Diphosphorus tetraiodide

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Diphosphorus tetraiodide
Diphosphorus-tetraiodide-3D-balls.png
Names
IUPAC name
Diphosphorus tetraiodide
Preferred IUPAC name
Tetraiododiphosphane
Other names
Phosphorus(II) iodide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.033.301 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 236-646-7
PubChem CID
  • InChI=1S/I4P2/c1-5(2)6(3)4
    Key: YXXQTQYRRHHWFL-UHFFFAOYSA-N
  • P(P(I)I)(I)I
Properties
P2I4
Molar mass 569.57 g/mol
AppearanceOrange crystalline solid
Melting point 125.5 °C (257.9 °F; 398.6 K)
Boiling point Decomposes
Decomposes
Hazards
GHS labelling:
GHS-pictogram-acid.svg
Danger
H314
P260, P264, P280, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P321, P363, P405, P501
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).
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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. [1]

Contents

Synthesis and structure

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

2 PI3 → P2I4 + I2

It can also be obtained by treating phosphorus trichloride and potassium iodide in anhydrous conditions. [2]

Another synthesis route involves combining phosphonium iodide with iodine in a solution of carbon disulfide. An advantage of this route is that the resulting product is virtually free of impurities. [3]

2PH4I + 5I2 → P2I4 + 8HI

The compound adopts a centrosymmetric structure with a P-P bond of 2.230 Å. [4]

Reactions

Inorganic chemistry

Diphosphorus tetraiodide reacts with bromine to form mixtures PI3−xBrx. With sulfur, it is oxidized to P2S2I4, retaining the P-P bond. [1] It reacts with elemental phosphorus and water to make phosphonium iodide, which is collected via sublimation at 80 °C. [3]

Organic chemistry

Diphosphorus tetraiodide is used in organic synthesis mainly as a deoxygenating agent. [5] 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 [6] and to convert α,β-unsaturated carboxylic acids to α,β-unsaturated bromides. [7]

As foreshadowed by the work of Bertholet in 1855, diphosphorus tetraiodide can convert glycols to trans alkenes. [5] [8] This reaction is known as the Kuhn–Winterstein reaction, after the chemists who applied it to the production of polyene chromophores. [5] [9]

Related Research Articles

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The Appel reaction is an organic reaction that converts an alcohol into an alkyl chloride using triphenylphosphine and carbon tetrachloride. The use of carbon tetrabromide or bromine as a halide source will yield alkyl bromides, whereas using carbon tetraiodide, methyl iodide or iodine gives alkyl iodides. The reaction is credited to and named after Rolf Appel, it had however been described earlier. The use of this reaction is becoming less common, due to carbon tetrachloride being restricted under the Montreal protocol.

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<span class="mw-page-title-main">Phosphorus triiodide</span> Chemical compound

Phosphorus triiodide (PI3) is an inorganic compound with the formula PI3. A red solid, it is a common misconception that PI3 is too unstable to be stored; it is, in fact, commercially available. It is widely used in organic chemistry for converting alcohols to alkyl iodides. It is also a powerful reducing agent. Note that phosphorus also forms a lower iodide, P2I4, but the existence of PI5 is doubtful at room temperature.

<span class="mw-page-title-main">Nucleophilic conjugate addition</span> Organic reaction

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<span class="mw-page-title-main">Phosphorus trioxide</span> Chemical compound

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<span class="mw-page-title-main">Aziridines</span>

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2
H
4
NH
. Several drugs feature aziridine rings, including mitomycin C, porfiromycin, and azinomycin B (carzinophilin).

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<span class="mw-page-title-main">Tetrakis(hydroxymethyl)phosphonium chloride</span> Chemical compound

Tetrakis(hydroxymethyl)phosphonium chloride (THPC) is an organophosphorus compound with the chemical formula [P(CH2OH)4]Cl. The cation P(CH2OH)4+ is four-coordinate, as is typical for phosphonium salts. THPC has applications as a precursor to fire-retardant materials, as well as a microbiocide in commercial and industrial water systems.

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<span class="mw-page-title-main">Phosphonium iodide</span> Chemical compound

Phosphonium iodide is a chemical compound with the formula PH
4
I
. It is an example of a salt containing an unsubstituted phosphonium cation. Phosphonium iodide is commonly used as storage for phosphine and as a reagent for substituting phosphorus into organic molecules.

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References

  1. 1 2 Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN   978-0-08-037941-8.
  2. 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.
  3. 1 2 Brown, Glenn Halstead (1951). Reactions of phosphine and phosphonium iodide (PhD). Iowa State College. Retrieved 5 Oct 2020.
  4. Z. Žák; M. Černík (1996). "Diphosphorus tetraiodide at 120 K". Acta Crystallographica Section C. C52 (2): 290–291. doi:10.1107/S0108270195012510.
  5. 1 2 3 Krief, Alain; Telvekar, Vikas N. (2009). "Diphosphorus Tetraiodide". Diphosphorus Tetraiodide. Encyclopedia for Reagents in Organic Synthesis 2009. doi:10.1002/047084289X.rd448.pub2. ISBN   978-0471936237.
  6. 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.
  7. 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.
  8. Kuhn, Richard; Winterstein, Alfred (1928). "Über konjugierte Doppelbindungen I. Synthese von Diphenyl-poly-enen" [Conjugated double-bonds I: Synthesis of diphenyl-polyenes]. Helvetica Chimica Acta (in German). 11 (1): 87–116. doi:10.1002/hlca.19280110107.
  9. Inhoffen, H. H.; Radscheit, K.; Stache, U.; Koppe, V. (1965). "Untersuchungen an hochsubstituierten äthylenen und Glykolen, II. Synthese des 3.4-Bis-[4-oxo-cyclohexyl]-hexens-(3) mit Hilfe der Kuhn-Winterstein-Reaktion" [Experiments on highly-substituted ethenes and glycols II: Synthesis of 3,4-bis-[4-oxo-cyclohexyl]-3-hexane via the Kuhn-Winterstein reaction]. Justus Liebigs Ann. Chem. (in German) (684): 24–36. doi:10.1002/jlac.19656840106.