“Vanadium tetrachloride”的意思、由来-开放百科全书

词条

Vanadium tetrachloride

释义

Synthesis, bonding, basic properties
Reactions
Organic chemistry
Applications
Safety considerations
References

{{chembox
| Watchedfields = changed
| verifiedrevid = 470628447
| Name = Vanadium tetrachloride
| ImageFileL1 = Vanadium tetrachloride.svg
| ImageNameL1 = Structural formula of the vanadium tetrachloride molecule
| ImageFileR1 = Vanadium-tetrachloride-3D-balls.png
| ImageNameR1 = 3D model of the vanadium tetrachloride molecule
| IUPACName = Vanadium tetrachloride
Vanadium(IV) chloride
| OtherNames =
|Section1={{Chembox Identifiers
| InChI = 1/4ClH.2V/h4*1H;;/q;;;;2*+2/p-4
| InChIKey = UNUHYFVFMNJHJW-XBHQNQODAR
| SMILES = Cl[V](Cl)(Cl)Cl
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/4ClH.2V/h4*1H;;/q;;;;2*+2/p-4
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = UNUHYFVFMNJHJW-UHFFFAOYSA-J
| CASNo = 7632-51-1
| CASNo_Ref = {{cascite|correct|CAS}}
| PubChem = 24273
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID =19956660
| RTECS = YW2625000
| EINECS = 231-561-1
|Section2={{Chembox Properties
| Formula = VCl₄
| MolarMass = 192.75 g/mol
| Appearance = bright red liquid, moisture sensitive
| Odor = pungent
| Density = 1.816 g/cm³, liquid
| Solubility = decomposes
| SolubleOther = soluble in CH₂Cl₂
| MeltingPtC = −24.5
| BoilingPtC = 148
| VaporPressure = 7.9 Pa
| MagSus = +1130.0·10⁻⁶ cm³/mol
|Section3={{Chembox Structure
| Coordination = tetrahedral
| CrystalStruct =
| Dipole = 0 D
|Section7={{Chembox Hazards
| ExternalSDS =
| MainHazards = toxic; oxidizer; hydrolyzes to release HCl
| RPhrases =
| SPhrases =
| NFPA-H = 3
| NFPA-F = 0
| NFPA-R = 2
| NFPA-S = W
| LD50 = 160 mg/kg (rat, oral)
|Section8={{Chembox Related
| OtherAnions = vanadium tetrafluoride, vanadium disulfide, vanadium tetrabromide
| OtherCations = titanium tetrachloride, chromium tetrachloride, niobium tetrachloride, tantalum tetrachloride
| OtherCompounds = vanadium trichloride
}}

Vanadium tetrachloride is the inorganic compound with the formula VCl₄. This bright red liquid serves as a useful reagent for the preparation of other vanadium compounds.

Synthesis, bonding, basic properties

With one more valence electron than diamagnetic TiCl₄, VCl₄ is a paramagnetic liquid. It is one of only a few paramagnetic compounds that is liquid at room temperature.

VCl₄ is prepared by chlorination of vanadium metal. VCl₅ does not form in this reaction; Cl₂ lacks the oxidizing power to attack VCl₄. VCl₅ can however be prepared indirectly from VF₅ at −78 °C.^[1] In contrast, the heavier analogues NbCl₅ and TaCl₅ are stable and not particularly oxidizing. VF₅ can be prepared directly by fluorination of vanadium metal, reflecting the increased oxidizing power of F₂ vs Cl₂. Indicative of its oxidizing power, VCl₄ releases Cl₂ at its boiling point (standard pressure) to afford VCl₃.

Reactions

Consistent with its high oxidizing power, VCl₄ reacts with HBr at -50 °C to produce VBr₃. The reaction proceeds via VBr₄, which releases Br₂ during warming to room temperature.^[2]

2 VCl₄ + 8 HBr → 2 VBr₃ + 8 HCl + Br₂

VCl₄ forms adducts with many donor ligands, for example, VCl₄(THF)₂.

It is the precursor to vanadocene dichloride.

Organic chemistry

In organic synthesis, VCl₄ is used for the oxidative coupling of phenols. For example, it converts phenol into a mixture of 4,4'-, 2,4'-, and 2,2'-biphenols:^[3]

2 C₆H₅OH + 2 VCl₄ → HOC₆H₄–C₆H₄OH + 2 VCl₃ + 2 HCl

Applications

VCl₄ is a catalyst for the polymerization of alkenes, especially those useful in the rubber industry. The underlying technology is related to Ziegler–Natta catalysis, which involves the intermediacy of vanadium alkyls.

Safety considerations

VCl₄ is a volatile, aggressive oxidant that readily hydrolyzes to release HCl.

References

1. ^{{ cite journal | first1 = Farhad | last1 = Tamadon | first2 = Konrad | last2 = Seppelt | title = The Elusive Halides VCl₅, MoCl₆, and ReCl₆ | journal = Angew. Chem. Int. Ed. | year = 2013 | volume = 52 | issue = 2 | pages = 767–769 | doi = 10.1002/anie.201207552 }}
2. ^{{cite journal | last1= Calderazzo|first1= F. |last2=Maichle-Mössmer|first2= C.|first3= Pampaloni|last3= G. |first4=Strähle|last4= J. | title = Low-temperature Syntheses of Vanadium(III) and Molybdenum(IV) Bromides by Halide Exchange | journal = Dalton Transactions |issue= 5 | year = 1993 | pages = 655–8| doi = 10.1039/DT9930000655}}
3. ^{{cite encyclopedia|first1=M. K.|last1= O’Brien|first2= B.|last2= Vanasse |title=Vanadium(IV) Chloride|encyclopedia= Encyclopedia of Reagents for Organic Synthesis |editor-first=L. |editor-last=Paquette |date=2004 |publisher=J. Wiley & Sons |location=New York, NY|doi=10.1002/047084289X.rv001}}

4 : Vanadium compounds|Chlorides|Metal halides|Reagents for organic chemistry

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