ETA-5-CYCLOHEXADIENYLTRICARBONYLCHROMIUM(0) COMPLEXES FROM ADDITION OF CARBON NUCLEOPHILES TO "ETA-6-BENZENETRICARBONYLCHROMIUM(0) - FORMATION, CHEMICAL AND SPECTROSCOPIC FEATURES, AND X-RAY-DIFFRACTION ANALYSIS

The addition of reactive carbanions to η6-benzenetricarbonylchromium(0) produced η5-(6-alkylcyclohexadienyl)tri-carbonylchromium(O) anion complexes, as the lithium salts. Reaction with a variety of oxidizing agents (iodine, cerium(lV), oxygen) removes the hydrogen from C-6 and detaches the Cr(CO)3 unit, to produce a substituted arene. Reaction with electrophiles (potential hydride acceptors) leads to cleavage of the carbon-carbon bond at C-6 with regeneration of η6-benzenetricar-bonylchromium(O). Solution spectral (1H NMR, IR) data are consistent with an η5-cyclohexadienyl structure. X-ray diffraction analysis on the crystalline adduct of η6-benzenetricarbonylchroinium(0) and 2-lithio-1,3-dithane defines the mode of addition (exo), the deformation (38.6°) of C-6 from the plane of carbons 1-5 in the cyclohexadienyl Iigand. and the preferred conformation of the Cr(CO)3 unit. Copyright © 1979, American Chemical Society. All rights reserved.