(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)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:
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.
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