Tributylphosphine

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Tributylphosphine
Tributylphosphine.png
Tributylphosphine-3D-vdW.png
Names
IUPAC name
Tributylphosphane
Preferred IUPAC name
Tributylphosphane
Other names
Tributylphosphine
Identifiers
3D model (Jmol)
ChemSpider
ECHA InfoCard 100.012.410
EC Number 213-651-2
Properties
C
12
H
27
P
Molar mass 202.32 g·mol−1
Appearance Colorless oily liquid
Density 0.82 g/ml
Melting point −60 °C; −76 °F; 213 K
Boiling point 240 °C; 464 °F; 513 K (150 °C (302 °F; 423 K) at 50 mmHg)
negligible
Solubility organic solvents such as heptane
Hazards
Main hazards Stench, Flammable, Corrosive
R-phrases R11 R17 R20/21/22 R34 R38
NFPA 704
Flammability code 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g., gasoline) Health code 1: Exposure would cause irritation but only minor residual injury. E.g., turpentine Reactivity code 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g., phosphorus Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point 117 °C (243 °F; 390 K)
168 °C (334 °F; 441 K)
Related compounds
Related Tertiary phosphine
Trimethylphosphine
Triphenylphosphine
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Tributylphosphine is the organophosphorus compound with the formula P(C
4
H
9
)
3
. Abbreviated or PBu
3
, it is a tertiary phosphine. It is an oily liquid at room temperature, with a nauseating odor. It reacts slowly with atmospheric oxygen, and rapidly with other oxidizing agents, to give the corresponding phosphine oxide. It is usually handled using air-free techniques.

Preparation[edit]

Tributylphosphine is prepared industrially by the addition of phosphine to butene: the addition proceeds by a free radical mechanism, and so the Markovnikov rule is not followed.

PH
3
+ 3CH
2
=CHCH
2
CH
3
→ P(CH
2
CH
2
CH
2
CH
3
)
3

Tributylphosphine can be prepared in the laboratory by reaction of the appropriate Grignard reagent with phosphorus trichloride although, as it is commercially available at reasonable prices, it is rare to have to perform the small-scale preparation.

3 BuMgCl + PCl
3
→ PBu
3
+ 3 MgCl
2

Reactions[edit]

Tributylphosphine reacts with oxygen to give the phosphine oxide:

2 PBu3 + O2 → 2 OPBu3

Because this reaction is so fast, the compound is usually handled under an inert atmosphere.

The phosphine is also easily alkylated. For example, benzyl chloride gives the phosphonium salt:[1]

PBu3 + PhCH2Cl → [PhCH2PBu3]Cl

Tributylphosphine most commonly encountered as a ligand in transition metal complexes. Tributylphosphine is also a common ligand for the preparation of complexes of transition metals in low oxidation states. It is cheaper and less air-sensitive than trimethylphosphine and other trialkylphosphines. Although its complexes are generally highly soluble, they are often more difficult to crystallize compared to complexes of more rigid phosphines. Furthermore, the 1H NMR properties are less easily interpreted and can mask signals for other ligands. Compared to other tertiary phosphines, it is compact (cone angle: 136°) and basic (χ-parameter: 5.25 cm−1)[2]

Use[edit]

Tributylphosphine finds some industrial use as a catalyst modifier in the cobalt-catalyzed hydroformylation of alkenes, where it greatly increases the ratio of straight-chain aldehydes to branched-chain aldehydes in the product mixture.[3] However, tricyclohexylphosphine is even more effective for this purpose (although more expensive) and, in any case, rhodium catalysts are usually preferred to cobalt catalysts for the hydroformylation of alkenes.

It is the precursor to the pesticide 2,4-dichlorobenzyltributylphosphoniumchloride ("Phosfleur").[1]

Odor[edit]

The main laboratory inconvenience of tributylphosphine is its strongly unpleasant smell. Manipulations must be carried out in an efficient fume hood, and glassware which has come into contact with the compound must be decontaminated before leaving the hood. The manipulation of large quantities requires specific precautions to prevent the release of the vapour into the environment.

Hazards[edit]

Tributylphosphine is moderately toxic, with an LD50 of 750 mg/kg (oral, rats).[1]

References[edit]

  1. ^ a b c Jürgen Svara, Norbert Weferling and Thomas Hofmann "Phosphorus Compounds, Organic" in Ullmann's Encyclopedia of Industrial Chemistry, 2006, Wiley-VCH, Weinheim. doi:10.1002/14356007.a19_545.pub2
  2. ^ Rahman, M. M.; Liu, H. Y.; Prock, A.; Giering, W. P. (1987). "Steric and Electronic Factors influencing Transition-Metal–Phosphorus(III) Bonding". Organometallics. 6 (3): 650–58. doi:10.1021/om00146a037. 
  3. ^ Bell, P.; Rupilus, W.; Asinger, F. (1968). "Zur Frage der Isomerenbildung bei der Hydroformylierung Höhermolekularer Olefine mit Komplexen Kobalt- und Rhodiumkatalysatoren". Tetrahedron Lett. 9 (29): 3261–66. doi:10.1016/S0040-4039(00)89542-8. 

External links[edit]