Dipotassium zinc tetra­iodate(V) dihydrate

Fábry, J.; Krupková, R.; Císařová, I.

doi:10.1107/S1600536810006008

inorganic compounds

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ISSN: 2056-9890

Volume 66| Part 3| March 2010| Pages i22-i23

doi:10.1107/S1600536810006008

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Dipotassium zinc tetraiodate(V) dihydrate

Jan Fábry,^a ^* Radmila Krupková ^a and Ivana Císařová ^b

^aInstitute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Praha 8, Czech Republic, and ^bDepartment of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 8, 128 43 Praha 2, Czech Republic
^*Correspondence e-mail: fabry@fzu.cz

(Received 1 February 2010; accepted 14 February 2010; online 20 February 2010)

The title compound, K₂Zn(IO₃)₄·2H₂O, contains two symmetry-independent K and I atoms. These atoms, as well as the Zn atom, are coordinated by shared O atoms and, moreover, the Zn atom is coordinated by two water molecules in trans positions. The K, Zn and water O atoms atoms are situated in special positions on twofold symmetry axes. The hydrogen atoms are involved in strong O—H⋯O hydrogen bonds and O—H⋯I interactions also occur. The crystals of the title compound are, in general, twinned, but the sample used for this experiment was free of twinning.

Related literature

Single crystals of KIO₃ grown from aqueous solution develop as domained crystals of poor quality but the quality of the crystals obtained can be affected by additional reagents such as HIO₃, see: Hamid (1974 ); Lü & Zhang (1987 ). For related structures, see Vinogradov et al. (1979 ); Maneva & Rabadjieva (1994 ); Juncheng et al. (2000 ); Lepeshkov et al. (1977 ); Lucas (1984 ). For hydrogen bonding, see: Desiraju & Steiner (1999 ). For a description of the Cambridge Structural Database, see: Allen (2002 ). For the PDF-2 Powder Diffraction Database, see: ICDD (2000 $[ICDD (2000). The Powder Diffraction Database. International Centre for Diffraction Data, Newtown Square, Pennsylvania, USA.]$ ) and for the Inorganic Crystal Structure Database, see: ICSD (2009 ). For the extinction correction, see: Becker & Coppens (1974 ).

Experimental

Crystal data

K₂Zn(IO₃)₄·2H₂O
M_r = 879.2
Monoclinic, C 2
a = 13.8044 (3) Å
b = 7.7285 (2) Å
c = 8.2860 (2) Å
β = 126.5726 (13)°
V = 709.95 (3) Å³
Z = 2
Mo Kα radiation
μ = 11.08 mm⁻¹
T = 295 K
0.17 × 0.12 × 0.05 mm

Data collection

Nonius KappaCCD area-detector diffractometer
Absorption correction: gaussian (Coppens, 1970 ) T_min = 0.241, T_max = 0.581
11909 measured reflections
1639 independent reflections
1595 reflections with I > 3σ(I)
R_int = 0.045

Refinement

R[F² > 2σ(F²)] = 0.019
wR(F²) = 0.055
S = 1.72
1639 reflections
105 parameters
4 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.60 e Å⁻³
Δρ_min = −0.61 e Å⁻³
Absolute structure: Flack (1983 ), 761 Friedel pairs
Flack parameter: −0.01 (3)

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O7—H1O7⋯O4ⁱ	0.85 (9)	1.88 (10)	2.672 (6)	155 (5)
O7—H1O7ⁱⁱ⋯O4ⁱⁱⁱ	0.85 (9)	1.88 (10)	2.672 (6)	155 (5)
O8—H1O8⋯O3ⁱⁱ	0.845 (16)	1.837 (16)	2.610 (4)	151 (4)
O8—H1O8⋯I1ⁱⁱ	0.845 (16)	2.96 (3)	3.4119 (10)	116 (3)
Symmetry codes: (i) $[-x+{\script{1\over 2}}, y+{\script{1\over 2}}, -z+1]$ ; (ii) -x+1, y, -z+1; (iii) $[x+{\script{1\over 2}}, y+{\script{1\over 2}}, z]$ .

