Trimethyl phosphite is an organophosphorus compound with the formula P(OCH₃)₃, often abbreviated P(OMe)₃. It is a colorless liquid with a highly pungent odor. It is the simplest

phosphite ester The general structure of a phosphite ester showing the lone pairs on the P In organic chemistry, a phosphite ester or organophosphite usually refers to an organophosphorous compound with the formula P(OR)3. They can be considered as esters of a ...

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 elec ...

in organometallic chemistry and as a reagent in organic synthesis. 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 a ...

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 toxi ...

, 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. P ...

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 oxychlor ...

: : 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"). It may refer to: * Aleksandr Arbuzov (1877–1968), Russian and ...

to give

dimethyl methylphosphonate Ethane ( , ) is an organic chemical compound with chemical formula . At standard temperature and pressure, ethane is a colorless, odorless gas. Like many hydrocarbons, ethane is isolated on an industrial scale from natural gas and as a petroc ...

: :P(OCH₃)₃ → CH₃P(O)(OCH₃)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 coordin ...

. A representative derivative is the colorless tetrahedral complex Ni(P(OMe)₃)₄ ( m.p. 108 °C). The tridentate ligand called the

Kläui ligand The Kläui ligand is the anion −. The ligand, popularized by Wolfgang Kläui, binds metals and metalloids via a facial O3 donor set. Related tridentate and tripodal anionic ligands include trispyrazolylborates. : 160px, General structure o ...

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 w ...

Toxicity

The LD₅₀ is 1600–2890 mg/kg (oral, rat).

References

{{Reflist

External links

WebBook page for C3H9PO3

Organophosphites Methyl esters Foul-smelling chemicals