Phosphonium

Phosphonium

Names
Systematic IUPAC name Phosphanium[1] (substitutive) Tetrahydridophosphorus(1+)[1] (additive)
Identifiers
ChEBI	CHEBI:30282
ChemSpider	4574014 Y
Gmelin Reference	292
InChI InChI=1S/H3P/h1H3/p+1 Y Key: XYFCBTPGUUZFHI-UHFFFAOYSA-O Y
Jmol-3D images	Image
PubChem	5460504
SMILES [PH4+]
Properties
Chemical formula	PH+ 4
Molar mass	35.00552 g mol−1
Related compounds
Other cations	Ammonium
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

The phosphonium (more obscurely: phosphinium) cation describes polyatomic cations with the chemical formula PR+
4.^[2] 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 through protonation of phosphines:

PR₃ + H⁺ → HPR₃⁺

Many organic quaternary phosphonium cations (P+
R
4) 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

References