Data collection: COLLECT (Nonius, 2000 ) and HKL DENZO and SCALEPACK (Otwinowski & Minor, 1997 ); cell refinement: COLLECT and HKL DENZO and SCALEPACK; data reduction: COLLECT and HKL DENZO and SCALEPACK; program(s) used to solve structure: SIR97 (Altomare et al., 1999 ); program(s) used to refine structure: JANA2006 (Petříček et al., 2006 ); molecular graphics: Spek (2009 ); software used to prepare material for publication: JANA2006.

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536810006008/fj2279sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536810006008/fj2279Isup2.hkl

checkCIF report

Comment top

Motivation for the present structure determination was growth of single crystals of KIO₃ that develop as domained crystals of poor quality from the water solution only (Hamid, 1974; Lü & Zhang, 1987). However, quality of the obtained crystals can be affected by additional reagents, such as HIO₃ (Hamid, 1974; Lü & Zhang, 1987). The matter of interest was to find a suitable solution with other additives from which good-quality crystals of KIO₃ can be obtained.

In this case, the title structure has been grown as it is given in the preparative section.

The compound of the same chemical composition has already been synthesized (Maneva & Rabadjieva, 1994; Juncheng et al., 2000; Vinogradov et al., 1979) along with similar compounds with different central atoms instead of Zn: According to the powder diffraction experiments, Ni and Co analogoues are isostructural to Zn (Maneva & Rabadjieva, 1994). (However, the powder diffractograms have been given only for the Ni and Co compounds in the latter reference.) Juncheng et al. (2000) investigated thermodynamic properties of K₂ME(IO₃)₄.2H₂O where ME=Mg, Ni and Zn. Lepeshkov et al. (1977) studied the systems Zn(IO₃)₂ - KIO₃ - H₂O as well as Co(IO₃)₂ - KIO₃ - H₂O at 50°C. The d values of K₂Zn(IO₃)₄.2H₂O obtained from the powder diffraction experiment by Lepeshkov et al. (1977) - see also ICDD Card 31-1135, PDF-2 database, ICDD (2000) - fairly correspond to the intensive peaks, that have been calculated from the title structure (Spek, 2009). However, Lepeshkov et al. (1977) did not give any details about the conditions of the powder diffraction experiment. Lepeshkov et al. (1977) have shown that infrared spectra as well as thermal and differential thermal gravimetric analyses (TGA and DTA) of K₂Zn(IO₃)₄.2H₂O and K₂Co(IO₃)₄.2H₂O are similar. The latter authors concluded from the infrared spectra that water molecules as well as four iodates are involved in the coordination sphere of the respective central atoms Zn and Co. Vinogradov et al. (1979) further studied systems of ME(IO₃)₂ - KIO₃ - H₂O, where ME=Co, Mn and Zn. The latter authors confirmed and extended the former findings (Lepeshkov et al., 1977) that the central metal atoms (Co, Mn and Zn) are situated in an octahedron formed by the oxygens stemming from four [IO₃]^- and two H₂O molecules.

However, the Inorganic Crystal Structure Database (ICSD, 2009) does not contain any structure of the composition given above. Nevertheless, the findings by Lepeshkov et al. (1977) as well as by Vinogradov et al. (1979) have been confirmed and precised in the present article: The environment of Zn in the title structure is formed by two pairs of symmetry independent iodate groups as well as two independent coordinated water molecules in trans positions.

There are several points of interest regarding the title structure. The primitive unit cell (p index) of the title structure can be obtained by the transformation from the centred C cell (C index) [a_p,b_p,c_p]=[//0 -1 0//1/2 -1/2 0//1/2 -1/2 1//][a_C,b_C,c_C]. ([a_p,b_p,c_p] and [a_C,b_C,c_C] are the column matrices while //0 -1 0//1/2 -1/2 0//1/2 -1/2 1// are the first, the second and the third row, respectively, of the 3×3 matrix.) The transformed unit cell parameters are equal to 7.7285 (2), 7.9103 (1), 7.9421 (3) Å, 63.0265 (25), 60.8856 (9), 60.7574 (13)°; V=354.978 (18) Å³.

