Phosphorus triiodide

Names
IUPAC names

Phosphorus triiodide
Phosphorus(III) iodide

Other names

Triiodophosphine

Identifiers

CAS Number

* 13455-01-1 Y

3D model (JSmol)

* Interactive image

ChemSpider |

* 75323 Y

ECHA InfoCard | 100.033.302
EC Number |

* 236-647-2

PubChem CID

* 83485

UNII |

* 82QUK78Y7Y Y

CompTox Dashboard (EPA)

* DTXSID1065475

InChI

* InChI=1S/I3P/c1-4(2)3 Y

Key: PZHNNJXWQYFUTD-UHFFFAOYSA-N Y

* InChI=1/I3P/c1-4(2)3

Key: PZHNNJXWQYFUTD-UHFFFAOYAR

SMILES

* IP(I)I

Properties

Chemical formula

| PI3
Molar mass | 411.68717 g/mol
Appearance  | dark red solid
Density | 4.18 g/cm3
Melting point | 61.2 °C (142.2 °F; 334.3 K)
Boiling point | 200 °C (392 °F; 473 K) (decomposes)

Solubility in water

| Decomposes
Structure

Molecular shape

| Trigonal pyramidal
Hazards
GHS labelling:[1]

Pictograms

Signal word

| Danger

Hazard statements

| H314, H335

Precautionary statements

| P260, P280, P301+P330+P331, P303+P361+P353, P305+P351+P338
NFPA 704 (fire diamond)  |

Flash point | non-flammable

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

N verify (what is YN ?)

Infobox references

Chemical compound

Phosphorus triiodide (PI3) is an inorganic compound with the formula PI3. A red solid, it is[2] too unstable to be stored for long periods of time; it is, nevertheless, commercially available. It is widely used in organic chemistry for converting alcohols to alkyl iodides. It is also a powerful reducing agent.

## Properties

[edit]

Although PI3 is a pyramidal molecule, it has only a small molecular dipole because each P-I bond has almost no bond dipole moment. The P-I bond is also weak; PI3 is much less stable than PBr3 and PCl3, with a standard enthalpy of formation for PI3 of only −46 kJ/ mol (solid). The phosphorus atom has an NMR chemical shift of 178 ppm (downfield of H3PO4).

## Reactions

[edit]

Phosphorus triiodide reacts vigorously with water, producing phosphorous acid (H3PO3) and hydroiodic acid (HI), along with smaller amounts of phosphine and various P-P-containing compounds. Alcohols likewise form alkyl iodides, this providing the main use for PI3.

PI3 is also a powerful reducing agent and deoxygenating agent. It reduces sulfoxides to sulfides, even at −78 °C.[3] Meanwhile, heating a 1-iodobutane solution of PI3 with red phosphorus causes reduction to P2I4.

## Preparation

[edit]

The usual method or preparation is by the union of the elements, often by addition of iodine to a solution of white phosphorus in carbon disulfide:

P4 + 6 I2 → 4 PI3

Alternatively, PCl3 may be converted to PI3 by the action of hydrogen iodide or certain metal iodides.

## Uses

[edit]

Phosphorus triiodide is commonly used in the laboratory for the conversion of primary or secondary alcohols to alkyl iodides.[4] The alcohol is frequently used as the solvent, on top of being the reactant. Often the PI3 is made in situ by the reaction of red phosphorus with iodine in the presence of the alcohol; for example, the conversion of methanol to give iodomethane:[5]

PI3 \+ 3 CH
3OH → 3 CH
3I \+ " H
3PO

These alkyl iodides are useful compounds for nucleophilic substitution reactions, and for the preparation of Grignard reagents.

## See also

[edit]

* Nitrogen triiodide
* Diphosphorus tetraiodide
* Phosphorus trifluoride
* Phosphorus trichloride
* Phosphorus tribromide
* Phosphorus pentaiodide

## References

[edit]

1. ^ GHS: Sigma-Aldsrich 241555
2. ^ L. G. Wade, Jr., Organic Chemistry, 6th ed., p. 477, Pearson/Prentice Hall, Upper Saddle River, New Jersey, USA, 2005.
3. ^ J. N. Denis; A. Krief (1980). "Phosphorus tri-iodide (PI3), a powerful deoxygenating agent". J. Chem. Soc., Chem. Commun. (12): 544–5. doi:10.1039/C39800000544.
4. ^ B. S. Furnell et al., Vogel's Textbook of Practical Organic Chemistry, 5th edition, Longman/Wiley, New York, 1989.
5. ^ King, C. S.; Hartman, W. W. (1933). "Methyl Iodide". Organic Syntheses. 13: 60. doi:10.15227/orgsyn.013.0060.

