Trimethylphosphine

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Trimethylphosphine - Wikipedia

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Trimethylphosphine
Names



Preferred IUPAC name Trimethylphosphane
Systematic IUPAC name Trimethylphosphane^[1] (substitutive) Trimethylphosphorus^[1] (additive)
Identifiers
CAS Number	594-09-2^Y
3D model (JSmol)	Interactive image
Beilstein Reference	969138
ChEBI	CHEBI:35890^N
ChemSpider	62205^N
ECHA InfoCard	100.008.932
EC Number	209-823-1
MeSH	trimethyl+phosphine
PubChem CID	68983
UNII	5FL6SQK9H3^Y
UN number	1993
CompTox Dashboard (EPA)	DTXSID00208120
InChI InChI=1S/C3H9P/c1-4(2)3/h1-3H3^N Key: YWWDBCBWQNCYNR-UHFFFAOYSA-N^N
SMILES CP(C)C
Properties
Chemical formula	C₃H₉P
Molar mass	76.079 g·mol⁻¹
Appearance	Colorless liquid
Density	735 mg cm⁻³
Melting point	−86 °C (−123 °F; 187 K)
Boiling point	38 to 39 °C (100 to 102 °F; 311 to 312 K)
Vapor pressure	49.9 kPa (at 20 °C)
Structure
Coordination geometry	Trigonal pyramidal
Dipole moment	1.19 Debye
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H225, H315, H319, H335
Precautionary statements	P210, P261, P305+P351+P338
Flash point	−19 °C (−2 °F; 254 K)
Related compounds
Related compounds	PEt₃ NMe₃ PH₃ PPh₃
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is ^YN ?) Infobox references

Trimethylphosphine is an 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 coordination chemistry.

Structure and bonding

It is a pyramidal molecule with approximate C_3v symmetry. The C–P–C bond angles are approximately 98.6°.^[2]

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.^[3]

PMe₃ can be prepared by the treatment of triphenyl phosphite with methylmagnesium chloride:^[4]

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

Structure of HW(PMe₃)₄(Me₂PCH₂), "W(PMe₃)₅".^[5]

With a pK_a of 8.65, PMe₃ reacts with strong acids to give salts [HPMe₃]X.^[2] This reaction is reversible. With strong bases, such as alkyl lithium compounds, a methyl group undergoes deprotonation to give PMe₂CH₂Li.

PMe₃ is easily oxidised to the phosphine oxide with oxygen. It reacts with methyl bromide to give tetramethylphosphonium bromide.^[6]

Coordination chemistry

Trimethylphosphine is a highly basic ligand that forms complexes with most metals. As a ligand, trimethylphosphine's Tolman cone angle is 118°.^[7] 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.^[8] Its complex with silver iodide, AgI(PMe₃) is an air-stable solid that releases PMe₃ upon heating.

Safety

PMe₃ is toxic and pyrophoric. It converts to a much safer phosphine oxide upon treatment with sodium hypochlorite or hydrogen peroxide.^[9]

References

^ ^a ^b "Trimethylphosphine (CHEBI:35890)". Chemical Entities of Biological Interest (ChEBI). UK: European Bioinformatics Institute. 6 June 2006. IUPAC Names. Retrieved 25 September 2011.
^ ^a ^b Schier, Annette; Schmidbaur, Hubert (2006). "P-Donor Ligands". In Charles A. McAuliffe, Anthony G. Mackie (ed.). Encyclopedia of Inorganic Chemistry, First Edition. doi:10.1002/0470862106.ia177. ISBN 0-470-86078-2.
^ E. Fluck, The Chemistry of Phosphine, Topics in Current Chemistry Vol. 35, 64 pp, 1973.
^ Leutkens Jr., M. L.; Sattelberger, A. P.; Murray, H. H.; Basil, J. D.; Fackler J. P. Jr. (1990). "Trimethylphosphine". Inorganic Syntheses. Inorganic Syntheses. Vol. 28. pp. 305–310. doi:10.1002/9780470132593.ch76. ISBN 978-0-470-13259-3.
^ Sattler, A.; Parkin, G. (2011). "Formation of a Cationic Alkylidene Complex via Formal Hydride Abstraction: Synthesis and Structural Characterization of [W(PMe₃)₄([η²-CHPMe₂)H]X (X = Br, I)". Chemical Communications. 47 (48): 12828–12830. doi:10.1039/C1CC15457E. PMID 22048609.
^ H. F. Klein (1978). "Trimethylphosphonium Methylide (Trimethyl Methylenephosphorane)". Inorganic Syntheses. Vol. XVIII. pp. 138–140. doi:10.1002/9780470132494.ch23. ISBN 978-0-470-13249-4.
^ G. L. Miessler and D. A. Tarr Inorganic Chemistry, 3rd Ed, Pearson/Prentice Hall publisher, ISBN 0-13-035471-6.
^ T. Yoshida; T. Matsuda; S. Otsuka (1990). "Tetrakis(Triethylphosphine)Platinum(0)". Inorganic Syntheses. Vol. 28. pp. 122–123. doi:10.1002/9780470132593.ch32. ISBN 978-0-470-13259-3.
^ "Trimethylphosphine solution". sigmaaldrich.com. Retrieved 1 August 2023.

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