Diphosphorus tetraiodide

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Diphosphorus tetraiodide
IUPAC name

Diphosphorus tetraiodide

Preferred IUPAC name

Tetraiododiphosphane

Other names

Phosphorus(II) iodide

Identifiers
CAS number 13455-00-0 YesY
Properties
Molecular formula 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
Solubility in water Decomposes
Hazards
EU classification C
R-phrases R14, R34, R37
Flash point Non-flammable
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Diphosphorus tetraiodide, P2I4, is an orange crystalline solid, and a versatile reducing agent. The phosphorus atom has an NMR chemical shift of about +100 ppm (downfield of H3PO4) (+108 ppm in CS2). Phosphorus contains a rare oxidation state of +2 in this compound.

Synthesis

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

2 PI3 → P2I4 + I2

It can also be obtained by reacting phosphorus trichloride and potassium iodide in anhydrous conditions.[1]

Reactions

Diphosphorus tetraiodide reacts with bromine to form a mixture of PI3, PBr3, PBr2I and PBrI2.[2]

Applications

Diphosphorus tetraiodide is used in organic chemistry for converting carboxylic acids to nitriles,[3] 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[4] and to convert α,β-unsaturated carboxylic acids to α,β-unsaturated bromides.[5]

In the Kuhn–Winterstein reaction, diphosphorus tetraiodide is used in the conversion of glycols to alkenes.[6]

See also

References

  1. ↑ H. Suzuki, T. Fuchita, A. Iwasa, T. Mishina (December 1978). "Diphosphorus Tetraiodide as a Reagent for Converting Epoxides into Olefins, and Aldoximes into Nitriles under Mild Conditions". Synthesis 1978 (12): 905–908. doi:10.1055/s-1978-24936. 
  2. ↑ A. H. Cowley and S. T. Cohen (June 1965). "The Iodides of Phosphorus. II. The Reaction of Bromine with Diphosphorus Tetraiodide". Tetrahedron Letters 4 (8): 1221–1222. doi:10.1021/ic50030a029. 
  3. ↑ Vikas N. Telvekar and Rajesh A. Rane (August 2007). "A novel system for the synthesis of nitriles from carboxylic acids". Tetrahedron Letters 48 (34): 6051–6053. doi:10.1016/j.tetlet.2007.06.108. 
  4. ↑ H. Suzuki, H. Tani (1984). "A mild cyclization of 2-aminoalcohols to aziridines using diphosphorus tetraiodide". Chemistry Letters 13 (12): 2129–2130. doi:10.1246/cl.1984.2129. 
  5. ↑ Vikas N. Telvekar, Somsundaram N. Chettiar (June 2007). "A novel system for decarboxylative bromination". Tetrahedron Letters 48 (26): 4529–4532. doi:10.1016/j.tetlet.2007.04.137. 
  6. ↑ Richard Kuhn, Alfred Winterstein (1928). "Über konjugierte Doppelbindungen I. Synthese von Diphenyl-poly-enen". Helvetica Chimica Acta 11 (1): 87–116. doi:10.1002/hlca.19280110107. 
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