Taking the metric of the unit cell into consideration there is no wonder that twinning has been observed in the title structure, either in the polarization microscope and by preliminary diffraction measurements of several samples that have shown rather broad peaks. However, it seems that the twinning is less severe in the title structure than in KIO₃. The single-domained crystals can be easily obtained mechanically. Observation of the crystals in the microscope did not show ferroelastic switching of the domains.

The volume of the primitive unit cell as well as lengths of the primitive unit cell axes of the title structure are comparable to those of KIO₃ that easily forms twins: 7.7436 (4), 7.7183 (4), 7.7328 (5) Å, 108.986 (4), 109.449 (4), 109.209 (5)°; V=359.11Å³ - Lucas (1984).

In the title structure, the I atoms are surrounded by a highly distorted oxygen environment, each I is bonded to three oxygens that are substantially closer. In the case of I1 the other three oxygens including the former ones form a distorted octahedron around I1 (Fig. 4) while in the case of I2 there are four more distant oxygens completing the coordination of the latter atom (Fig. 5). The environments of the iodines (Figs. 4 and 5) are rather similar to that in KIO₃ where are also 3 oxygens substantially closer to the central I atom with respect to the remaining three. Especially the coordination of I1 resembles that of I in KIO₃ where I is coordinated in a distorted octahedron (Lucas, 1984).

There are two strong hydrogen O—H···O bonds in the structure (Desiraju & Steiner, 1999) - see Tab. 1, Fig. 1. Moreover, there is also O-H···I interaction present in the structure (Tab. 1). Lepeshkov et al. (1977) report that dehydration takes place at 210°C, i.e. at quite a high temperature. Various sections from the title structure are depicted in Figs 1-5.

Related literature top

Single crystals of KIO₃ grown from aqueous solution develop as domained crystals of poor quality but the quality of the crystals obtained can be affected by additional reagents such as HIO₃, see: Hamid (1974); Lü & Zhang (1987). For related structures, see Vinogradov et al. (1979); Maneva & Rabadjieva (1994); Juncheng et al. (2000); Lepeshkov et al. (1977); Lucas (1984). For hydrogen bonding, see: Desiraju & Steiner (1999). For a description of the Cambridge Structural Database, see: Allen (2002). For the PDF-2 Powder Diffraction Database, see: ICDD (2000) and for the Inorganic Crystal Structure Database, see: ICSD (2009). For the extinction correction, see: Becker & Coppens (1974).

Experimental top

The title structure has been prepared by adding to 0.93 g of dissolved KIO₃ in 20 ml of water of 0.4 g of KCl and 0.364 g of ZnCl₂. The solution was heated up to 60 °C while adding water to 300 ml. A very fine precipitate has developed that did not dissolve completely. Fragile prism-like colourless crystals with length of several tenths of mm have developed in the course of three months. The crystals were twinned by a domain boundary perpendicular to the longer axis of the prism. The crystals that served for the measurement could be easily separated mechanically. However, these parts in some cases were not single-domained crystals. There seem to be other domain states as indicated measurement of several samples.

Computing details top

Data collection: COLLECT (Nonius, 2000) and HKL DENZO and SCALEPACK (Otwinowski & Minor, 1997); cell refinement: COLLECT (Nonius, 2000) and HKL DENZO and SCALEPACK (Otwinowski & Minor, 1997); data reduction: COLLECT (Nonius, 2000) and HKL DENZO and SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: JANA2006 (Petříček et al., 2006); molecular graphics: Spek (2009); software used to prepare material for publication: JANA2006 (Petříček et al., 2006).

