Phenylation of cyclic and acyclic pentadienyl carbanions by pi-fluorobenzenetricarbonylchromium

Phenylation of cyclopentadienyl, indenyl, fluorenyl, 1,3-pentadienyl, 2,4-dimethyl-1,3_pentadienyl, and 1,1',5,5'-tetramethyl-1,3-pentadienyl carbanions by pi-fluorobenzenetricarbonylchromium in ethereal solvents at 0" C gives good yields (> 70%) of complexes in which the phenyl-Cr(CO)3 group is sigma-bonded to a pentadienyl skeleton. The regio and stereo isomers obtained have been identified by accurate 1H NMR study. Monotoring of the reaction by IR spectroscopy has shown that the mechanism of substitution of fluorine by the cyclic anions is different from that for substitution by the acyclic anions.