A
phosphonium salt is a salt containing the
phosphonium (PH
4+) ion such as phosphonium iodide (PH
4+I
-). More commonly, phosphonium refers to a
quaternary organic derivative such as
tetraphenylphosphonium chloride, (C
6H
5)
4P
+ Cl
- and tetramethylphosphonium iodide,
[P(CH
3)
4]+I
-.