Figures top

	Fig. 1. View of the environment of Zn atoms (Spek, 2009) with omission of the K atoms. The displacement ellipsoids are shown at the 50% probability level. The hydrogen bonds are indicated by the dashed lines. The arrows depict two-fold axes. Symmetry code: (i) -x + 1/2, y + 1/2, -z + 1; (ii) -x + 1, y, -z + 1; (iii) -x + 3/2, y + 1/2, -z + 1.
	Fig. 2. View of of the environment of K1 atom (Spek, 2009). The displacement ellipsoids are shown at the 50% probability level. Symmetry code: as above and (iv) -x + 3/2, y - 1/2, -z + 1; (v) x - 1/2, y - 1/2, z - 1; (vi) x, y, z - 1; (vii) x + 1/2, y - 1/2, z; (viii) -x + 1/2, y - 1/2, -z.
	Fig. 3. View of of the environment of K2 atom (Spek, 2009). The displacement ellipsoids are shown at the 50% probability level. Symmetry code: as above and (ix) x - 1/2, y + 1/2, z - 1.
	Fig. 4. View of of the environment of I1 atom (Spek, 2009). The displacement ellipsoids are shown at the 50% probability level. Symmetry code: as above and (x) -x + 1, y, -z + 2; (xi) -x + 3/2, y + 1/2, -z + 2; (xii) -x + 3/2, y - 1/2, -z + 2.
	Fig. 5. View of of the environment of I2 atom (Spek, 2009). The displacement ellipsoids are shown at the 50% probability level. Symmetry code: as above and (xiii) -x + 1/2, y - 1/2, -z + 1.

dipotassium zinc tetraiodate(V) dihydrate top

Crystal data top

K₂Zn(IO₃)₄·2H₂O	F(000) = 792
M_r = 879.2	D_x = 4.112 (1) Mg m⁻³
Monoclinic, C2	Mo Kα radiation, λ = 0.71069 Å
Hall symbol: C 2y	Cell parameters from 8075 reflections
a = 13.8044 (3) Å	θ = 2.9–27.5°
b = 7.7285 (2) Å	µ = 11.08 mm⁻¹
c = 8.2860 (2) Å	T = 295 K
β = 126.5726 (13)°	Prism, colourless
V = 709.95 (3) Å³	0.17 × 0.12 × 0.05 mm
Z = 2

Data collection top

Nonius KappaCCD area-detector diffractometer	1639 independent reflections
Radiation source: X-ray tube	1595 reflections with I > 3σ(I)
Graphite monochromator	R_int = 0.045
Detector resolution: 9.091 pixels mm^-1	θ_max = 27.5°, θ_min = 3.1°
ϕ and ω scans	h = −17→17
Absorption correction: gaussian (Coppens, 1970)	k = −10→10
T_min = 0.241, T_max = 0.581	l = −10→10
11909 measured reflections

Refinement top

Refinement on F²	Hydrogen site location: difference Fourier map
R[F² > 2σ(F²)] = 0.019	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.055	Weighting scheme based on measured s.u.'s w = 1/(σ²(I) + 0.0004I²)
S = 1.72	(Δ/σ)_max = 0.040
1639 reflections	Δρ_max = 0.60 e Å⁻³
105 parameters	Δρ_min = −0.61 e Å⁻³
4 restraints	Extinction correction: B-C type 1 Lorentzian isotropic (Becker & Coppens, 1974)
3 constraints	Extinction coefficient: 1040 (40)
Primary atom site location: structure-invariant direct methods	Absolute structure: Flack (1983), 761 Friedel pairs
Secondary atom site location: difference Fourier map	Absolute structure parameter: −0.01 (3)

Crystal data top

K₂Zn(IO₃)₄·2H₂O	V = 709.95 (3) Å³
M_r = 879.2	Z = 2
Monoclinic, C2	Mo Kα radiation
a = 13.8044 (3) Å	µ = 11.08 mm⁻¹
b = 7.7285 (2) Å	T = 295 K
c = 8.2860 (2) Å	0.17 × 0.12 × 0.05 mm
β = 126.5726 (13)°

