(Benzene)chromium tricarbonyl

(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]

(Benzene)chromium(0) tricarbonyl

Names
IUPAC name (benzene)tricarbonylchromium
Other names benzene tricarbonyl chromium, (benzene)chromium tricarbonyl, Benchrotrene, pi-benzenetricarbonylchromium
Identifiers
CAS Number	12082-08-5 N
3D model (JSmol)	Interactive image
ChemSpider	9130108 Y
ECHA InfoCard	100.031.939
EC Number	235-146-6
PubChem CID	10954891
InChI InChI=1S/C6H6.3CO.Cr/c1-2-4-6-5-3-1;3*1-2;/h1-6H;;;; Y Key: WVSBQYMJNMJHIM-UHFFFAOYSA-N Y InChI=1/C6H6.3CO.Cr/c1-2-4-6-5-3-1;3*1-2;/h1-6H;;;; Key: WVSBQYMJNMJHIM-UHFFFAOYAR
SMILES [Cr].[O+]#[C-].[O+]#[C-].[O+]#[C-].c1ccccc1
Properties
Chemical formula	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)
Solubility in water	nonsoluble
Solubility	THF, ether, benzene
Structure
Coordination geometry	tetrahedral, "piano stool"
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Harmful through inhalation, contact with skin, or swallowed
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H302, H312, H332
Precautionary statements	P261, P264, P270, P271, P280, P301+P312, P302+P352, P304+P312, P304+P340, P312, P322, P330, P363, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

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

Complexes of the type (Arene)Cr(CO)₃ have been well investigated as reagents in organic synthesis..^[3] The aromatic ring of (benzene)tricarbonylchromium is substantially more electrophilic than benzene itself, allowing it to undergo nucleophilic addition reactions.^[4]

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.