Phosphorane

Phosphorane

A phosphorane is a functional group in chemistry with pentavalent phosphorus. It has the general structure PR5. The parent compound is the non-stable phosphoran PH5 or λ5-Phosphan (lambda5phosphan) according to IUPAC nomenclature. In the same vein Pentaphenylphosphoran Ph5P is properly named Pentaphenyl-λ5-Phosphan.

Phosphoranes adopt a trigonal bipyramidal molecular geometry with the two apical bonds longer than the three equatorial bonds. The accepted view for the chemical bonding taking place is that of a rehybridization in phosphorus of sp³ orbitals with a dz² to a new sp³p orbital. The dz² is considered very energetic and alternative theories attempt to explain this type of bonding better. In a three-center four-electron bond model two resonance structures along the apical bonds are X-...P+-X and X-P+...X- Ref|Quin.

Phosphoranes of the type R3P=CR2 with a phosphorus carbon double bond or ylide are reagents in the Wittig reaction, for instance methylenetriphenylphosphorane or Ph3P=CH2.

Other phosphorus compounds are trivalent phosphines and tetravalent phosphonium salts.

See also

* Organophosphorus chemistry

References

# "A Guide to Organophosphorus Chemistry" Louis D. Quin 2000 John Wiley & Sons ISBN 0-471-31824-8


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