Data collection top

Nonius KappaCCD area-detector diffractometer	1639 independent reflections
Absorption correction: gaussian (Coppens, 1970)	1595 reflections with I > 3σ(I)
T_min = 0.241, T_max = 0.581	R_int = 0.045
11909 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.019	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.055	Δρ_max = 0.60 e Å⁻³
S = 1.72	Δρ_min = −0.61 e Å⁻³
1639 reflections	Absolute structure: Flack (1983), 761 Friedel pairs
105 parameters	Absolute structure parameter: −0.01 (3)
4 restraints

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
K1	0.5	0.0000 (3)	0	0.0217 (9)
K2	0.5	0.5290 (3)	0	0.0239 (10)
I1	0.73832 (3)	0.270215	0.98624 (4)	0.01481 (16)
I2	0.27889 (3)	0.28124 (7)	0.51786 (4)	0.01419 (16)
Zn	0.5	0.45608 (17)	0.5	0.0173 (4)
O1	0.8188 (3)	0.2594 (6)	0.8770 (5)	0.0199 (17)
O2	0.3446 (3)	0.2678 (6)	0.7822 (5)	0.0230 (16)
O3	0.6415 (4)	0.0814 (5)	0.8708 (5)	0.0220 (19)
O4	0.1355 (4)	0.3798 (5)	0.4160 (6)	0.023 (2)
O5	0.3581 (3)	0.4756 (5)	0.5308 (5)	0.0201 (18)
O6	0.6246 (4)	0.4346 (5)	0.8313 (5)	0.0207 (18)
O7	0.5	0.7158 (7)	0.5	0.039 (4)
O8	0.5	0.1904 (7)	0.5	0.033 (3)
H1O8	0.471 (6)	0.1269 (7)	0.3979 (19)	0.05*
H1O7	0.478 (7)	0.7793 (7)	0.556 (10)	0.0591*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
K1	0.0231 (11)	0.0199 (9)	0.0240 (8)	0	0.0151 (8)	0
K2	0.0164 (10)	0.0199 (9)	0.0345 (10)	0	0.0148 (9)	0
I1	0.01408 (17)	0.0169 (2)	0.01324 (16)	0.0000 (2)	0.00804 (13)	0.00000 (15)
I2	0.01437 (18)	0.01408 (19)	0.01467 (16)	0.00005 (19)	0.00895 (13)	0.00057 (14)
Zn	0.0182 (5)	0.0151 (4)	0.0223 (4)	0	0.0142 (4)	0
O1	0.0197 (17)	0.0216 (19)	0.0229 (17)	0.0030 (18)	0.0152 (15)	0.0003 (16)
O2	0.0221 (18)	0.0275 (19)	0.0177 (16)	−0.005 (2)	0.0111 (14)	−0.0010 (18)
O3	0.022 (2)	0.0181 (18)	0.0195 (18)	0.0001 (17)	0.0090 (18)	0.0001 (15)
O4	0.017 (2)	0.024 (2)	0.031 (2)	0.0035 (15)	0.0160 (18)	0.0061 (15)
O5	0.0208 (19)	0.0138 (18)	0.0319 (19)	−0.0002 (15)	0.0191 (17)	−0.0002 (15)
O6	0.017 (2)	0.0214 (19)	0.0191 (17)	0.0056 (17)	0.0080 (16)	0.0004 (15)
O7	0.052 (4)	0.017 (3)	0.082 (5)	0	0.058 (4)	0
O8	0.041 (4)	0.016 (3)	0.024 (3)	0	0.009 (3)	0

