Selenium tetrafluoride: Difference between revisions

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{{chembox

{{expert-subject|chemistry|date=january 2007}}

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{{importance|date=June 2006}}

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{| class="toccolours" border="1" style="float: right; clear: right; margin: 0 0 1em 1em; border-collapse: collapse;"

| verifiedrevid = 477000495

! {{chembox header}} | Selenium tetrafluoride

| ImageFile = Selenium-tetrafluoride-gas-3D-balls.png

|-

| ImageClass = bg-transparent

| align="center" colspan="2" | <!-- Unsourced image removed: [[Image:Selenium_tetrafluoride.jpg|200px|Selenium tetrafluoride]] -->

| ImageSize =

|-

| IUPACName =

! {{chembox header}} | General

| OtherNames =

|-

|Section1={{Chembox Identifiers

| Other names

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

|

| ChemSpiderID = 109914

|-

| InChI = 1/F4Se/c1-5(2,3)4

| [[Chemical formula|Molecular formula]]

| InChIKey = PMOBWAXBGUSOPS-UHFFFAOYAQ

| SeF₄

| StdInChI_Ref = {{stdinchicite|correct|chemspider}}

|-

| StdInChI = 1S/F4Se/c1-5(2,3)4

| [[Molar mass]]

| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}

| 220.77 g/mol

| StdInChIKey = PMOBWAXBGUSOPS-UHFFFAOYSA-N

|-

| CASNo_Ref = {{cascite|correct|CAS}}

| Appearance

| CASNo = 13465-66-2

| white-yellow cubic crystals

| UNII_Ref = {{fdacite|correct|FDA}}

|-

| UNII = 73U0ARO564

| [[CAS registry number|CAS number]]

| PubChem = 123311

| [10026-03-6]

| ChEBI_Ref = {{ebicite|correct|EBI}}

|-

| ChEBI = 30435

! {{chembox header}} | Properties

| SMILES = F[Se](F)(F)F

|-

}}

| [[Density]] and [[Phase (matter)|phase]]

|Section2={{Chembox Properties

| 2.6 g/cm³, solid

| Formula = SeF₄

|-

| MolarMass = 154.954 g/mol

| [[Soluble|Solubility]]

| Appearance = colourless liquid

| decomposes in [[water]] <br> insoluble in liquid [[bromine]] <br> decomposes in dry [[ammonia]]

| Density = 2.77 g/cm³

|-

| MeltingPtC = -13.2

| [[Melting point]]

| MeltingPt_notes =

| 205°C, sublimes

| BoilingPtC = 101

|-

| BoilingPt_notes =

| [[Boiling point]]

| Solubility =

| 288°C, decomposes

}}

|-

! |Section7={{chembox header}} |Chembox '''Hazards'''

| MainHazards =

|-

| FlashPt =

| [[Directive 67/548/EEC|EU classification]]

| AutoignitionPt =

| not listed

| NFPA-H = 3

|-

| [[NFPA-F 704]]= 0

| NFPA-R = 2

| [[Image:nfpa_h4.png]][[Image:nfpa_f0.png]][[Image:nfpa_r0.png]]

| NFPA-S = W

|-

}}

| {{chembox header}} | <small>Except where noted otherwise, data are given for<br> materials in their [[standard state|standard state (at 25 °C, 100 kPa)]]<br/>[[wikipedia:Chemical infobox|Infobox disclaimer and references]]</small>

|Section8={{Chembox Related

|-

| OtherAnions = [[selenium dioxide]], [[selenium(IV) chloride]], [[selenium(IV) bromide]]

|}

| OtherCations = [[sulfur tetrafluoride]], [[tellurium(IV) fluoride]]

| OtherCompounds = [[selenium difluoride]], [[selenium hexafluoride]]

}}

}}

'''Selenium tetrafluoride''' ([[Selenium|Se]][[Fluorine|F₄]]) is aan [[chemicalinorganic compound]]. It is a colourless liquid that reacts readily with water. It can be used as a fluorinating reagent in organic syntheses (fluorination of alcohols, carboxylic acids or carbonyl compounds) and has advantages over sulfur tetrafluoride in that milder conditions can be employed and it is a liquid rather than a gas.

