Iodine oxide

Short description: Class of chemical compounds

Iodine pentoxide (I2O5)

Iodine oxides are chemical compounds of oxygen and iodine. Iodine has at least three stable oxides which are isolable in bulk, diiodine tetroxide, iodine pentoxide, and diiodine hexaoxide, but a number of other oxides are formed in trace quantities or have been hypothesized to exist. The most significant of these is iodine pentoxide, which is distinguished by being the most thermodynamically and kinetically stable of all halogen oxides. The chemistry of these compounds is complicated, with only a few having been well characterized. Many have been detected in the atmosphere and are believed to be particularly important in the marine boundary layer.[1]

## Contents

* 1 Molecular compounds
* 2 Iodate anions
* 3 See also
* 4 References

## Molecular compounds

Iodine oxides[2] Molecular formula | I2O | IO[3] | IO2 | I2O4 | I4O9 | I2O5 | I2O6 | I2O7

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Name  | diiodine oxide | iodine monoxide | iodine dioxide | iodine tetroxide (diiodine tetroxide) | tetraiodine nonoxide | Iodine pentoxide (diiodine pentoxide) | Diiodine hexaoxide | Diiodine heptoxide
Structure | I2O | IO | IO2 | O2IOIO | I(OIO2)3 | O(IO2)2 | (I4O12)n[4][5][6] | polymeric[4]
Molecular model  |  |  |  |  |  |  |  |
CAS registry  | 39319-71-6 | 14696-98-1 | 13494-92-3 | 1024652-24-1 | 66523-94-2 | 12029-98-0 | 65355-99-9 |
Appearance | Unknown |  | dilute gas; condenses to I2O4[7] | yellow solid | dark yellow solid | white crystalline solid | yellow solid | unstable yellow solid
Oxidation state | +1 | +2 | +4 | +3 and +5 | +3 and +5 | +5 | +5 and +7 | +7
Melting point | not isolable | not isolable | not isolable | decomp. 100 °C | decomp. 75 °C | decomp. 300-350 °C | decomp. 179-197 °C[4] | decomp. <60 °C[4]
Solubility in water |  |  |  | decomp. to HIO3 \+ I2 | decomp. to HIO3 \+ I2 | 187 g/100 mL (hydrolyzes into HIO3) |  |

Diiodine monoxide has largely been the subject of theoretical study,[8] but there is some evidence that it may be prepared in a similar manner to dichlorine monoxide, via a reaction between HgO and I2.[9] The compound appears to be highly unstable but can react with alkenes to give halogenated products.[10]

Radical iodine oxide (IO) and iodine dioxide (IO2), collectively referred to as IOx, and also iodine tetroxide (I2O4) all possess significant and interconnected atmospheric chemistry. They are formed, in very small quantities, in the marine boundary layer by the photochemical reaction of ozone with diiodomethane, produced by macroalga such as seaweed, or through the oxidation of molecular iodine, produced by the reaction of gaseous ozone and iodide present at the seasurface.[7][11] Despite the small quantities produced (typically below ppt) they are thought to be powerful ozone depletion agents.[12][13]

Diiodine pentoxide (I2O5) is the anhydride of iodic acid and the only stable anhydride of out of all halogen oxoacids. Unlike other halogen oxides, it can be synthesized by thermal dehydration of iodic acid. Iodine pentoxide adopts multiple polymorphs that can be synthesized by varying pressures.[6]

Tetraiodine nonoxide (I4O9) has been prepared by the gas-phase reaction of I2 with O3 but has not been extensively studied.[14]

Diiodine hexaoxide (I2O6), also known as iodine trioxide or diiodine(V,VII) oxide, is a hygroscopic yellow solid. It has been isolated in bulk and has been studied as a mix with aluminium for destroying chemical and biological agents.[4] It can be synthesized in hot concentrated sulfuric acid, starting either with pure H5IO6 or a mix of H5IO6 and HIO3[5][4] It adopts a polymeric structure consisting of IV and IVII centers.

