Iminophosphorane
Image:Ph3P=NPh.png, an example of a phosphanimine.]]
Iminophosphorane (or, more correctly, phosphanimine) is a kind of organophosphorus compound with the formula {{chem2|R3PNR'}}. Like the corresponding phosphine oxides and Wittig reagents, phosphanimines are ylides. Their bonding is described by two resonance structures.{{cite journal |doi=10.1039/D3CS00290J |title=Reactions of main group compounds with azides forming organic nitrogen-containing species |date=2023 |last1=Zhu |first1=Lizhao |last2=Kinjo |first2=Rei |journal=Chemical Society Reviews |volume=52 |issue=16 |pages=5563–5606 |pmid=37519098 |hdl=10356/174235 |hdl-access=free }}
Preparation
File:Iminophosphorane formation.png
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 phosphanimine has the formula {{chem2|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 {{chem2|Ph3P}}:{{cite book | last1 = Ruff|first1=J.K.|last2=Schlientz|first2=W.J. |chapter=μ-Nitridobis(triphenylphosphorus)(l+) ("PPN") Salts with Metal Carbonyl Anions |title=Inorganic Syntheses | series = Inorganic Synthesis | volume = 15 | year = 1974 | pages = 84–90 | doi = 10.1002/9780470132463.ch19|isbn=9780470132463}}
:{{chem2|Ph3P + Cl2 → Ph3PCl2}}
:{{chem2|2 Ph3PCl2 + NH2OH*HCl + Ph3P → [(Ph3P)2N]Cl + 4HCl + Ph3PO}}
A phosphanimine is obtainable from trimethylsilyl azide and triphenylphosphine. Desilylation gives the anion {{chem2|Ph3P\dN-}}.{{cite journal |doi=10.1016/s0277-5387(00)83838-3 |title=Phosphorane iminato complexes of transition metals |date=1989 |last1=Dehnicke |first1=Kurt |last2=Strähle |first2=Joachim |journal=Polyhedron |volume=8 |issue=6 |pages=707–726 }}
Reactions
Phosphanimines 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.{{cite journal |doi=10.1021/acs.chemrev.9b00665 |title=The Staudinger Ligation |date=2020 |last1=Bednarek |first1=Christin |last2=Wehl |first2=Ilona |last3=Jung |first3=Nicole |last4=Schepers |first4=Ute |last5=Bräse |first5=Stefan |journal=Chemical Reviews |volume=120 |issue=10 |pages=4301–4354 |pmid=32356973 }}
See also
- Phosphazenes are analogues of iminophosphoranes with the formula {{chem2|(R2N)3P\dNR'}}