==Synthesis==

Conditions/substances to avoid are: [[heat]], [[flame]].

The first reported synthesis of selenium tetrafluoride was by [[Paul Lebeau]] in 1907, who treated [[selenium]] with [[fluorine]]:<ref>{{cite journal

| title = Action of Fluorine on Selenium Tetrafluoride of Selenium

| author = [[Paul Lebeau]]

| journal = Comptes Rendus de l'Académie des Sciences de Paris

| year = 1907

| volume = 144

| issue =

| pages = 1042

| doi =

}}</ref>

:Se + 2 F₂ → SeF₄

A synthesis involving more easily handled reagents entails the fluorination of [[selenium dioxide]] with [[sulfur tetrafluoride]]:<ref>Konrad Seppelt, Dieter Lentz, Gerhard Klöter "Selenium Tetrafluoride, Selenium Difluoride Oxide (Seleninyl Fluoride), and Xenon Bis[Pentafluorooxoselenate(VI)]" ''Inorg. Synth.'', 1987, vol. 24, 27-31. {{doi|10.1002/9780470132555.ch9}}</ref>

:SF₄ + SeO₂ → SeF₄ + SO₂

An intermediate in this reaction is seleninyl fluoride (SeOF₂).

Other methods of preparation include fluorinating elemental selenium with [[chlorine trifluoride]]:

:3 Se + 4 ClF₃ → 3 SeF₄ + 2 Cl₂

==Structure and bonding==

==External links==

Selenium in SeF₄ has an oxidation state of +4. Its shape in the gaseous phase is similar to that of SF₄, having a see-saw shape. [[VSEPR theory]] predicts a pseudo-trigonal pyramidal disposition of the five electron pairs around the selenium atom. The axial Se-F bonds are 177&nbsp;[[picometre|pm]] with an F-Se-F bond angle of 169.2°. The two other fluorine atoms are attached by shorter bonds (168&nbsp;pm), with an F-Se-F bond angle of 100.6°. In solution at low concentrations this monomeric structure predominates, but at higher concentrations evidence suggests weak association between SeF₄ molecules leading to a distorted octahedral coordination around the selenium atom. In the solid the selenium center also has a distorted octahedral environment.

==Reactions==

{{ChemicalSources}}

In [[hydrogen fluoride|HF]], SeF₄ behaves as a weak base, weaker than [[sulfur tetrafluoride]], SF₄ (K_b= 2 X 10⁻²):

:SeF₄ + HF → SeF₃⁺ + HF₂⁻; (K_b = 4 X 10⁻⁴)

Ionic adducts containing the SeF₃⁺ cation are formed with SbF₅, AsF₅, NbF₅, TaF₅, and BF₃.<ref>{{cite journal

[[Category:Fluorides]]

| title = Selenium tetrafluoride adducts. II. Adducts with boron trifluoride and some pentafluorides

[[Category:Selenium compounds]]

| author1 = R. J. Gillespie

[[Category:Inorganic compound stubs]]

| author2 = A. Whitla

| journal = Can. J. Chem.

