(Benzene)chromium tricarbonyl

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(Benzene)chromium(0) tricarbonyl
Names
IUPAC name
(benzene)tricarbonylchromium
Other names
benzene tricarbonyl chromium, (benzene)chromium tricarbonyl, Benchrotrene, pi-benzenetricarbonylchromium
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.031.939 Edit this at Wikidata
  • InChI=1S/C6H6.3CO.Cr/c1-2-4-6-5-3-1;3*1-2;/h1-6H;;;; checkY
    Key: WVSBQYMJNMJHIM-UHFFFAOYSA-N checkY
  • InChI=1/C6H6.3CO.Cr/c1-2-4-6-5-3-1;3*1-2;/h1-6H;;;;
    Key: WVSBQYMJNMJHIM-UHFFFAOYAR
  • [Cr].[O+]#[C-].[O+]#[C-].[O+]#[C-].c1ccccc1
Properties
Cr(C6H6)(CO)3
Molar mass 214.14 g/mol
Appearance solid yellow crystals
Melting point 163 to 166 °C (325 to 331 °F; 436 to 439 K)
nonsoluble
Solubility THF, ether, benzene
Structure
tetrahedral, "piano stool"
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Harmful through inhalation, contact with skin, or swallowed
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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(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

(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

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

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)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

  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
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