Chemical Properties
Colorless to light yellow liqui
Physical properties
mp 24 °C; bp 243–244 °C; d 0.863 g cm?3; n20
D
1.501–1.503.
Uses
It is used as the intermediate in organic synthesis.
Uses
Tris(trimethylsilyl)phosphine is a more stable analog of phosphine, but retains high reactivity due to the presence of the weak polar Si–P bond. It is nucleophilic and readily reacts with a range of electrophiles. Reaction with alkylating agents provides substituted phosphines, with acid chlorides phosphaalkenes can be obtained, and phosphabenzenes can be synthesized upon reaction with pyrylium salts.
It can be used as user-friendly phosphorus source and alternative to phosphine
gas, precursor of (Me3Si)2PLi, covalent synthon for the
anion P3?).
Preparation
several preparative methods are known.
These include the following: reaction of alkali metal phosphides
(NaPH2, KPH2, Li3P, usually prepared by reaction
of metal and phosphine gas or via metal alkyl derivative) with
chlorotrimethylsilane or fluorotrimethylsilane in 1,2-dimethoxyethane
or diethyl ether; reaction of sodium–potassium
alloy with white or red phosphorus in refluxing 1,2-
dimethoxyethane for 24 h followed by addition of
chlorotrimethylsilane and heating at reflux for 72 h (good
stirring is necessary for high yield of product), evaporation of
the solvent, and vacuum distillation (75% yield); reaction
of piperidinodichlorophosphine with lithium powder and
chlorotrimethylsilane in refluxing tetrahydrofuran (71%
yield); reaction of phosphine with excess of trimethylsilyl
triflate in the presence of a tertiary amine in an inert solvent
(Et2O) at low temperature (90% yield); reaction of phosphorus
trichloride, magnesium, and chlorotrimethylsilane (62%
yield). The last method is considered to be the most cost
effective and also the safest approach.
Synthesis
Tris(trimethylsilyl)phosphine is prepared by treating trimethylsilyl chloride, white phosphorus, and sodium-potassium alloy:
1/4 P4 + 3 Me3SiCl+ 3 K → P(SiMe3)3 + 3 KCl
