Diphosphorus tetraiodide
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| Names | |
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IUPAC name
Diphosphorus tetraiodide
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Preferred IUPAC name
Tetraiododiphosphane
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| Other names
Phosphorus(II) iodide
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| Identifiers | |
13455-00-0 
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| 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 | |
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EU classification (DSD)
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 C |
| R-phrases | R14, R34, R37 |
| Flash point | Non-flammable |
| Related compounds | |
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Other anions
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Diphosphorus tetrafluoride Diphosphorus tetrachloride Diphosphorus tetrabromide |
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Other cations
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diarsenic tetraiodide |
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Related Binary Phosphorus halides
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phosphorus triiodide |
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Related compounds
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diphosphane diphosphines |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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| 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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