78.80.30.91 at 05:50, 18 October 2024

2024-10-18T05:50:54Z

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{{chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 477163163
| Name = Selenium tetrachloride
| ImageFile1 = SeCl4-from-alpha-xtal-1981-CM-3D-ellipsoids.png
| ImageFile2 = Selenium tetrachloride.png
| ImageSize2 =
| ImageName2 =
| IUPACName = Selenium tetrachloride
| OtherNames = Selenium(IV) chloride, tetrachloro-λ4-selane
| Section1 = {{Chembox Identifiers
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 10026-03-6
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 59590
| EC_number = 233-053-5
| RTECS = VS7875000
| PubChem = 66205
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 4GB8868P5J
| InChI = 1/Cl4Se/c1-5(2,3)4
| InChIKey = LNBXMNQCXXEHFT-UHFFFAOYAD
| SMILES = Cl[Se](Cl)(Cl)Cl
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/Cl4Se/c1-5(2,3)4
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = LNBXMNQCXXEHFT-UHFFFAOYSA-N
}}
| Section2 = {{Chembox Properties
| Formula = SeCl4
| MolarMass = 220.771 g/mol
| Appearance = white to yellow crystals
| Density = 2.6 g/cm3, solid
| Solubility = decomposes in water
| MeltingPt = [[Sublimation (chemistry)|sublimes]] at 191.4 °C<ref name="hand">
{{Cite book | last = Lide | first = David R. | year = 1998
| title = Handbook of Chemistry and Physics
| edition = 87 | location = Boca Raton, Florida | publisher = CRC Press | isbn = 0-8493-0594-2
| pages = 487
| url = https://books.google.com/books?id=lFjg0L-uOxoC&pg=PT872 | access-date = 2008-07-02 }}</ref>
| BoilingPt =
}}
| Section3 = {{Chembox Structure
| CrystalStruct = [[Monoclinic]], [[Pearson symbol|mS80]]
| SpaceGroup = C12/c1, No. 15
| MolShape = Seesaw (gas phase){{Citation needed|date=February 2012}}
}}
| Section7 = {{Chembox Hazards
| NFPA-H = 3
| NFPA-F = 0
| NFPA-R = 2
| NFPA-S = W
| GHSPictograms = {{GHS06}}{{GHS08}}{{GHS09}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|301|331|373|410}}
| PPhrases = {{P-phrases|260|261|264|270|271|273|301+310|304+340|311|314|321|330|391|403+233|405|501}}
| Hazards_ref=<ref name="sa">
{{cite web |url= http://www.sigmaaldrich.com/catalog/search/ProductDetail/ALDRICH/323527/ |title= 323527 Selenium tetrachloride |access-date=2008-07-02 |publisher= Sigma-Aldrich}}</ref>
| FlashPt = non-flammable
}}
| Section8 = {{Chembox Related
| OtherAnions = [[Selenium tetrafluoride]] [[Selenium tetrabromide]] [[Selenium dioxide]]
| OtherCations = [[Dichlorine monoxide]] [[Sulfur tetrachloride]] [[Tellurium tetrachloride]]
| OtherCompounds = [[Selenium dichloride]]
}}
}}

'''Selenium tetrachloride''' is the [[inorganic compound]] composed with the [[chemical formula|formula]] SeCl4. This compound exists as yellow to white volatile solid. It is one of two commonly available [[Selenium chloride (disambiguation)|selenium chlorides]], the other example being [[selenium monochloride]], Se2Cl2. SeCl4 is used in the synthesis of other [[selenium]] compounds.

==Synthesis and structure==
[[File:TeCl4structure.jpg|thumb|left|Structure of selenium tetrachloride]]
The compound is prepared by treating [[selenium]] with [[chlorine]].<ref>{{Cite book | last1 = Nowak | first1 = H. G. | last2 = Suttle | first2 = J. F. | last3 = Parker | first3 = W. E. | last4 = Kleinberg | first4 = J. | chapter = Selenium (IV) Chloride | doi = 10.1002/9780470132364.ch33 | title = Inorganic Syntheses | volume = 5 | pages = 125 | year = 1957 | isbn = 9780470132364 }}</ref> When the reacting selenium is heated, the product [[Sublimation (phase transition)|sublimes]] from the reaction flask. The volatility of selenium tetrachloride can be exploited to purification of selenium.

Solid SeCl4 is actually a [[tetramer]]ic [[cubane-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°.<ref>Kristallstruktur der stabilen Modifikation von SeCl4, Zeitschrift für Naturforschung, 36b, 1660, 1981</ref>

SeCl4 has often been used as an example for teaching [[VSEPR theory|VSEPR]] rules of [[hypervalent molecule]]s. As such, one would predict four bonds but five electron groups giving rise to a [[Seesaw molecular geometry|seesaw geometry]]. This clearly is not the case in the [[crystal structure]]. Others have suggested that the crystal structure can be represented as SeCl3+ and Cl−. This formulation would predict a [[Trigonal pyramidal molecular geometry|pyramidal 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,<ref>Wells, ''Structural Inorganic Chemistry'', fifth ed, Oxford, p. 709, {{ISBN|0-19-855370-6}}</ref> 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.

==Reactions==
Selenium tetrachloride can be reduced in situ to the dichloride using [[triphenylstibine]]:
:SeCl4 + SbPh3 → SeCl2 + Cl2SbPh3

Selenium tetrachloride reacts with water to give [[selenous acid|selenous]] and [[hydrochloric acid|hydrochloric]] [[acid]]s:<ref name=Greenwood>{{Greenwood&Earnshaw2nd}}</ref>{{page needed|date=April 2013}}
:SeCl4 + 3 H2O → H2SeO3 + 4 HCl

Upon treatment with [[selenium dioxide]], it gives [[selenium oxychloride]]:<ref name=Greenwood/>{{page needed|date=April 2013}}
:SeCl4 + SeO2 → 2SeOCl2

==References==
{{Reflist}}

{{Selenium compounds}}
{{Chlorides}}
{{Prostanoidergics}}

[[Category:Selenium(IV) compounds]]
[[Category:Chlorides]]
[[Category:Nonmetal halides]]
[[Category:Chalcohalides]]
[[Category:Selenium halides]]

Selenium tetrachloride - Revision history

78.80.30.91 at 05:50, 18 October 2024