Phosphonium
Encyclopedia
The phosphonium cation describes positively charged polyatomic cation
s with the chemical formula
. Salts of the parent PH4+ are rarely encountered, but this ion is an intermediate in the preparation of the industrially useful tetrakis(hydroxymethyl)phosphonium chloride
:
Organic phosphonium salts are common reagents in the laboratory. Those with a P-H bond are produced protonation of phosphines:
Many organic quaternary phosphonium cations are produced by alkylation of organophosphines. For example the reaction of triphenylphosphine
with methyl iodide gives methyltriphenylphosphonium iodide, the precursor to a Wittig reagent:
The cation tetraphenylphosphonium (PPh4+) is a useful precipitating agent, analogous to quaternary ammonium salts used in phase transfer catalysis.
Polyatomic ion
A polyatomic ion, also known as a molecular ion, is a charged species composed of two or more atoms covalently bonded or of a metal complex that can be considered as acting as a single unit in the context of acid and base chemistry or in the formation of salts. The prefix "poly-" means "many," in...
s with the chemical formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
. Salts of the parent PH4+ are rarely encountered, but this ion is an intermediate in the preparation of the industrially useful tetrakis(hydroxymethyl)phosphonium chloride
Tetrakis(hydroxymethyl)phosphonium chloride
Tetrakisphosphonium chloride is a phosphonium salt with the chemical formula [4P]Cl. The cation 4P+ is a four-coordinate phosphorus compound with the phosphorus atom carrying a positive charge...
:
- PH3 + HCl + 4 CH2O → P(CH2OH)4+Cl-
Organic phosphonium salts are common reagents in the laboratory. Those with a P-H bond are produced protonation of phosphines:
- PR3 + H+ → HPR3+
Many organic quaternary phosphonium cations are produced by alkylation of organophosphines. For example the reaction of triphenylphosphine
Triphenylphosphine
Triphenylphosphine is a common organophosphorus compound with the formula P3 - often abbreviated to PPh3 or Ph3P. It is widely used in the synthesis of organic and organometallic compounds. PPh3 exists as relatively air stable, colorless crystals at room temperature...
with methyl iodide gives methyltriphenylphosphonium iodide, the precursor to a Wittig reagent:
- PPh3 + CH3I → CH3PPh3+I-
The cation tetraphenylphosphonium (PPh4+) is a useful precipitating agent, analogous to quaternary ammonium salts used in phase transfer catalysis.
See also
- AmmoniumAmmoniumThe ammonium cation is a positively charged polyatomic cation with the chemical formula NH. It is formed by the protonation of ammonia...
(NH4+) - HydroniumHydroniumIn chemistry, a hydronium ion is the cation , a type of oxonium ion produced by protonation of water. This cation is often used to represent the nature of the proton in aqueous solution, where the proton is highly solvated...
(H3O+) - Onium compoundsOnium compoundsOnium compounds are cations derived by the protonation of mononuclear parent hydrides of elements of the nitrogen group , chalcogens , or halogens , and similar cations derived by the substitution of hydrogen atoms in the former by other groups, such as organic radicals, or halogens, for example...