Phosphorus trifluoride

Phosphorus trifluoride

Names
IUPAC names Phosphorus trifluoride Phosphorus(III) fluoride Trifluorophosphane Trifluoridophosphorus
Other names Trifluorophosphine Phosphorous fluoride
Identifiers
CAS Number	7783-55-3 Y
ChEBI	CHEBI:30205 Y
ChemSpider	56416 Y
Jmol 3D model	Interactive image
PubChem	62665
RTECS number	TH3850000
InChI InChI=1S/F3P/c1-4(2)3 Y Key: WKFBZNUBXWCCHG-UHFFFAOYSA-N Y InChI=1/F3P/c1-4(2)3 Key: WKFBZNUBXWCCHG-UHFFFAOYAK
SMILES FP(F)F
Properties
Chemical formula	PF3
Molar mass	87.968971 g/mol
Appearance	colorless gas
Density	3.91 g/L, gas
Melting point	−151.5 °C (−240.7 °F; 121.6 K)
Boiling point	−101.8 °C (−151.2 °F; 171.3 K)
Solubility in water	slow hydrolysis
Structure
Molecular shape	Trigonal pyramidal
Dipole moment	1.03 D
Vapor pressure	{{{value}}}
Related compounds
Other anions	Phosphorus trichloride Phosphorus tribromide Phosphorus triiodide Phosphane
Other cations	Nitrogen trifluoride Arsenic trifluoride Antimony trifluoride Bismuth trifluoride
Related ligands	Carbon monoxide
Related compounds	Phosphorus pentafluoride
Supplementary data page
Structure and properties	Refractive index (n), Dielectric constant (εr), etc.
Thermodynamic data	Phase behaviour solid–liquid–gas
Spectral data	UV, IR, NMR, MS
Y verify (what is YN ?)
Infobox references

Phosphorus trifluoride (formula PF₃), is a colorless and odorless gas. It is highly toxic and reacts slowly with water. Its main use is as a ligand in metal complexes. As a ligand, it parallels carbon monoxide in metal carbonyls, and indeed its toxicity is due to its binding with the iron in blood hemoglobin in a similar way to carbon monoxide.

Physical properties

Phosphorus trifluoride has a bond angle of 107°, F-P-F bond angle being 96.3°. Gaseous PF₃ has a standard enthalpy of formation of -945 kJ/mol (-226 kcal/mol). The phosphorus atom has a nuclear magnetic resonance chemical shift of 97 ppm (downfield of H₃PO₄).

Properties

Phosphorus trifluoride hydrolyzes especially at high pH, but it is less hydrolytically sensitive than phosphorus trichloride. It does not attack glass except at high temperatures, and anhydrous potassium hydroxide may be used to dry it with little loss. With hot metals, phosphides and fluorides are formed. With Lewis bases such as ammonia addition products (adducts) are formed, and PF₃ is oxidized by oxidizing agents such as bromine or potassium permanganate.

As a ligand for transition metals, PF₃ is a strong π-acceptor. It forms a variety of metal complexes with metals in low oxidation states. PF₃ forms several complexes for which the corresponding CO derivatives (see metal carbonyl) are unstable or nonexistent. Thus, Pd(PF₃)₄ is known, but Pd(CO)₄ is not. Such complexes are usually prepared directly from the related metal carbonyl compound, with loss of CO. However, Nickel metal reacts directly with PF₃ at 100 °C under 35 MPa pressure to form Ni(PF₃)₄, which is analogous to Ni(CO)₄. Cr(PF₃)₆, the analogue of Cr(CO)₆, may be prepared from dibenzenechromium:

Cr(C₆H₆)₂ + 6 PF₃ → Cr(PF₃)₆ + 2 C₆H₆

Ball-and-stick model of [Pt(PF3)4]	Space-filling model of [Pt(PF3)4]

Preparation

Phosphorus trifluoride is usually prepared from phosphorus trichloride via halogen exchange using various fluorides such as hydrogen fluoride, calcium fluoride, arsenic trifluoride, antimony trifluoride, or zinc fluoride:

2 PCl₃ + 3 ZnF₂ → 2 PF₃ + 3 ZnCl₂

Biological activity

Phosphorus trifluoride is similar to carbon monoxide in that it is a gas which strongly binds to iron in hemoglobin, preventing the blood from absorbing oxygen.

Precautions

PF₃ is highly toxic, comparable to phosgene.

External links

• National Pollutant Inventory - Fluoride and compounds fact sheet
• WebBook page for PF3