1i95.539 (7)C1—C2—H2A109.9
K1—I1—K1i164.312 (9)O3—C2—H2B109.9
I3—I2—I1178.67 (1)C1—C2—H2B109.9
I3—I2—I3ii80.08 (1)H2A—C2—H2B108.3
I1—I2—I3ii98.77 (1)C2—O3—C4112.0 (2)
I2—I3—I2iii171.91 (1)C2—O3—K1117.28 (17)
O3iv—K1—O3180.00 (12)C4—O3—K1114.63 (17)
O3iv—K1—O9iv119.90 (6)O3—C4—C5108.6 (3)
O3—K1—O9iv60.10 (6)O3—C4—H4A110.0
O3iv—K1—O960.10 (6)C5—C4—H4A110.0
O3—K1—O9119.90 (6)O3—C4—H4B110.0
O9iv—K1—O9180.00 (12)C5—C4—H4B110.0
O3iv—K1—O6iv60.65 (6)H4A—C4—H4B108.3
O3—K1—O6iv119.35 (6)O6—C5—C4109.3 (3)
O9iv—K1—O6iv60.67 (6)O6—C5—H5A109.8
O9—K1—O6iv119.33 (6)C4—C5—H5A109.8
O3iv—K1—O6119.35 (6)O6—C5—H5B109.8
O3—K1—O660.65 (6)C4—C5—H5B109.8
O9iv—K1—O6119.33 (6)H5A—C5—H5B108.3
O9—K1—O660.67 (6)C5—O6—C7112.2 (2)
O6iv—K1—O6180.00 (8)C5—O6—K1114.10 (18)
O3iv—K1—I1iv76.52 (5)C7—O6—K1112.03 (16)
O3—K1—I1iv103.48 (5)O6—C7—C8109.1 (2)
O9iv—K1—I1iv81.75 (5)O6—C7—H7A109.9
O9—K1—I1iv98.25 (5)C8—C7—H7A109.9
O6iv—K1—I1iv79.82 (5)O6—C7—H7B109.9
O6—K1—I1iv100.18 (5)C8—C7—H7B109.9
O3iv—K1—I1103.48 (5)H7A—C7—H7B108.3
O3—K1—I176.52 (5)O9—C8—C7108.8 (2)
O9iv—K1—I198.25 (5)O9—C8—H8A109.9
O9—K1—I181.75 (5)C7—C8—H8A109.9
O6iv—K1—I1100.18 (5)O9—C8—H8B109.9
O6—K1—I179.82 (5)C7—C8—H8B109.9
I1iv—K1—I1180.000 (9)H8A—C8—H8B108.3
O9iv—C1—C2108.8 (2)C1iv—O9—C8112.2 (2)
O9iv—C1—H1A109.9C1iv—O9—K1114.34 (17)
C2—C1—H1A109.9C8—O9—K1115.48 (17)
O9iv—C1—H1B109.9
Symmetry codes: (i) x+1, y, z+1/2; (ii) x+1/2, y1/2, z+1/2; (iii) x+1/2, y+1/2, z+1/2; (iv) x+1, y, z.

Experimental details

Crystal data
Chemical formula[K(C12H24O6)]I5
Mr937.91
Crystal system, space groupMonoclinic, C2/c
Temperature (K)170
a, b, c (Å)19.9194 (17), 8.6554 (7), 14.6049 (14)
β (°) 91.208 (7)
V3)2517.5 (4)
Z4
Radiation typeMo Kα
µ (mm1)6.36
Crystal size (mm)0.31 × 0.22 × 0.05
Data collection
DiffractometerStoe IPDS II image-plate
diffractometer
Absorption correctionNumerical
The absorption correction (X-RED; Stoe & Cie, 2001) was performed after optimizing the crystal shape using X-SHAPE (Stoe & Cie, 1999).
Tmin, Tmax0.193, 0.691
No. of measured, independent and
observed [I > 2σ(I)] reflections
26538, 3513, 2779
Rint0.056
(sin θ/λ)max1)0.695
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.024, 0.057, 1.02
No. of reflections3513
No. of parameters113
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.90, 1.03

Computer programs: X-AREA (Stoe & Cie, 2001), X-AREA, SIR92 (Altomare et al., 1993), SHELXL97 (Sheldrick, 1997), DIAMOND (Brandenburg, 2001), SHELXL97.

Selected geometric parameters (Å, º) top
I1—I23.1162 (3)C2—O31.417 (4)
I2—I32.7915 (4)O3—C41.420 (4)
I2—I3i3.9090 (4)C4—C51.498 (5)
I1—K13.6857 (3)C5—O61.418 (4)
K1—O32.777 (2)O6—C71.424 (4)
K1—O92.794 (2)C7—C81.489 (5)
K1—O62.812 (2)C8—O91.425 (3)
C1—C21.500 (4)O9—C1ii1.421 (4)
I2iii—I1—I2102.83 (1)I3—I2—I1178.67 (1)
Symmetry codes: (i) x+1/2, y1/2, z+1/2; (ii) x+1, y, z; (iii) x+1, y, z+1/2.
 

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