Diphosphane

Diphosphane

Names
IUPAC name Diphosphane
Systematic IUPAC name Diphosphane (substitutive) Tetrahydidodiphosphorus(P—P) (additive)
Other names Diphosphine
Identifiers
CAS Number	13445-50-6
3D model (Jmol)	Interactive image
ChEBI	CHEBI:35880
ChemSpider	122832
PubChem	139283
InChI InChI=1S/H4P2/c1-2/h1-2H2 Key: VURFVHCLMJOLKN-UHFFFAOYSA-N
SMILES PP
Properties
Chemical 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 hydrazine triazane
Other cations	diphosphines
Related Binary Phosphorus halides	diphosphorus tetrafluoride diphosphorus tetrachloride diphosphorus tetrabromide diphosphorus tetraiodide
Related compounds	phosphane triphosphane diphosphene diphosphenes
Except where otherwise noted, 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

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

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

2ClPPh₂ + 2 Na → Ph₂PPPh₂ + 2 NaCl

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

See also

• Pnictogen hydride

References

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