text: The benzene ligand in (η-CH)Cr(CO)Mi is prone to deprotonation.  For example, Organolithium compounds form adducts featuring cyclohexadienyl ligands.  Subsequent oxidation of the complex results in the release of a substituted benzene.  Oxidation of the chromium atom by I and other iodine reagents has been shown to promote exchange of arene ligands, but the intermediate chromium iodide species has not been characterized.
  (η-CH)Cr(CO) complexes exhibit "cine" and "tele" nucleophilic aromatic addition.   Processes of this type involve reaction of (η-CH)Cr(CO) with an alkyl lithium reagent.  Subsequent treatment with an acid results in the addition of a nucleophile to the benzene ring at a site ortho ("cine"), meta or para ("tele") to the ipso carbon (see Arene substitution patterns).
  Reflecting its increased acidity, the benzene ligand can be lithiated with n-butyllithium.  The resulting organolithium compound serves as a nucleophile in various reactions, for example, with trimethylsilyl chloride:
  (η-CH)Cr(CO) 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.
  A variety of arenes ligands have been installed aside from benzene. Weakly coordinating ligands may be employed to improve ligand exchange and thus the turnover rates for (η-CH)M(CO) complexes.(η-CH)M(CO) complexes have been incorporated into high surface area porous materials.
  (η-CH)M(CO) complexes serve as models for the interaction of metal carbonyls with graphene and carbon nanotubes. The presence of M(CO) on extended π-network materials has been shown to improve electrical conductivity across the material.