Diphosphorus tetraiodide

Diphosphorus tetraiodide
IUPAC name Diphosphorus tetraiodide
Preferred IUPAC name Tetraiododiphosphane
Other names phosphorus(II) iodide
Identifiers
CAS number	13455-00-0
Properties
Molecular formula	P2I4
Molar mass	569.57 g mol−1
Appearance	orange crystalline solid
Density	? g cm−3, solid
Melting point	124-127 °C
Boiling point	Decomposes
Solubility in water	Decomposes
Hazards
EU classification	not listed
Flash point	non-flammable
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 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:

2PI₃ → P₂I₄ + I₂

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

Reactions

P₂I₄ 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]

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. ^ Über konjugierte Doppelbindungen I. Synthese von Diphenyl-poly-enen Richard Kuhn, Alfred Winterstein Helvetica Chimica Acta Volume 11 Issue 1, Pages 87 - 116 1928 doi:10.1002/hlca.19280110107

See also

• phosphorus triiodide