 | |
 | |
| Names | |
|---|---|
| IUPAC name Selenium tetrachloride | |
| Other names Selenium(IV) chloride, tetrachloro-λ4-selane | |
| Identifiers | |
3D model (JSmol) | |
| ChemSpider |
|
| ECHA InfoCard | 100.030.036 |
| EC Number |
|
| RTECS number |
|
| UNII | |
| |
| |
| Properties | |
| SeCl4 | |
| Molar mass | 220.771 g/mol |
| Appearance | white to yellow crystals |
| Density | 2.6 g/cm3, solid |
| Melting point | sublimes at 191.4 °C[1] |
| decomposes in water | |
| Structure | |
| Monoclinic,mS80 | |
| C12/c1, No. 15 | |
| Seesaw (gas phase)[citation needed] | |
| Hazards[2] | |
| GHS labelling: | |
   | |
| Danger | |
| H301,H331,H373,H410 | |
| P260,P261,P264,P270,P271,P273,P301+P310,P304+P340,P311,P314,P321,P330,P391,P403+P233,P405,P501 | |
| NFPA 704 (fire diamond) | |
| Flash point | non-flammable |
| Related compounds | |
Otheranions | Selenium tetrafluoride Selenium tetrabromide Selenium dioxide |
Othercations | Dichlorine monoxide Sulfur tetrachloride Tellurium tetrachloride |
Related compounds | Selenium dichloride |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Selenium tetrachloride is theinorganic compound composed with theformula SeCl4. This compound exists as yellow to white volatile solid. It is one of two commonly availableselenium chlorides, the other example beingselenium monochloride, Se2Cl2. SeCl4 is used in the synthesis of otherselenium compounds.
The compound is prepared by treatingselenium withchlorine.[3] When the reacting selenium is heated, the productsublimes from the reaction flask. The volatility of selenium tetrachloride can be exploited to purification of selenium.
Solid SeCl4 is actually atetramericcubane-type cluster, for which the Se atom of an SeCl6 octahedron sits on four corners of the cube and the bridging Cl atoms sit on the other four corners. The bridging Se-Cl distances are longer than the terminal Se-Cl distances, but all Cl-Se-Cl angles are approximately 90°.[4]
SeCl4 has often been used as an example for teachingVSEPR rules ofhypervalent molecules. As such, one would predict four bonds but five electron groups giving rise to aseesaw geometry. This clearly is not the case in thecrystal structure. Others have suggested that the crystal structure can be represented as SeCl3+ and Cl−. This formulation would predict apyramidal geometry for the SeCl3+ cation with a Cl-Se-Cl bond angle of approximately 109°. However, this molecule is an excellent example of a situation where maximal bonding cannot be achieved with the simplest molecular formula. The formation of the tetramer (SeCl4)4,[5] with delocalized sigma bonding of the bridging chloride is clearly preferred over a "hypervalent" small molecule.Gaseous SeCl4 contains SeCl2 and chlorine, which recombine upon condensation.
Selenium tetrachloride can be reduced in situ to the dichloride usingtriphenylstibine:
Selenium tetrachloride reacts with water to giveselenous andhydrochloricacids:[6][page needed]
Upon treatment withselenium dioxide, it givesselenium oxychloride:[6][page needed]
{{cite book}}:ISBN / Date incompatibility (help)