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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

what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
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Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
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Damian Reply
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Akash Reply
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characteristics of micro business
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Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
waht is hydrating power of lithium carbonates
Mahar Reply

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Source:  OpenStax, Chemistry of the main group elements. OpenStax CNX. Aug 20, 2010 Download for free at http://cnx.org/content/col11124/1.25
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