Trimethylphosphine

Trimethylphosphine

Names
IUPAC name Trimethylphosphane
Other names TMP Trimethylphosphorus
Properties
Chemical formula	C3H9P P(CH3)3 PMe3
Molar mass	76.079 g/mol
Appearance	Colorless volatile liquid
Odor	Unpleasant, pungent
Density	0.738 g/cm3 (20 °C)
Melting point	−86 °C (−123 °F; 187 K)
Boiling point	38 °C (100 °F; 311 K)
Solubility in water	Soluble
Solubility	Miscible with THF, toluene
Vapor pressure	374.3 mmHg at 20 °C 1232.6 mmHg at 55 °C
Acidity (pKa)	8.65
Hazards
Safety data sheet	Sigma-Aldrich
Flash point	−19 °C (−2 °F; 254 K)
Related compounds
Related compounds	Phosphine Triphenylphosphine
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Trimethylphosphine is the organophosphorus compound with the formula P(CH₃)₃, commonly abbreviated as PMe₃. This colorless liquid has a strongly unpleasant odor, characteristic of alkylphosphines. It is often used as ligand in coordination chemistry.

Properties

Chemical

Trimethylphosphine is a weak base, but does form stable salts with strong acids.

Trimethylphosphine is a highly basic ligand that forms complexes with most metals. As a ligand, trimethylphosphine's Tolman cone angle is 118°.

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.

Physical

Trimethylphosphine is a volatile toxic colorless liquid, with a strong repulsive odor, described by some as somewhere between smelly goat and vomit. It is miscible with many organic solvents.

Availability

This compound is sold by many chemical suppliers, but due to its hazards it's hard to acquire and quite expensive.

Preparation

Trimethylphosphine can be prepared by the treatment of triphenyl phosphite with methylmagnesium chloride:

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.

Projects

• Ligand in coordination chemistry
• Make trimethylphosphine oxide

Handling

Safety

Trimethylphosphine is pyrophoric and very toxic.

Storage

Trimethylphosphine must be kept in airtight containers, in specially designed storage cabinets, in a dry and well ventilated place. Containers which are opened must be carefully resealed and kept upright to prevent leakage.

Recommended storage temperature 2 - 8 °C

Disposal

Trimethylphosphine is best neutralized by burning it outside or in a special incinerator.

Trimethylphosphine converts to non-pyrophoric phosphine oxide by treatment with dilute bleach.

References

Relevant Sciencemadness threads

• Things I Will Never Make
• Best and worst smelling chemicals?