Geometric parameters (Å, º) top

K1—O1ⁱ	2.778 (4)	I1—O6	1.823 (4)
K1—O1ⁱⁱ	2.778 (4)	I1—O6^xi	3.031 (4)
K1—O2ⁱⁱⁱ	2.744 (4)	I2—O1^iv	2.701 (4)
K1—O2^iv	2.744 (4)	I2—O2	1.807 (4)
K1—O3ⁱⁱⁱ	2.802 (6)	I2—O4	1.795 (5)
K1—O3^iv	2.802 (6)	I2—O4^xii	3.248 (4)
K1—O4^v	2.925 (4)	I2—O5	1.823 (4)
K1—O4^vi	2.925 (4)	I2—O5^xii	2.900 (4)
K2—O1^vii	2.726 (4)	I2—O8	3.2202 (13)
K2—O1^viii	2.726 (4)	Zn—O5	2.126 (6)
K2—O2ⁱⁱⁱ	2.706 (4)	Zn—O5^iv	2.126 (6)
K2—O2^iv	2.706 (4)	Zn—O6	2.212 (3)
K2—O5ⁱⁱⁱ	3.170 (4)	Zn—O6^iv	2.212 (3)
K2—O5^iv	3.170 (4)	Zn—O7	2.007 (6)
K2—O6ⁱⁱⁱ	2.883 (6)	Zn—O8	2.053 (6)
K2—O6^iv	2.883 (6)	O7—H1o7	0.85 (9)
I1—O1	1.805 (5)	O7—H1o7^iv	0.85 (9)
I1—O2^ix	2.758 (5)	O8—H1o8	0.845 (16)
I1—O3	1.818 (4)	O8—H1o8^iv	0.845 (16)
I1—O3^x	2.756 (4)

