Phosphoranes

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The structure of a typical phosphorane group.

A phosphorane (

pentavalent phosphorus
. Phosphoranes have the general formula PR5.

Phosphoranes of the type PX5 adopt a

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

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

sulfenates:[3]

P(OR)3 + 2 ROSC6H5 → P(OR)5 + (SC6H5)2

Wittig reagents

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

References

  1. ISBN 0-13-035471-6
    .
  2. ISBN 0-471-31824-8
  3. doi:10.1021/ja00449a044
    .
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