(Benzene)chromium tricarbonyl

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(Benzene)chromium(0) tricarbonyl
Benzenetricarbonylchromium.svg (benzene)chromium-tricarbonyl-from-xtal-1987-3D-balls.png
Identifiers
CAS number 12082-08-5 N
ChemSpider 9130108 YesY
Jmol-3D images Image 1
Properties
Molecular formula Cr(C6H6)(CO)3
Molar mass 214.14 g/mol
Appearance solid yellow crystals
Melting point 163 - 166 °C
Solubility in water nonsoluble
Solubility THF, ether, benzene
Structure
Coordination
geometry
tetrahedral, "piano stool"
Hazards
R-phrases 20/21/22
S-phrases 36/37
Main hazards Harmful through inhalation, contact with skin, or swallowed
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
Infobox references

(Benzene)chromium tricarbonyl is an organometallic compound with the formula Cr(C6H6)(CO)3. This yellow crystalline solid compound is soluble in common nonpolar organic solvents. The molecule adopts a geometry known as “piano stool” because of the planar arrangement of the aryl group and the presence of three CO ligands as "legs" on the chromium-bond axis.[1]

Preparation[edit]

(Benzene)tricarbonylchromium was first reported in 1957 by Fischer and Öfele, who prepared the compound by the carbonylation of bis(benzene)chromium.[2] They obtained mainly chromium carbonyl (Cr(CO)6) and traces of Cr(C6H6)(CO)3. The synthesis was optimized through the reaction of Cr(CO)6 and Cr(C6H6)2. For commercial purposes, a reaction of Cr(CO)6 and benzene is used:

Cr(CO)6 + C6H6 → Cr(C6H6)(CO)3 + 3 CO

Applications[edit]

The aromatic ring of (benzene)tricarbonylchromium is substantially more electrophilic than benzene itself, allowing it to undergo nucleophilic addition reactions.[3]

(Benzene)chromiumtricarbonyl electrophile nucleophilic carbonylation.png

It is also more acidic, undergoing lithiation upon treatment with n-butyllithium. The resulting organolithium compound can then be used as a nucleophile in various reactions, for example, with trimethylsilyl chloride:

(Benzene)chromiumtricarbonyl lithiation TMS.png

(Benzene)tricarbonylchromium is a useful catalyst for the hydrogenation of 1,3-dienes. The product alkene results from 1,4-addition of hydrogen. The complex does not hydrogenate isolated double bonds.

References[edit]

  1. ^ Gilbert T. M. Bauer C. B., Rogers R. D. (1996). "Structures of (η6-benzene dimethylacetal)- and (η6-benzene diethylacetal)chromium tricarbonyl: structural evidence for the near-electroneutrality of the dialkylacetal substituent". Journal of Chemical Crystallography 26 (5): 355. doi:10.1007/BF01677100. 
  2. ^ Fischer, Ernst Otto; Őfele, Karl. (1957). “Über Aromatenkomplexe von Metallen, XIII Benzol-Chrom-Tricarbonyl,” Chemische Berichte, 90, 2532-5. doi:10.1002/cber.19570901117.
  3. ^ Herndon, James W; Laurent, Stéphane E. (2008). “(η6-Benzene)tricarbonylchromium,” in Encyclopedia of Reagents for Organic Synthesis, John Wiley & Sons, Chichester, 2008. doi:10.1002/047084289X.rb025.pub2. Article Online Posting Date: March 15, 2009