Phosphoranes
A phosphorane (IUPAC name: λ5-phosphane) is a functional group in organophosphorus chemistry with pentavalent phosphorus. Phosphoranes have the general formula PR5.
Phosphoranes of the type PX5 adopt a trigonal bipyramidal molecular geometry with the two apical bonds longer than the three equatorial bonds. Hypervalent bonding is described by inclusion of non-bonding MOs, as also invoked for the closely related molecule phosphorus pentafluoride.[1]
Examples
[edit | edit source]The parent hydride compound is the hypothetical molecule PH5.
Pentaphenylphosphorane (Ph5P) is stable.[2]
Pentaalkoxyphosphoranes are more common with electronegative substituents. Examples of P(OR)5 (R = alkyl), have however been prepared by reaction of phosphites with benzene alkyl sulfenates:[3]
- P(OR)3 + 2 ROSC6H5 → P(OR)5 + (SC6H5)2
Wittig reagents
[edit | edit source]Phosphoranes of the type R3P=CR2 are more common and more important. Phosphoranes are also considered to be one of the resonance structures of ylides, these compounds feature a tetrahedral phosphorus center including a phosphorus–carbon double bond. These compounds are used as reagents in the Wittig reaction, for instance methylenetriphenylphosphorane or Ph3P=CH2.
See also
[edit | edit source]References
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- ^ ^ A Guide to Organophosphorus Chemistry Louis D. Quin 2000 John Wiley & Sons Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
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