Redetermination of HI₃O₈, an adduct of formula HIO₃·I₂O₅

Crystals of commercial iodic(V) acid, HIO₃, were investigated using single-crystal and powder X-ray diffraction. The crystals turned out to be HI₃O₈ or HIO₃·I₂O₅ [iodic acid-diiodine penta­oxide (1/1)] instead, whose structure has been determined previously [Feikema & Vos (1966). Acta Cryst. 20, 769-777]. Redetermination of the structure gave higher precision and allowed the location of the H atom.

Key indicators

• Single-crystal X-ray study
• T = 299 K
• Mean [sigma](I-O) = 0.002 Å
• R factor = 0.020
• wR factor = 0.044
• Data-to-parameter ratio = 18.9

checkCIF/PLATON results

No syntax errors found



Alert level A
PLAT431_ALERT_2_A Short Inter HL..A Contact  I1     ..  O7      ..       2.58 Ang.
PLAT431_ALERT_2_A Short Inter HL..A Contact  I1     ..  O8      ..       2.64 Ang.
PLAT431_ALERT_2_A Short Inter HL..A Contact  I2     ..  O8      ..       2.57 Ang.
PLAT431_ALERT_2_A Short Inter HL..A Contact  I3     ..  O3      ..       2.55 Ang.
PLAT431_ALERT_2_A Short Inter HL..A Contact  I3     ..  O4      ..       2.59 Ang.

Alert level B
PLAT430_ALERT_2_B Short Inter D...A Contact  O4     ..  O7      ..       2.84 Ang.
PLAT430_ALERT_2_B Short Inter D...A Contact  O5     ..  O8      ..       2.78 Ang.

Alert level C
PLAT431_ALERT_2_C Short Inter HL..A Contact  I3     ..  O1      ..       3.37 Ang.

   5 ALERT level A = In general: serious problem
   2 ALERT level B = Potentially serious problem
   1 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   8 ALERT type 2 Indicator that the structure model may be wrong or deficient
   0 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion

---

Computing details

Data collection: COLLECT (Nonius, 1999); cell refinement: DIRAX/LSQ (Duisenberg et al., 2003); data reduction: EVALCCD (Duisenberg, 1992); program(s) used to solve structure: coordinates taken from previous determination; program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg, 2005); software used to prepare material for publication: maXus (Mackay et al., 1999).

Iodic acid–diiodine pentaoxide (1/1)

Crystal data

HIO3·I2O5	F(000) = 896
Mr = 509.71	Dx = 5.120 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 108 reflections
a = 7.5529 (4) Å	θ = 5.6–23.0°
b = 7.6961 (4) Å	µ = 14.18 mm^−1
c = 11.3787 (5) Å	T = 299 K
β = 90.178 (4)°	Fragment, colourless
V = 661.42 (6) Å^3	0.23 × 0.17 × 0.16 mm
Z = 4

Data collection

Nonius KappaCCD area-detector diffractometer	1847 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.042
φ and ω scans	θmax = 30.0°, θmin = 5.2°
Absorption correction: numerical (HABITUS; Herrendorf & Bärnighausen, 1997)	h = −10→10
Tmin = 0.189, Tmax = 0.355	k = −10→10
12999 measured reflections	l = −15→16
1913 independent reflections

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	H-atom parameters constrained
R[F^2 > 2σ(F^2)] = 0.020	w = 1/[σ^2(Fo^2) + (0.0157P)^2 + 1.6864P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.044	(Δ/σ)max = 0.001
S = 1.27	Δρmax = 0.78 e Å^−3
1913 reflections	Δρmin = −1.49 e Å^−3
101 parameters	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.0185 (4)
Primary atom site location: structure-invariant direct methods

