Trimethylphosphine

Trimethylphosphine
Preferred IUPAC name

Trimethylphosphine
Systematic name

Trimethylphosphane[1] (substitutive)
Trimethylphosphorus[1] (additive)
Identifiers
CAS number 594-09-2 Y
PubChem 68983
ChemSpider 62205 N
EC number 209-823-1
UN number 1993
MeSH trimethyl+phosphine
ChEBI CHEBI:35890 N
Beilstein Reference 969138
Jmol-3D images Image 1
Properties
Molecular formula C3PH9
Molar mass 76.0773 g mol-1
Exact mass 76.044186800 g mol-1
Appearance Colorless liquid
Density 735 mg cm-3
Melting point

-86 °C, 187 K, -123 °F
Boiling point

38-39 °C, 311-312 K, 100-102 °F
Vapor pressure 49.9 kPa (at 20 °C)
Structure
Coordination
geometry		 Trigonal pyramidal
Dipole moment 1.19 Debye
Hazards
GHS pictograms
GHS signal word DANGER
GHS hazard statements H225, H315, H319, H335
GHS precautionary statements P210, P261, P305+351+338
EU classification F Xi
R-phrases R11, R36/37/38
S-phrases S9, S16, S26, S36/37/39
Flash point -19 °C
Related compounds
Related compounds NMe3
PH3
PPh3
 N (verify) (what is: Y/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Trimethylphosphine is the organophosphorus compound with the formula P(CH3)3, commonly abbreviated PMe3. This colorless liquid has a strongly unpleasant odour, which is characteristic of alkylphosphines. It is a pyramidal molecule with C3v symmetry, similar to ammonia (NH3) and phosphine (PH3). As a ligand, its cone angle is 118°.[2] This angle, close to the optimal angles for sp2-hybridisation, is an indication for the hybridisation of the phosphorus atom. The lone pair is left in an almost straight p-orbital, so it points rather localized outward, in contrast to the higher members of the nitrogen group, to open the route to the rather hard basic properties of the compound.

PMe3 is prepared using Grignard reagents:[3]

3 CH3MgCl + P(OC6H5)3 → P(CH3)3 + 3 C6H5OMgBr

The synthesis is conducted in a dibutyl ether, from which the more volatile PMe3 can be distilled.

Coordination chemistry

Trimethylphosphine is a highly basic ligand that forms complexes with most metals. The synthesis of an illustrative example is shown:

PMe3 + Fe(CO)5 → Fe(CO)4PMe3 + CO

Its complex with silver iodide, AgI(PMe3) is a weighable, air stable solid that releases PMe3 upon heating.

Safety

PMe3 is potentially pyrophoric as well as toxic. PMe3 can be converted to non-pyrophoric phosphine oxide by treatment with dilute bleach.

References

  1. ^ a b "trimethylphosphine (CHEBI:35890)". Chemical Entities of Biological Interest (ChEBI). UK: European Bioinformatics Institute. 06 June 2006. IUPAC Names. https://www.ebi.ac.uk/chebi/searchId.do?chebiId=35890. Retrieved 25 September 2011. 
  2. ^ G. L. Miessler and D. A. Tarr “Inorganic Chemistry” 3rd Ed, Pearson/Prentice Hall publisher, ISBN 0-13-035471-6.
  3. ^ Leutkens, Jr., M. L.; Sattelberger, A. P.; Murray, H. H.; Basil, J. D.; Fackler, Jr., J. P. (1990). Robert J. Angelici. ed. "Trimethylphosphine". Inorganic Syntheses. Inorganic Syntheses (New York: J. Wiley & Sons) 28: 305–310. doi:10.1002/9780470132593.ch76. ISBN 0-471-52619-3.