Diphosphane, or diphosphine, is an
inorganic compound
An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bondsthat is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''.
Inorgan ...
with the chemical formula . This colourless liquid is one of several binary phosphorus hydrides. It is the impurity that typically causes samples of
phosphine
Phosphine (IUPAC name: phosphane) is a colorless, flammable, highly toxic compound with the chemical formula , classed as a pnictogen hydride. Pure phosphine is odorless, but technical grade samples have a highly unpleasant odor like rotting ...
to ignite in air.
Properties, preparation, reactions
Diphosphane adopts the
gauche conformation (like
hydrazine
Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly hazardous unless handled in solution as, for example, hydraz ...
, 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 A
2XX'A'
2 splitting system.
Diphosphane is produced by the hydrolysis of
calcium monophosphide, which can be described as the Ca
2+ derivative of . According to an optimized procedure, hydrolysis of 400 g of CaP at −30 °C gives about 20 g of product, slightly contaminated with
phosphine
Phosphine (IUPAC name: phosphane) is a colorless, flammable, highly toxic compound with the chemical formula , classed as a pnictogen hydride. Pure phosphine is odorless, but technical grade samples have a highly unpleasant odor like rotting ...
.
Reaction of diphosphane with
butyllithium affords a variety of condensed polyphosphine compounds.
Organic diphosphanes
A variety of organic derivatives of diphosphane are known, but asymmetric diphosphanes are only stable at cryogenic temperatures. Otherwise, the substituents facily redistribute on the phosphorus centers to give a mixture of products. On the other hand, there appears to be a substantial barrier to
chiral inversion.
The central bond is weak, and easily adds substituents.
The simplest synthesis method heats a phosphorus halide and a phosphane:
:
Alkali metals can replace the hydrogen in that reaction (i.e., a dialkyl
phosphide), and in some rare cases a dialkylamine can replace the halide. Symmetric diphosphanes are easily prepared by reductive coupling, e.g.
tetraphenyldiphosphine from
chlorodiphenylphosphine:
:
Ultraviolet radiation decomposes
mercury(II) dialkylphosphides to the metal and a dialkylphosphane.
The methyl compound is prepared by the reduction of , which is produced by methylation of
thiophosphoryl chloride with methylmagnesium bromide.
See also
*
Pnictogen hydride
References
Phosphorus hydrides
Foul-smelling chemicals
Pyrophoric materials
{{Hydrides by group