Trimethylphosphine is a neutral

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 i ...

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 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 elect ...

coordination chemistry A coordination complex consists of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as ''ligands'' or complexing agents. Man ...

Structure and bonding

It is a pyramidal molecule with approximate ''C''_3''v''

symmetry Symmetry (from grc, συμμετρία "agreement in dimensions, due proportion, arrangement") in everyday language refers to a sense of harmonious and beautiful proportion and balance. In mathematics, "symmetry" has a more precise definiti ...

. The C–P–C bond angles are approximately 98.6°. The C–P–C bond angles are consistent with the notion that phosphorus predominantly uses the 3p orbitals for forming bonds and that there is little sp hybridization of the phosphorus atom. The latter is a common feature of the chemistry of phosphorus. As a result, the lone pair of trimethylphosphine has predominantly s-character as is the case for phosphine, PH₃. PMe₃ can be prepared by the treatment of

triphenyl phosphite Triphenyl phosphite is the organophosphorus compound with the formula P(OC6H5)3. It is a colourless viscous liquid. Preparation Triphenylphosphite is prepared from phosphorus trichloride and phenol in the presence of a catalytic amount of base: :P ...

with

methylmagnesium chloride Methylmagnesium chloride is an organometallic compound with the general formula CH3MgCl. This highly flammable, colorless, and moisture sensitive material is the simplest Grignard reagent and is commercially available, usually as a solution in ...

: : 3 CH₃MgCl + P(OC₆H₅)₃ → P(CH₃)₃ + 3 C₆H₅OMgCl The synthesis is conducted in dibutyl ether, from which the more volatile PMe₃ can be distilled.

Reactions

With a pK_a of 8.65, PMe₃ reacts with strong acids to give salts PMe₃. This reaction is reversible. With strong bases, such as

alkyl lithium compound In organometallic chemistry, organolithium reagents are chemical compounds that contain carbon–lithium (C–Li) bonds. These reagents are important in organic synthesis, and are frequently used to transfer the organic group or the lithium atom ...

s, a methyl group undergoes deprotonation to give PMe₂CH₂Li. PMe₃ is easily oxidised to the phosphine oxide with oxygen. It reacts with

methyl bromide Bromomethane, commonly known as methyl bromide, is an organobromine compound with formula C H3 Br. This colorless, odorless, nonflammable gas is produced both industrially and biologically. It has a tetrahedral shape and it is a recognized ozo ...

to give

tetramethylphosphonium bromide Tetramethylphosphonium bromide is an organophosphorus compound with the formula (CH3)4PBr. It is a white, water-soluble solid, the salt of the cation tetramethylphosphonium and the bromide anion. It is prepared by treating trimethylphosphine wit ...

Coordination chemistry

Trimethylphosphine is a highly basic

that forms complexes with most metals. As a ligand, trimethylphosphine's

Tolman 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 met ...

is 118°. This angle is an indication of the amount of steric protection that this ligand provides to the metal that to which it is bound. Being a relatively compact phosphine, several can bind to a single transition metal, as illustrated by the existence of Pt(PEt₃)₄. Its complex with silver iodide, AgI(PMe₃) is an air-stable solid that releases PMe₃ upon heating.

Safety

PMe₃ is toxic and

pyrophoric A substance is pyrophoric (from grc-gre, πυροφόρος, , 'fire-bearing') if it ignites spontaneously in air at or below (for gases) or within 5 minutes after coming into contact with air (for liquids and solids). Examples are organolith ...

. It converts to a much safer

phosphine oxide Phosphine oxides are phosphorus compounds with the formula OPX3. When X = alkyl or aryl, these are organophosphine oxides. Triphenylphosphine oxide is an example. An inorganic phosphine oxide is phosphoryl chloride (POCl3). Structure and bondi ...

upon treatment with

sodium hypochlorite Sodium hypochlorite (commonly known in a dilute solution as bleach) is an inorganic chemical compound with the formula NaOCl (or NaClO), comprising a sodium cation () and a hypochlorite anion (or ). It may also be viewed as the sodium s ...

hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3 ...

.http://www.sigmaaldrich.com/catalog/product/aldrich/324116?lang=en®ion=US&cm_sp=Insite-_-prodRecCold_xorders-_-prodRecCold2-2

References

{{reflist Tertiary phosphines Foul-smelling chemicals