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Phosphorus pentaiodide
Names
	IUPAC name Phosphorus(V) iodide
	Other names Pentaiodophosphorane; Pentaiodophosphorus; Phosphorus pentaiodide; Tetraiodophosphonium iodide;
Identifiers
CAS Number	66656-29-9 ;
3D model (JSmol)	Interactive image;
PubChem CID	12617301;
CompTox Dashboard (EPA)	DTXSID30504485 ;
	InChI InChI=1S/I5P/c1-6(2,3,4)5 Key: NCCBCEHAGCSKEA-UHFFFAOYSA-N;
	SMILES P(I)(I)(I)(I)I;
Properties
Chemical formula	PI5
Molar mass	665.49611 g·mol−1
Appearance	Brown-black crystalline solid (disputed)
Melting point	41 °C (106 °F; 314 K) (disputed)
Related compounds
Related compounds	Phosphorus pentafluoride; Phosphorus pentachloride; Phosphorus pentabromide;
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Phosphorus pentaiodide is a hypothetical inorganic compound with formula P I₅. The existence of this compound has been claimed intermittently since the early 1900s.^[2] The claim is disputed: "The pentaiodide does not exist (except perhaps as PI₃·I₂, but certainly not as [PI₄]⁺I⁻...)".^[3]

Claims

Phosphorus pentaiodide was reported to be a brown-black crystalline solid melting at 41 °C produced by the reaction of lithium iodide and phosphorus pentachloride in methyl iodide, however, this claim is disputed and probably generated a mixture of phosphorus triiodide and iodine.^[1]^[4]

Although phosphorus pentaiodide has been claimed to exist in the form of [PI₄]⁺I⁻ (tetraiodophosphonium iodide), experimental and theoretical data refutes this claim.^[5]^[1]

Derivatives

Unlike the elusive PI₅, the [PI₄]⁺ cation (tetraiodophosphonium cation) is widely known. This cation is known with the anions tetraiodoaluminate [AlI₄]⁻, hexafluoroarsenate [AsF₆]⁻, hexafluoroantimonate [SbF₆]⁻ and tetraiodogallate [GaI₄]⁻. ^[4]^[5]

References

^ ^a ^b ^c ^d N. G. Feshchenko; V. G. Kostina; A. V. Kirsanov (1978). "Chem Inform Abstract: SYNTHESIS OF PHOSPHORUS PENTAIODIDE". Russian Journal of General Chemistry. 48 (23): 195. doi:10.1002/chin.197823039.
^ Walker and Johnson, J. Chem. Soc. 87, 1595 (1905).
^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
^ ^a ^b Inis Tornieporth-Getting; Thomas Klapötke (1990). "The preparation and characterization by Raman spectroscopy of Pl4+AsF6– containing the tetraiodophosphonium cation". Journal of the Chemical Society, Chemical Communications (2): 132–133. doi:10.1039/C39900000132.
^ ^a ^b Martin Kaupp; Christoph Aubauer; Günter Engelhardt; Thomas M. Klapötke; Olga L. Malkina (1999). "The PI+4 cation has an extremely large negative 31P nuclear magnetic resonance chemical shift, due to spin–orbit coupling: A quantum-chemical prediction and its confirmation by solid-state nuclear magnetic resonance spectroscopy". The Journal of Chemical Physics. 110 (8): 3897–3902. Bibcode:1999JChPh.110.3897K. doi:10.1063/1.478243.

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[claim-1] N. G. Feshchenko; V. G. Kostina; A. V. Kirsanov (1978). "Chem Inform Abstract: SYNTHESIS OF PHOSPHORUS PENTAIODIDE". Russian Journal of General Chemistry. 48 (23): 195. doi:10.1002/chin.197823039.

[2] Walker and Johnson, J. Chem. Soc. 87, 1595 (1905).

[3] Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.

[refute-4] Inis Tornieporth-Getting; Thomas Klapötke (1990). "The preparation and characterization by Raman spectroscopy of Pl4+AsF6– containing the tetraiodophosphonium cation". Journal of the Chemical Society, Chemical Communications (2): 132–133. doi:10.1039/C39900000132.

[pi4-5] Martin Kaupp; Christoph Aubauer; Günter Engelhardt; Thomas M. Klapötke; Olga L. Malkina (1999). "The PI+4 cation has an extremely large negative 31P nuclear magnetic resonance chemical shift, due to spin–orbit coupling: A quantum-chemical prediction and its confirmation by solid-state nuclear magnetic resonance spectroscopy". The Journal of Chemical Physics. 110 (8): 3897–3902. Bibcode:1999JChPh.110.3897K. doi:10.1063/1.478243.

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