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

metal complexes A coordination complex consists of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as ''ligands'' or complexing agents. Many ...

. 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 simpl ...

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 in blood hemoglobin 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 In chemistry and thermodynamics, the standard enthalpy of formation or standard heat of formation of a compound is the change of enthalpy during the formation of 1 mole of the substance from its constituent elements in their reference state, wi ...

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 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. Ro ...

, 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

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 typica ...

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 agents 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 simila ...

or potassium permanganate. As a ligand for transition metals, PF₃ is a strong π-acceptor. It forms a variety of

with

s in low oxidation states. 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

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 * Moun ...

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

fluoride Fluoride (). According to this source, is a possible pronunciation in British English. is an inorganic, monatomic anion of fluorine, with the chemical formula (also written ), whose salts are typically white or colorless. Fluoride salts ty ...

s 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 Zinc fluoride ( Zn F2) is an inorganic chemical compound. It is encountered as the anhydrous form and also as the tetrahydrate, ZnF2 · 4H2O (rhombohedral crystal structure). It has a high melting point and has the rutile structure containing 6 ...

: :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 iron in hemoglobin, 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 Phosgene is the organic chemical compound with the formula COCl2. It is a toxic, colorless gas; in low concentrations, its musty odor resembles that of freshly cut hay or grass. Phosgene is a valued and important industrial building block, esp ...

References

External links

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