H1o7—O7—H1o7^iv	109 (6)	O5—Zn—O5^iv	171.86 (15)
H1o8—O8—H1o8^iv	109.0 (13)	O5—Zn—O6	86.97 (18)
O1ⁱ—K1—O1ⁱⁱ	95.96 (14)	O5—Zn—O6^iv	93.64 (18)
O1ⁱ—K1—O2ⁱⁱⁱ	94.78 (12)	O5—Zn—O7	85.93 (10)
O1ⁱ—K1—O2^iv	157.90 (15)	O5—Zn—O8	94.07 (10)
O1ⁱ—K1—O3ⁱⁱⁱ	133.68 (13)	O5^iv—Zn—O6	93.64 (18)
O1ⁱ—K1—O3^iv	67.05 (13)	O5^iv—Zn—O6^iv	86.97 (18)
O1ⁱ—K1—O4^v	91.35 (12)	O5^iv—Zn—O7	85.93 (10)
O1ⁱ—K1—O4^vi	63.35 (14)	O5^iv—Zn—O8	94.07 (10)
O1ⁱⁱ—K1—O2ⁱⁱⁱ	157.90 (15)	O6—Zn—O6^iv	171.39 (16)
O1ⁱⁱ—K1—O2^iv	94.78 (12)	O6—Zn—O7	94.30 (11)
O1ⁱⁱ—K1—O3ⁱⁱⁱ	67.05 (13)	O6—Zn—O8	85.70 (11)
O1ⁱⁱ—K1—O3^iv	133.68 (13)	O6^iv—Zn—O7	94.30 (11)
O1ⁱⁱ—K1—O4^v	63.35 (14)	O6^iv—Zn—O8	85.70 (11)
O1ⁱⁱ—K1—O4^vi	91.35 (12)	O7—Zn—O8	180
O2ⁱⁱⁱ—K1—O2^iv	82.07 (13)	O1—I1—O2^ix	169.37 (11)
O2ⁱⁱⁱ—K1—O3ⁱⁱⁱ	91.68 (14)	O1—I1—O3	100.2 (2)
O2ⁱⁱⁱ—K1—O3^iv	68.40 (13)	O1—I1—O3^x	82.15 (18)
O2ⁱⁱⁱ—K1—O4^v	135.62 (14)	O1—I1—O6	102.0 (2)
O2ⁱⁱⁱ—K1—O4^vi	76.36 (11)	O1—I1—O6^xi	79.79 (17)
O2^iv—K1—O3ⁱⁱⁱ	68.40 (13)	O1—I1—O8	81.25 (8)
O2^iv—K1—O3^iv	91.68 (14)	O2^ix—I1—O3	83.2 (2)
O2^iv—K1—O4^v	76.36 (11)	O2^ix—I1—O3^x	95.72 (15)
O2^iv—K1—O4^vi	135.62 (14)	O2^ix—I1—O6	87.4 (2)
O3ⁱⁱⁱ—K1—O3^iv	154.04 (14)	O2^ix—I1—O6^xi	92.39 (14)
O3ⁱⁱⁱ—K1—O4^v	114.81 (13)	O2^ix—I1—O8	108.21 (6)
O3ⁱⁱⁱ—K1—O4^vi	73.91 (13)	O3—I1—O3^x	172.60 (14)
O3^iv—K1—O4^v	73.91 (13)	O3—I1—O6	97.71 (16)
O3^iv—K1—O4^vi	114.81 (13)	O3—I1—O6^xi	67.69 (14)
O4^v—K1—O4^vi	142.99 (13)	O3—I1—O8	49.04 (14)
O1^vii—K2—O1^viii	98.42 (15)	O3^x—I1—O6	74.92 (14)
O1^vii—K2—O2ⁱⁱⁱ	92.96 (12)	O3^x—I1—O6^xi	119.70 (10)
O1^vii—K2—O2^iv	157.39 (15)	O3^x—I1—O8	125.11 (11)
O1^vii—K2—O5ⁱⁱⁱ	82.40 (11)	O6—I1—O6^xi	165.29 (13)
O1^vii—K2—O5^iv	107.60 (12)	O6—I1—O8	58.30 (14)
O1^vii—K2—O6ⁱⁱⁱ	131.60 (13)	O6^xi—I1—O8	108.09 (11)
O1^vii—K2—O6^iv	70.54 (13)	O1^iv—I2—O2	173.13 (18)
O1^viii—K2—O2ⁱⁱⁱ	157.39 (15)	O1^iv—I2—O4	80.92 (18)
O1^viii—K2—O2^iv	92.96 (12)	O1^iv—I2—O4^xii	90.78 (12)
O1^viii—K2—O5ⁱⁱⁱ	107.60 (12)	O1^iv—I2—O5	88.38 (16)
O1^viii—K2—O5^iv	82.40 (11)	O1^iv—I2—O5^xii	88.12 (13)
O1^viii—K2—O6ⁱⁱⁱ	70.54 (13)	O1^iv—I2—O8	74.54 (9)
O1^viii—K2—O6^iv	131.60 (13)	O2—I2—O4	102.2 (2)
O2ⁱⁱⁱ—K2—O2^iv	83.50 (13)	O2—I2—O4^xii	82.61 (17)
O2ⁱⁱⁱ—K2—O5ⁱⁱⁱ	54.54 (12)	O2—I2—O5	97.22 (19)
O2ⁱⁱⁱ—K2—O5^iv	112.69 (13)	O2—I2—O5^xii	86.36 (17)
O2ⁱⁱⁱ—K2—O6ⁱⁱⁱ	87.30 (14)	O2—I2—O8	103.80 (15)
O2ⁱⁱⁱ—K2—O6^iv	70.70 (13)	O4—I2—O4^xii	132.34 (15)
O2^iv—K2—O5ⁱⁱⁱ	112.69 (13)	O4—I2—O5	97.63 (19)
O2^iv—K2—O5^iv	54.54 (12)	O4—I2—O5^xii	80.51 (16)
O2^iv—K2—O6ⁱⁱⁱ	70.70 (13)	O4—I2—O8	151.77 (18)
O2^iv—K2—O6^iv	87.30 (14)	O4^xii—I2—O5	129.17 (17)
O5ⁱⁱⁱ—K2—O5^iv	165.03 (13)	O4^xii—I2—O5^xii	52.21 (12)
O5ⁱⁱⁱ—K2—O6ⁱⁱⁱ	58.89 (11)	O4^xii—I2—O8	62.61 (14)
O5ⁱⁱⁱ—K2—O6^iv	116.79 (11)	O5—I2—O5^xii	176.26 (13)
O5^iv—K2—O6ⁱⁱⁱ	116.79 (11)	O5—I2—O8	68.31 (19)
O5^iv—K2—O6^iv	58.89 (11)	O5^xii—I2—O8	111.94 (14)
O6ⁱⁱⁱ—K2—O6^iv	150.67 (15)

