- Chromium carbonyl
Chembox new
Name = Chromium carbonyl
ImageFile = Cr(CO)6.png
ImageSize = 150px
ImageName =
IUPACName = hexacarbonylchromium(0)
OtherNames = chromium carbonyl
Section1 = Chembox Identifiers
CASNo = 13007-92-6
RTECS = GB5075000
Section2 = Chembox Properties
Formula = C6CrO6
MolarMass = 220.06 g/mol
Appearance = colorless crystals
Density = 1.77 g/cm3, solid
Solubility = insoluble
Solvent = other solvents
SolubleOther = soluble inbenzene ,THF
MeltingPt = 150 °C (decomposition)
BoilingPt = sublimes
Section3 = Chembox Structure
Coordination = octahedral
CrystalStruct = orthrhombic
Dipole = 0 D
Section7 = Chembox Hazards
ExternalMSDS =
MainHazards = CO source
RPhrases = R22
SPhrases = S53 S36 S45
Section8 = Chembox Related
Function = compounds
OtherFunctn = V(CO)6, Fe(CO)5-] , CrCl3Chromium carbonyl, also known as chromium hexacarbonyl, is the
chemical compound with the formula Cr(CO)6. Atroom temperature the solid is stable to air, although it does have a highvapor pressure and sublimes readily. Cr(CO)6 is zerovalent, meaning that Cr has aformal charge of zero, and it is called ahomoleptic complex, which means that all theligand s are the same. The complex isoctahedral with Cr-C and C-O distances of 1.92 and 1.17 Å, respectively. [Whitaker A.; Jeffery, J. W. “The Crystal Structure of Chromium Hexacarbonyl” Acta Crystallographica 1967, volume 23, pp. 977-984. doi|10.1107/S0365110X67004153.]Reactions
When heated or photolyzed in
tetrahydrofuran (THF) solution, Cr(CO)6 converts to Cr(CO)5(THF) with loss of one CO ligand. Similarly, heating a solution of Cr(CO)6 in anaromatic solvent results in replacement of three CO ligands::Cr(CO)6 + C6H5R → Cr(CO)3(C6H5R) + 3 COSuch reactions proceed particularly well with electron-rich arenes such as
anisole , either as the neat reagent or using a mixture of THF anddibutyl ether , the latter to increase theboiling point of the mixture. The products adopt a "piano-stool" structure. These species are typicallyyellow solids, which dissolve well in common organicsolvent s. The arene can be liberated from the chromium withiodine or by photolysis inair . In general, substituted derivatives of Cr(CO)6 decompose upon exposure to air.Alkyl and aryl
organolithium reagent s RLi add to a carbonyl ligand to give anionicacyl complexes. [Elschenbroich, C. ”Organometallics” (2006) Wiley-VCH: Weinheim. ISBN 978-3-29390-6] These species react with alkylating agents such as Me3O+ to form (OC)5Cr=C(OMe)R, an example of a Fischer carbene. If the R group is a vinyl or an aryl group, then the resulting carbene complex can react with anacetylene to form a newbenzene ring to which is bonded the chromium tricarbonyl fragment. The two acetylene carbon atoms become part of the new ring, as does a carbon from one of the carbonyl ligands. Also the three carbons from thevinyl carbene become part of the new benzene ring.afety
In common with many of the other homoleptic metal carbonyls (e.g.
nickel carbonyl andiron carbonyl ), chromium hexacarbonyl is toxic and thought to becarcinogenic . Its vapor pressure is relatively high for a metal complex, 1 mm Hg ( 36 °C).References
External links
* [http://www.npi.gov.au/database/substance-info/profiles/24.html National Pollutant Inventory - Chromium (III) and compounds fact sheet]
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