Phosphonium iodide
Space-filling model of the crystal structure of phosphonium iodide
Names
IUPAC name
Phosphanium iodide
Other names
Iodine phosphide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.031.978 Edit this at Wikidata
EC Number
  • 235-189-0
UNII
  • InChI=1S/HI.H3P/h1H;1H3
    Key: LSMAIBOZUPTNBR-UHFFFAOYSA-N
  • [PH4+].[I-]
Properties
PH
4I
Molar mass 161.910 g/mol
Boiling point 62 °C (144 °F; 335 K) Sublimes[1]
decomposes
Structure
Tetragonal (P4/nmm)
a = 6.34 Å, c = 4.62 Å
185.7 Å3
2
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Phosphonium iodide is a chemical compound with the formula PH
4I. It is an example of a salt containing an unsubstituted phosphonium cation (PH+
4). Phosphonium iodide is commonly used as storage for phosphine[2] and as a reagent for substituting phosphorus into organic molecules.[3]

Preparation

Phosphonium iodide is prepared by mixing diphosphorus tetraiodide (P
2I
4) with elemental phosphorus and water at 80 °C and allowing the salt to sublime.[4][5]

10 P2I4 + 13 P4 + 128 H2O → 40 PH4I + 32 H3PO4

Properties

Structure

Its crystal structure has the tetragonal space group P4/nmm, which is a distorted version of the NH4Cl crystal structure; the unit cell has approximate dimensions 634×634×462 pm.[6] The hydrogen bonding in the system causes the PH+
4 cations to orient such that the hydrogen atoms point toward the I−
 anions.[7]

Chemical

At 62 °C and atmospheric pressure, phosphonium iodide sublimates and dissociates reversibly into phosphine and hydrogen iodide (HI).[1] It oxidizes slowly in air to give iodine and phosphorus oxides; it is hygroscopic[4] and is hydrolyzed into phosphine and HI:[8]

PH4I ⇌ PH3 + HI

Phosphine gas may be devolved from phosphonium iodide by mixing an aqueous solution with potassium hydroxide:[9]

PH4I + KOH → PH3 + KI + H2O

It reacts with elemental iodine and bromine in a nonpolar solution to give phosphorus halides; for example:

2PH4I + 5I2 → P2I4 + 8HI[4]

Phosphonium iodide is a powerful substitution reagent in organic chemistry; for example, it can convert a pyrilium into a phosphinine via substitution.[3] In 1951, Glenn Halstead Brown found that PH4I reacts with acetyl chloride to produce an unknown phosphine derivative, possibly CH3C(=PH)PH2·HI.[4]

References

  1. ^ a b Smith, Alexander.; Calvert, Robert Peyton. (July 1914). "The Dissociation Pressures of Ammonium- and Tetramethylammonium Halides and of Phosphonium Iodide and Phosphorus Pentachloride". Journal of the American Chemical Society. 36 (7): 1363–1382. doi:10.1021/ja02184a003. Retrieved 6 October 2020.
  2. ^ Morrow, B. A.; McFarlane, Richard A. (July 1986). "Trimethylgallium adsorbed on silica and its reaction with phosphine, arsine, and hydrogen chloride: an infrared and Raman study". The Journal of Physical Chemistry. 90 (14): 3192–3197. doi:10.1021/j100405a029. ISSN 0022-3654.
  3. ^ a b Mei, Yanbo (2020). Complexes, Heterocycles, and Depolymerizable Polymers. Made from Building Blocks with Low-coordinated Phosphorus (Thesis). ETH Zurich. p. 18. doi:10.3929/ethz-b-000431853. hdl:20.500.11850/431853. Retrieved 6 October 2020.
  4. ^ a b c d Brown, Glenn Halstead (1951). Reactions of phosphine and phosphonium iodide (PhD). Iowa State College. Retrieved 5 Oct 2020.
  5. ^ Work, J. B.; Mattern, J. A.; Antonucci, R. (5 January 2007). "Phosphonium Iodide". Inorganic Syntheses: 141–144. doi:10.1002/9780470132333.ch41.
  6. ^ Dickinson, Roscoe G. (July 1922). "The Crystal Structure of Phosphonium Iodide". Journal of the American Chemical Society. 44 (7): 1489–1497. doi:10.1021/ja01428a015.
  7. ^ Sequeira, A.; Hamilton, Walter C. (September 1967). "Hydrogen Bonding in Phosphonium Iodide: A Neutron-Diffraction Study". The Journal of Chemical Physics. 47 (5): 1818–1822. Bibcode:1967JChPh..47.1818S. doi:10.1063/1.1712171.
  8. ^ Levchuk, Ievgen (2017). Design and optimization of luminescent semiconductor nanocrystals for optoelectronic applications (PDF) (faculty). University of Erlangen–Nuremberg. p. 140. Retrieved 6 Oct 2020.
  9. ^ Osadchenko, Ivan M; Tomilov, Andrei P (30 June 1969). "Phosphorus Hydrides". Russian Chemical Reviews. 38 (6): 495–504. Bibcode:1969RuCRv..38..495O. doi:10.1070/RC1969v038n06ABEH001756. S2CID 250872306.
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