Phosphorus pentaiodide

Phosphorus pentaiodide is a hypothetical inorganic compound with formula PI5. 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]

"PI5" redirects here. Not to be confused with Pi5.
Phosphorus pentaiodide
Names
IUPAC name
Phosphorus(V) iodide
Other names
  • Pentaiodophosphorane
  • Pentaiodophosphorus
  • Phosphorus pentaiodide
  • Tetraiodophosphonium iodide
Identifiers
Properties
PI5
Molar mass 665.49611 g·mol−1
Appearance Brown-black crystalline solid (disputed)[1]
Melting point 41 °C (106 °F; 314 K) (disputed)[1]
Related compounds
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

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
  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.
  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.
  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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