Diiodine heptoxide (I2O7) has been reported as a yellow solid that slowly decomposes into oxygen at room temperature with rapid decomposition beginning at 60 °C, converting it into I2O6.[4]

## Iodate anions

Iodine oxides also form negatively charged anions, which (associated with complementary cations) are components of acids or salts. These include the iodates and periodates, which can form multinuclear structures such as [I2O9]4-.[15]

The conjugate acids of the iodine oxides are:

Iodine oxidation state  | +1  | +3  | +5  | +7

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Name  | Hypoiodous acid | Iodous acid | Iodic acid | Periodic acid
Formula  | HIO  | HIO2 | HIO3 | HIO4 or H5IO6

The periodates include two main variants: metaperiodate IO−4 and orthoperiodate IO5−6.

## See also

* Oxygen fluoride
* Chlorine oxide
* Bromine oxide

## References

1. ↑ Kaltsoyannis, Nikolas; Plane, John M. C. (2008). "Quantum chemical calculations on a selection of iodine-containing species (IO, OIO, INO3, (IO)2, I2O3, I2O4 and I2O5) of importance in the atmosphere". Physical Chemistry Chemical Physics 10 (13): 1723–33. doi:10.1039/B715687C. PMID 18350176. Bibcode: 2008PCCP...10.1723K.
2. ↑ Lide, D. R., ed (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.
3. ↑ Nikitin, I V (31 August 2008). "Halogen monoxides". Russian Chemical Reviews 77 (8): 739–749. doi:10.1070/RC2008v077n08ABEH003788. Bibcode: 2008RuCRv..77..739N.
4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 Christe, K. O., Haiges, R., & Vashista, P. (2013). Synthesis, Characterization, and Multimillion-Atom Simulation of Halogen-Based Energetic Materials for Agent Defeat (No. USCDTRAF2012).
5. ↑ 5.0 5.1 Kraft, T., & Jansen, M. (1995). Synthesis and crystal structure of diiodine (V/VII) hexaoxide: An intermediate between a molecular and a polymer solid. Journal of the American Chemical Society, 117(25), 6795-6796.
6. ↑ 6.0 6.1 Teichtmeister, T. A., Johrendt, D., Bernhart, A. H., Heymann, G., & Huppertz, H. (2024). A Comparative Study of a High‐Pressure Polymorph of I2O5 and its Ambient‐Pressure Modification. Chemistry–A European Journal, 30(68), e202402801.
7. ↑ 7.0 7.1 Hoffmann, Thorsten; O'Dowd, Colin D.; Seinfeld, John H. (15 May 2001). "Iodine oxide homogeneous nucleation: An explanation for coastal new particle production". Geophysical Research Letters 28 (10): 1949–1952. doi:10.1029/2000GL012399. Bibcode: 2001GeoRL..28.1949H. https://authors.library.caltech.edu/50961/1/grl14261.pdf.
8. ↑ Novak, Igor (1998). "Theoretical study of I2O". Heteroatom Chemistry 9 (4): 383–385. doi:10.1002/(SICI)1098-1071(1998)9:4<383::AID-HC6>3.0.CO;2-9.
9. ↑ Forbes, Craig P.; Goosen, André; Laue, Hugh A. H. (1974). "Hypoiodite reaction: kinetic study of the reaction of 1,1-diphenyl-ethylene with mercury(II) oxide iodine". Journal of the Chemical Society, Perkin Transactions 1: 2350–2353. doi:10.1039/P19740002350.
10. ↑ Cambie, Richard C.; Hayward, Rodney C.; Lindsay, Barry G.; Phan, Alice I. T.; Rutledge, Peter S.; Woodgate, Paul D. (1976). "Reactions of iodine oxide with alkenes". Journal of the Chemical Society, Perkin Transactions 1 (18): 1961. doi:10.1039/P19760001961.
11. ↑ Carpenter, Lucy J.; MacDonald, Samantha M.; Shaw, Marvin D.; Kumar, Ravi; Saunders, Russell W.; Parthipan, Rajendran; Wilson, Julie; Plane, John M.C. (13 January 2013). "Atmospheric iodine levels influenced by seasurface emissions of inorganic iodine". Nature Geoscience 6 (2): 108–111. doi:10.1038/ngeo1687. Bibcode: 2013NatGe...6..108C. http://eprints.whiterose.ac.uk/76461/7/Nge01687 - pre-publication version_with_coversheet.pdf.
12. ↑ Saiz-Lopez, A.; Fernandez, R. P.; Ordóñez, C.; Kinnison, D. E.; Gómez Martín, J. C.; Lamarque, J.-F.; Tilmes, S. (10 December 2014). "Iodine chemistry in the troposphere and its effect on ozone". Atmospheric Chemistry and Physics 14 (23): 13119–13143. doi:10.5194/acp-14-13119-2014. Bibcode: 2014ACP....1413119S.
13. ↑ Cox, R. A.; Bloss, W. J.; Jones, R. L.; Rowley, D. M. (1 July 1999). "OIO and the atmospheric cycle of iodine". Geophysical Research Letters 26 (13): 1857–1860. doi:10.1029/1999GL900439. Bibcode: 1999GeoRL..26.1857C. http://pure-oai.bham.ac.uk/ws/files/11849889/Cox_OIO_and_the_Atmospheric_Cycle_of_Iodine_GRL_1999.pdf.
14. ↑ Sunder, S.; Wren, J. C.; Vikis, A. C. (December 1985). "Raman spectra of I4O9 formed by the reaction of iodine with ozone". Journal of Raman Spectroscopy 16 (6): 424–426. doi:10.1002/jrs.1250160611. Bibcode: 1985JRSp...16..424S.
15. ↑ Nikitina, N. I., & Nikitina, Z. K. (2005). Synthesis and interconversion of cesium salts with polynuclear orthoperiodate anions.

