Editing Iodine (section)

===Iodine halides===
The halogens form many binary, [[Diamagnetism|diamagnetic]] [[interhalogen]] compounds with stoichiometries XY, XY<sub>3</sub>, XY<sub>5</sub>, and XY<sub>7</sub> (where X is heavier than Y), and iodine is no exception. Iodine forms all three possible diatomic interhalogens, a trifluoride and trichloride, as well as a pentafluoride and, exceptionally among the halogens, a heptafluoride. Numerous cationic and anionic derivatives are also characterised, such as the wine-red or bright orange compounds of {{chem|ICl|2|+}} and the dark brown or purplish black compounds of I<sub>2</sub>Cl<sup>+</sup>. Apart from these, some [[pseudohalogen|pseudohalides]] are also known, such as [[cyanogen iodide]] (ICN), iodine [[thiocyanate]] (ISCN), and iodine [[azide]] (IN<sub>3</sub>).<ref name="Greenwood824">Greenwood and Earnshaw, pp. 824–828</ref>

[[File:Iodine monochloride1.jpg|thumb|right|Iodine monochloride]]
[[Iodine monofluoride]] (IF) is unstable at room temperature and disproportionates very readily and irreversibly to iodine and [[iodine pentafluoride]], and thus cannot be obtained pure. It can be synthesised from the reaction of iodine with fluorine gas in [[trichlorofluoromethane]] at −45&nbsp;°C, with [[iodine trifluoride]] in trichlorofluoromethane at −78&nbsp;°C, or with [[silver(I) fluoride]] at 0&nbsp;°C.<ref name="Greenwood824" /> [[Iodine monochloride]] (ICl) and [[iodine monobromide]] (IBr), on the other hand, are moderately stable. The former, a volatile red-brown compound, was discovered independently by [[Joseph Louis Gay-Lussac]] and [[Humphry Davy]] in 1813–1814 not long after the discoveries of chlorine and iodine, and it mimics the intermediate halogen bromine so well that [[Justus von Liebig]] was misled into mistaking bromine (which he had found) for iodine monochloride. Iodine monochloride and iodine monobromide may be prepared simply by reacting iodine with chlorine or bromine at room temperature and purified by [[fractional crystallization (chemistry)|fractional crystallisation]]. Both are quite reactive and attack even [[platinum]] and [[gold]], though not [[boron]], [[carbon]], [[cadmium]], [[lead]], [[zirconium]], [[niobium]], [[molybdenum]], and [[tungsten]]. Their reaction with organic compounds depends on conditions. Iodine chloride vapour tends to chlorinate [[phenol]] and [[salicylic acid]], since when iodine chloride undergoes [[Homolysis (chemistry)|homolytic fission]], chlorine and iodine are produced and the former is more reactive. However, iodine chloride in [[carbon tetrachloride]] solution results in iodination being the main reaction, since now [[Heterolysis (chemistry)|heterolytic fission]] of the I–Cl bond occurs and I<sup>+</sup> attacks phenol as an electrophile. However, iodine monobromide tends to brominate phenol even in carbon tetrachloride solution because it tends to dissociate into its elements in solution, and bromine is more reactive than iodine.<ref name="Greenwood824" /> When liquid, iodine monochloride and iodine monobromide dissociate into {{chem|I|2|X|+}} and {{chem|IX|2|-}} ions (X = Cl, Br); thus they are significant conductors of electricity and can be used as ionising solvents.<ref name="Greenwood824" />

[[Iodine trifluoride]] (IF<sub>3</sub>) is an unstable yellow solid that decomposes above −28&nbsp;°C. It is thus little-known. It is difficult to produce because fluorine gas would tend to oxidise iodine all the way to the pentafluoride; reaction at low temperature with [[xenon difluoride]] is necessary. [[Iodine trichloride]], which exists in the solid state as the planar dimer I<sub>2</sub>Cl<sub>6</sub>, is a bright yellow solid, synthesised by reacting iodine with liquid chlorine at −80&nbsp;°C; caution is necessary during purification because it easily dissociates to iodine monochloride and chlorine and hence can act as a strong chlorinating agent. Liquid iodine trichloride conducts electricity, possibly indicating dissociation to {{chem|ICl|2|+}} and {{chem|ICl|4|-}} ions.<ref name="Greenwood828">Greenwood and Earnshaw, pp. 828–831</ref>

[[Iodine pentafluoride]] (IF<sub>5</sub>), a colourless, volatile liquid, is the most thermodynamically stable iodine fluoride, and can be made by reacting iodine with fluorine gas at room temperature. It is a fluorinating agent, but is mild enough to store in glass apparatus. Again, slight electrical conductivity is present in the liquid state because of dissociation to {{chem|IF|4|+}} and {{chem|IF|6|-}}. The [[pentagonal bipyramidal molecular geometry|pentagonal bipyramidal]] [[iodine heptafluoride]] (IF<sub>7</sub>) is an extremely powerful fluorinating agent, behind only [[chlorine trifluoride]], [[chlorine pentafluoride]], and [[bromine pentafluoride]] among the interhalogens: it reacts with almost all the elements even at low temperatures, fluorinates [[Pyrex]] glass to form iodine(VII) oxyfluoride (IOF<sub>5</sub>), and sets [[carbon monoxide]] on fire.<ref name="Greenwood832">Greenwood and Earnshaw, pp. 832–835</ref>