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Bis(triphenylphosphine)iminium chloride

Bis(triphenylphosphine)iminium chloride
IUPAC name μ-nitrido-Bis(triphenylphosphorus) chloride
Other names PPN chloride
Bis(triphenylphosphine)iminium chloride
Hexaphenyldiphosphazenium chloride
CAS number 21050-13-5
Molecular formula C36H30ClNP2
Molar mass 574.03 g/mol
Appearance colourless solid
Density  ?? g/cm3, solid
Melting point

260-2 °C

Solubility in water moderate
R-phrases 36/37/38
S-phrases 26-36
Related Compounds
Related compounds Tetraphenylarsonium chloride
Tetrabutylammonium chloride
tetrabutylammonium chloride
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

Bis(triphenylphosphine)iminium chloride is the chemical compound with the formula [(C6H5)3P)2N]Cl, often written [(Ph3P)2N]Cl and abbreviated PPNCl. This colorless salt is a useful source of the PPN+ cation, which is used to isolate reactive anions. PPN+ is a phosphazene.

Synthesis and structure

PPNCl is prepared in two steps from triphenylphosphine:[1]

Ph3P + Cl2 → Ph3PCl2

This phosphorus(V) chloride is related to phosphorus pentachloride. Treatment of this species with hydroxylamine in the presence of Ph3P results in replacement of the P-Cl bonds by P=N bonds:

2 Ph3PCl2 + NH2OH.HCl + Ph3P → {[Ph3P]2N}Cl + 4HCl + Ph3PO

In PPN+ salts, P-N bond lengths are equivalent, 1.58 Å. The cation is centrosymmetric; its connectivity is indicated by Ph3P=N=PPh3+.


PPN chloride is the main precursor to PPN+ salts. Using salt metathesis reactions, nitrite, azide, and other small inorganic anions can be obtained with PPN+ cations. These salts are soluble in polar organic solvents.

PPN+ forms crystalline salts with a range of anions that are otherwise difficult to crystallize. Its effectiveness is partially attributed to its rigidity, reflecting the presence of six phenyl rings. Often PPN+ forms salts that are more air-stable than salts with smaller cations such as those containing quaternary ammonium or alkali metal cations. This effect is attributed to the steric shielding provided by this voluminous cation. Illustrative PPN+ salts of reactive anions include PPN[HFe(CO)4], PPN[Co(CO)4], and PPN[Fe(CO)3NO]. The role of ion pairing in chemical reactions is often clarified by examination of the related salt derived from PPN+.


  1. ^ Ruff, J. K.; Schlientz, W. J. “μ-nitrido-Bis(triphenylphosphorus)(1+ (“PPN”) Salts with Metal Carbonyl Anions” Inorganic Syntheses, 1974, volume XV, pages 84-90.
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Bis(triphenylphosphine)iminium_chloride". A list of authors is available in Wikipedia.
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