* v
* t
* e

Phosphorus compounds

Phosphides|

* AlP
* AsP
* BP
* BiP
* Cs2P5
* Ca3P2
* Cd3P2
* Cu3P
* DyP
* ErP
* EuP
* GdP
* AuP
* FeP
* Fe3P
* HfP
* HoP
* InP
* LaP
* Li3P
* LuP
* MoP
* MoP2
* Mo3P
* NbP
* NdP
* NpP
* Np3P4
* OsP2
* Ru2P
* PtP2
* PrP
* PrP5
* PuP
* ScP
* SmP
* SmP5
* Sr3P2
* TbP
* SnP3
* ThP7
* TmP
* YP
* YbP
* ZnP2
* Zn3P2
* ZrP
* ZrP2

Other compounds|

* PBr3
* PBr5
* PBr7
* PCl3
* PCl5
* P2Cl4
* PF3
* PF5
* PI3
* PH3
* PN
* P3N5
* PO
* P2O3
* P2O4
* P2O5
* P4S3
* P4Sx
* P4S10

* v
* t
* e

Salts and covalent derivatives of the iodide ion

| HI
+H |  |  |  | He

|
|
|
|

LiI | BeI2 | BI3
+BO3 | CI4
+C | NI3
NH4I
+N | I2O4
I2O5
I2O6
I4O9 | IF
IF3
IF5
IF7 | Ne
NaI | MgI2 | AlI
AlI3 | SiI4 | PI3
P2I4

PI5 | S2I2 | ICl
ICl3 | Ar
KI | CaI2 |  | ScI3 | TiI2
TiI3
TiI4 | VI2
VI3 | CrI2
CrI3
CrI4 | MnI2 | FeI2
FeI3 | CoI2 | NiI2
-Ni | CuI | ZnI2 | GaI
GaI3 | GeI2
GeI4
+Ge | AsI3
As2I4
+As | Se  | IBr
IBr3 | Kr
RbI
RbI3 | SrI2 |  | YI3 | ZrI2
ZrI3
ZrI4 | NbI4
NbI5 | MoI2
MoI3 | TcI3 | RuI3 | RhI3 | PdI2 | AgI | CdI2 | InI
InI3 | SnI2
SnI4 | SbI3
+Sb | TeI4
+Te | I−

3 | Xe
CsI
CsI3 | BaI2 |  | LuI3 | HfI3
HfI4 | TaI4
TaI5 | WI2
WI3
WI4 | ReI3
ReI
4 | OsI
OsI2
OsI3 | IrI3
IrI
4 | PtI2
PtI4 | AuI
AuI3 | Hg2I2
HgI2 | TlI
TlI3 | PbI2 | BiI3 | PoI2
PoI4 | AtI | Rn
Fr  | RaI2 |  | Lr  | Rf  | Db  | Sg  | Bh  | Hs  | Mt  | Ds  | Rg  | Cn  | Nh  | Fl  | Mc  | Lv  | Ts  | Og
| ↓  |  |
| LaI2
LaI3 | CeI2
CeI3 | PrI2
PrI3 | NdI2
NdI3 | PmI3 | SmI2
SmI3 | EuI2
EuI3 | GdI2
GdI3 | TbI3 | DyI2
DyI
3 | HoI3 | ErI3 | TmI2
TmI3 | YbI2
YbI3
AcI3 | ThI2
ThI3
ThI4 | PaI4
PaI5 | UI3
UI4 | NpI3 | PuI3 | AmI2
AmI3 | CmI3 | BkI
3 | CfI

CfI
3 | EsI2
EsI3 | Fm  | Md  | No
*[CID]: Compound ID
*[EPA]: U.S. Environmental Protection Agency
*[H314]: H314: Causes severe skin burns and eye damage
*[H335]: H335: May cause respiratory irritation
*[P260]: P260: Do not breathe dust/fume/gas/mist/vapours/spray.
*[P280]: P280: Wear protective gloves/protective clothing/eye protection/face protection.
*[P301+P330+P331]: P301+P330+P331: IF SWALLOWED: Rinse mouth. Do NOT induce vomiting.
*[P303+P361+P353]: P303+P361+P353: IF ON SKIN (or hair): Remove/Take off immediately all contaminated clothing. Rinse skin with water [or shower].
*[P305+P351+P338]: P305+P351+P338: IF IN EYES: Rinse continuously with water for several minutes. Remove contact lenses if present and easy to do. Continue rinsing.
*[v]: View this template
*[t]: Discuss this template
*[e]: Edit this template