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
I1	0.24144 (3)	0.22767 (3)	0.095268 (19)	0.00977 (7)
I2	0.33769 (3)	0.73614 (3)	0.103605 (19)	0.00941 (7)
I3	0.75579 (3)	0.04724 (3)	0.191590 (19)	0.01001 (7)
O1	0.4572 (3)	0.3010 (4)	0.0539 (2)	0.0162 (5)
O2	0.1298 (4)	0.4313 (4)	0.0870 (3)	0.0162 (5)
O3	0.1711 (3)	0.8224 (4)	0.0080 (2)	0.0154 (5)
O4	0.4408 (4)	0.9407 (4)	0.1359 (3)	0.0154 (5)
O5	0.1833 (3)	0.7451 (4)	0.2407 (2)	0.0125 (5)
O6	0.7837 (4)	0.4546 (4)	0.1579 (3)	0.0174 (6)
O7	0.8028 (4)	0.8423 (4)	0.1242 (2)	0.0165 (5)
O8	0.9774 (3)	0.1143 (4)	0.2253 (2)	0.0153 (5)
H6	0.8731	0.4653	0.1213	0.021*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
I1	0.00976 (11)	0.01153 (12)	0.00803 (11)	−0.00084 (7)	0.00119 (8)	0.00027 (7)
I2	0.01121 (11)	0.00968 (12)	0.00734 (11)	−0.00024 (7)	−0.00018 (8)	0.00038 (7)
I3	0.00851 (11)	0.01091 (12)	0.01060 (11)	−0.00110 (7)	−0.00052 (7)	−0.00053 (7)
O1	0.0124 (12)	0.0228 (14)	0.0134 (12)	−0.0058 (11)	0.0054 (10)	−0.0027 (11)
O2	0.0171 (12)	0.0124 (13)	0.0191 (13)	0.0036 (10)	−0.0014 (10)	0.0019 (10)
O3	0.0147 (12)	0.0217 (14)	0.0098 (11)	0.0032 (10)	−0.0022 (9)	0.0049 (10)
O4	0.0138 (12)	0.0119 (13)	0.0203 (13)	−0.0036 (9)	−0.0017 (10)	−0.0019 (10)
O5	0.0111 (12)	0.0190 (14)	0.0076 (12)	0.0016 (9)	0.0012 (10)	0.0007 (9)
O6	0.0170 (13)	0.0220 (15)	0.0133 (12)	0.0013 (10)	0.0032 (10)	−0.0049 (10)
O7	0.0197 (13)	0.0124 (13)	0.0175 (13)	0.0020 (10)	0.0005 (10)	−0.0052 (10)
O8	0.0108 (11)	0.0207 (14)	0.0145 (12)	−0.0042 (10)	−0.0028 (9)	0.0010 (10)

Geometric parameters (Å, º)

I1—O2	1.782 (3)	I2—O1^ii	2.390 (2)
I1—O1	1.789 (3)	I2—O8^v	2.569 (3)
I1—O5^i	1.953 (3)	I2—O2	2.829 (3)
I1—O7^ii	2.575 (2)	I3—O7^iv	1.790 (3)
I1—O8^iii	2.636 (2)	I3—O8	1.792 (3)
I1—O4^iv	2.712 (3)	I3—O6^vi	1.880 (3)
I2—O3	1.788 (3)	I3—O3^ii	2.545 (3)
I2—O4	1.794 (3)	I3—O4^iv	2.593 (3)
I2—O5	1.952 (2)	O6—H6	0.7988
O2—I1—O1	98.06 (14)	O5—I2—O1^ii	173.70 (11)
O2—I1—O5^i	97.27 (12)	O7^iv—I3—O8	99.15 (13)
O1—I1—O5^i	88.11 (12)	O7^iv—I3—O6^vi	95.06 (13)
O3—I2—O4	95.92 (13)	O8—I3—O6^vi	93.75 (12)
O3—I2—O5	92.96 (11)	I1—O1—I2^ii	138.85 (15)
O4—I2—O5	93.76 (12)	I2—O5—I1^vii	126.02 (14)
O3—I2—O1^ii	92.58 (11)	I3^v—O6—H6	124.9
O4—I2—O1^ii	88.64 (11)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O6—H6···O2^viii	0.80	2.00	2.744 (4)	156

Symmetry code: (viii) x+1, y, z.