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This article is about P2H4. For other uses, see diphosphines.
Stereo structural formula of diphosphane with explicit hydrogens Ball-and-stick model of diphosphane
CAS number 13445-50-6 N
PubChem 139283
ChemSpider 122832 N
Jmol-3D images Image 1
Molecular formula H4P2
Molar mass 65.98 g mol−1
Melting point −99 °C (−146 °F; 174 K)
Boiling point 63.5 °C (146.3 °F; 336.6 K) (Extrapolated, decomposes)
Related compounds
Other anions ammonia
Other cations diphosphines
Related Binary Phosphorus halides diphosphorus tetrafluoride
diphosphorus tetrachloride
diphosphorus tetrabromide
diphosphorus tetraiodide
Related compounds phosphane
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Diphosphane is an inorganic compound with the chemical formula P2H4. This colourless liquid is one of several binary phosphorus hydrides. It is the impurity that typically causes samples of phosphine to ignite in air. An older name is diphosphine.

Properties, preparation, reactions[edit]

Diphosphane adopts the gauche conformation (like hydrazine, less symmetrical than shown in the image) with a P-P distance of 2.219 angstroms. It is nonbasic, unstable at room temperature, and spontaneously flammable in air. It is only poorly soluble in water but dissolves in organic solvents. Its 1H NMR spectrum consists of 32 lines resulting from an A2XX'A'2 splitting system.[1]

Diphosphane is produced by the hydrolysis of calcium monophosphide, which can be described as the Ca2+ derivative of P24-. According to an optimized procedure, hydrolysis of 400 g of CaP at -30 °C gives about 20 g of product, slightly contaminated with phosphine.

Reaction of diphosphine with butyllithium affords a variety of condensed polyphosphine compounds.

Organic diphosphanes[edit]

A variety of organic derivatives of diphosphane are known. These species are prepared by reductive coupling, e.g. from chlorodiphenylphosphine:

ClPPh2 + 2 Na → Ph2PPPh2 + 2 NaCl

The methyl compound P2Me4 is prepared by the reaction of thiophosphoryl chloride with methylmagnesium bromide.


  1. ^ Marianne Baudler, Klaus Glinka (1993). "Monocyclic and polycyclic phosphines". Chem. Rev. 93 (4): 1623–1667. doi:10.1021/cr00020a010.