Symmetry codes: (i) x−1/2, y−1/2, z−1; (ii) −x+3/2, y−1/2, −z+1; (iii) x, y, z−1; (iv) −x+1, y, −z+1; (v) x+1/2, y−1/2, z; (vi) −x+1/2, y−1/2, −z; (vii) x−1/2, y+1/2, z−1; (viii) −x+3/2, y+1/2, −z+1; (ix) −x+1, y, −z+2; (x) −x+3/2, y+1/2, −z+2; (xi) −x+3/2, y−1/2, −z+2; (xii) −x+1/2, y−1/2, −z+1.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O7—H1O7···O4^xiii	0.85 (9)	1.88 (10)	2.672 (6)	155 (5)
O7—H1O7^iv···O4^xiv	0.85 (9)	1.88 (10)	2.672 (6)	155 (5)
O8—H1O8···O3^iv	0.845 (16)	1.837 (16)	2.610 (4)	151 (4)
O8—H1O8···I1^iv	0.845 (16)	2.96 (3)	3.4119 (10)	116 (3)

Symmetry codes: (iv) −x+1, y, −z+1; (xiii) −x+1/2, y+1/2, −z+1; (xiv) x+1/2, y+1/2, z.

Experimental details

Crystal data
Chemical formula	K₂Zn(IO₃)₄·2H₂O
M_r	879.2
Crystal system, space group	Monoclinic, C2
Temperature (K)	295
a, b, c (Å)	13.8044 (3), 7.7285 (2), 8.2860 (2)
β (°)	126.5726 (13)
V (Å³)	709.95 (3)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	11.08
Crystal size (mm)	0.17 × 0.12 × 0.05

Data collection
Diffractometer	Nonius KappaCCD area-detector diffractometer
Absorption correction	Gaussian (Coppens, 1970)
T_min, T_max	0.241, 0.581
No. of measured, independent and observed [I > 3σ(I)] reflections	11909, 1639, 1595
R_int	0.045
(sin θ/λ)_max (Å⁻¹)	0.649

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.019, 0.055, 1.72
No. of reflections	1639
No. of parameters	105
No. of restraints	4
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.60, −0.61
Absolute structure	Flack (1983), 761 Friedel pairs
Absolute structure parameter	−0.01 (3)

Computer programs: COLLECT (Nonius, 2000) and HKL DENZO and SCALEPACK (Otwinowski & Minor, 1997), SIR97 (Altomare et al., 1999), JANA2006 (Petříček et al., 2006), Spek (2009).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O7—H1O7···O4ⁱ	0.85 (9)	1.88 (10)	2.672 (6)	155 (5)
O7—H1O7ⁱⁱ···O4ⁱⁱⁱ	0.85 (9)	1.88 (10)	2.672 (6)	155 (5)
O8—H1O8···O3ⁱⁱ	0.845 (16)	1.837 (16)	2.610 (4)	151 (4)
O8—H1O8···I1ⁱⁱ	0.845 (16)	2.96 (3)	3.4119 (10)	116 (3)

Symmetry codes: (i) −x+1/2, y+1/2, −z+1; (ii) −x+1, y, −z+1; (iii) x+1/2, y+1/2, z.

Acknowledgements

IC gratefully acknowledges support under grant MSM0021620857.

References

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