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 C3vsymmetry. 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]
With a pKa 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.[6]
Trimethylphosphine is a highly basic ligand that forms complexes with most metals. As a ligand, trimethylphosphine's Tolman cone angle is 118°.[8] This angle is an indication of the amount of steric protection that this ligand provides to the metal that to which it is bound.
Since trimethylphosphine is a compact ligand, several can bind to a single transition metal, as illustrated by the tungsten complex shown in the figure.
Its complex with silver iodide, AgI(PMe3) is an air-stable solid that releases PMe3 upon heating.[9]
^ ab"Trimethylphosphine (CHEBI:35890)". Chemical Entities of Biological Interest (ChEBI). UK: European Bioinformatics Institute. 6 June 2006. IUPAC Names. Retrieved 25 September 2011.
^ abSchier, 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. ISBN0-470-86078-2.
^E. Fluck, The Chemistry of Phosphine, Topics in Current Chemistry Vol. 35, 64 pp, 1973.
^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. PMID22048609.
^Byrne, Lindsay T.; Engelhardt, Lutz M.; Jacobsen, Geraldine E.; Leung, Wing-Por; Papasergio, Rocco I.; Raston, Colin L.; Skelton, Brian W.; Twiss, Paul; White, Allan H. (1989). "Synthesis of α-, γ-phosphorus functionalized alkyl lithium species; X-ray structures of [{Li(L)(Ch2PMeR)}2][L =NNN′N′-tetramethylethylenediamine (Tmen), R = Me or Ph; L =(–)sparteine, R = Ph] and [Li(tmen){CH(SiMe3)C6H4PPH2-o}]". J. Chem. Soc., Dalton Trans.: 105–113. doi:10.1039/dt9890000105.