* v
* t
* e

Iodine compounds

Iodine(-I)|

* HI
* AtI
* ICN
* I−

Iodine(I)|

* HIO
* ICl
* IF
* IBr

Iodine(III)|

* HIO2
* ICl3
* IF3

Iodine(V)|

* HIO3
* IF5
* I2O5

Iodine(VII)|

* HIO4
* H5IO6
* IF7

HI |  |  |  | He

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LiI | BeI2 | BI3 | CI4 | NI3 | I2O4,
I2O5,
I4O9 | IF,
IF3,
IF5,
IF7 | Ne
NaI | MgI2 | AlI3 | SiI4 | PI3,
P2I4 | S  | ICl,
ICl3 | Ar
KI | CaI2 | Sc  | TiI4 | VI3 | CrI3 | MnI2 | FeI2 | CoI2 | NiI2 | CuI | ZnI2 | Ga2I6 | GeI2,
GeI4 | AsI3 | Se  | IBr | Kr
RbI | SrI2 | YI3 | ZrI4 | NbI5 | Mo  | Tc  | Ru  | Rh  | Pd  | AgI | CdI2 | InI3 | SnI4,
SnI2 | SbI3 | TeI4 | I  | Xe
CsI | BaI2 |  | HfI4 | TaI5 | W  | Re  | Os  | Ir  | Pt  | AuI | Hg2I2,
HgI2 | TlI | PbI2 | BiI3 | Po  | AtI | Rn
Fr  | RaI2 |  | Rf  | Db  | Sg  | Bh  | Hs  | Mt  | Ds  | Rg  | Cn  | Nh  | Fl  | Mc  | Lv  | Ts  | Og
| ↓  |  |
La  | Ce  | Pr  | Nd  | Pm  | SmI2 | Eu  | Gd  | TbI3 | Dy  | Ho  | Er  | Tm  | Yb  | Lu
Ac  | ThI4 | Pa  | UI3,
UI4 | Np  | Pu  | Am  | Cm  | Bk  | Cf  | EsI3 | Fm  | Md  | No  | Lr

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