Oxidation State +3 (PX3)
| Chemical formula | CAS number | Melting point | Boiling point | P–X bond length | X–P–X bond angle | Dipole moment |
|---|---|---|---|---|---|---|
| PF3 | -151.5°C | -101.8°C | 156 pm | 96.3° | 1.03 D | |
| PCl3 | -93.6°C | 76.1°C | 204 pm | 100° | 0.56 D | |
| PBr3 | -41.5°C | 173.2°C | 222 pm | 101° | ||
| PI3 | 61.2°C | 227°C | 243 pm | 102° |
The phosphorus(III) halides are the best known of the three series. They are usually prepared by direct reaction of the elements, or by transhalogenation.
Phosphorus trifluoride is used as a ligand in coordination chemistry, where it resembles carbon monoxide. Phosphorus trichloride is a major industrial chemical and widely-used starting material for phosphorus chemistry. Phosphorus tribromide is used in organic chemistry to convert alcohols to alkyl bromides and carboxylic acids to acyl bromides (e.g. in the Hell-Volhard-Zelinsky reaction). Phosphorus triiodide also finds use in organic chemistry, as a mild oxygen acceptor.
The trihalides are fairly readily oxidized by chalcogens to give the corresponding oxyhalides or equivalents.
Read more about this topic: Phosphorus Halide
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