Trimethyl phosphite is an
organophosphorus compound
Organophosphorus compounds are organic compounds containing phosphorus. They are used primarily in pest control as an alternative to chlorinated hydrocarbons that persist in the environment. Some organophosphorus compounds are highly effective in ...
with the
formula P(OCH
3)
3, often abbreviated P(OMe)
3. It is a colorless liquid with a highly pungent odor. It is the simplest
phosphite ester and finds used as a
ligand
In coordination chemistry, a ligand is an ion or molecule ( functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's ele ...
in
organometallic chemistry and as a reagent in
organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one o ...
. The molecule features a pyramidal phosphorus(III) center bound to three
methoxy
In organic chemistry, a methoxy group is the functional group consisting of a methyl group bound to oxygen. This alkoxy group has the formula .
On a benzene ring, the Hammett equation classifies a methoxy substituent at the ''para'' position ...
groups.
Synthesis
Trimethyl phosphite is in principle obtainable by methanolysis of
phosphorus trichloride
Phosphorus trichloride is an inorganic compound with the chemical formula PCl3. A colorless liquid when pure, it is an important industrial chemical, being used for the manufacture of phosphites and other organophosphorus compounds. It is toxic a ...
, say in the presence of a proton accepting base. This method suffers from numerous side reactions however. The use of
sodium methoxide
Sodium methoxide is the simplest sodium alkoxide. With the formula , it is a white solid, which is formed by the deprotonation of methanol. Itis a widely used reagent in industry and the laboratory. It is also a dangerously caustic base. ...
is superior:
:
Reactions
Trimethyl phosphite is susceptible to oxidation to
trimethyl phosphate
Trimethyl phosphate is the trimethyl ester of phosphoric acid. It is a colourless, nonvolatile liquid. It has some specialized uses in the production of other compounds.
Production
Trimethyl phosphate is prepared by treating phosphorus oxychlo ...
:
:
It reacts with a catalytic amount of methyl iodide in the
Arbuzov reaction Arbuzov (masculine, russian: Арбузов) or Arbuzova (feminine, russian: Арбузовa) is a Russian surname, derived from the word арбуз (''arbooz'', meaning "watermelon
Watermelon (''Citrullus lanatus'') is a flowering plant spec ...
to give
dimethyl methylphosphonate:
:P(OCH
3)
3 → CH
3P(O)(OCH
3)
2
As a ligand, trimethyl phosphite has a smaller
cone angle
In coordination chemistry, the ligand cone angle (a common example being the Tolman cone angle or ''θ'') is a measure of the steric bulk of a ligand in a transition metal coordination complex. It is defined as the solid angle formed with the me ...
and better acceptor properties relative to
trimethylphosphine
Trimethylphosphine is a neutral organophosphorus compound with the formula P(CH3)3, commonly abbreviated as PMe3. This colorless liquid has a strongly unpleasant odor, characteristic of alkylphosphines. The compound is a common ligand in coordi ...
. A representative derivative is the colorless tetrahedral complex Ni(P(OMe)
3)
4 (
m.p.
A member of parliament (MP) is the representative in parliament of the people who live in their electoral district. In many countries with bicameral parliaments, this term refers only to members of the lower house since upper house members of ...
108 °C). The tridentate ligand called the
Kläui ligand is derived from trimethyl phosphite. The formation of this ligand illustrates the susceptibility of trimethyl phosphite (and metal complexes thereof) to the Arbuzov reaction.
Trimethyl phosphite is also used as a mild desulfurization reagent in organic synthesis, for example in the preparation of derivatives of
tetrathiafulvalene
Tetrathiafulvalene is an organosulfur compound with the formula (. Studies on this heterocyclic compound contributed to the development of molecular electronics. TTF is related to the hydrocarbon fulvalene, , by replacement of four CH groups ...
.
Toxicity
The
LD50 is 1600–2890 mg/kg (oral, rat).
References
{{Reflist
External links
WebBook page for C3H9PO3
Organophosphites
Methyl esters
Foul-smelling chemicals