Phosphonium

Phosphonium
Systematic name Phosphanium (substitutive) Tetrahydridophosphorus(1+) (additive)
Identifiers
PubChem	5460504
ChemSpider	4574014 Y
ChEBI	CHEBI:30282
Gmelin Reference	292
Jmol-3D images	Image 1
SMILES [PH4+]
InChI InChI=1S/H3P/h1H3/p+1 Y Key: XYFCBTPGUUZFHI-UHFFFAOYSA-O Y
Properties
Molecular formula	PH+ 4
Molar mass	35.00552 g mol-1
Exact mass	35.005061640 g mol-1
Related compounds
Other cations	Ammonium
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

The phosphonium (more obscurely: phosphinium) cation describes positively charged polyatomic cations with the chemical formula PR+
4. 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:

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 (P⁺R₄) are produced by alkylation of organophosphines. For example the reaction of triphenylphosphine 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

• Ammonium (NH₄⁺)
• Hydronium (H₃O⁺)
• Onium compounds