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Diphosphorus tetraiodide

Diphosphorus tetraiodide
Ball-and-stick model of the diphosphorus tetraiodide molecule
Names
IUPAC name
Diphosphorus tetraiodide
Preferred IUPAC name
Tetraiododiphosphane
Other names
Phosphorus(II) iodide
Identifiers
13455-00-0 YesY
ECHA InfoCard 100.033.301
Properties
P2I4
Molar mass 569.57 g/mol
Appearance Orange crystalline solid
Melting point 124 to 127 °C (255 to 261 °F; 397 to 400 K)
Boiling point Decomposes
Decomposes
Hazards
Corrosive C
R-phrases R14, R34, R37
Flash point Non-flammable
Related compounds
Other anions
Diphosphorus tetrafluoride
Diphosphorus tetrachloride
Diphosphorus tetrabromide
Other cations
diarsenic tetraiodide
Related Binary Phosphorus halides
phosphorus triiodide
Related compounds
diphosphane
diphosphines
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
YesY  (what is YesYN ?)
Infobox references

Diphosphorus tetraiodide is an orange crystalline solid with the formula P2I4. It has been used as a reducing agent in organic chemistry. It is a rare example of a compound with phosphorus in the +2 oxidation state, and can be classified as a subhalide of phosphorus. It is the most stable of the diphosphorus tetrahalides.

Diphosphorus tetraiodide is easily generated by the disproportionation of phosphorus triiodide in dry ether:

It can also be obtained by treating phosphorus trichloride and potassium iodide in anhydrous conditions.

The compound adopts a centrosymmetric structure with a P-P bond of 2.230 Å.

Diphosphorus tetraiodide reacts with bromine to form mixtures PI3-xBrx. With sulfur, it is oxidized to P2S2I4, retaining the P-P bond.

Diphosphorus tetraiodide is used in organic synthesis mainly as a deoxygenating agent. It is used for deprotecting acetals and ketals to aldehydes and ketones, and for converting epoxides into alkenes and aldoximes into nitriles. It can also cyclize 2-aminoalcohols to aziridines and to convert α,β-unsaturated carboxylic acids to α,β-unsaturated bromides.

As foreshadowed by the work of Bertholet in 1855, diphosphorus tetraiodide is used in the Kuhn–Winterstein reaction, the conversion of glycols to alkenes.


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