Phosphorus trifluoride (formula P F₃), is a colorless and odorless

gas Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...

. It is highly toxic and reacts slowly with water. Its main use is as a

ligand In coordination chemistry, a ligand is an ion or molecule ( functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's elec ...

in metal complexes. As a ligand, it parallels

carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...

metal carbonyl Metal carbonyls are coordination complexes of transition metals with carbon monoxide ligands. Metal carbonyls are useful in organic synthesis and as catalysts or catalyst precursors in homogeneous catalysis, such as hydroformylation and Reppe c ...

s, and indeed its toxicity is due to its binding with the

iron Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundanc ...

in blood

hemoglobin Hemoglobin (haemoglobin BrE) (from the Greek word αἷμα, ''haîma'' 'blood' + Latin ''globus'' 'ball, sphere' + ''-in'') (), abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein present in red blood cells (erythrocyt ...

in a similar way to carbon monoxide.

Physical properties

Phosphorus trifluoride has an F−P−F bond angle of approximately 96.3°.

Gas Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...

eous PF₃ has a standard enthalpy of formation of −945 kJ/mol (−226

kcal The calorie is a unit of energy. For historical reasons, two main definitions of "calorie" are in wide use. The large calorie, food calorie, or kilogram calorie was originally defined as the amount of heat needed to raise the temperature of o ...

/ mol). The phosphorus atom has a

nuclear magnetic resonance Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a strong constant magnetic field are perturbed by a weak oscillating magnetic field (in the near field) and respond by producing an electromagnetic signal with a ...

chemical shift of 97 ppm (downfield of H₃PO₄).

Properties

Phosphorus trifluoride hydrolyzes especially at

high pH In chemistry, there are three definitions in common use of the word base, known as Arrhenius bases, Brønsted bases, and Lewis bases. All definitions agree that bases are substances that react with acids, as originally proposed by G.-F. Rou ...

, but it is less hydrolytically sensitive than phosphorus trichloride. It does not attack glass except at high temperatures, and anhydrous

potassium hydroxide Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash. Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which exp ...

may be used to dry it with little loss. With hot

metal A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typicall ...

s, phosphides and fluorides are formed. With Lewis bases such as

ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...

addition products (adducts) are formed, and PF₃ is oxidized by

oxidizing agent An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxi ...

s such as

bromine Bromine is a chemical element with the symbol Br and atomic number 35. It is the third-lightest element in group 17 of the periodic table ( halogens) and is a volatile red-brown liquid at room temperature that evaporates readily to form a simi ...

potassium permanganate Potassium permanganate is an inorganic compound with the chemical formula KMnO4. It is a purplish-black crystalline salt, that dissolves in water as K+ and , an intensely pink to purple solution. Potassium permanganate is widely used in the c ...

. As a ligand for transition metals, PF₃ is a strong π-acceptor. It forms a variety of metal complexes with

s in low

oxidation state In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...

s. PF₃ forms several complexes for which the corresponding CO derivatives (see

) 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

compound, with loss of CO. However,

nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow ...

reacts directly with PF₃ at 100 °C under 35

MPa MPA or mPa may refer to: Academia Academic degrees * Master of Performing Arts * Master of Professional Accountancy * Master of Public Administration * Master of Public Affairs Schools * Mesa Preparatory Academy * Morgan Park Academy * Mou ...

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

Preparation

Phosphorus trifluoride is usually prepared from phosphorus trichloride via halogen exchange using various fluorides such as hydrogen fluoride,

calcium fluoride Calcium fluoride is the inorganic compound of the elements calcium and fluorine with the formula CaF2. It is a white insoluble solid. It occurs as the mineral fluorite (also called fluorspar), which is often deeply coloured owing to impurities. ...

, arsenic trifluoride,

antimony trifluoride Antimony trifluoride is the inorganic compound with the formula SbF3. Sometimes called Swarts' reagent, is one of two principal fluorides of antimony, the other being SbF5. It appears as a white solid. As well as some industrial applications, i ...

, or zinc fluoride: :2 PCl₃ + 3 ZnF₂ → 2 PF₃ + 3 ZnCl₂

Biological activity

Phosphorus trifluoride is similar to

in that it is a gas which strongly binds to

, preventing the blood from absorbing oxygen.

Precautions

PF₃ is highly

toxic Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subs ...

, comparable to phosgene.

References

External links

National Pollutant Inventory - Fluoride and compounds fact sheetWebBook page for PF3
{{DEFAULTSORT:Phosphorus Trifluoride Phosphorus fluorides Phosphorus(III) compounds Blood agents