<< Chapter < Page Chapter >> Page >

Phosphorous trihalides

Phosphorous trihalides, PX 3 , are produced from the direct reaction of phosphorous with the appropriate halogen, [link] . The fluoride is readily made from the halide exchange reaction of PCl 3 with fluoride salts, [link] . Mixed trihalides are formed by halide exchange, [link] .

A summary of the physical properties of the phosphorous trihalides is given in [link] . All the compounds have a pyramidal structure in the vapor phase and in solution.

Selected physical properties of the phosphorous trihalides.
Compound Mp (°C) Bp (°C) P-X (Å) X-P-X (°)
PF 3 -151.5 -101.8 1.56 96.3
PCl 3 -93.6 76.1 2.04 100
PBr 3 -41.5 173.2 2.22 101
PI 3 61.2 200 (dec.) 2.43 102

The phosphorous trihalides hydrolyze to phosphoric acid, [link] , and undergo alcoholysis to form the trialkyl phosphite derivative, [link] . Phosphorous trifluoride is only slowly hydrolyzed by water, but reacts readily with alakaline solutions. In contrast, phosphorus triiodide is an unstable red solid that reacts violently with water. Phosphorous trichloride in particular is an excellent synthon for most trialkyl phosphines, [link] .

As with other P(III) compounds such as trialkyl phosphines, phosphorous trihalides can be oxidized to the analogous phosphene oxide, e.g., [link] .

Phosphorous trihalides form Lewis acid-base complexes with main group metals, but the bonding to d n (n ≠ 0) transition metals occurs in the same manner to that of trialkyl phosphine, i.e., with dπ-pπ back donation. In fact one of the first examples of complexation of phosphorous to a low oxidation metal was the formation of PF 3 complexes with Fe-porphyrin.

Phosphorous pentahalides

The reaction of white phosphorous with excess halogen yields the pentahalides, [link] . However, the pentafluoride is best prepared by halide exchange, [link] .

The pentaiodide is unknown, however, selected physical properties are given for the others in [link] .

Selected physical properties of phosphorous pentahalides.
Compound Mp (°C) Bp (°C)
PF 5 -93.78 -84.5
PCl 5 166.8 160 (subl.)
PBr 5 100 106.0

The structures of the phosphorous pentahalides are all trigonal bipyramidal in the gas phase ( [link] ). Phosphorous pentafluoride maintains the trigonal bipyramidal structure in solid state, but the chloride and bromide are ionic solids, [PCl 4 ] + [PCl 6 ] - and [PBr 4 ]Br ( [link] ), respectively. The tetrahedral [PCl 4 ] + ion is also formed with the reaction of PCl 5 with other chloride ion acceptors, [link] and [link] .

The structures of (a) PF 5 and (b) PCl 5 .
The crystal structure of phosphorous pentabromide.

All of the pentahalides undergo thermal decomposition, [link] .

Careful hydrolysis of the pentahalides yields the oxide of the appropriate trihalide, [link] , while excess hydrolysis yields phosphoric acid, [link] .

Questions & Answers

Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
hi
Loga
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Good
waht is hydrating power of lithium carbonates
Mahar Reply

Get the best Algebra and trigonometry course in your pocket!





Source:  OpenStax, Chemistry of the main group elements. OpenStax CNX. Aug 20, 2010 Download for free at http://cnx.org/content/col11124/1.25
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Chemistry of the main group elements' conversation and receive update notifications?

Ask