| year = 1970

| volume = 48

| issue = 4

| pages = 657–663

| doi = 10.1139/v70-106

| doi-access = free

}}</ref>

With [[caesium fluoride]], CsF, the SeF₅⁻ anion is formed, which has a square pyramidal structure similar to the isoelectronic [[chlorine pentafluoride]], ClF₅ and [[bromine pentafluoride]], BrF₅.<ref>{{cite journal

| title = Vibrational Spectra and Force Constants of the Square-Pyramidal Anions SF₅⁻, SeF₅⁻, and TeF₅⁻

|author1=K. O. Christe |author2=E. C. Curtis |author3=C. J. Schack |author4=D. Pilipovich | journal = Inorganic Chemistry

| year = 1972

| volume = 11

| issue = 7

| pages = 1679–1682

| doi =10.1021/ic50113a046

}}</ref>

With 1,1,3,3,5,5-hexamethylpiperidinium fluoride or 1,2-dimethylpropyltrimethylammonium fluoride, the SeF₆²⁻ anion is formed. This has a distorted octahedral shape which contrasts to the regular octahedral shape of the analogous SeCl₆²⁻.

<ref>{{cite journal

| title = Reactions of the Naked Fluoride Ion: Syntheses and Structures of SeF₆²⁻ and BrF₆⁻

|author1=Ali Reza Mahjoub |author2=Xiongzhi Zhang |author3=Konrad Seppelt | journal = Chemistry: A European Journal

| year = 1995

| volume = 1

| issue = 4

| pages = 261–265

| doi = 10.1002/chem.19950010410

| doi-access = free}}</ref>

==References==

{{reflist}}

{{refbegin}}

* ''Selenium: Inorganic Chemistry'' Krebs. B., Bonmann S., Eidenschink I.; Encyclopedia of Inorganic Chemistry (1994) John Wiley and Sons {{ISBN|0-471-93620-0}}

{{refend}}

<!-- *{{cite journal

| title = On selenium tetrafluoride

|author1=Edmund Brydges Rudhall Prideaux |author2=Charles Beresford Cox

|name-list-style=amp | journal = [[Journal of the Chemical Society]]

| year = 1928

| pages = 1603

| doi = 10.1039/JR9280001603

}}

*{{cite journal

| title = The preparation and properties of selenium tetrafluoride and oxyfluoride

| author = E. E. Aynsley, R. D. Peacock and P. L. Robinson

| journal = [[Journal of the Chemical Society]]

| year = 1952

| volume =

| issue =

| pages = 1231

| doi = 10.1039/JR9520001231

}}

*{{cite journal

| title = Some properties of selenium tetrafluoride

| author = R. D. Peacock

| journal = [[Journal of the Chemical Society]]

| year = 1953

| volume =

| issue =

| pages = 3617

| doi = 10.1039/JR9530003617

}}

*{{cite journal

| title = Structure of Selenium Tetrafluoride

| author = H. J. M. Bowen

| journal = [[Nature (journal)|Nature]]

| year = 1953

| volume = 172

| issue = 4369

| pages = 131–172

| doi = 10.1038/172171a0

}}

*{{cite journal

| title = Structure of Selenium Tetrafluoride

| author = F. Lachman

| journal = [[Nature (journal)|Nature]]

| year = 1953

| volume = 172

| issue = 4376

| pages = 467–510

| doi = 10.1038/172499a0

}}

*{{cite journal

| title = Investigation by electron diffraction of the molecular structures of sulphur hexafluoride, sulphur tetrafluoride, selenium hexafluoride and selenium tetrafluoride

|author1=V. C. Ewing |author2=L. E. Sutton | journal = Transactions of the Faraday Society

| year = 1963

| volume = 59

| issue =

| pages = 1241

| doi = 10.1039/TF9635901241

}}

-->

==See also==

{{inorganic-compound-stub}}

*[[Selenium hexafluoride]]

*[[Sulfur tetrafluoride]]

*[[Tellurium tetrafluoride]]

==External links==

* [http://webbook.nist.gov/cgi/cbook.cgi?ID=C13465662 WebBook page for SeF4]

{{Selenium compounds}}

{{fluorine compounds}}

[[Category:Fluorides]]

[[Category:Selenium(IV) compounds]]

[[Category:Fluorinating agents]]

[[Category:Chalcohalides]]

[[Category:Selenium halides]]

[[Category:Substances discovered in the 1900s]]