Iminophosphorane



Iminophosphorane is a kind of organophosphorus compound with the formula R3PNR'. Like the corresponding phosphine oxides and Wittig reagents, iminophosphoranes are ylides. Their bonding is described by two resonance structures.



Preparation
Aza-ylides can be obtained via the reaction of a tertiary phosphine and an organic azide with the loss of dinitrogen. Triphenylphosphine is a commonly used phosphine.

Examples
The parent iminophosphorane has the formula H3P\dNH (registry number 25682-80-8) remains only of theoretical interest. Of practical value are derivatives of triorganophosphines and organic amines. A prototype is the phenyl imide derivative of triphenylphosphine, a white, lipophilic solid.

Bis(triphenylphosphine)iminium chloride, a common iminophosphorane, is prepared in two steps from triphenylphosphine Ph3P:
 * Ph3P + Cl2 → Ph3PCl2
 * 2 Ph3PCl2 + NH2OH*HCl + Ph3P → [(Ph3P)2N]Cl + 4HCl + Ph3PO

An iminophosphorane is obtainable from trimethylsilyl azide and triphenylphosphine. Desilylation gives the anion Ph3P\dN-.

Reactions
Iminophosphoranes are one of the components in the aza-Wittig reaction. The other component is an aldehyde or a ketone. They also are components of the Staudinger ligation.