Tributylphosphine

Tributylphosphine
	; Phosphorus, P Carbon, C Hydrogen, H
Names
	Preferred IUPAC name Tributylphosphane
	Other names Tributylphosphine
Identifiers
CAS Number	998-40-3 ;
3D model (JSmol)	Interactive image;
ChEMBL	ChEMBL3185473;
ChemSpider	13231 ;
ECHA InfoCard	100.012.410
EC Number	213-651-2;
PubChem CID	13831;
UNII	0O52FJR7WN ;
UN number	3254
CompTox Dashboard (EPA)	DTXSID9046998 ;
	InChI InChI=1/C12H27P/c1-4-7-10-13(11-8-5-2)12-9-6-3/h4-12H2,1-3H3 Key: TUQOTMZNTHZOKS-UHFFFAOYAQ;
	SMILES CCCCP(CCCC)CCCC;
Properties
Chemical formula	P(CH2CH2CH2CH3)3
Molar mass	202.322 g·mol−1
Appearance	Colorless oily liquid
Odor	Stench, nauseating
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)
Solubility in water	negligible
Solubility	organic solvents such as heptane
Related compounds
Related	Trimethylphosphine; Triphenylphosphine; Tributylamine;
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	Stench, Flammable, Corrosive
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H226, H250, H251, H302, H312, H314, H411
Precautionary statements	P210, P222, P233, P235+P410, P240, P241, P242, P243, P260, P264, P270, P273, P280, P301+P312, P301+P330+P331, P302+P334, P302+P352, P303+P361+P353, P304+P340, P305+P351+P338, P310, P312, P321, P322, P330, P363, P370+P378, P391, P403+P235, P405, P407, P413, P420, P422, P501
NFPA 704 (fire diamond)	1 3 2
Flash point	117 °C (243 °F; 390 K)
Autoignition; temperature	168 °C (334 °F; 441 K)
	Lethal dose or concentration (LD, LC):
LD50 (median dose)	750 mg/kg (oral, rats)
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Tributylphosphine is the organophosphorus compound with the chemical formula P(CH₂CH₂CH₂CH₃)₃, often abbreviated as PBu₃. 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

Tributylphosphine is prepared industrially by the hydrophosphination of phosphine with 1-butene: the addition proceeds by a free radical mechanism, and so the Markovnikov rule is not followed.^[1]

PH₃ + 3 CH₂=CHCH₂CH₃ → P(CH₂CH₂CH₂CH₃)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 CH₃CH₂CH₂CH₂MgCl + PCl₃ → P(CH₂CH₂CH₂CH₃)₃ + 3 MgCl₂

Reactions

Tributylphosphine reacts with oxygen to give a phosphine oxide (here tributylphosphine oxide):

2 P(CH₂CH₂CH₂CH₃)₃ + O₂ → 2 O=P(CH₂CH₂CH₂CH₃)₃

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 a phosphonium salt (here tributyl(phenylmethyl)phosphonium chloride):^[2]

P(CH₂CH₂CH₂CH₃)₃ + PhCH₂Cl → [PhCH₂P(CH₂CH₂CH₂CH₃)₃]⁺Cl⁻

Tributylphosphine is 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)^[3]

Use

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.^[4] 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-dichlorobenzyl)tributylphosphonium chloride ("Phosfleur").^[2]

Although tributylphosphine is generally regarded as toxic, its biological effects can be manipulated by drug delivery strategies. For example, a photoactivatable version of tributylphosphine has been used to induce disulfide bond cleavage and reductive stress in living cells.^[5]

Odor

The main laboratory inconvenience of tributylphosphine is its unpleasant smell.

Hazards

Tributylphosphine is moderately toxic, with an LD50 of 750 mg/kg (oral, rats).^[2]

References

^ Trofimov, Boris A.; Arbuzova, Svetlana N.; Gusarova, Nina K. (1999). "Phosphine in the synthesis of organophosphorus compounds". Russian Chemical Reviews. 68 (3): 215–227. Bibcode:1999RuCRv..68..215T. doi:10.1070/RC1999v068n03ABEH000464. S2CID 250775640.
^ ^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
^ 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.
^ 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.
^ Tirla, A.; Rivera-Fuentes, P. (2016). "Development of a Photoactivatable Phosphine Probe for Induction of Intracellular Reductive Stress with Single-Cell Precision". Angew. Chem. Int. Ed. 55 (47): 14709–14712. doi:10.1002/anie.201608779. hdl:20.500.11850/123593. PMID 27763731.