What is "phosphorane"

n. (context chemistry English) the hydride of phosphorus PH₅ and any of its hydrocarbyl derivatives

A phosphorane ( IUPAC name: λ-phosphane) is a functional group in organophosphorus chemistry with pentavalent phosphorus. It has the general formula PR. The parent hydride compound is the hypothetical molecule PH. The derivative pentaphenylphosphorane (PhP) is stable.

Phosphoranes 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.

Phosphoranes of the type RP=CR 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 PhP=CH.